ORCID Profile
0000-0002-1651-8969
Current Organisations
Western Sydney University
,
University of Wyoming
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Research Topics
In Research Link Australia (RLA), "Research Topics" refer to ANZSRC FOR and SEO codes. These topics are either sourced from ANZSRC FOR and SEO codes listed in researchers' related grants or generated by a large language model (LLM) based on their publications.
Top 5 Research Topics
ANZSRC Field of Research (FoR)
Ecological Impacts of Climate Change | Ecosystem Function | Ecological Applications | Other Biological Sciences | Global Change Biology | Ecological Physiology | Global Change Biology | Terrestrial Ecology | Soil Sciences | Soil Biology | Soil Chemistry |
ANZSRC Socio-Economic Objective (SEO)
Climate change | Biological sciences | Sparseland, Permanent Grassland and Arid Zone Soils | Ecosystem Adaptation to Climate Change | Effects of Climate Change and Variability on Australia (excl. Social Impacts) | Climate Change Mitigation Strategies | Management of Greenhouse Gas Emissions from Plant Production | Native and Residual Pastures | Native vegetation | Pasture, browse and fodder crops | Native Forests
Related Links
Publications
Remarkable Resilience of Forest Structure and Biodiversity Following Fire in the Peri-Urban Bushland of Sydney, Australia
Publisher: MDPI AG
Date: 16-06-2022
DOI: 10.3390/CLI10060086
Abstract: In rapidly urbanizing areas, natural vegetation becomes fragmented, making conservation planning challenging, particularly as climate change accelerates fire risk. We studied urban forest fragments in two threatened eucalypt-dominated (scribbly gum woodland, SGW, and ironbark forest, IF) communities across ~2000 ha near Sydney, Australia, to evaluate effects of fire frequency (0–4 in last 25 years) and time since fire (0.5 to years) on canopy structure, habitat quality and bio ersity (e.g., species richness). Airborne lidar was used to assess canopy height and density, and ground-based surveys of 148 (400 m2) plots measured leaf area index (LAI), plant species composition and habitat metrics such as litter cover and hollow-bearing trees. LAI, canopy density, litter, and microbiotic soil crust increased with time since fire in both communities, while tree and mistletoe cover increased in IF. Unexpectedly, plant species richness increased with fire frequency, owing to increased shrub richness which offset decreased tree richness in both communities. These findings indicate bio ersity and canopy structure are generally resilient to a range of times since fire and fire frequencies across this study area. Nevertheless, reduced arboreal habitat quality and subtle shifts in community composition of resprouters and obligate seeders signal early concern for a scenario of increasing fire frequency under climate change. Ongoing assessment of fire responses is needed to ensure that bio ersity, canopy structure and ecosystem function are maintained in the remaining fragments of urban forests under future climate change which will likely drive hotter and more frequent fires.
Modelling soil CO<sub>2</sub> production and transport with dynamic source and diffusion terms: Testing the steady-state assumption using DETECT v1.0
Publisher: Copernicus GmbH
Date: 10-10-2017
DOI: 10.5194/GMD-2017-223
Abstract: Abstract. The flux of CO2 from the soil to the atmosphere (soil respiration, Rsoil) is a major component of the global carbon cycle. Methods to measure and model Rsoil, or partition it into different components, often rely on the assumption that soil CO2 concentrations and fluxes are in steady state, implying that Rsoil is equal to the rate at which CO2 is produced by soil microbial and root respiration. Recent research, however, questions the validity of this assumption. Thus, the aim of this work was two-fold: (1) to describe a non-steady state (NSS) soil CO2 transport and production model, DETECT, and (2) to use this model to evaluate the environmental conditions under which Rsoil and CO2 production are likely in NSS. The backbone of DETECT is a non-homogeneous, partial differential equation (PDE) that describes production and transport of soil CO2, which we solve numerically at fine spatial and temporal resolution (e.g., 0.01 m increments to 1 m, every 6 hours). Production of soil CO2 is simulated for every depth and time increment as the sum of root respiration and microbial decomposition of soil organic matter, both of which can be driven by current and antecedent soil water content and temperature, which can also vary by time and depth. We also analytically solved the ordinary differential equation (ODE) corresponding to the steady-state (SS) solution to the PDE model. We applied the DETECT NSS and SS models to the 6-month growing season period representative of a native grassland in Wyoming. Simulation experiments were conducted with both model versions to evaluate factors that could affect departure from SS: (1) varying soil texture (2) shifting the timing or frequency of precipitation and (3) with and without the environmental antecedent drivers. For a coarse-textured soil, Rsoil from the SS model closely matched that of the NSS model. However, in a fine-textured (clay) soil, growing season Rsoil was ~ 3 % higher under the assumption of NSS (versus SS). These differences were exaggerated in clay soil at daily time-scales whereby Rsoil under the SS assumption deviated from NSS by up to ~ 20 % in the 10 days following a major precipitation event. Moreover, incorporation of antecedent drivers increased the magnitude of Rsoil by 15 % to 37 % for coarse- and fine-textured soils, respectively. However, the responses of Rsoil to the timing of precipitation and antecedent drivers did not differ between SS and NSS assumptions. In summary, the assumption of SS conditions can be violated depending on soil type and soil moisture status, as affected by precipitation inputs, and the DETECT model provides a framework for accommodating NSS conditions to better predict Rsoil and associated soil carbon cycling processes.
Towards a predictive understanding of belowground process responses to climate change: have we moved any closer?
Publisher: Wiley
Date: 03-11-2008
Effect of water addition and nitrogen fertilization on the fluxes of CH<sub>4</sub>, CO<sub>2</sub>, NO<sub>x</sub>,
Publisher: Copernicus GmbH
Date: 13-10-2003
Abstract: Abstract. An open-top-chamber (OTC) CO2 enrichment (~720 mmol mol-1) study was conducted in the Colorado shortgrass steppe from April 1997 through October 2001. Aboveground plant biomass increased under elevated CO2 and soil moisture content was typically higher than under ambient CO2 conditions. Fluxes of CH4, CO2, NOx and N2O, measured weekly year round were not significantly altered by CO2 enrichment over the 55 month period of observation. During early summer of 2002, following the removal of the open-top-chambers from the CO2 enrichment sites in October 2001, we conducted a short term study to determine if soil microbial processes were altered in soils that had been exposed to double ambient CO2 concentrations during the growing season for the past five years. Microplots were established within each experimental site and 10 mm of water or 10 mm of water containing the equivalent of 10 g m-2 of ammonium nitrate-N was applied to the soil surface. Fluxes of CO2, CH4, NOx and N2O fluxes within control (unchambered), ambient CO2 and elevated CO2 OTC soils were measured at one to three day intervals for the next month. With water addition alone, CO2 and NO emission did not differ between ambient and elevated CO2 soils, while CH4 uptake rates were higher and N2O fluxes lower in elevated CO2 soils. Adding water and mineral N resulted in increased CO2 emissions, increased CH4 uptake and decreased NO emissions in elevated CO2 soils. The N addition study confirmed previous observations that soil respiration is enhanced under elevated CO2 and N immobilization is increased, thereby decreasing NO emission.
Ecological stoichiometry reveals variation in phosphorus and nitrogen responses to warming and drought across mycorrhizal partners
Publisher: Copernicus GmbH
Date: 04-03-2021
DOI: 10.5194/EGUSPHERE-EGU21-14036
Abstract: & & Ecological stoichiometry provides a valuable framework to understand functional variation among organisms, particularly with respect to responses to stress. Trophic dynamics are an important element of this framework, although symbiotic interactions are poorly integrated. Here, we assessed concentrations and ratios of carbon ([C]), nitrogen ([N]) and phosphorus ([P]) in tissues of lucerne (Medicago sativa) and their associated arbuscular mycorrhizal (AM) fungi growing under ambient or extreme (high temperature and/or low soil moisture) environmental conditions. In general, the AM fungal mycelium was depleted in [C] by 50% and [N] by 46% but enriched in [P] by more than six times when compared to plant shoots and roots. Warming and moisture limitation resulted in further increases in [P] and reduced C:P and N:P ratios in all tissues, while AM fungal [N] and C:N responses were muted and decoupled from those in plant tissues. Using high-throughput DNA sequencing and joint species distribution modelling, we were also able to link compositional shifts in AM fungal communities in roots and soil to variation in hyphal chemistry. As such, this work provides insight into the ecological strategies of AM fungi associated with an important pasture legume (among many other species) some potential consequences for carbon and nutrient exchange between soil, fungal and plant pools and how these interactions are impacted by climate extremes.& &
Root responses to elevated CO 2, warming and irrigation in a semi‐arid grassland: Integrating biomass, length and life span in a 5‐year field experiment
Publisher: Wiley
Date: 14-05-2018
Rhizodeposition stimulated by elevated CO2 in a semiarid grassland
Publisher: Wiley
Date: 19-03-2004
Long-term exposure to elevated CO 2 enhances plant community stability by suppressing dominant plant species in a mixed-grass prairie
Publisher: Proceedings of the National Academy of Sciences
Date: 13-10-2014
Abstract: Evaluating ecological responses to climate change is essential to predict ecosystem function under future climate scenarios. In a mixed-grass prairie, we use a multifactor field experiment to show that the effects of elevated CO 2 and warming on plant community structure and productivity depend on interannual variation in precipitation. We also show that shifts in plant dominance patterns driven by elevated CO 2 in a mixed-grass prairie ecosystem promoted biomass and compositional stability and resistance to interannual variation in precipitation. The economic value of grasslands is largely dependent on the relative abundance of key forage species. Thus, our results have implications for how we manage native grasslands in the face of changing climate.
The carbon dioxide evasion cycle of an intermittent first-order stream: contrasting water–air and soil–air exchange
Publisher: Springer Science and Business Media LLC
Date: 30-12-2017
Elevated carbon dioxide accelerates the spatial turnover of soil microbial communities
Publisher: Wiley
Date: 23-10-2015
DOI: 10.1111/GCB.13098
Abstract: Although elevated CO2 (eCO2 ) significantly affects the α- ersity, composition, function, interaction and dynamics of soil microbial communities at the local scale, little is known about eCO2 impacts on the geographic distribution of micro-organisms regionally or globally. Here, we examined the β- ersity of 110 soil microbial communities across six free air CO2 enrichment (FACE) experimental sites using a high-throughput functional gene array. The β- ersity of soil microbial communities was significantly (P < 0.05) correlated with geographic distance under both CO2 conditions, but declined significantly (P < 0.05) faster at eCO2 with a slope of -0.0250 than at ambient CO2 (aCO2 ) with a slope of -0.0231 although it varied within each in idual site, indicating that the spatial turnover rate of soil microbial communities was accelerated under eCO2 at a larger geographic scale (e.g. regionally). Both distance and soil properties significantly (P < 0.05) contributed to the observed microbial β- ersity. This study provides new hypotheses for further understanding their assembly mechanisms that may be especially important as global CO2 continues to increase.
Alfalfa-grass biomass, soil organic carbon, and total nitrogen under different management approaches in an irrigated agroecosystem
Publisher: Springer Science and Business Media LLC
Date: 18-08-2013
Phosphorus availability and arbuscular mycorrhizal fungi limit soil C cycling and influence plant responses to elevated CO2 conditions
Publisher: Springer Science and Business Media LLC
Date: 07-06-2022
Supplementary material to "Examining the evidence for sustained transpiration during heat extremes"
Publisher: Copernicus GmbH
Date: 24-09-0100
Pastures and Climate Extremes: Impacts of cool season warming and drought on the productivity of key pasture species in a field experiment
Publisher: Cold Spring Harbor Laboratory
Date: 22-12-2020
DOI: 10.1101/2020.12.21.423155
Abstract: Shifts in the timing, intensity and/or frequency of climate extremes, such as severe drought and heatwaves, can generate sustained shifts in ecosystem function with important ecological and economic impacts for rangelands and managed pastures. The Pastures and Climate Extremes experiment (PACE) in Southeast Australia was designed to investigate the impacts of a severe winter/spring drought (60% rainfall reduction) and, for a subset of species, a factorial combination of drought and elevated temperature (ambient +3 °C) on pasture productivity. The experiment included nine common pasture and Australian rangeland species from three plant functional groups (C 3 grasses, C 4 grasses and legumes) planted in monoculture. Winter/spring drought resulted in productivity declines of 45% on average and up to 74% for the most affected species ( Digitaria eriantha ) during the 6-month treatment period, with eight of the nine species exhibiting significant yield reductions. Despite considerable variation in species’ sensitivity to drought, C 4 grasses were more strongly affected by this treatment than C 3 grasses or legumes. Warming also had negative effects on cool-season productivity, associated at least partially with exceedance of optimum growth temperatures in spring and indirect effects on soil water content. The combination of winter/spring drought and year-round warming resulted in the greatest yield reductions. We identified responses that were either additive such that there was only as significant warming effect under drought ( Festuca ), or less-than-additive, where there was no drought effect under warming ( Medicago ), compared to ambient plots. Results from this study highlight the sensitivity of erse pasture species to increases in winter and spring drought severity similar to those predicted for this region, and that anticipated benefits of cool-season warming are unlikely to be realised. Overall, the substantial negative impacts on productivity suggest that future, warmer, drier climates will result in shortfalls in cool-season forage availability, with profound implications for the livestock industry and natural grazer communities.
Climate change alters stoichiometry of phosphorus and nitrogen in a semiarid grassland
Publisher: Wiley
Date: 25-09-2012
DOI: 10.1111/J.1469-8137.2012.04349.X
Abstract: Nitrogen ( N ) and phosphorus ( P ) are essential nutrients for primary producers and decomposers in terrestrial ecosystems. Although climate change affects terrestrial N cycling with important feedbacks to plant productivity and carbon sequestration, the impacts of climate change on the relative availability of N with respect to P remain highly uncertain. In a semiarid grassland in Wyoming, USA , we studied the effects of atmospheric CO 2 enrichment (to 600 ppmv) and warming (1.5/3.0°C above ambient temperature during the day/night) on plant, microbial and available soil pools of N and P. Elevated CO 2 increased P availability to plants and microbes relative to that of N , whereas warming reduced P availability relative to N . Across years and treatments, plant N : P ratios varied between 5 and 18 and were inversely related to soil moisture. Our results indicate that soil moisture is important in controlling P supply from inorganic sources, causing reduced P relative to N availability during dry periods. Both wetter soil conditions under elevated CO 2 and drier conditions with warming can further alter N : P . Although warming may alleviate N constraints under elevated CO 2 , warming and drought can exacerbate P constraints on plant growth and microbial activity in this semiarid grassland.
Impacts of warming and elevated CO 2 on a semi‐arid grassland are non‐additive, shift with precipitation, and reverse over time
Publisher: Wiley
Date: 24-06-2016
DOI: 10.1111/ELE.12634
Abstract: It is unclear how elevated CO2 (eCO2 ) and the corresponding shifts in temperature and precipitation will interact to impact ecosystems over time. During a 7-year experiment in a semi-arid grassland, the response of plant biomass to eCO2 and warming was largely regulated by interannual precipitation, while the response of plant community composition was more sensitive to experiment duration. The combined effects of eCO2 and warming on aboveground plant biomass were less positive in 'wet' growing seasons, but total plant biomass was consistently stimulated by ~ 25% due to unique, supra-additive responses of roots. Independent of precipitation, the combined effects of eCO2 and warming on C3 graminoids became increasingly positive and supra-additive over time, reversing an initial shift toward C4 grasses. Soil resources also responded dynamically and non-additively to eCO2 and warming, shaping the plant responses. Our results suggest grasslands are poised for drastic changes in function and highlight the need for long-term, factorial experiments.
Climate warming alters photosynthetic responses to elevated CO2 in prairie plants
Publisher: Wiley
Date: 09-2020
DOI: 10.1002/AJB2.1532
Response of soil organic matter pools to elevated CO2 and warming in a semi-arid grassland
Publisher: Springer Science and Business Media LLC
Date: 17-06-2011
Long‐term enhancement of N availability and plant growth under elevated CO2 in a semi‐arid grassland
Publisher: Wiley
Date: 03-11-2008
Temporal Coupling of Subsurface and Surface Soil CO2 Fluxes: Insights From a Nonsteady State Model and Cross‐Wavelet Coherence Analysis
Publisher: Wiley
Date: 04-2018
DOI: 10.1002/2017JG004207
Warming Reduces Carbon Losses from Grassland Exposed to Elevated Atmospheric Carbon Dioxide
Publisher: Public Library of Science (PLoS)
Date: 19-08-2013
C4 grasses prosper as carbon dioxide eliminates desiccation in warmed semi-arid grassland
Publisher: Springer Science and Business Media LLC
Date: 08-2011
DOI: 10.1038/NATURE10274
Abstract: Global warming is predicted to induce desiccation in many world regions through increases in evaporative demand. Rising CO(2) may counter that trend by improving plant water-use efficiency. However, it is not clear how important this CO(2)-enhanced water use efficiency might be in offsetting warming-induced desiccation because higher CO(2) also leads to higher plant biomass, and therefore greater transpirational surface. Furthermore, although warming is predicted to favour warm-season, C(4) grasses, rising CO(2) should favour C(3), or cool-season plants. Here we show in a semi-arid grassland that elevated CO(2) can completely reverse the desiccating effects of moderate warming. Although enrichment of air to 600 p.p.m.v. CO(2) increased soil water content (SWC), 1.5/3.0 °C day/night warming resulted in desiccation, such that combined CO(2) enrichment and warming had no effect on SWC relative to control plots. As predicted, elevated CO(2) favoured C(3) grasses and enhanced stand productivity, whereas warming favoured C(4) grasses. Combined warming and CO(2) enrichment stimulated above-ground growth of C(4) grasses in 2 of 3 years when soil moisture most limited plant productivity. The results indicate that in a warmer, CO(2)-enriched world, both SWC and productivity in semi-arid grasslands may be higher than previously expected.
Inter-annual variability in the response of soil respiration to elevated CO2 concentrations in the atmosphere
Publisher: Copernicus GmbH
Date: 15-05-2023
DOI: 10.5194/EGUSPHERE-EGU23-11200
Abstract: In this research we consider the response of soil respiration under elevated CO2 (eCO2) in an oak-dominated temperate forest. We hypothesised that under elevated CO2 (550 ppm) soil moisture would increase as a result of reduced stomatal conductance, which would in turn lead to higher soil respiration. Continuous measurements were performed on three pairs of plots near Stafford (United Kingdom). Respiration was measured diurnally for 2 minutes each time, using the LI-COR 8100A set-up, and the rate of respiration (flux rate) was calculated SoilFluxPro software. Next, an empirical model was fitted to the dataset based on hourly averages of the flux rates, soil temperature, and soil moisture. Three respiration collars per plot were averaged, thus accounting for spatial variability within the site. Model parameterization and gap filling were conducted on in idual plots to calculate annual rates for 2019-2021. Cross-validation was performed by using 80% (randomly selected) of each dataset for training and the remaining 20% for testing the data against the parameters obtained by the empirical models. Preliminary results suggest that annual respiration rates were significantly higher for the eCO2 across all pairs in 2019. However, 2 out of 3 pairs in 2020 and 2021 showed significantly higher respiration for the aCO2 plots compared to eCO2, which is not in line with our hypothesis. Relationships with soil moisture and temperature help to explain what drives the difference in these fluxes. Our findings show that the relationship between higher CO2 concentrations in the atmosphere and soil respiration is not a straightforward one, which is of interest when considering the role of forest C-cycling on a global scale.
Soil aggregate size distribution mediates microbial climate change feedbacks
Publisher: Elsevier BV
Date: 2014
Soil physico-chemical properties are critical for predicting carbon storage and nutrient availability across Australia
Publisher: IOP Publishing
Date: 09-2020
Abstract: Soil carbon and nutrient availability play crucial roles in ecosystem sustainability, and they are controlled by the interaction of climatic, biotic, and soil physico-chemical variables. Although soil physico-chemical properties have been recognized as vital variables for predicting soil organic carbon (SOC) and nutrients, their relative influence across broad geographical scales has yet to be evaluated when simultaneously considering many other drivers. Using boosted regression tree and structural equation modelling analyses of observations from topsoil (0–10 cm) and subsoil (20–30 cm) at 628 sites across Australia, we investigated the effects and relative influence of climate (mean annual temperature and aridity index), plant productivity, soil bio ersity (bacterial and fungal richness), and soil physical (clay and silt) and chemical (pH and iron) properties on SOC content and nutrient availability (i.e. nitrogen, phosphorus, and potassium). Among these variables, we found that soil physico-chemical properties primarily predicted the continent-scale SOC storage and nutrient availability. In contrast, climate, plant productivity, and soil bio ersity played relatively small roles. The importance of physico-chemical properties was evident across soil depths and ecosystem types (i.e. tropical, temperate, arid, and cropland). Our findings point to the need to better understand the role of soil physico-chemical properties in soil carbon and nutrient cycling and including these variables in predictions of SOC and nutrient dynamics at the ecosystem to continental scale.
Soil/landform relationships surrounding the Harappa archaeological site, Pakistan
Publisher: Wiley
Date: 1990
Bark beetle-induced tree mortality alters stand energy budgets due to water budget changes
Publisher: Springer Science and Business Media LLC
Date: 19-10-2016
Warming and elevated CO2 alter the suberin chemistry in roots of photosynthetically divergent grass species
Publisher: Oxford University Press (OUP)
Date: 09-2017
Controls over Soil Nitrogen Pools in a Semiarid Grassland Under Elevated CO2 and Warming
Publisher: Springer Science and Business Media LLC
Date: 08-05-2012
Carbon isotopic tracing of sugars throughout whole‐trees exposed to climate warming
Publisher: Wiley
Date: 21-08-2019
DOI: 10.1111/PCE.13625
Abstract: Trees allocate C from sources to sinks by way of a series of processes involving carbohydrate transport and utilization. Yet these dynamics are not well characterized in trees, and it is unclear how these dynamics will respond to a warmer world. Here, we conducted a warming and pulse-chase experiment on Eucalyptus parramattensis growing in a whole-tree chamber system to test whether warming impacts carbon allocation by increasing the speed of carbohydrate dynamics. We pulse-labelled large (6-m tall) trees with
The effect of experimental warming and precipitation change on proteolytic enzyme activity: positive feedbacks to nitrogen availability are not universal
Publisher: Wiley
Date: 09-04-2012
Stable‐carbon isotopes and soil organic carbon in wheat under CO2 enrichment
Publisher: Wiley
Date: 05-2001
Gross primary production responses to warming, elevated CO 2, and irrigation: quantifying the drivers of ecosystem physiology in a semiarid grassland
Publisher: Wiley
Date: 22-03-2017
DOI: 10.1111/GCB.13602
Abstract: Determining whether the terrestrial biosphere will be a source or sink of carbon (C) under a future climate of elevated CO
Antecedent moisture and temperature conditions modulate the response of ecosystem respiration to elevated CO 2 and warming
Publisher: Wiley
Date: 30-04-2015
DOI: 10.1111/GCB.12910
Abstract: Terrestrial plant and soil respiration, or ecosystem respiration (R
Trading water for carbon in the future: Effects of elevated CO
Publisher: Wiley
Date: 04-08-2022
DOI: 10.1111/GCB.16314
Abstract: The effects of climate change on plants and ecosystems are mediated by plant hydraulic traits, including interspecific and intraspecific variability of trait phenotypes. Yet, integrative and realistic studies of hydraulic traits and climate change are rare. In a semiarid grassland, we assessed the response of several plant hydraulic traits to elevated CO
Effect of crop residue addition on soil organic carbon priming as influenced by temperature and soil properties
Publisher: Elsevier BV
Date: 08-2019
Predicting soil carbon loss with warming
Publisher: Springer Science and Business Media LLC
Date: 02-2018
DOI: 10.1038/NATURE25745
Biophysical Factors and Canopy Coupling Control Ecosystem Water and Carbon Fluxes of Semiarid Sagebrush Ecosystems
Publisher: Elsevier BV
Date: 05-2018
The fate of carbon in a mature forest under carbon dioxide enrichment
Publisher: Springer Science and Business Media LLC
Date: 08-04-2020
Do rhizosphere priming effects enhance plant nitrogen uptake under elevated CO2?
Publisher: Elsevier BV
Date: 05-2016
Carbon uptake and water use in woodlands and forests in southern Australia during an extreme heat wave event in the ‘Angry Summer’ of 2012/2013
Publisher: Copernicus GmbH
Date: 03-06-2016
DOI: 10.5194/BG-2016-183
Abstract: Abstract. As a result of climate change warmer temperatures are projected through the 21st century and are already increasing above modelled predictions. Apart from increases in the mean, warm/hot temperature extremes are expected to become more prevalent in the future, along with an increase in the frequency of droughts. It is crucial to better understand the response of terrestrial ecosystems to such temperature extremes for predicting land-surface feedbacks in a changing climate. During the 2012/2013 summer, Australia experienced a record-breaking heat wave with an exceptional spatial extent that lasted for several weeks. We synthesized eddy-covariance measurements from seven woodland and forest sites across climate zones in southern Australia, which we combined with model simulations from the CABLE land surface model to investigate the effect of this summer heat wave on the carbon and water exchange of terrestrial ecosystems. We found that the water-limited woodlands and the energy-limited forest ecosystem responded differently to the heat wave. During the most intense part of the heat wave, the woodlands experienced decreased latent heat flux, an increased Bowen ratio and a reduced carbon uptake while the forest ecosystem had increased latent heat flux, reduced Bowen ratio and increased carbon uptake. Ecosystem respiration was increased at all sites resulting in reduced net ecosystem productivity in the woodlands and constant net ecosystem productivity in the forest. Importantly all ecosystems remained carbon sinks during the event. Precipitation after the most intense first part of the heat wave and slightly cooler temperatures led to a decrease of the Bowen ratio and hence increased evaporative cooling. Carbon uptake in the woodlands also recovered quickly but respiration remained high. While woodlands and forest proved relatively resistant to this short-term heat extreme these carbon sinks may not sustainable in a future with an increased number, intensity and duration of heat waves.
Results of a water based thermoelectric energy harvesting device for powering wireless sensor nodes
Publisher: SPIE
Date: 26-03-2009
DOI: 10.1117/12.815440
Mistletoe, friend and foe: synthesizing ecosystem implications of mistletoe infection
Publisher: IOP Publishing
Date: 11-2017
Rhizosphere stoichiometry: are C : N : P ratios of plants, soils, and enzymes conserved at the plant species‐level?
Publisher: Wiley
Date: 04-10-2013
DOI: 10.1111/NPH.12531
Abstract: As a consequence of the tight linkages among soils, plants and microbes inhabiting the rhizosphere, we hypothesized that soil nutrient and microbial stoichiometry would differ among plant species and be correlated within plant rhizospheres. We assessed plant tissue carbon (C) : nitrogen (N) : phosphorus (P) ratios for eight species representing four different plant functional groups in a semiarid grassland during near‐peak biomass. Using intact plant species‐specific rhizospheres, we examined soil C : N : P, microbial biomass C : N, and soil enzyme C : N : P nutrient acquisition activities. We found that few of the plant species' rhizospheres demonstrated distinct stoichiometric properties from other plant species and unvegetated soil. Plant tissue nutrient ratios and components of below‐ground rhizosphere stoichiometry predominantly differed between the C 4 plant species Buchloe dactyloides and the legume Astragalus laxmannii . The rhizospheres under the C 4 grass B. dactyloides exhibited relatively higher microbial C and lower soil N, indicative of distinct soil organic matter ( SOM ) decomposition and nutrient mineralization activities. Assessing the ecological stoichiometry among plant species' rhizospheres is a high‐resolution tool useful for linking plant community composition to below‐ground soil microbial and nutrient characteristics. By identifying how rhizospheres differ among plant species, we can better assess how plant–microbial interactions associated with ecosystem‐level processes may be influenced by plant community shifts.
The Australian SuperSite Network
Publisher: Elsevier BV
Date: 10-2016
DOI: 10.1016/J.SCITOTENV.2016.05.170
Abstract: Ecosystem monitoring networks aim to collect data on physical, chemical and biological systems and their interactions that shape the biosphere. Here we introduce the Australian SuperSite Network that, along with complementary facilities of Australia's Terrestrial Ecosystem Research Network (TERN), delivers field infrastructure and erse, ecosystem-related datasets for use by researchers, educators and policy makers. The SuperSite Network uses infrastructure replicated across research sites in different biomes, to allow comparisons across ecosystems and improve scalability of findings to regional, continental and global scales. This conforms with the approaches of other ecosystem monitoring networks such as Critical Zone Observatories, the U.S. National Ecological Observatory Network Analysis and Experimentation on Ecosystems, Europe Chinese Ecosystem Research Network International Long Term Ecological Research network and the United States Long Term Ecological Research Network. The Australian SuperSite Network currently involves 10 SuperSites across a erse range of biomes, including tropical rainforest, grassland and savanna wet and dry sclerophyll forest and woodland and semi-arid grassland, woodland and savanna. The focus of the SuperSite Network is on using vegetation, faunal and biophysical monitoring to develop a process-based understanding of ecosystem function and change in Australian biomes and to link this with data streams provided by the series of flux towers across the network. The Australian SuperSite Network is also intended to support a range of auxiliary researchers who contribute to the growing body of knowledge within and across the SuperSite Network, public outreach and education to promote environmental awareness and the role of ecosystem monitoring in the management of Australian environments.
Below‐ground process responses to elevated CO2 and temperature: a discussion of observations, measurement methods, and models
Publisher: Wiley
Date: 11-03-2004
DOI: 10.1111/J.1469-8137.2004.01053.X
Abstract: Rising atmospheric CO 2 and temperatures are probably altering ecosystem carbon cycling, causing both positive and negative feedbacks to climate. Below‐ground processes play a key role in the global carbon (C) cycle because they regulate storage of large quantities of C, and are potentially very sensitive to direct and indirect effects of elevated CO 2 and temperature. Soil organic matter pools, roots and associated rhizosphere organisms all have distinct responses to environmental change drivers, although availability of C substrates will regulate all the responses. Elevated CO 2 increases C supply below‐ground, whereas warming is likely to increase respiration and decomposition rates, leading to speculation that these effects will moderate one another. However, indirect effects on soil moisture availability and nutrient supply may alter processes in unexpected directions. Detailed, mechanistic understanding and modelling of below‐ground flux components, pool sizes and turnover rates is needed to adequately predict long‐term, net C storage in ecosystems. In this synthesis, we discuss the current status of below‐ground responses to elevated CO 2 and temperature and potential feedback effects, methodological challenges, and approaches to integrating models and measurements.
Examining the evidence for sustained transpiration during heat extremes
Publisher: Copernicus GmbH
Date: 24-09-2018
DOI: 10.5194/BG-2018-399
Abstract: Abstract. Recent experimental evidence suggests that during heat extremes, wooded ecosystems may decouple photosynthesis and transpiration: reducing photosynthesis to near zero but increasing transpiration into the boundary layer. This feedback may act to d en, rather than lify, heat extremes in wooded ecosystems. We examined eddy-covariance databases (OzFlux and FLUXNET2015) to identify whether there was field-based evidence to support these experimental findings. We focused on two types of heat extremes: (i) the three days leading up to a temperature extreme, defined as including a daily maximum temperature 37 °C (similar to the widely used TXx metric) and (ii) heatwaves, defined as three or more consecutive days above 35 °C. When focussing on (i), we found some evidence of reduced photosynthesis and sustained or increased latent heat fluxes in seven Australian evergreen wooded flux sites. However, when considering the role of vapour pressure deficit and focusing on (ii), we were unable to conclusively disentangle the decoupling between photosynthesis and latent heat flux from the effect of increasing vapour pressure deficit. Outside of Australia, the Tier-1 FLUXNET2015 database provided limited scope to tackle this issue as it does not s le sufficient high temperature events with which to probe the physiological response of trees to extreme heat. Thus, further work is required to determine whether this photosynthetic decoupling occurs widely, ideally by matching experimental species with those found at eddy-covariance towers sites. Such measurements would allow this decoupling mechanism to be probed experimentally and at the ecosystem scale. Transpiration during heatwaves remains a key issue to resolve, as no land surface model includes a decoupling mechanism, and any potential d ening of the land-atmosphere lification is thus not included in climate model projections.
Shrub encroachment in North American grasslands: shifts in growth form dominance rapidly alters control of ecosystem carbon inputs
Publisher: Wiley
Date: 27-11-2007
Supplementary material to "Modelling soil CO<sub>2</sub> production and transport with dynamic source and diffusion terms: Testing the steady-state assumption usin
Publisher: Copernicus GmbH
Date: 10-10-2017
Elevated CO2 and warming shift the functional composition of soil nematode communities in a semiarid grassland
Publisher: Elsevier BV
Date: 12-2016
Emissions of BVOC from lodgepole pine in response to mountain pine beetle attack in high and low mortality forest stands
Publisher: Copernicus GmbH
Date: 25-01-2013
Abstract: Abstract. In this screening study, biogenic volatile organic compound (BVOC) emissions from intact branches of lodgepole pine (Pinus contorta) trees were measured from trees at two forested sites that have been impacted differently by the mountain pine beetle (MPB), with one having higher mortality and the other with lower mortality. Differences in the amounts and chemical ersity of BVOC between the two sites and from apparently healthy trees versus trees in different stages of MPB attack are presented, as well as (for one site) observed seasonal variability in emissions. A brief comparison is made of geological and climatic characteristics as well as prior disturbances (both natural and man-made) at each site. Trees s led at the site experiencing high MPB-related tree mortality had lower chemo ersity in terms of monoterpene (MT) emission profiles, while profiles were more erse at the lower-mortality site. Also at the higher-mortality site, MPB-infested trees in various stages of decline had lower emissions of sesquiterpenes (SQTs) compared to healthy trees, while at the site with lower mortality, MPB-survivors had significantly higher SQT emissions during part of the growing season when compared to both uninfested and newly infested trees. SQT profiles differed between the two sites and, like monoterpene and oxygenated VOC profiles, varied through the season. For the low-mortality site in which repeated measurements were made over the course of the early summer–late fall, higher chemical ersity was observed in early- compared to late-season measurements for all compound classes investigated (MT, oxygenated VOC, and SQT), with the amount of change appearing to correlate to the MPB status of the trees studied. Emissions of 2-methyl-3-buten-2-ol (MBO) had a distinct seasonal signal but were not much different between healthy or infested trees, except in trees with dead needles, from which emissions of this compound were negligible, and in late-season MPB survivors, in which they were higher than in newly infested or uninfested trees. Emissions of SQT were significantly higher in the MPB survivors during both mid- and late-season s ling at the low-mortality site. The changes in emissions could have implications for regional air quality and climate through changes in ozone and aerosol distributions, although this study was designed as a preliminary screening effort and not enough in iduals were s led for all of the observed differences to be statistically demonstrated. Despite this, the compelling differences in emissions observed between the sites and in idual trees with differing MPB-infestation statuses and the potential impacts these have on regional atmospheric chemistry argue for further research in this topic.
Supplementary material to "Upside-down fluxes Down Under: CO<sub>2</sub> net sink in winter and net source in summer in a temperate evergreen broadleaf forest"
Publisher: Copernicus GmbH
Date: 02-01-2018
Soil disturbance and invasion magnify CO
Publisher: Wiley
Date: 12-09-2022
DOI: 10.1111/GCB.16383
Abstract: Climate change, disturbance, and plant invasion threaten grassland ecosystems, but their combined and interactive effects are poorly understood. Here, we examine how the combination of disturbance and plant invasion influences the sensitivity of mixed-grass prairie to elevated carbon dioxide (eCO
Bridge to the future: Important lessons from 20 years of ecosystem observations made by the OzFlux network
Publisher: Wiley
Date: 22-03-2022
DOI: 10.1111/GCB.16141
Abstract: In 2020, the Australian and New Zealand flux research and monitoring network, OzFlux, celebrated its 20 th anniversary by reflecting on the lessons learned through two decades of ecosystem studies on global change biology. OzFlux is a network not only for ecosystem researchers, but also for those ‘next users’ of the knowledge, information and data that such networks provide. Here, we focus on eight lessons across topics of climate change and variability, disturbance and resilience, drought and heat stress and synergies with remote sensing and modelling. In distilling the key lessons learned, we also identify where further research is needed to fill knowledge gaps and improve the utility and relevance of the outputs from OzFlux. Extreme climate variability across Australia and New Zealand (droughts and flooding rains) provides a natural laboratory for a global understanding of ecosystems in this time of accelerating climate change. As evidence of worsening global fire risk emerges, the natural ability of these ecosystems to recover from disturbances, such as fire and cyclones, provides lessons on adaptation and resilience to disturbance. Drought and heatwaves are common occurrences across large parts of the region and can tip an ecosystem's carbon budget from a net CO 2 sink to a net CO 2 source. Despite such responses to stress, ecosystems at OzFlux sites show their resilience to climate variability by rapidly pivoting back to a strong carbon sink upon the return of favourable conditions. Located in under‐represented areas, OzFlux data have the potential for reducing uncertainties in global remote sensing products, and these data provide several opportunities to develop new theories and improve our ecosystem models. The accumulated impacts of these lessons over the last 20 years highlights the value of long‐term flux observations for natural and managed systems. A future vision for OzFlux includes ongoing and newly developed synergies with ecophysiologists, ecologists, geologists, remote sensors and modellers.
The impact of soil microorganisms on the global budget of δ 18 O in atmospheric CO 2
Publisher: Proceedings of the National Academy of Sciences
Date: 29-12-2009
Abstract: Improved global estimates of terrestrial photosynthesis and respiration are critical for predicting the rate of change in atmospheric CO 2 . The oxygen isotopic composition of atmospheric CO 2 can be used to estimate these fluxes because oxygen isotopic exchange between CO 2 and water creates distinct isotopic flux signatures. The enzyme carbonic anhydrase (CA) is known to accelerate this exchange in leaves, but the possibility of CA activity in soils is commonly neglected. Here, we report widespread accelerated soil CO 2 hydration. Exchange was 10–300 times faster than the uncatalyzed rate, consistent with typical population sizes for CA-containing soil microorganisms. Including accelerated soil hydration in global model simulations modifies contributions from soil and foliage to the global CO 18 O budget and eliminates persistent discrepancies existing between model and atmospheric observations. This enhanced soil hydration also increases the differences between the isotopic signatures of photosynthesis and respiration, particularly in the tropics, increasing the precision of CO 2 gross fluxes obtained by using the δ 18 O of atmospheric CO 2 by 50%.
Upside-down fluxes Down Under: CO<sub>2</sub> net sink in winter and net source in summer in a temperate evergreen broadleaf forest
Publisher: Copernicus GmbH
Date: 02-01-2018
DOI: 10.5194/BG-2017-526
Abstract: Abstract. Predicting the seasonal dynamics of ecosystem carbon fluxes is challenging in broadleaved evergreen forests because of their moderate climates and subtle changes in canopy phenology. We assessed the climatic and biotic drivers of the seasonality of net ecosystem-atmosphere CO2 exchange (NEE) of a eucalyptus-dominated forest near Sydney, Australia, using the eddy covariance method. The climate is characterized by a mean annual precipitation of 800 mm and a mean annual temperature of 18 °C, hot summers and mild winters, with highly variable precipitation. In the three-year study, the ecosystem was a small sink in 2014 (54 g C m−2 y−1), a stronger sink in 2015 (183 g C m−2 y−1) and even stronger sink in 2016 (337 g C m−2 y−1), but these variations were not related to precipitation. Daily net C uptake was always detected during the cooler, drier winter months (June through August), while net C loss occurred during the warmer, wetter summer months (December through February). Gross primary productivity (GPP) seasonality was low, despite longer days with higher light intensity in summer, because vapour pressure deficit (D) and air temperature (Ta) restricted surface conductance during summer while winter temperatures were still high enough to support photosynthesis. Maximum GPP during ideal environmental conditions was correlated with canopy leaf area index (LAI) (r2 = 0.24), which increased rapidly after mid-summer rainfall events. Ecosystem respiration (ER) was highest during summer in wet soils and lowest during winter months. ER had larger seasonal litude compared to GPP, and therefore drove the seasonal variation of NEE. Because summer carbon uptake may become increasingly limited by atmospheric drought and high temperature, and ecosystem respiration could be enhanced by rising temperature, our results suggest the potential for large-scale seasonal shifts in NEE in sclerophyll vegetation under climate change.
Land use and season affect fluxes of CO2, CH4, CO, N2O, H2 and isotopic source signatures in Panama: evidence from nocturnal boundary layer profiles
Publisher: Wiley
Date: 19-08-2010
Introducing BASE: The Biomes of Australian Soil Environments soil microbial diversity database
Publisher: Oxford University Press (OUP)
Date: 28-09-2021
Cheatgrass is favored by warming but not CO2 enrichment in a semi‐arid grassland
Publisher: Wiley
Date: 19-04-2016
DOI: 10.1111/GCB.13278
Abstract: Elevated CO2 and warming may alter terrestrial ecosystems by promoting invasive plants with strong community and ecosystem impacts. Invasive plant responses to elevated CO2 and warming are difficult to predict, however, because of the many mechanisms involved, including modification of phenology, physiology, and cycling of nitrogen and water. Understanding the relative and interactive importance of these processes requires multifactor experiments under realistic field conditions. Here, we test how free-air CO2 enrichment (to 600 ppmv) and infrared warming (+1.5 °C day/3 °C night) influence a functionally and phenologically distinct invasive plant in semi-arid mixed-grass prairie. Bromus tectorum (cheatgrass), a fast-growing Eurasian winter annual grass, increases fire frequency and reduces biological ersity across millions of hectares in western North America. Across 2 years, we found that warming more than tripled B. tectorum biomass and seed production, due to a combination of increased recruitment and increased growth. These results were observed with and without competition from native species, under wet and dry conditions (corresponding with tenfold differences in B. tectorum biomass), and despite the fact that warming reduced soil water. In contrast, elevated CO2 had little effect on B. tectorum invasion or soil water, while reducing soil and plant nitrogen (N). We conclude that (1) warming may expand B. tectorum's phenological niche, allowing it to more successfully colonize the extensive, invasion-resistant northern mixed-grass prairie, and (2) in ecosystems where elevated CO2 decreases N availability, CO2 may have limited effects on B. tectorum and other nitrophilic invasive species.
Seasonally contrasting responses of evapotranspiration to warming and elevated CO2 in a semiarid grassland
Publisher: Wiley
Date: 17-07-2017
DOI: 10.1002/ECO.1880
Testing sagebrush allometric relationships across three fire chronosequences in Wyoming, USA
Publisher: Elsevier BV
Date: 04-2008
Paleoclimatic significance of δD and δ13C values in piñon pine needles from packrat middens spanning the last 40,000 years
Publisher: Elsevier BV
Date: 03-1999
Comparison of measured and modeled variations in piñon pine leaf water isotopic enrichment across a summer moisture gradient
Publisher: Springer Science and Business Media LLC
Date: 13-07-2005
DOI: 10.1007/S00442-005-0164-7
Abstract: Stable hydrogen and oxygen isotopic composition of bulk leaf water (deltaD(lw) and delta(18)O(lw)) in piñon pine (Pinus edulis and P. monophylla) and gas exchange parameters were measured under field conditions to examine the effects of seasonal moisture stress on leaf water isotopic enrichment. Study sites were located near the lower elevation limit for piñon in the southwestern USA. Leaf-level transpiration measurements were made four times daily in spring, summer and early autumn simultaneously, leaf s les were collected for water extraction and stable isotope analysis. Diurnal variations in deltaD(lw) and delta(18)O(lw) values were small, especially when leaf water residence times (molar leaf water content ided by transpiration rate) were high. Stomatal conductance explained most of the variance (60%) in leaf water enrichment across the dataset. Observed leaf water enrichment was compared with predictions of steady-state and nonsteady-state models. Nonsteady-state predictions fit observations the best, although D enrichment was often lower than predicted by any model. Hydrogen isotope ratios of leaf water and cellulose nitrate were strongly correlated, demonstrating preservation of a leaf water signal in wood and leaf cellulose.
Evapotranspiration (ET) and regulating mechanisms in two semiarid Artemisia-dominated shrub steppes at opposite sides of the globe
Publisher: Elsevier BV
Date: 11-2010
Management Implications of Global Change for Great Plains Rangelands
Publisher: Elsevier BV
Date: 06-2008
Tree water uptake in a tropical plantation varying in tree diversity: interspecific differences, seasonal shifts and complementarity
Publisher: Wiley
Date: 28-02-2014
DOI: 10.1002/ECO.1479
Aboveground and Belowground Carbon Pools After Fire in Mountain Big Sagebrush Steppe
Publisher: Elsevier BV
Date: 03-2010
Belowground carbon allocation, root trait plasticity, and productivity during drought and warming in a pasture grass
Publisher: Oxford University Press (OUP)
Date: 14-01-2023
DOI: 10.1093/JXB/ERAD021
Abstract: Sustaining grassland production in a changing climate requires an understanding of plant adaptation strategies, including trait plasticity under warmer and drier conditions. However, our knowledge to date disproportionately relies on aboveground responses, despite the importance of belowground traits in maintaining aboveground growth, especially in grazed systems. We subjected a perennial pasture grass, Festuca arundinacea, to year-round warming (+3 °C) and cool-season drought (60% rainfall reduction) in a factorial field experiment to test the hypotheses that: (i) drought and warming increase carbon allocation belowground and shift root traits towards greater resource acquisition and (ii) increased belowground carbon reserves support post-drought aboveground recovery. Drought and warming reduced plant production and biomass allocation belowground. Drought increased specific root length and reduced root diameter in warmed plots but increased root starch concentrations under ambient temperature. Higher diameter and soluble sugar concentrations of roots and starch storage in crowns explained aboveground production under climate extremes. However, the lack of association between post-drought aboveground biomass and belowground carbon and nitrogen reserves contrasted with our predictions. These findings demonstrate that root trait plasticity and belowground carbon reserves play a key role in aboveground production during climate stress, helping predict pasture responses and inform management decisions under future climates.
Seasonality of soil moisture mediates responses of ecosystem phenology to elevated CO 2 and warming in a semi‐arid grassland
Publisher: Wiley
Date: 07-08-2015
Digging into the roots of belowground carbon cycling following seven years of Prairie Heating and CO2 Enrichment (PHACE), Wyoming USA
Publisher: Elsevier BV
Date: 12-2017
Soil organic matter dynamics in grassland soils under elevated CO2: Insights from long-term incubations and stable isotopes
Publisher: Elsevier BV
Date: 10-2007
Examining the evidence for decoupling between photosynthesis and transpiration during heat extremes
Publisher: Copernicus GmbH
Date: 26-02-2019
Abstract: Abstract. Recent experimental evidence suggests that during heat extremes, wooded ecosystems may decouple photosynthesis and transpiration, reducing photosynthesis to near zero but increasing transpiration into the boundary layer. This feedback may act to d en, rather than lify, heat extremes in wooded ecosystems. We examined eddy covariance databases (OzFlux and FLUXNET2015) to identify whether there was field-based evidence to support these experimental findings. We focused on two types of heat extremes: (i) the 3 days leading up to a temperature extreme, defined as including a daily maximum temperature ∘C (similar to the widely used TXx metric), and (ii) heatwaves, defined as 3 or more consecutive days above 35 ∘C. When focusing on (i), we found some evidence of reduced photosynthesis and sustained or increased latent heat fluxes at seven Australian evergreen wooded flux sites. However, when considering the role of vapour pressure deficit and focusing on (ii), we were unable to conclusively disentangle the decoupling between photosynthesis and latent heat flux from the effect of increasing the vapour pressure deficit. Outside of Australia, the Tier-1 FLUXNET2015 database provided limited scope to tackle this issue as it does not s le sufficient high temperature events with which to probe the physiological response of trees to extreme heat. Thus, further work is required to determine whether this photosynthetic decoupling occurs widely, ideally by matching experimental species with those found at eddy covariance tower sites. Such measurements would allow this decoupling mechanism to be probed experimentally and at the ecosystem scale. Transpiration during heatwaves remains a key issue to resolve, as no land surface model includes a decoupling mechanism, and any potential d ening of the land–atmosphere lification is thus not included in climate model projections.
Elevated CO 2 and water addition enhance nitrogen turnover in grassland plants with implications for temporal stability
Publisher: Wiley
Date: 05-03-2018
DOI: 10.1111/ELE.12935
Abstract: Temporal variation in soil nitrogen (N) availability affects growth of grassland communities that differ in their use and reuse of N. In a 7-year-long climate change experiment in a semi-arid grassland, the temporal stability of plant biomass production varied with plant N turnover (reliance on externally acquired N relative to internally recycled N). Species with high N turnover were less stable in time compared to species with low N turnover. In contrast, N turnover at the community level was positively associated with asynchrony in biomass production, which in turn increased community temporal stability. Elevated CO
Spring drought regulates summer net ecosystem CO2 exchange in a sagebrush-steppe ecosystem
Publisher: Elsevier BV
Date: 03-2008
Carbon uptake and water use in woodlands and forests in southern Australia during an extreme heat wave event in the angry Summer of 2012/2013
Publisher: Copernicus GmbH
Date: 11-2016
Abstract: Abstract. As a result of climate change warmer temperatures are projected through the 21st century and are already increasing above modelled predictions. Apart from increases in the mean, warm/hot temperature extremes are expected to become more prevalent in the future, along with an increase in the frequency of droughts. It is crucial to better understand the response of terrestrial ecosystems to such temperature extremes for predicting land-surface feedbacks in a changing climate. While land-surface feedbacks in drought conditions and during heat waves have been reported from Europe and the US, direct observations of the impact of such extremes on the carbon and water cycles in Australia have been lacking. During the 2012/2013 summer, Australia experienced a record-breaking heat wave with an exceptional spatial extent that lasted for several weeks. In this study we synthesised eddy-covariance measurements from seven woodlands and one forest site across three biogeographic regions in southern Australia. These observations were combined with model results from BIOS2 (Haverd et al., 2013a, b) to investigate the effect of the summer heat wave on the carbon and water exchange of terrestrial ecosystems which are known for their resilience toward hot and dry conditions. We found that water-limited woodland and energy-limited forest ecosystems responded differently to the heat wave. During the most intense part of the heat wave, the woodlands experienced decreased latent heat flux (23 % of background value), increased Bowen ratio (154 %) and reduced carbon uptake (60 %). At the same time the forest ecosystem showed increased latent heat flux (151 %), reduced Bowen ratio (19 %) and increased carbon uptake (112 %). Higher temperatures caused increased ecosystem respiration at all sites (up to 139 %). During daytime all ecosystems remained carbon sinks, but carbon uptake was reduced in magnitude. The number of hours during which the ecosystem acted as a carbon sink was also reduced, which switched the woodlands into a carbon source on a daily average. Precipitation occurred after the first, most intense part of the heat wave, and the subsequent cooler temperatures in the temperate woodlands led to recovery of the carbon sink, decreased the Bowen ratio (65 %) and hence increased evaporative cooling. Gross primary productivity in the woodlands recovered quickly with precipitation and cooler temperatures but respiration remained high. While the forest proved relatively resilient to this short-term heat extreme the response of the woodlands is the first direct evidence that the carbon sinks of large areas of Australia may not be sustainable in a future climate with an increased number, intensity and duration of heat waves.
Rhizosphere priming: a nutrient perspective
Publisher: Frontiers Media SA
Date: 2013
Daily and seasonal changes in soil amino acid composition in a semiarid grassland exposed to elevated CO2 and warming
Publisher: Springer Science and Business Media LLC
Date: 10-12-2014
Warming and Elevated CO2 Interact to Alter Seasonality and Reduce Variability of Soil Water in a Semiarid Grassland
Publisher: Springer Science and Business Media LLC
Date: 08-03-2018
Thermal optima of gross primary productivity are closely aligned with mean air temperatures across Australian wooded ecosystems
Publisher: Wiley
Date: 20-07-2021
DOI: 10.1111/GCB.15760
Abstract: Gross primary productivity (GPP) of wooded ecosystems (forests and savannas) is central to the global carbon cycle, comprising 67%–75% of total global terrestrial GPP. Climate change may alter this flux by increasing the frequency of temperatures beyond the thermal optimum of GPP ( T opt ). We examined the relationship between GPP and air temperature (Ta) in 17 wooded ecosystems dominated by a single plant functional type (broadleaf evergreen trees) occurring over a broad climatic gradient encompassing five ecoregions across Australia ranging from tropical in the north to Mediterranean and temperate in the south. We applied a novel boundary‐line analysis to eddy covariance flux observations to (a) derive ecosystem GPP–Ta relationships and T opt (including seasonal analyses for five tropical savannas) (b) quantitatively and qualitatively assess GPP–Ta relationships within and among ecoregions (c) examine the relationship between T opt and mean daytime air temperature (MDTa) across all ecosystems and (d) examine how down‐welling short‐wave radiation (Fsd) and vapour pressure deficit (VPD) influence the GPP–Ta relationship. GPP–Ta relationships were convex parabolas with narrow curves in tropical forests, tropical savannas (wet season), and temperate forests, and wider curves in temperate woodlands, Mediterranean woodlands, and tropical savannas (dry season). Ecosystem T opt ranged from 15℃ (temperate forest) to 32℃ (tropical savanna—wet and dry seasons). The shape of GPP–Ta curves was largely determined by daytime Ta range, MDTa, and maximum GPP with the upslope influenced by Fsd and the downslope influenced by VPD. Across all ecosystems, there was a strong positive linear relationship between T opt and MDTa (Adjusted R 2 : 0.81 Slope: 1.08) with T opt exceeding MDTa by ℃ at all but two sites. We conclude that ecosystem GPP has adjusted to local MDTa within Australian broadleaf evergreen forests and that GPP is buffered against small Ta increases in the majority of these ecosystems.
Quantifying global soil carbon losses in response to warming
Publisher: Springer Science and Business Media LLC
Date: 30-11-2016
DOI: 10.1038/NATURE20150
Abstract: The majority of the Earth's terrestrial carbon is stored in the soil. If anthropogenic warming stimulates the loss of this carbon to the atmosphere, it could drive further planetary warming. Despite evidence that warming enhances carbon fluxes to and from the soil, the net global balance between these responses remains uncertain. Here we present a comprehensive analysis of warming-induced changes in soil carbon stocks by assembling data from 49 field experiments located across North America, Europe and Asia. We find that the effects of warming are contingent on the size of the initial soil carbon stock, with considerable losses occurring in high-latitude areas. By extrapolating this empirical relationship to the global scale, we provide estimates of soil carbon sensitivity to warming that may help to constrain Earth system model projections. Our empirical relationship suggests that global soil carbon stocks in the upper soil horizons will fall by 30 ± 30 petagrams of carbon to 203 ± 161 petagrams of carbon under one degree of warming, depending on the rate at which the effects of warming are realized. Under the conservative assumption that the response of soil carbon to warming occurs within a year, a business-as-usual climate scenario would drive the loss of 55 ± 50 petagrams of carbon from the upper soil horizons by 2050. This value is around 12-17 per cent of the expected anthropogenic emissions over this period. Despite the considerable uncertainty in our estimates, the direction of the global soil carbon response is consistent across all scenarios. This provides strong empirical support for the idea that rising temperatures will stimulate the net loss of soil carbon to the atmosphere, driving a positive land carbon-climate feedback that could accelerate climate change.
Drought and warming alter gross primary production allocation and reduce productivity in a widespread pasture grass
Publisher: Wiley
Date: 23-04-2022
DOI: 10.1111/PCE.14334
Abstract: Carbon allocation determines plant growth, fitness and reproductive success. However, climate warming and drought impacts on carbon allocation patterns in grasses are not well known, particularly following grazing or clipping. A widespread C 3 pasture grass, Festuca arundinacea , was grown at 26 and 30°C in controlled environment chambers and subjected to drought (65% reduction relative to well‐watered controls). Leaf, root and whole‐plant carbon fluxes were measured and linked to growth before and after clipping. Both drought and warming reduced gross primary production and plant biomass. Drought reduced net leaf photosynthesis but increased the leaf respiratory fraction of assimilated carbon. Warming increased root respiration but did not affect either net leaf photosynthesis or leaf respiration. There was no evidence of thermal acclimation. Moreover, root respiratory carbon loss was lified in the combined drought and warming treatment and, in addition to a negative carbon balance aboveground, explained an enhanced reduction in plant biomass. Plant regrowth following clipping was strongly suppressed by drought, reflecting increased tiller mortality and exacerbated respiratory carbon loss. These findings emphasize the importance of considering carbon allocation patterns in response to grazing or clipping and interactions with climatic factors for sustainable pasture production in a future climate.
Mediation of soil C decomposition by arbuscular mycorrizhal fungi in grass rhizospheres under elevated CO2
Publisher: Springer Science and Business Media LLC
Date: 17-12-2015
Elevated CO 2 and warming cause interactive effects on soil carbon and shifts in carbon use by bacteria
Publisher: Wiley
Date: 29-08-2018
DOI: 10.1111/ELE.13140
Abstract: Accurate predictions of soil C feedbacks to climate change depend on an improved understanding of responses of soil C pools and C use by soil microbial groups. We assessed soil and microbial C in a 7-year manipulation of CO
Concurrent Measurements of Soil and Ecosystem Respiration in a Mature Eucalypt Woodland: Advantages, Lessons, and Questions
Publisher: American Geophysical Union (AGU)
Date: 03-2021
DOI: 10.1029/2020JG006221
Abstract: Understanding seasonal and diurnal dynamics of ecosystem respiration (R eco ) in forests is challenging, because R eco can only be measured directly during night‐time by eddy‐covariance flux towers. R eco is the sum of soil respiration (R soil ) and above‐ground respiration (in theory, R AG = R eco − R soil ). R soil can be measured day and night and can provide a check of consistency on R eco , as the difference in magnitude and time dynamic between R eco and R soil should be explained by R AG . We assessed the temporal patterns and climatic drivers of R soil and R eco in a mature eucalypt woodland, using continuous measurements (only at night for R eco ) at half‐hourly resolution over 4 years (2014–2017). Our data showed large seasonal and diurnal (overnight) variation of R eco , while R soil had a low diurnal litude and their difference (R eco − R soil, or R AG ) had a low seasonal litude. This result implies at first glance that seasonal variation of R eco was mainly influenced by R soil while its diurnal variation was mainly influenced by R AG . However, our analysis suggests that the night‐time R eco decline cannot realistically be explained by a decline of R AG . Chamber measurements of autotrophic components at half‐hourly time resolution are needed to quantify how much of the R eco decline overnight is due to declines in leaf or stem respiration, and how much is due to missing storage or advection, which may create a systematic bias in R eco measurements. Our findings emphasize the need for reconciling bottom‐up (via components measured with chambers) and direct estimates of R eco (via eddy‐covariance method).
Sap flux-scaled transpiration and stomatal conductance response to soil and atmospheric drought in a semi-arid sagebrush ecosystem
Publisher: Elsevier BV
Date: 09-2012
Erratum to: The carbon dioxide evasion cycle of an intermittent first-order stream: contrasting water–air and soil–air exchange (Biogeochemistry, (2017), 132, 1-2, (87-102), 10.1007/s10533-016-0289-2)
Publisher: Springer Science and Business Media LLC
Date: 29-05-2017
An incubation study of temperature sensitivity of greenhouse gas fluxes in three land-cover types near Sydney, Australia
Publisher: Elsevier BV
Date: 10-2019
DOI: 10.1016/J.SCITOTENV.2019.06.206
Abstract: Greenhouse gas (GHG) fluxes play crucial roles in regulating the Earth surface temperature. However, our understanding of the effect of land-cover and soil depth on the potential GHG fluxes and their temperature sensitivities (Q
Biogeographic variation in temperature sensitivity of decomposition in forest soils.
Publisher: Wiley
Date: 21-10-2020
DOI: 10.1111/GCB.14838
Abstract: Determining soil carbon (C) responses to rising temperature is critical for projections of the feedbacks between terrestrial ecosystems, C cycle, and climate change. However, the direction and magnitude of this feedback remain highly uncertain due largely to our limited understanding of the spatial heterogeneity of soil C decomposition and its temperature sensitivity. Here we quantified C decomposition and its response to temperature change with an incubation study of soils from 203 sites across tropical to boreal forests in China spanning a wide range of latitudes (18°16' to 51°37'N) and longitudes (81°01' to 129°28'E). Mean annual temperature (MAT) and mean annual precipitation primarily explained the biogeographic variation in the decomposition rate and temperature sensitivity of soils: soil C decomposition rate decreased from warm and wet forests to cold and dry forests, while Q
Increased plant productivity and decreased microbial respiratory C loss by plant growth-promoting rhizobacteria under elevated CO2
Publisher: Springer Science and Business Media LLC
Date: 18-03-2015
DOI: 10.1038/SREP09212
Abstract: Increased plant productivity and decreased microbial respiratory C loss can potentially mitigate increasing atmospheric CO 2 , but we currently lack effective means to achieve these goals. Soil microbes may play critical roles in mediating plant productivity and soil C/N dynamics under future climate scenarios of elevated CO 2 (eCO 2 ) through optimizing functioning of the root-soil interface. By using a labeling technique with 13 C and 15 N, we examined the effects of plant growth-promoting Pseudomonas fluorescens on C and N cycling in the rhizosphere of a common grass species under eCO 2 . These microbial inoculants were shown to increase plant productivity. Although strong competition for N between the plant and soil microbes was observed, the plant can increase its capacity to store more biomass C per unit of N under P. fluorescens addition. Unlike eCO 2 effects, P. fluorescens inoculants did not change mass-specific microbial respiration and accelerate soil decomposition related to N cycling, suggesting these microbial inoculants mitigated positive feedbacks of soil microbial decomposition to eCO 2 . The potential to mitigate climate change by optimizing soil microbial functioning by plant growth-promoting Pseudomonas fluorescens is a prospect for ecosystem management.
An introduction to the Australian and New Zealand flux tower network – OzFlux
Publisher: Copernicus GmbH
Date: 31-10-2016
Abstract: Abstract. OzFlux is the regional Australian and New Zealand flux tower network that aims to provide a continental-scale national research facility to monitor and assess trends, and improve predictions, of Australia's terrestrial biosphere and climate. This paper describes the evolution, design, and current status of OzFlux as well as provides an overview of data processing. We analyse measurements from all sites within the Australian portion of the OzFlux network and two sites from New Zealand. The response of the Australian biomes to climate was largely consistent with global studies except that Australian systems had a lower ecosystem water-use efficiency. Australian semi-arid/arid ecosystems are important because of their huge extent (70 %) and they have evolved with common moisture limitations. We also found that Australian ecosystems had a similar radiation-use efficiency per unit leaf area compared to global values that indicates a convergence toward a similar biochemical efficiency. The two New Zealand sites represented extremes in productivity for a moist temperate climate zone, with the grazed dairy farm site having the highest GPP of any OzFlux site (2620 gC m−2 yr−1) and the natural raised peat bog site having a very low GPP (820 gC m−2 yr−1). The paper discusses the utility of the flux data and the synergies between flux, remote sensing, and modelling. Lastly, the paper looks ahead at the future direction of the network and concludes that there has been a substantial contribution by OzFlux, and considerable opportunities remain to further advance our understanding of ecosystem response to disturbances, including drought, fire, land-use and land-cover change, land management, and climate change, which are relevant both nationally and internationally. It is suggested that a synergistic approach is required to address all of the spatial, ecological, human, and cultural challenges of managing the delicately balanced ecosystems in Australasia.
Multiproxy Record of Late Pleistocene–Holocene Climate and Vegetation Changes from a Peat Bog in Patagonia
Publisher: Cambridge University Press (CUP)
Date: 03-2001
Abstract: Pollen assemblage changes and stable hydrogen isotope analysis of mosses ( Sphagnum magellanicum and Drepanocladus s.l.) from a bog in Tierra del Fuego, Argentina, provided independent proxies for reconstructing changes in effective moisture and temperature over the past 16,000 cal yr B.P. A deterministic model was used to reconstruct the stable hydrogen isotope composition of meteoric water from the D/H ratios of bog mosses over the last 16,000 years. Abrupt changes in temperature, as recorded in D/H ratios of moss cellulose, were accompanied by synchronous changes in vegetation composition during the late Pleistocene and early and middle Holocene, when moisture levels were lower than today. In contrast, temperature variability during the late Holocene was not accompanied by comparable vegetation changes. In particular, grass pollen (Poaceae) increased during periodic cold spells between 15,000 and 11,000 cal yr B.P., but a cold spell of similar magnitude ca. 2000 cal yr B.P. did not appear to affect vegetation. During the late Pleistocene, the isotopic record from the peat core shows variations similar to the D/H ratios in the Antarctic Taylor Dome ice core. However, the timing of the changes in the Harberton record is more in line with the timing of other Southern Hemisphere records.
Soil – atmosphere exchange of greenhouse gases under future climates
Publisher: Copernicus GmbH
Date: 28-03-2022
DOI: 10.5194/EGUSPHERE-EGU22-10237
Abstract: & & This research investigates the cascading effects of elevated carbon dioxide (eCO& sub& & /sub& ) fumigation of a mature temperature forest, with a particular focus on the fluxes of greenhouse gases (GHG) nitrous oxide (N& sub& & /sub& O), methane (CH& sub& & /sub& ) and carbon dioxide (CO& sub& & /sub& ). A field experiment was performed at the Birmingham Institute of Forest Research Free Air Carbon dioxide Enrichment facility (BIFoR FACE), where an oak dominated mixed mature woodland has been under eCO& sub& & /sub& since 2017. Fluxes were quantified in situ using the Licor 8100A & #8211 an infrared gas analyser measuring total soil respiration (R& sub& s& /sub& ) as CO& sub& & /sub& , and a Picarro greenhouse gas analyser (G2508), measuringN& sub& & /sub& O and CH& sub& & /sub& . Preliminary data from 2019 & #8211 2021 have been analysed and are built on an earlier dataset from 2017-2018, and the role of soil temperature and soil moisture is considered. With more carbon allocation belowground, we expect an increase in microbial activity and consequently larger R& sub& s& /sub& . Overall, R& sub& s& /sub& was higher under eCO& sub& & /sub& in 2017-2018 however, in years 2019 to 2021, the absolute difference in respiration between eCO& sub& & /sub& and control plots gradually decreased and even switched in 2021, with a slight increase in R& sub& s& /sub& for control plots compared to eCO& sub& & /sub& plots. Moreover, annual fluxes of N& sub& & /sub& O and CH& sub& & /sub& were detectable and in general we observed N& sub& & /sub& O emission and CH& sub& & /sub& consumption. My presentation will discuss R& sub& s& /sub& and N& sub& & /sub& O and CH& sub& & /sub& fluxes and highlight the role of eCO& sub& & /sub& as well as environmental and soil conditions that regulate the GHG fluxes, allowing us to compute the net global warming potential of forests under future climates.& &
Fast microbes regulate slow soil feedbacks
Publisher: Springer Science and Business Media LLC
Date: 17-09-2018
Decomposition and nitrogen transformation rates in a temperate grassland vary among co-occurring plant species
Publisher: Springer Science and Business Media LLC
Date: 30-07-2011
Response of sagebrush carbon metabolism to experimental precipitation pulses
Publisher: Elsevier BV
Date: 12-2016
Nitrogen niche partitioning between tropical legumes and grasses strengthens under elevated CO2
Publisher: Cold Spring Harbor Laboratory
Date: 19-01-2023
DOI: 10.1101/2023.01.16.524162
Abstract: Plant community bio ersity can be maintained, at least partially, by shifts in species interactions between facilitation and competition for resources as environmental conditions change. These interactions also drive ecosystem functioning, including productivity, and can promote over-yielding-an ecosystem service prioritized in working landscapes that occurs when there is either less competition, more facilitation, or both, between species in a community than within species. Importantly, shifts in species interactions that can result in over-yielding are unclear given rising CO 2 concentrations, especially in the context of tropical mixed-species grasslands. We examined the relative performance of two species pairs of tropical pasture grasses and legumes growing in monoculture and mixtures in a glasshouse experiment manipulating CO 2 . We investigated how over-yielding can arise from nitrogen (N) niche partitioning and biotic facilitation using stable isotopes to differentiate soil N from biological N fixation (BNF) within N acquisition into aboveground biomass for these two-species mixtures. We found that N niche partitioning in species-level use of soil N vs. BNF drove species interactions in mixtures. Importantly partitioning, though not necessarily overyielding, was generally enhanced under elevated CO 2 . However, this finding was mixture-dependent based on biomass of dominant species in mixtures and the strength of selection effects for the dominant mixture species. This study demonstrates that rising atmospheric CO 2 may alter niche partitioning between co-occurring species, with negative implications for the over-yielding benefits predicted for legume-grass mixtures in working landscapes with tropical species. Furthermore, these changes in inter-species interactions have consequences for shifts in grassland composition that are not yet considered in larger-scale projections for impacts of climate change and species distributions. Among our tropical pasture species we found that grasses (dotted lines) grown in monoculture rely fully on soil nitrogen (N), while legumes (solid lines) grown in monoculture relied approximately equally on soil N and biological nitrogen fixation (BNF) to meet N requirements. When grown with tropical grasses, however, legumes shifted to rely more strongly on BNF, indicative of niche partitioning and decreased competition for soil nutrients with grasses. This separation of niche space was strengthened under elevated CO 2 conditions, ultimately reducing legume production.
Plant rhizosphere influence on microbial C metabolism: the role of elevated CO2, N availability and root stoichiometry
Publisher: Springer Science and Business Media LLC
Date: 09-02-2014
Spatial heterogeneity of temperature sensitivity of soil respiration: A global analysis of field observations
Publisher: Elsevier BV
Date: 02-2020
Does soil respiration decline following bark beetle induced forest mortality? Evidence from a lodgepole pine forest
Publisher: Elsevier BV
Date: 12-2015
Rising Temperature May Trigger Deep Soil Carbon Loss Across Forest Ecosystems
Publisher: Wiley
Date: 06-08-2020
Abstract: Significantly more carbon (C) is stored in deep soil than in shallow horizons, yet how the decomposition of deep soil organic C (SOC) will respond to rising temperature remains unexplored on large scales, leading to considerable uncertainties to predictions of the magnitude and direction of C‐cycle feedbacks to climate change. Herein, short‐term temperature sensitivity of SOC decomposition (expressed as Q 10 ) from six depths within the top 1 m soil from 90 upland forest sites (540 soil s les) across China is reported. Results show that Q 10 significantly increases with soil depth, suggesting that deep SOC is more vulnerable to loss with rising temperature in comparison to shallow SOC. Climate is the primary regulator of shallow soil Q 10 but its relative influence declines with depth in contrast, soil C quality has a minor influence on Q 10 in shallow soil but increases its influence with depth. When considering the depth‐dependent Q 10 variations, results further show that using the thermal response of shallow soil layer for the whole soil profile, as is usually done in model predictions, would significantly underestimate soil C‐climate feedbacks. The results highlight that Earth system models need to consider multilayer soil C dynamics and their controls to improve prediction accuracy.
Multiscale observations of snow accumulation and peak snowpack following widespread, insect‐induced lodgepole pine mortality
Publisher: Wiley
Date: 05-11-2012
DOI: 10.1002/ECO.1342
Where does all the carbon go? The missing sink
Publisher: Wiley
Date: 02-2002
Response of soil organic matter dynamics to conversion from tropical forest to grassland as determined by long-term incubation
Publisher: Springer Science and Business Media LLC
Date: 25-11-2008
Phosphorus availability and arbuscular mycorrhizal fungi limit soil C cycling and influence plant responses to elevated CO2 conditions
Publisher: Cold Spring Harbor Laboratory
Date: 18-07-2021
DOI: 10.1101/2021.07.16.452715
Abstract: Enhanced soil organic matter (SOM) decomposition and organic phosphorus (P) cycling may help sustain plant productivity under elevated CO 2 (eCO 2 ) and P-limiting conditions. P-acquisition by arbuscular mycorrhizal (AM) fungi and their impacts on SOM decomposition may become even more relevant in these conditions. Yet, experimental evidence of the interactive effect of AM fungi and P availability influencing altered SOM cycling under eCO 2 is scarce and the mechanisms of this control are poorly understood. Here, we performed a pot experiment manipulating P availability, AM fungal presence and atmospheric CO 2 levels and assessed their impacts on soil C cycling and plant growth. Plants were grown in chambers with a continuous 13 C-input that allowed differentiation between plant- and SOM-derived fractions of respired CO 2 (R), dissolved organic C (DOC) and microbial biomass (MBC) as relevant C pools in the soil C cycle. We hypothesised that under low P availability, increases in SOM cycling may support sustained plant growth under eCO 2 and that AM fungi would intensify this effect. We found the impacts of CO 2 enrichment and P availability on soil C cycling were generally independent of each other with higher root biomass and slight increases in soil C cycling under eCO 2 occurring regardless of the P treatment. Contrary to our hypotheses, soil C cycling was enhanced with P addition suggesting that low P conditions were limiting soil C cycling. eCO 2 conditions increased the fraction of SOM-derived DOC pointing to increased SOM decomposition with eCO 2 . Finally, AM fungi increased microbial biomass under eCO 2 conditions and low-P without enhanced soil C cycling, probably due to competitive interactions with free-living microorganisms over nutrients. Our findings in this plant-soil system suggest that, contrary to what has been reported for N-limited systems, the impacts of eCO 2 and P availability on soil C cycling are independent of each other.
Positive climate feedbacks of soil microbial communities in a semi‐arid grassland
Publisher: Wiley
Date: 16-11-2012
DOI: 10.1111/ELE.12034
Abstract: Soil microbial communities may be able to rapidly respond to changing environments in ways that change community structure and functioning, which could affect climate-carbon feedbacks. However, detecting microbial feedbacks to elevated CO(2) (eCO(2) ) or warming is h ered by concurrent changes in substrate availability and plant responses. Whether microbial communities can persistently feed back to climate change is still unknown. We overcame this problem by collecting microbial inocula at subfreezing conditions under eCO(2) and warming treatments in a semi-arid grassland field experiment. The inoculant was incubated in a sterilised soil medium at constant conditions for 30 days. Microbes from eCO(2) exhibited an increased ability to decompose soil organic matter (SOM) compared with those from ambient CO(2) plots, and microbes from warmed plots exhibited increased thermal sensitivity for respiration. Microbes from the combined eCO(2) and warming plots had consistently enhanced microbial decomposition activity and thermal sensitivity. These persistent positive feedbacks of soil microbial communities to eCO(2) and warming may therefore stimulate soil C loss.
Contrasting effects of elevated CO2 and warming on nitrogen cycling in a semiarid grassland
Publisher: Wiley
Date: 10-05-2010
DOI: 10.1111/J.1469-8137.2010.03293.X
Abstract: *Simulation models indicate that the nitrogen (N) cycle plays a key role in how other ecosystem processes such as plant productivity and carbon (C) sequestration respond to elevated CO(2) and warming. However, combined effects of elevated CO(2) and warming on N cycling have rarely been tested in the field. *Here, we studied N cycling under ambient and elevated CO(2) concentrations (600 micromol mol(-1)), and ambient and elevated temperature (1.5 : 3.0 degrees C warmer day:night) in a full factorial semiarid grassland field experiment in Wyoming, USA. We measured soil inorganic N, plant and microbial N pool sizes and NO(3)(-) uptake (using a (15)N tracer). *Soil inorganic N significantly decreased under elevated CO(2), probably because of increased microbial N immobilization, while soil inorganic N and plant N pool sizes significantly increased with warming, probably because of increased N supply. We observed no CO(2 )x warming interaction effects on soil inorganic N, N pool sizes or NO(3)(-) uptake in plants and microbes. *Our results indicate a more closed N cycle under elevated CO(2) and a more open N cycle with warming, which could affect long-term N retention, plant productivity, and C sequestration in this semiarid grassland.
Quantifying and reducing uncertainties in estimated soil CO2 fluxes with hierarchical data‐model integration
Publisher: American Geophysical Union (AGU)
Date: 12-2016
DOI: 10.1002/2016JG003385
Isotopic Approach to Soil Carbonate Dynamics and Implications for Paleoclimatic Interpretations
Publisher: Cambridge University Press (CUP)
Date: 07-1994
Abstract: The radiocarbon content and stable isotope composition of soil carbonate are best described by a dynamic system in which isotopic reequilibration occurs as a result of recurrent dissolution and reprecipitation. Depth of water penetration into the soil profile, as well as soil age, determines the degree of carbonate isotope reequilibration. We measured δ 13 C, δ 18 O and radiocarbon content of gravel rinds and fine ( mm) carbonate in soils of 3 .different ages (1000, 3800, and 6300 14 C yr B.P.) to assess the degree to which they record and preserve a climatic signal. In soils developing in deposits independently dated at 3800 and 6300 radiocarbon yr B.P., carbonate radiocarbon content above 40 cm depth suggests continual dissolution and reprecipitation, presumably due to frequent wetting events. Between 40 and 90 cm depth, fine carbonate is dissolved and precipitated as rinds that are not redissolved subsequently. Below 90 cm depth in these soils, radiocarbon content indicates that inherited, fine carbonate undergoes little dissolution and reprecipitation. In the 3800- and 6300-yr-old soils, δ 13 C in rind and fine carbonate follows a decreasing trend with depth, apparently in equilibrium with modern soil gas, as predicted by a diffusive model for soil CO 2 . δ 18 O also decreases with depth due to greater evaporative enrichment above 50 cm depth. In contrast, carbonate isotopes in a 1000-yr-old deposit do not reflect modern conditions even in surficial horizons this soil has not undergone significant pedogenesis. There appears to be a lag of at least 1000 but less than 3800 yr before carbonate inherited with parent material is modified by ambient climatic conditions. Although small amounts of carbonate are inherited with the parent material, the rate of pedogenic carbonate accumulation indicates that Ca is derived primarily from eolian and rainfall sources. A model describing carbonate input and radiocarbon decay suggests that fine carbonate below 90 cm is mostly detrital (inherited) and that carbonate rinds have been forming pedogenically at a constant rate since alluvial fans were deposited.
Microbial carbon use efficiency, biomass residence time and temperature sensitivity across ecosystems and soil depths
Publisher: Elsevier BV
Date: 03-2021
The three major axes of terrestrial ecosystem function
Publisher: Springer Science and Business Media LLC
Date: 22-09-2021
DOI: 10.1038/S41586-021-03939-9
Abstract: The leaf economics spectrum 1,2 and the global spectrum of plant forms and functions 3 revealed fundamental axes of variation in plant traits, which represent different ecological strategies that are shaped by the evolutionary development of plant species 2 . Ecosystem functions depend on environmental conditions and the traits of species that comprise the ecological communities 4 . However, the axes of variation of ecosystem functions are largely unknown, which limits our understanding of how ecosystems respond as a whole to anthropogenic drivers, climate and environmental variability 4,5 . Here we derive a set of ecosystem functions 6 from a dataset of surface gas exchange measurements across major terrestrial biomes. We find that most of the variability within ecosystem functions (71.8%) is captured by three key axes. The first axis reflects maximum ecosystem productivity and is mostly explained by vegetation structure. The second axis reflects ecosystem water-use strategies and is jointly explained by variation in vegetation height and climate. The third axis, which represents ecosystem carbon-use efficiency, features a gradient related to aridity, and is explained primarily by variation in vegetation structure. We show that two state-of-the-art land surface models reproduce the first and most important axis of ecosystem functions. However, the models tend to simulate more strongly correlated functions than those observed, which limits their ability to accurately predict the full range of responses to environmental changes in carbon, water and energy cycling in terrestrial ecosystems 7,8 .
Soil carbon storage under simulated climate change is mediated by plant functional type
Publisher: Wiley
Date: 12-2010
Influence of precipitation seasonality on piñon pine cellulose δD values
Publisher: Wiley
Date: 03-2000
An introduction to the Australian and New Zealand flux tower network – OzFlux
Publisher: Copernicus GmbH
Date: 28-04-2016
DOI: 10.5194/BG-2016-152
Abstract: Abstract. OzFlux is the regional Australian and New Zealand flux tower network that aims to provide a continental-scale national research facility to monitor and assess trends, and improve predictions, of Australia’s terrestrial biosphere and climate. This paper describes the evolution, design and current status of OzFlux as well as an overview of data processing. We analyse measurements from the Australian portion of the OzFlux network and found that the response of Australian biomes to climate was largely consistent with global studies but that Australian systems had a lower ecosystem water-use efficiency. Australian semi-arid/arid ecosystems are important because of their huge extent (70 %) and they have evolved with common moisture limitations. We also found that Australian ecosystems had similar radiation use efficiency per unit leaf area compared to global values that indicates a convergence toward a similar biochemical efficiency. The paper discusses the utility of the flux data and the synergies between flux, remote sensing and modelling. Lastly, the paper looks ahead at the future direction of the network and concludes that there has been a substantial contribution by OzFlux and considerable opportunities remain to further advance our understanding of ecosystem response to disturbances including drought, fire, land use and land cover change, land management and climate change that are relevant both nationally and internationally. It is suggested that a synergistic approach is required to address all of the spatial, ecological, human and cultural challenges of managing the delicately balanced ecosystems in Australia.
Wetting and drying cycles drive variations in the stable carbon isotope ratio of respired carbon dioxide in semi-arid grassland
Publisher: Springer Science and Business Media LLC
Date: 04-03-2009
DOI: 10.1007/S00442-009-1302-4
Abstract: In semi-arid regions, where plants using both C(3) and C(4) photosynthetic pathways are common, the stable C isotope ratio (delta(13)C) of ecosystem respiration (delta(13)C(R)) is strongly variable seasonally and inter-annually. Improved understanding of physiological and environmental controls over these variations will improve C cycle models that rely on the isotopic composition of atmospheric CO(2). We hypothesized that timing of precipitation events and antecedent moisture interact with activity of C(3) and C(4) grasses to determine net ecosystem CO(2) exchange (NEE) and delta(13)C(R). Field measurements included CO(2) and delta(13)C fluxes from the whole ecosystem and from patches of different plant communities, biomass and delta(13)C of plants and soils over the 2000 and 2001 growing seasons. NEE shifted from C source to sink in response to rainfall events, but this shift occurred after a time lag of up to 2 weeks if a dry period preceded the rainfall. The seasonal average of delta(13)C(R) was higher in 2000 (-16 per thousand) than 2001 (20 per thousand), probably due to drier conditions during the 2000 growing season (79.7 mm of precipitation from April up to and including July) than in 2001 (189 mm). During moist conditions, delta(13)C averaged -22 per thousand from C(3) patches, -16 per thousand from C(4) patches, and -19 per thousand from mixed C(3) and C(4) patches. However, during dry conditions the apparent spatial differences were not obvious, suggesting reduced autotrophic activity in C(4) grasses with shallow rooting depth, soon after the onset of dry conditions. Air and soil temperatures were negatively correlated with delta(13)C(R) vapor pressure deficit was a poor predictor of delta(13)C(R), in contrast to more mesic ecosystems. Responses of respiration components to precipitation pulses were explained by differences in soil moisture thresholds between C(3) and C(4) species. Stable isotopic composition of respiration in semi-arid ecosystems is more temporally and spatially variable than in mesic ecosystems owing to dynamic aspects of pulse precipitation episodes and biological drivers.
Differential hydrogen isotopic ratios of Sphagnum and vascular plant biomarkers in ombrotrophic peatlands as a quantitative proxy for precipitation—evaporation balance
Publisher: Elsevier BV
Date: 02-2010
Does vegetation structure regulate the spatial structure of soil respiration within a sagebrush steppe ecosystem?
Publisher: Elsevier BV
Date: 04-2014
Modeling soil CO2 emissions from ecosystems
Publisher: Springer Science and Business Media LLC
Date: 03-2005
Separating contributions from natural and anthropogenic sources in atmospheric methane from the Black Sea region, Romania
Publisher: Elsevier BV
Date: 10-2008
The influence of roots on mycorrhizal fungi, saprotrophic microbes and carbon dynamics in a low‐phosphorus Eucalyptus forest under elevated CO2
Publisher: Wiley
Date: 03-06-2021
Abstract: Elevated atmospheric carbon dioxide (eCO 2 ) can impact soil organic matter (SOM) dynamics by changing the rates of carbon (C) losses and gains. In the rhizosphere, these changes are usually assumed to be the result of root‐mediated eCO 2 impacts on saprotrophic microbes via altered below‐ground C allocation. This C allocation can also impact mycorrhizal fungi and their role in SOM dynamics. However, direct field quantifications of the influence of roots on both mycorrhizal fungi and saprotrophs together with SOM dynamics in forests exposed to eCO 2 are rare. This is especially true in phosphorus (P)‐limited systems, even though ecosystem responses to eCO 2 are known to depend on P availability. We assessed root mediation of eCO 2 impacts on saprotrophs, mycorrhizal fungi, and C dynamics of root litter and mineral soil C (SOM‐C) in a mature, P‐limited Eucalyptus woodland exposed to eCO 2 . We used a novel nested‐mesh‐bag method to manipulate roots access to the substrates in a 1‐year field incubation. We used an isotopic approach to trace C dynamics and performed a comprehensive microbial community analysis, along with nutrients and enzymatic activity measurements. Roots increased microbial biomass, fungal:bacterial ratio, plant‐derived C gains and substrate C losses while decreasing P availability and specific enzymatic activity. eCO 2 increased bacterial relative abundance in root litter and protozoa in SOM‐C, but it did not enhance root impacts or mycorrhizal fungi biomass. Our combination of in‐situ approaches allowed us to demonstrate that while roots have multiple impacts on soil microbial communities and C dynamics, they are not the main drivers of responses to eCO 2 in this P‐limited forest. Other factors beyond enhanced root‐derived below‐ground C inputs such as seasonality of nutrient and water availability, and shifts in plant communities may be more important in modulating eCO 2 impacts on soil dynamics in P‐limited systems. A free Plain Language Summary can be found within the Supporting Information of this article.
Stimulation of soil microbial functioning by elevated CO2 may surpass effects mediated by irrigation in a semiarid grassland
Publisher: Elsevier BV
Date: 11-2021
Timber harvesting alters soil carbon mineralization and microbial community structure in coniferous forests
Publisher: Elsevier BV
Date: 07-2008
Role of plant-fungal nutrient trading and host control in determining the competitive success of ectomycorrhizal fungi
Publisher: Springer Science and Business Media LLC
Date: 21-07-2017
Paleohydrologic reconstruction based on n-alkane distributions in ombrotrophic peat
Publisher: Elsevier BV
Date: 11-2006
A global perspective on agroecosystem nitrogen cycles after returning crop residue
Publisher: Elsevier BV
Date: 11-2018
Does declining carbon‐use efficiency explain thermal acclimation of soil respiration with warming?
Publisher: Wiley
Date: 22-10-2012
DOI: 10.1111/GCB.12036
Abstract: Enhanced soil respiration in response to global warming may substantially increase atmospheric CO2 concentrations above the anthropogenic contribution, depending on the mechanisms underlying the temperature sensitivity of soil respiration. Here, we compared short-term and seasonal responses of soil respiration to a shifting thermal environment and variable substrate availability via laboratory incubations. To analyze the data from incubations, we implemented a novel process-based model of soil respiration in a hierarchical Bayesian framework. Our process model combined a Michaelis-Menten-type equation of substrate availability and microbial biomass with an Arrhenius-type nonlinear temperature response function. We tested the competing hypotheses that apparent thermal acclimation of soil respiration can be explained by depletion of labile substrates in warmed soils, or that physiological acclimation reduces respiration rates. We demonstrated that short-term apparent acclimation can be induced by substrate depletion, but that decreasing microbial biomass carbon (MBC) is also important, and lower MBC at warmer temperatures is likely due to decreased carbon-use efficiency (CUE). Observed seasonal acclimation of soil respiration was associated with higher CUE and lower basal respiration for summer- vs. winter-collected soils. Whether the observed short-term decrease in CUE or the seasonal acclimation of CUE with increased temperatures dominates the response to long-term warming will have important consequences for soil organic carbon storage.
Upscaling CO2 fluxes using leaf, soil and chamber measurements across successional growth stages in a sagebrush steppe ecosystem
Publisher: Elsevier BV
Date: 10-2015
Challenging terrestrial biosphere models with data from the long‐term multifactor Prairie Heating and CO 2 Enrichment experiment
Publisher: Wiley
Date: 06-03-2017
DOI: 10.1111/GCB.13643
Abstract: Multifactor experiments are often advocated as important for advancing terrestrial biosphere models (TBMs), yet to date, such models have only been tested against single-factor experiments. We applied 10 TBMs to the multifactor Prairie Heating and CO
Depth dependence of soil carbon temperature sensitivity across Tibetan permafrost regions
Publisher: Elsevier BV
Date: 11-2018
Microclimatic Performance of a Free-Air Warming and CO2 Enrichment Experiment in Windy Wyoming, USA
Publisher: Public Library of Science (PLoS)
Date: 06-02-2015
Constraining Simulated Respiration Fluxes with Component Measurements in a Dry Eucalypt Forest
Publisher: Wiley
Date: 03-01-2019
Shallow snowpack inhibits soil respiration in sagebrush steppe through multiple biotic and abiotic mechanisms
Publisher: Wiley
Date: 05-2016
DOI: 10.1002/ECS2.1297
Spatial patterns in leaf area and plant functional type cover across chronosequences of sagebrush ecosystems
Publisher: Springer Science and Business Media LLC
Date: 27-03-2007
Can UAV-Based Infrared Thermography Be Used to Study Plant-Parasite Interactions between Mistletoe and Eucalypt Trees?
Publisher: MDPI AG
Date: 19-12-2018
DOI: 10.3390/RS10122062
Abstract: Some of the remnants of the Cumberland Plain woodland, an endangered dry sclerophyllous forest type of New South Wales, Australia, host large populations of mistletoe. In this study, the extent of mistletoe infection was investigated based on a forest inventory. We found that the mistletoe infection rate was relatively high, with 69% of the Eucalyptus fibrosa and 75% of the E. moluccana trees being infected. Next, to study the potential consequences of the infection for the trees, canopy temperatures of mistletoe plants and of infected and uninfected trees were analyzed using thermal imagery acquired during 10 flights with an unmanned aerial vehicle (UAV) in two consecutive summer seasons. Throughout all flight c aigns, mistletoe canopy temperature was 0.3–2 K lower than the temperature of the eucalypt canopy it was growing in, suggesting higher transpiration rates. Differences in canopy temperature between infected eucalypt foliage and mistletoe were particularly large when incoming radiation peaked. In these conditions, eucalypt foliage from infected trees also had significantly higher canopy temperatures (and likely lower transpiration rates) compared to that of uninfected trees of the same species. The study demonstrates the potential of using UAV-based infrared thermography for studying plant-water relations of mistletoe and its hosts.
Does root respiration in Australian rainforest tree seedlings acclimate to experimental warming?
Publisher: Oxford University Press (OUP)
Date: 27-04-2020
Abstract: Plant respiration can acclimate to changing environmental conditions and vary between species as well as biome types, although belowground respiration responses to ongoing climate warming are not well understood. Understanding the thermal acclimation capacity of root respiration (Rroot) in relation to increasing temperatures is therefore critical in elucidating a key uncertainty in plant function in response to warming. However, the degree of temperature acclimation of Rroot in rainforest trees and how root chemical and morphological traits are related to acclimation is unknown. Here we investigated the extent to which respiration of fine roots (≤2 mm) of four tropical and four warm-temperate rainforest tree seedlings differed in response to warmer growth temperatures (control and +6 °C), including temperature sensitivity (Q10) and the degree of acclimation of Rroot. Regardless of biome type, we found no consistent pattern in the short-term temperature responses of Rroot to elevated growth temperature: a significant reduction in the temperature response of Rroot to +6 °C treatment was only observed for a tropical species, Cryptocarya mackinnoniana, whereas the other seven species had either some stimulation or no alteration. Across species, Rroot was positively correlated with root tissue nitrogen concentration (mg g−1), while Q10 was positively correlated with root tissue density (g cm−3). Warming increased root tissue density by 20.8% but did not alter root nitrogen across species. We conclude that thermal acclimation capacity of Rroot to warming is species-specific and suggest that root tissue density is a useful predictor of Rroot and its thermal responses in rainforest tree seedlings.
Response of soil organic matter dynamics to conversion from tropical forest to grassland as determined by long-term incubation
Publisher: Springer Science and Business Media LLC
Date: 28-05-2008
Plant traits, stoichiometry and microbes as drivers of decomposition in the rhizosphere in a temperate grassland
Publisher: Wiley
Date: 13-04-2017
Impact of mountain pine beetle induced mortality on forest carbon and water fluxes
Publisher: IOP Publishing
Date: 10-2014
Corrigendum to “Sap flux-scaled transpiration and stomatal conductance response to soil and atmospheric drought in a semi-arid sagebrush ecosystem” [464–465C (2012) 176–185]
Publisher: Elsevier BV
Date: 2013
Upside-down fluxes Down Under: CO 2 net sink in winter and net source in summer in a temperate evergreen broadleaf forest
Publisher: Copernicus GmbH
Date: 19-06-2018
Abstract: Abstract. Predicting the seasonal dynamics of ecosystem carbon fluxes is challenging in broadleaved evergreen forests because of their moderate climates and subtle changes in canopy phenology. We assessed the climatic and biotic drivers of the seasonality of net ecosystem–atmosphere CO2 exchange (NEE) of a eucalyptus-dominated forest near Sydney, Australia, using the eddy covariance method. The climate is characterised by a mean annual precipitation of 800 mm and a mean annual temperature of 18 ∘C, hot summers and mild winters, with highly variable precipitation. In the 4-year study, the ecosystem was a sink each year (−225 g C m−2 yr−1 on average, with a standard deviation of 108 g C m−2 yr−1) inter-annual variations were not related to meteorological conditions. Daily net C uptake was always detected during the cooler, drier winter months (June through August), while net C loss occurred during the warmer, wetter summer months (December through February). Gross primary productivity (GPP) seasonality was low, despite longer days with higher light intensity in summer, because vapour pressure deficit (D) and air temperature (Ta) restricted surface conductance during summer while winter temperatures were still high enough to support photosynthesis. Maximum GPP during ideal environmental conditions was significantly correlated with remotely sensed enhanced vegetation index (EVI r2 = 0.46) and with canopy leaf area index (LAI r2 = 0.29), which increased rapidly after mid-summer rainfall events. Ecosystem respiration (ER) was highest during summer in wet soils and lowest during winter months. ER had larger seasonal litude compared to GPP, and therefore drove the seasonal variation of NEE. Because summer carbon uptake may become increasingly limited by atmospheric demand and high temperature, and because ecosystem respiration could be enhanced by rising temperatures, our results suggest the potential for large-scale seasonal shifts in NEE in sclerophyll vegetation under climate change.
Impacts of elevated carbon dioxide on carbon gains and losses from soil and associated microbes in a Eucalyptus woodland
Publisher: Elsevier BV
Date: 04-2020
Invasive forb benefits from water savings by native plants and carbon fertilization under elevated CO 2 and warming
Publisher: Wiley
Date: 23-08-2013
DOI: 10.1111/NPH.12459
Abstract: As global changes reorganize plant communities, invasive plants may benefit. We hypothesized that elevated CO 2 and warming would strongly influence invasive species success in a semi‐arid grassland, as a result of both direct and water‐mediated indirect effects. To test this hypothesis, we transplanted the invasive forb L inaria dalmatica into mixed‐grass prairie treated with free‐air CO 2 enrichment and infrared warming, and followed survival, growth, and reproduction over 4 yr. We also measured leaf gas exchange and carbon isotopic composition in L . dalmatica and the dominant native C 3 grass P ascopyrum smithii . CO 2 enrichment increased L . dalmatica biomass 13‐fold, seed production 32‐fold, and clonal expansion seven‐fold, while warming had little effect on L . dalmatica biomass or reproduction. Elevated CO 2 decreased stomatal conductance in P . smithii , contributing to higher soil water, but not in L . dalmatica . Elevated CO 2 also strongly increased L . dalmatica photosynthesis (87% versus 23% in P . smithii ), as a result of both enhanced carbon supply and increased soil water. More broadly, rapid growth and less conservative water use may allow invasive species to take advantage of both carbon fertilization and water savings under elevated CO 2 . Water‐limited ecosystems may therefore be particularly vulnerable to invasion as CO 2 increases.
Soil Microbes Compete Strongly with Plants for Soil Inorganic and Amino Acid Nitrogen in a Semiarid Grassland Exposed to Elevated CO2 and Warming
Publisher: Springer Science and Business Media LLC
Date: 02-04-2015
Root trait shifts towards an avoidance strategy promote productivity and recovery in C3 and C4 pasture grasses under drought
Publisher: Wiley
Date: 30-05-2022
Abstract: Plant species show a broad spectrum of plasticity in their covarying root traits in response to soil water limitation ranging from no change to shifts towards traits that enhance water and nutrient acquisition. Knowledge of root trait correlations and associated trait plasticity under drought is crucial to sustaining grassland production, including rangelands and pastures, under future, drier climates. Here, we investigated below‐ground responses to drought in four C 3 and three C 4 grasses and whether these explain above‐ground responses during extreme cool‐season drought and post‐drought recovery in a well‐replicated field experiment. We hypothesised that (a) C 3 and C 4 functional groups differ in their below‐ground trait responses to drought: C 3 species shift their traits in line with a drought avoidance strategy and C 4 species shift towards drought tolerance strategies (b) post‐drought recovery is associated with below‐ground carbon reserves in both functional groups. Root traits in the C 3 functional group differed from C 4 by having higher values for specific root length, nitrogen and soluble sugar concentrations, while C 4 root traits were associated with higher mean diameter, tissue density and starch concentrations. Drought‐induced plasticity in root traits in both functional groups was evidenced by increased values for specific root length, soluble sugars and nitrogen concentrations, and reduced values for tissue density, which we interpret as a drought avoidance strategy. Increasing root soluble sugars in C 3 and C 4 grasses and lower root tissue density in C 4 species under drought were associated with greater above‐ground productivity. Above‐ground biomass recovery post‐drought was predicted by root and crown soluble sugar concentrations and root longevity across both plant functional groups. These findings highlight the importance of understanding links between root trait plasticity and plant productivity during and following drought for predicting plant species' responses to changes in a future climate. Read the free Plain Language Summary for this article on the Journal blog.
Partitioning evapotranspiration fluxes from a Colorado grassland using stable isotopes: Seasonal variations and ecosystem implications of elevated atmospheric CO2
Publisher: Springer Science and Business Media LLC
Date: 2003
Elevated carbon dioxide alters impacts of precipitation pulses on ecosystem photosynthesis and respiration in a semi-arid grassland
Publisher: Springer Science and Business Media LLC
Date: 27-11-2009
DOI: 10.1007/S00442-009-1511-X
Abstract: Predicting net C balance under future global change scenarios requires a comprehensive understanding of how ecosystem photosynthesis (gross primary production GPP) and respiration (Re) respond to elevated atmospheric [CO(2)] and altered water availability. We measured net ecosystem exchange of CO(2) (NEE), GPP and Re under ambient and elevated [CO(2)] in a northern mixed-grass prairie (Wyoming, USA) during dry intervals and in response to simulated precipitation pulse events. Elevated [CO(2)] resulted in higher rates of both GPP and Re across the 2006 growing season, and the balance of these two fluxes (NEE) accounted for cumulative growing season C uptake (-14.4 +/- 8.3 g C m(-2)). Despite lower GPP and Re, experimental plots under ambient [CO(2)] had greater cumulative uptake (-36.2 +/- 8.2 g C m(-2)) than plots under elevated [CO(2)]. Non-irrigated control plots received 50% of average precipitation during the drought of 2006, and had near-zero NEE (1.9 +/- 6.4 g C m(-2)) for the growing season. Elevated [CO(2)] extended the magnitude and duration of pulse-related increases in GPP, resulting in a significant [CO(2)] treatment by pulse day interaction, demonstrating the potential for elevated [CO(2)] to increase the capacity of this ecosystem to respond to late-season precipitation. However, stimulation of Re throughout the growing season under elevated [CO(2)] reduced net C uptake compared to plots under ambient [CO(2)]. These results indicate that although elevated [CO(2)] stimulates gross rates of ecosystem C fluxes, it does not necessarily enhance net C uptake, and that C cycle responses in semi-arid grasslands are likely to be more sensitive to changes in precipitation than atmospheric [CO(2)].
Coordinated approaches to quantify long‐term ecosystem dynamics in response to global change
Publisher: Wiley
Date: 04-01-2011
Climate warming and tree carbon use efficiency in a whole-tree
Publisher: Wiley
Date: 06-03-2019
DOI: 10.1111/NPH.15721
Abstract: Autotrophic respiration is a major driver of the global C cycle and may contribute a positive climate warming feedback through increased atmospheric concentrations of CO
Erratum: Introducing BASE: The Biomes of Australian Soil Environments soil microbial diversity database [GigaScience. 5, 1, (2016) (1-11)] DOI: 10.1186/s13742-016-0126-5
Publisher: Oxford University Press (OUP)
Date: 05-2017
Using a paired tower approach and remote sensing to assess carbon sequestration and energy distribution in a heterogeneous sclerophyll forest
Publisher: Elsevier BV
Date: 2020
DOI: 10.1016/J.SCITOTENV.2019.133918
Abstract: The critically endangered Cumberland Plain woodland within the greater Sydney metropolitan area hosts a dwindling refuge for melaleuca trees, an integral part of Australia's native vegetation. Despite their high carbon stocks, melaleucas have not explicitly been targeted for studies assessing their carbon sequestration potential, and especially little is known about their energy cycling or their response to increasing climate stress, precluding a holistic assessment of the resilience of Australia's forests to climate change. To improve our understanding of the role of melaleuca forest responses to climate stress, we combined forest inventory and airborne LiDAR data to identify species distribution and associated variations in forest structure, and deployed flux towers in a melaleuca-dominated (AU-Mel) and in a eucalypt-dominated (AU-Cum) stand to simultaneously monitor carbon and energy fluxes under typical growing conditions, as well as during periods with high atmospheric demand and low soil water content. We discovered that the species distribution at our study site affected the vertical vegetation structure, leading to differences in canopy coverage (75% at AU-Cum vs. 84% at AU-Mel) and plant area index (2.1 m
Altered root traits due to elevated CO2 : a meta‐analysis
Publisher: Wiley
Date: 17-04-2013
DOI: 10.1111/GEB.12062
The temperature responses of soil respiration in deserts: a seven desert synthesis
Publisher: Springer Science and Business Media LLC
Date: 23-06-2010
Faster turnover of new soil carbon inputs under increased atmospheric CO 2
Publisher: Wiley
Date: 02-06-2017
DOI: 10.1111/GCB.13752
Abstract: Rising levels of atmospheric CO
Stable Isotope Constraints on Net Ecosystem Production Under Elevated CO2
Publisher: Elsevier
Date: 2005
Effects of forest conversion into grassland on soil aggregate structure and carbon storage in Panama: evidence from soil carbon fractionation and stable isotopes
Publisher: Springer Science and Business Media LLC
Date: 21-09-2006
Elevated CO2 alters the temperature sensitivity of stem CO2 efflux in a mature eucalypt woodland
Publisher: Elsevier BV
Date: 08-2021
Model–data fusion approach to quantify evapotranspiration and net ecosystem exchange across the sagebrush ecosystem at different temporal resolutions
Publisher: Wiley
Date: 06-04-2018
DOI: 10.1002/ECO.1957
Effects of elevated CO2 on fine root biomass are reduced by aridity but enhanced by soil nitrogen: A global assessment
Publisher: Springer Science and Business Media LLC
Date: 10-11-2017
DOI: 10.1038/S41598-017-15728-4
Abstract: Plant roots play a crucial role in regulating key ecosystem processes such as carbon (C) sequestration and nutrient solubilisation. Elevated (e)CO 2 is expected to alter the biomass of fine, coarse and total roots to meet increased demand for other resources such as water and nitrogen (N), however, the magnitude and direction of observed changes vary considerably between ecosystems. Here, we assessed how climate and soil properties mediate root responses to eCO 2 by comparing 24 field-based CO 2 experiments across the globe including a wide range of ecosystem types. We calculated response ratios (i.e. effect size) and used structural equation modelling (SEM) to achieve a system-level understanding of how aridity, mean annual temperature and total soil nitrogen simultaneously drive the response of total, coarse and fine root biomass to eCO 2 . Models indicated that increasing aridity limits the positive response of fine and total root biomass to eCO 2 , and that fine (but not coarse or total) root responses to eCO 2 are positively related to soil total N. Our results provide evidence that consideration of factors such as aridity and soil N status is crucial for predicting plant and ecosystem-scale responses to future changes in atmospheric CO 2 concentrations, and thus feedbacks to climate change.
Disentangling root responses to climate change in a semiarid grassland
Publisher: Springer Science and Business Media LLC
Date: 19-03-2014
DOI: 10.1007/S00442-014-2912-Z
Abstract: Future ecosystem properties of grasslands will be driven largely by belowground biomass responses to climate change, which are challenging to understand due to experimental and technical constraints. We used a multi-faceted approach to explore single and combined impacts of elevated CO2 and warming on root carbon (C) and nitrogen (N) dynamics in a temperate, semiarid, native grassland at the Prairie Heating and CO2 Enrichment experiment. To investigate the indirect, moisture mediated effects of elevated CO2, we included an irrigation treatment. We assessed root standing mass, morphology, residence time and seasonal appearance/disappearance of community-aggregated roots, as well as mass and N losses during decomposition of two dominant grass species (a C3 and a C4). In contrast to what is common in mesic grasslands, greater root standing mass under elevated CO2 resulted from increased production, unmatched by disappearance. Elevated CO2 plus warming produced roots that were longer, thinner and had greater surface area, which, together with greater standing biomass, could potentially alter root function and dynamics. Decomposition increased under environmental conditions generated by elevated CO2, but not those generated by warming, likely due to soil desiccation with warming. Elevated CO2, particularly under warming, slowed N release from C4-but not C3-roots, and consequently could indirectly affect N availability through treatment effects on species composition. Elevated CO2 and warming effects on root morphology and decomposition could offset increased C inputs from greater root biomass, thereby limiting future net C accrual in this semiarid grassland.
Modeling soil CO<sub>2</sub> production and transport with dynamic source and diffusion terms: testing the steady-state assumption using DETECT v1.0
Publisher: Copernicus GmbH
Date: 28-05-2018
Abstract: Abstract. The flux of CO2 from the soil to the atmosphere (soil respiration, Rsoil) is a major component of the global carbon (C) cycle. Methods to measure and model Rsoil, or partition it into different components, often rely on the assumption that soil CO2 concentrations and fluxes are in steady state, implying that Rsoil is equal to the rate at which CO2 is produced by soil microbial and root respiration. Recent research, however, questions the validity of this assumption. Thus, the aim of this work was two-fold: (1) to describe a non-steady state (NSS) soil CO2 transport and production model, DETECT, and (2) to use this model to evaluate the environmental conditions under which Rsoil and CO2 production are likely in NSS. The backbone of DETECT is a non-homogeneous, partial differential equation (PDE) that describes production and transport of soil CO2, which we solve numerically at fine spatial and temporal resolution (e.g., 0.01 m increments down to 1 m, every 6 h). Production of soil CO2 is simulated for every depth and time increment as the sum of root respiration and microbial decomposition of soil organic matter. Both of these factors can be driven by current and antecedent soil water content and temperature, which can also vary by time and depth. We also analytically solved the ordinary differential equation (ODE) corresponding to the steady-state (SS) solution to the PDE model. We applied the DETECT NSS and SS models to the six-month growing season period representative of a native grassland in Wyoming. Simulation experiments were conducted with both model versions to evaluate factors that could affect departure from SS, such as (1) varying soil texture (2) shifting the timing or frequency of precipitation and (3) with and without the environmental antecedent drivers. For a coarse-textured soil, Rsoil from the SS model closely matched that of the NSS model. However, in a fine-textured (clay) soil, growing season Rsoil was ∼ 3 % higher under the assumption of NSS (versus SS). These differences were exaggerated in clay soil at daily time scales whereby Rsoil under the SS assumption deviated from NSS by up to 35 % on average in the 10 days following a major precipitation event. Incorporation of antecedent drivers increased the magnitude of Rsoil by 15 to 37 % for coarse- and fine-textured soils, respectively. However, the responses of Rsoil to the timing of precipitation and antecedent drivers did not differ between SS and NSS assumptions. In summary, the assumption of SS conditions can be violated depending on soil type and soil moisture status, as affected by precipitation inputs. The DETECT model provides a framework for accommodating NSS conditions to better predict Rsoil and associated soil carbon cycling processes.
Cascading impacts of bark beetle‐caused tree mortality on coupled biogeophysical and biogeochemical processes
Publisher: Wiley
Date: 10-09-2012
DOI: 10.1890/110173
A trade-off between plant and soil carbon storage under elevated CO2
Publisher: Springer Science and Business Media LLC
Date: 24-03-2021
DOI: 10.1038/S41586-021-03306-8
Abstract: Terrestrial ecosystems remove about 30 per cent of the carbon dioxide (CO
Recovery of soil microbial community structure after fire in a sagebrush-grassland ecosystem
Publisher: No publisher found
Date: 2010
DOI: 10.1002/LDR.975
Isotope partitioning of soil respiration: A Bayesian solution to accommodate multiple sources of variability
Publisher: American Geophysical Union (AGU)
Date: 02-2015
DOI: 10.1002/2014JG002794
Arbuscular mycorrhizal fungal-mediated reductions in N2O emissions were not impacted by experimental warming for two common pasture species
Publisher: Elsevier BV
Date: 08-2021
Related Organisations
University Of California, Berkeley
Location: United States of America
Related Funding Activities
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End Date: 06-2022
Amount: $405,500.00
Funder: Australian Research Council
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End Date: 11-2025
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View Funded ActivityDiscovery Projects - Grant ID: DP180102203
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End Date: 04-2022
Amount: $485,949.00
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View Funded ActivityDiscovery Projects - Grant ID: DP0984779
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End Date: 06-2014
Amount: $450,000.00
Funder: Australian Research Council
View Funded ActivityDiscovery Projects - Grant ID: DP0772319
Start Date: 2007
End Date: 12-2011
Amount: $178,000.00
Funder: Australian Research Council
View Funded Activity