ORCID Profile
0000-0003-2259-5853
Current Organisation
University of Minnesota
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Applied Statistics | Ecosystem Function | Statistics |
Expanding Knowledge in the Environmental Sciences | Expanding Knowledge in the Mathematical Sciences
Publisher: Wiley
Date: 16-10-2013
DOI: 10.1111/GCB.12370
Abstract: Invasions have increased the size of regional species pools, but are typically assumed to reduce native ersity. However, global-scale tests of this assumption have been elusive because of the focus on exotic species richness, rather than relative abundance. This is problematic because low invader richness can indicate invasion resistance by the native community or, alternatively, dominance by a single exotic species. Here, we used a globally replicated study to quantify relationships between exotic richness and abundance in grass-dominated ecosystems in 13 countries on six continents, ranging from salt marshes to alpine tundra. We tested effects of human land use, native community ersity, herbivore pressure, and nutrient limitation on exotic plant dominance. Despite its widespread use, exotic richness was a poor proxy for exotic dominance at low exotic richness, because sites that contained few exotic species ranged from relatively pristine (low exotic richness and cover) to almost completely exotic-dominated ones (low exotic richness but high exotic cover). Both exotic cover and richness were predicted by native plant ersity (native grass richness) and land use (distance to cultivation). Although climate was important for predicting both exotic cover and richness, climatic factors predicting cover (precipitation variability) differed from those predicting richness (maximum temperature and mean temperature in the wettest quarter). Herbivory and nutrient limitation did not predict exotic richness or cover. Exotic dominance was greatest in areas with low native grass richness at the site- or regional-scale. Although this could reflect native grass displacement, a lack of biotic resistance is a more likely explanation, given that grasses comprise the most aggressive invaders. These findings underscore the need to move beyond richness as a surrogate for the extent of invasion, because this metric confounds monodominance with invasion resistance. Monitoring species' relative abundance will more rapidly advance our understanding of invasions.
Publisher: Springer Science and Business Media LLC
Date: 11-10-2023
Publisher: Springer Science and Business Media LLC
Date: 04-02-2019
DOI: 10.1038/S41559-018-0790-1
Abstract: Leaf traits are frequently measured in ecology to provide a 'common currency' for predicting how anthropogenic pressures impact ecosystem function. Here, we test whether leaf traits consistently respond to experimental treatments across 27 globally distributed grassland sites across 4 continents. We find that specific leaf area (leaf area per unit mass)-a commonly measured morphological trait inferring shifts between plant growth strategies-did not respond to up to four years of soil nutrient additions. Leaf nitrogen, phosphorus and potassium concentrations increased in response to the addition of each respective soil nutrient. We found few significant changes in leaf traits when vertebrate herbivores were excluded in the short-term. Leaf nitrogen and potassium concentrations were positively correlated with species turnover, suggesting that interspecific trait variation was a significant predictor of leaf nitrogen and potassium, but not of leaf phosphorus concentration. Climatic conditions and pretreatment soil nutrient levels also accounted for significant amounts of variation in the leaf traits measured. Overall, we find that leaf morphological traits, such as specific leaf area, are not appropriate indicators of plant response to anthropogenic perturbations in grasslands.
Publisher: Cold Spring Harbor Laboratory
Date: 10-03-2021
DOI: 10.1101/2021.03.09.434527
Abstract: Interannual variability in grassland primary production is strongly driven by precipitation, nutrient availability and herbivory, but there is no general consensus on the mechanisms linking these variables. If grassland biomass is limited by the single most limiting resource at a given time, then we expect that nutrient addition will not affect biomass production at arid sites. We conducted a distributed experiment manipulating nutrients and herbivores at 44 grassland sites in 8 regions around the world, spanning a broad range in aridity. We estimated the effects of 5-11 years of nutrient addition and herbivore exclusion treatments on precipitation sensitivity of biomass (proportional change in biomass relative to proportional change in rainfall among years), and the biomass in the driest year (to measure treatment effects when water was most limiting) at each site. Grazer exclusion did not interact with nutrients to influence driest year biomass or sensitivity. Nutrient addition increased driest year biomass by 74% and sensitivity by 0.12 (proportional units), and that effect did not change across the range of aridity spanned by our sites. Grazer exclusion did not interact with nutrients to influence sensitivity or driest year biomass. At almost half of our sites, the previous year's rainfall explained as much variation in biomass as current year precipitation. Overall, our distributed fertilization experiment detected co-limitation between nutrients and water governing grasslands, with biomass sensitivity to precipitation being limited by nutrient availability irrespective of site aridity and herbivory. Our findings refute the classical ideas that grassland plant performance is limited by the single most limiting resource at a site. This suggests that nutrient eutrophication will destabilize grassland ecosystems through increased sensitivity to precipitation variation.
Publisher: Wiley
Date: 06-2023
DOI: 10.1002/ECS2.4542
Abstract: Human activities are altering ecological communities around the globe. Understanding the implications of these changes requires that we consider the composition of those communities. However, composition can be summarized by many metrics which in turn are influenced by different ecological processes. For ex le, incidence‐based metrics strongly reflect species gains or losses, while abundance‐based metrics are minimally affected by changes in the abundance of small or uncommon species. Furthermore, metrics might be correlated with different predictors. We used a globally distributed experiment to examine variation in species composition within 60 grasslands on six continents. Each site had an identical experimental and s ling design: 24 plots × 4 years. We expressed compositional variation within each site—not across sites—using abundance‐ and incidence‐based metrics of the magnitude of dissimilarity (Bray–Curtis and Sorensen, respectively), abundance‐ and incidence‐based measures of the relative importance of replacement (balanced variation and species turnover, respectively), and species richness at two scales (per plot‐year [alpha] and per site [gamma]). Average compositional variation among all plot‐years at a site was high and similar to spatial variation among plots in the pretreatment year, but lower among years in untreated plots. For both types of metrics, most variation was due to replacement rather than nestedness. Differences among sites in overall within‐site compositional variation were related to several predictors. Environmental heterogeneity (expressed as the CV of total aboveground plant biomass in unfertilized plots of the site) was an important predictor for most metrics. Biomass production was a predictor of species turnover and of alpha ersity but not of other metrics. Continentality (measured as annual temperature range) was a strong predictor of Sorensen dissimilarity. Metrics of compositional variation are moderately correlated: knowing the magnitude of dissimilarity at a site provides little insight into whether the variation is driven by replacement processes. Overall, our understanding of compositional variation at a site is enhanced by considering multiple metrics simultaneously. Monitoring programs that explicitly incorporate these implications, both when designing s ling strategies and analyzing data, will have a stronger ability to understand the compositional variation of systems and to quantify the impacts of human activities.
Publisher: Wiley
Date: 09-2017
Publisher: Springer Science and Business Media LLC
Date: 15-06-2022
DOI: 10.1007/S11104-022-05498-Y
Abstract: The amount of nitrogen (N) derived from symbiotic N 2 fixation by legumes in grasslands might be affected by anthropogenic N and phosphorus (P) inputs, but the underlying mechanisms are not known. We evaluated symbiotic N 2 fixation in 17 natural and semi-natural grasslands on four continents that are subjected to the same full-factorial N and P addition experiment, using the 15 N natural abundance method. N as well as combined N and P (NP) addition reduced aboveground legume biomass by 65% and 45%, respectively, compared to the control, whereas P addition had no significant impact. Addition of N and/or P had no significant effect on the symbiotic N 2 fixation per unit legume biomass. In consequence, the amount of N fixed annually per grassland area was less than half in the N addition treatments compared to control and P addition, irrespective of whether the dominant legumes were annuals or perennials. Our results reveal that N addition mainly impacts symbiotic N 2 fixation via reduced biomass of legumes rather than changes in N 2 fixation per unit legume biomass. The results show that soil N enrichment by anthropogenic activities significantly reduces N 2 fixation in grasslands, and these effects cannot be reversed by additional P amendment.
Publisher: Springer Science and Business Media LLC
Date: 04-12-2017
DOI: 10.1038/S41559-017-0395-0
Abstract: Bio ersity is declining in many local communities while also becoming increasingly homogenized across space. Experiments show that local plant species loss reduces ecosystem functioning and services, but the role of spatial homogenization of community composition and the potential interaction between ersity at different scales in maintaining ecosystem functioning remains unclear, especially when many functions are considered (ecosystem multifunctionality). We present an analysis of eight ecosystem functions measured in 65 grasslands worldwide. We find that more erse grasslands-those with both species-rich local communities (α- ersity) and large compositional differences among localities (β- ersity)-had higher levels of multifunctionality. Moreover, α- and β- ersity synergistically affected multifunctionality, with higher levels of ersity at one scale lifying the contribution to ecological functions at the other scale. The identity of species influencing ecosystem functioning differed among functions and across local communities, explaining why more erse grasslands maintained greater functionality when more functions and localities were considered. These results were robust to variation in environmental drivers. Our findings reveal that plant ersity, at both local and landscape scales, contributes to the maintenance of multiple ecosystem services provided by grasslands. Preserving ecosystem functioning therefore requires conservation of bio ersity both within and among ecological communities.
Publisher: Wiley
Date: 18-03-2019
DOI: 10.1111/ELE.13258
Abstract: Soil stores approximately twice as much carbon as the atmosphere and fluctuations in the size of the soil carbon pool directly influence climate conditions. We used the Nutrient Network global change experiment to examine how anthropogenic nutrient enrichment might influence grassland soil carbon storage at a global scale. In isolation, enrichment of nitrogen and phosphorous had minimal impacts on soil carbon storage. However, when these nutrients were added in combination with potassium and micronutrients, soil carbon stocks changed considerably, with an average increase of 0.04 KgCm
Publisher: Wiley
Date: 06-10-2021
DOI: 10.1111/ELE.13894
Abstract: Fertilisation experiments have demonstrated that nutrient availability is a key determinant of biomass production and carbon sequestration in grasslands. However, the influence of nutrients in explaining spatial variation in grassland biomass production has rarely been assessed. Using a global dataset comprising 72 sites on six continents, we investigated which of 16 soil factors that shape nutrient availability associate most strongly with variation in grassland aboveground biomass. Climate and N deposition were also considered. Based on theory‐driven structural equation modelling, we found that soil micronutrients (particularly Zn and Fe) were important predictors of biomass and, together with soil physicochemical properties and C:N, they explained more unique variation (32%) than climate and N deposition (24%). However, the association between micronutrients and biomass was absent in grasslands limited by NP. These results highlight soil properties as key predictors of global grassland biomass production and point to serial co‐limitation by NP and micronutrients.
Publisher: Springer Science and Business Media LLC
Date: 2016
DOI: 10.1038/NATURE16524
Abstract: How ecosystem productivity and species richness are interrelated is one of the most debated subjects in the history of ecology. Decades of intensive study have yet to discern the actual mechanisms behind observed global patterns. Here, by integrating the predictions from multiple theories into a single model and using data from 1,126 grassland plots spanning five continents, we detect the clear signals of numerous underlying mechanisms linking productivity and richness. We find that an integrative model has substantially higher explanatory power than traditional bivariate analyses. In addition, the specific results unveil several surprising findings that conflict with classical models. These include the isolation of a strong and consistent enhancement of productivity by richness, an effect in striking contrast with superficial data patterns. Also revealed is a consistent importance of competition across the full range of productivity values, in direct conflict with some (but not all) proposed models. The promotion of local richness by macroecological gradients in climatic favourability, generally seen as a competing hypothesis, is also found to be important in our analysis. The results demonstrate that an integrative modelling approach leads to a major advance in our ability to discern the underlying processes operating in ecological systems.
Publisher: Springer Science and Business Media LLC
Date: 16-02-2014
DOI: 10.1038/NATURE13014
Abstract: Studies of experimental grassland communities have demonstrated that plant ersity can stabilize productivity through species asynchrony, in which decreases in the biomass of some species are compensated for by increases in others. However, it remains unknown whether these findings are relevant to natural ecosystems, especially those for which species ersity is threatened by anthropogenic global change. Here we analyse ersity-stability relationships from 41 grasslands on five continents and examine how these relationships are affected by chronic fertilization, one of the strongest drivers of species loss globally. Unmanipulated communities with more species had greater species asynchrony, resulting in more stable biomass production, generalizing a result from bio ersity experiments to real-world grasslands. However, fertilization weakened the positive effect of ersity on stability. Contrary to expectations, this was not due to species loss after eutrophication but rather to an increase in the temporal variation of productivity in combination with a decrease in species asynchrony in erse communities. Our results demonstrate separate and synergistic effects of ersity and eutrophication on stability, emphasizing the need to understand how drivers of global change interactively affect the reliable provisioning of ecosystem services in real-world systems.
Publisher: Springer Science and Business Media LLC
Date: 31-10-2019
DOI: 10.1038/S41467-019-12948-2
Abstract: Soil nitrogen mineralisation (N min ), the conversion of organic into inorganic N, is important for productivity and nutrient cycling. The balance between mineralisation and immobilisation (net N min ) varies with soil properties and climate. However, because most global-scale assessments of net N min are laboratory-based, its regulation under field-conditions and implications for real-world soil functioning remain uncertain. Here, we explore the drivers of realised (field) and potential (laboratory) soil net N min across 30 grasslands worldwide. We find that realised N min is largely explained by temperature of the wettest quarter, microbial biomass, clay content and bulk density. Potential N min only weakly correlates with realised N min , but contributes to explain realised net N min when combined with soil and climatic variables. We provide novel insights of global realised soil net N min and show that potential soil net N min data available in the literature could be parameterised with soil and climate data to better predict realised N min .
Publisher: American Association for the Advancement of Science (AAAS)
Date: 06-11-2020
Abstract: Increasing plant ersity controls herbivory by limiting energetic gains and enhancing predation of arthropod herbivores.
Publisher: Springer Science and Business Media LLC
Date: 19-10-2023
Publisher: Proceedings of the National Academy of Sciences
Date: 06-07-2021
Abstract: Predicting the effects of anthropogenic nutrient enrichment on plant communities is critical for managing implications for bio ersity and ecosystem services. Plant functional types that fix atmospheric nitrogen (e.g., legumes) may be at particular risk of nutrient-driven global decline, yet global-scale evidence is lacking. Using an experiment in 45 grasslands across six continents, we showed that legume cover, richness, and biomass declined substantially with nitrogen additions. Although legumes benefited from phosphorus, potassium, and other nutrients, these nutrients did not ameliorate nitrogen-induced legume decline. Given global trends in anthropogenic nutrient enrichment, our results indicate the potential for global decline in grassland legumes, with likely consequences for bio ersity, food webs, soil health, and genetic improvement of protein-rich plant species for food production.
Publisher: Springer Science and Business Media LLC
Date: 24-08-2016
DOI: 10.1038/NATURE19324
Publisher: Springer Science and Business Media LLC
Date: 14-06-2023
DOI: 10.1038/S41467-023-39179-W
Abstract: All multicellular organisms host a erse microbiome composed of microbial pathogens, mutualists, and commensals, and changes in microbiome ersity or composition can alter host fitness and function. Nonetheless, we lack a general understanding of the drivers of microbiome ersity, in part because it is regulated by concurrent processes spanning scales from global to local. Global-scale environmental gradients can determine variation in microbiome ersity among sites, however an in idual host’s microbiome also may reflect its local micro-environment. We fill this knowledge gap by experimentally manipulating two potential mediators of plant microbiome ersity (soil nutrient supply and herbivore density) at 23 grassland sites spanning global-scale gradients in soil nutrients, climate, and plant biomass. Here we show that leaf-scale microbiome ersity in unmanipulated plots depended on the total microbiome ersity at each site, which was highest at sites with high soil nutrients and plant biomass. We also found that experimentally adding soil nutrients and excluding herbivores produced concordant results across sites, increasing microbiome ersity by increasing plant biomass, which created a shaded microclimate. This demonstration of consistent responses of microbiome ersity across a wide range of host species and environmental conditions suggests the possibility of a general, predictive understanding of microbiome ersity.
Publisher: Wiley
Date: 24-01-2013
DOI: 10.1111/ELE.12078
Abstract: Plant growth can be limited by resource acquisition and defence against consumers, leading to contrasting trade-off possibilities. The competition-defence hypothesis posits a trade-off between competitive ability and defence against enemies (e.g. herbivores and pathogens). The growth-defence hypothesis suggests that strong competitors for nutrients are also defended against enemies, at a cost to growth rate. We tested these hypotheses using observations of 706 plant populations of over 500 species before and following identical fertilisation and fencing treatments at 39 grassland sites worldwide. Strong positive covariance in species responses to both treatments provided support for a growth-defence trade-off: populations that increased with the removal of nutrient limitation (poor competitors) also increased following removal of consumers. This result held globally across 4 years within plant life-history groups and within the majority of in idual sites. Thus, a growth-defence trade-off appears to be the norm, and mechanisms maintaining grassland bio ersity may operate within this constraint.
Publisher: Springer Science and Business Media LLC
Date: 25-07-2022
DOI: 10.1038/S41559-022-01809-9
Abstract: Ecological models predict that the effects of mammalian herbivore exclusion on plant ersity depend on resource availability and plant exposure to ungulate grazing over evolutionary time. Using an experiment replicated in 57 grasslands on six continents, with contrasting evolutionary history of grazing, we tested how resources (mean annual precipitation and soil nutrients) determine herbivore exclusion effects on plant ersity, richness and evenness. Here we show that at sites with a long history of ungulate grazing, herbivore exclusion reduced plant ersity by reducing both richness and evenness and the responses of richness and ersity to herbivore exclusion decreased with mean annual precipitation. At sites with a short history of grazing, the effects of herbivore exclusion were not related to precipitation but differed for native and exotic plant richness. Thus, plant species' evolutionary history of grazing continues to shape the response of the world's grasslands to changing mammalian herbivory.
Publisher: Springer Science and Business Media LLC
Date: 09-03-2014
DOI: 10.1038/NATURE13144
Abstract: Human alterations to nutrient cycles and herbivore communities are affecting global bio ersity dramatically. Ecological theory predicts these changes should be strongly counteractive: nutrient addition drives plant species loss through intensified competition for light, whereas herbivores prevent competitive exclusion by increasing ground-level light, particularly in productive systems. Here we use experimental data spanning a globally relevant range of conditions to test the hypothesis that herbaceous plant species losses caused by eutrophication may be offset by increased light availability due to herbivory. This experiment, replicated in 40 grasslands on 6 continents, demonstrates that nutrients and herbivores can serve as counteracting forces to control local plant ersity through light limitation, independent of site productivity, soil nitrogen, herbivore type and climate. Nutrient addition consistently reduced local ersity through light limitation, and herbivory rescued ersity at sites where it alleviated light limitation. Thus, species loss from anthropogenic eutrophication can be ameliorated in grasslands where herbivory increases ground-level light.
Publisher: Wiley
Date: 17-07-2018
Publisher: Public Library of Science (PLoS)
Date: 06-02-2013
Publisher: Springer Science and Business Media LLC
Date: 12-07-2023
Publisher: Wiley
Date: 10-06-2020
DOI: 10.1111/GCB.15146
Abstract: Microbial processing of aggregate‐unprotected organic matter inputs is key for soil fertility, long‐term ecosystem carbon and nutrient sequestration and sustainable agriculture. We investigated the effects of adding multiple nutrients (nitrogen, phosphorus and potassium plus nine essential macro‐ and micro‐nutrients) on decomposition and biochemical transformation of standard plant materials buried in 21 grasslands from four continents. Addition of multiple nutrients weakly but consistently increased decomposition and biochemical transformation of plant remains during the peak‐season, concurrent with changes in microbial exoenzymatic activity. Higher mean annual precipitation and lower mean annual temperature were the main climatic drivers of higher decomposition rates, while biochemical transformation of plant remains was negatively related to temperature of the wettest quarter. Nutrients enhanced decomposition most at cool, high rainfall sites, indicating that in a warmer and drier future fertilized grassland soils will have an even more limited potential for microbial processing of plant remains.
Publisher: Wiley
Date: 31-03-2018
DOI: 10.1002/ECY.2175
Abstract: Plant stoichiometry, the relative concentration of elements, is a key regulator of ecosystem functioning and is also being altered by human activities. In this paper we sought to understand the global drivers of plant stoichiometry and compare the relative contribution of climatic vs. anthropogenic effects. We addressed this goal by measuring plant elemental (C, N, P and K) responses to eutrophication and vertebrate herbivore exclusion at eighteen sites on six continents. Across sites, climate and atmospheric N deposition emerged as strong predictors of plot-level tissue nutrients, mediated by biomass and plant chemistry. Within sites, fertilization increased total plant nutrient pools, but results were contingent on soil fertility and the proportion of grass biomass relative to other functional types. Total plant nutrient pools erged strongly in response to herbivore exclusion when fertilized responses were largest in ungrazed plots at low rainfall, whereas herbivore grazing d ened the plant community nutrient responses to fertilization. Our study highlights (1) the importance of climate in determining plant nutrient concentrations mediated through effects on plant biomass, (2) that eutrophication affects grassland nutrient pools via both soil and atmospheric pathways and (3) that interactions among soils, herbivores and eutrophication drive plant nutrient responses at small scales, especially at water-limited sites.
Publisher: Proceedings of the National Academy of Sciences
Date: 17-08-2015
Abstract: Human activities have resulted in large increases in the availability of nutrients in terrestrial ecosystems worldwide. Although plant community responses to elevated nutrients have been well studied, soil microbial community responses remain poorly understood, despite their critical importance to ecosystem functioning. Using DNA-sequencing approaches, we assessed the response of soil microbial communities to experimentally added nitrogen and phosphorus at 25 grassland sites across the globe. Our results demonstrate that the composition of these communities shifts in consistent ways with elevated nutrient inputs and that there are corresponding shifts in the ecological attributes of the community members. This study represents an important step forward for understanding the connection between elevated nutrient inputs, shifts in soil microbial communities, and altered ecosystem functioning.
Publisher: Wiley
Date: 02-12-2015
DOI: 10.1111/JBI.12451
Publisher: Springer Science and Business Media LLC
Date: 27-11-2020
DOI: 10.1038/S41467-020-19870-Y
Abstract: Human activities are transforming grassland biomass via changing climate, elemental nutrients, and herbivory. Theory predicts that food-limited herbivores will consume any additional biomass stimulated by nutrient inputs (‘consumer-controlled’). Alternatively, nutrient supply is predicted to increase biomass where herbivores alter community composition or are limited by factors other than food (‘resource-controlled’). Using an experiment replicated in 58 grasslands spanning six continents, we show that nutrient addition and vertebrate herbivore exclusion each caused sustained increases in aboveground live biomass over a decade, but consumer control was weak. However, at sites with high vertebrate grazing intensity or domestic livestock, herbivores consumed the additional fertilization-induced biomass, supporting the consumer-controlled prediction. Herbivores most effectively reduced the additional live biomass at sites with low precipitation or high ambient soil nitrogen. Overall, these experimental results suggest that grassland biomass will outstrip wild herbivore control as human activities increase elemental nutrient supply, with widespread consequences for grazing and fire risk.
Publisher: Wiley
Date: 14-03-2014
DOI: 10.1111/GEB.12157
Publisher: Wiley
Date: 22-09-2020
DOI: 10.1111/GCB.15308
Publisher: Springer Science and Business Media LLC
Date: 06-07-2015
Abstract: Terrestrial ecosystem productivity is widely accepted to be nutrient limited(1). Although nitrogen (N) is deemed a key determinant of aboveground net primary production (ANPP)(2,3), the prevalence of co-limitation by N and phosphorus (P) is increasingly recognized(4-8). However, the extent to which terrestrial productivity is co-limited by nutrients other than N and P has remained unclear. Here, we report results from a standardized factorial nutrient addition experiment, in which we added N, P and potassium (K) combined with a selection of micronutrients (K+μ), alone or in concert, to 42 grassland sites spanning five continents, and monitored ANPP. Nutrient availability limited productivity at 31 of the 42 grassland sites. And pairwise combinations of N, P, and K+μ co-limited ANPP at 29 of the sites. Nitrogen limitation peaked in cool, high latitude sites. Our findings highlight the importance of less studied nutrients, such as K and micronutrients, for grassland productivity, and point to significant variations in the type and degree of nutrient limitation. We suggest that multiple-nutrient constraints must be considered when assessing the ecosystem-scale consequences of nutrient enrichment.
Publisher: Springer Science and Business Media LLC
Date: 23-10-2020
DOI: 10.1038/S41467-020-19252-4
Abstract: Eutrophication is a widespread environmental change that usually reduces the stabilizing effect of plant ersity on productivity in local communities. Whether this effect is scale dependent remains to be elucidated. Here, we determine the relationship between plant ersity and temporal stability of productivity for 243 plant communities from 42 grasslands across the globe and quantify the effect of chronic fertilization on these relationships. Unfertilized local communities with more plant species exhibit greater asynchronous dynamics among species in response to natural environmental fluctuations, resulting in greater local stability (alpha stability). Moreover, neighborhood communities that have greater spatial variation in plant species composition within sites (higher beta ersity) have greater spatial asynchrony of productivity among communities, resulting in greater stability at the larger scale (gamma stability). Importantly, fertilization consistently weakens the contribution of plant ersity to both of these stabilizing mechanisms, thus diminishing the positive effect of bio ersity on stability at differing spatial scales. Our findings suggest that preserving grassland functional stability requires conservation of plant ersity within and among ecological communities.
Publisher: Wiley
Date: 25-08-2021
DOI: 10.1002/ECY.3504
Abstract: Spatial rarity is often used to predict extinction risk, but rarity can also occur temporally. Perhaps more relevant in the context of global change is whether a species is core to a community (persistent) or transient (intermittently present), with transient species often susceptible to human activities that reduce niche space. Using 5-12 yr of data on 1,447 plant species from 49 grasslands on five continents, we show that local abundance and species persistence under ambient conditions are both effective predictors of local extinction risk following experimental exclusion of grazers or addition of nutrients persistence was a more powerful predictor than local abundance. While perturbations increased the risk of exclusion for low persistence and abundance species, transient but abundant species were also highly likely to be excluded from a perturbed plot relative to ambient conditions. Moreover, low persistence and low abundance species that were not excluded from perturbed plots tended to have a modest increase in abundance following perturbance. Last, even core species with high abundances had large decreases in persistence and increased losses in perturbed plots, threatening the long-term stability of these grasslands. Our results demonstrate that expanding the concept of rarity to include temporal dynamics, in addition to local abundance, more effectively predicts extinction risk in response to environmental change than either rarity axis predicts alone.
Publisher: Wiley
Date: 30-11-2022
Abstract: Declines in grassland ersity in response to nutrient addition are a general consequence of global change. This decline in species richness may be driven by multiple underlying processes operating at different time‐scales. Nutrient addition can reduce ersity by enhancing the rate of local extinction via competitive exclusion, or by reducing the rate of colonization by constraining the pool of species able to colonize under new conditions. Partitioning net change into extinction and colonization rates will better delineate the long‐term effect of global change in grasslands. We synthesized changes in richness in response to experimental fertilization with nitrogen, phosphorus and potassium with micronutrients across 30 grasslands. We quantified changes in local richness, colonization, and extinction over 8–10 years of nutrient addition, and compared these rates against control conditions to isolate the effect of nutrient addition from background dynamics. Total richness at steady state in the control plots was the sum of equal, relatively high rates of local colonization and extinction. On aggregate, 30%–35% of initial species were lost and the same proportion of new species were gained at least once over a decade. Absolute turnover increased with site‐level richness but was proportionately greater at lower‐richness sites relative to starting richness. Loss of total richness with nutrient addition, especially N in combination with P or K, was driven by enhanced rates of extinction with a smaller contribution from reduced colonization. Enhanced extinction and reduced colonization were disproportionately among native species, perennials, and forbs. Reduced colonization plateaued after the first few ( ) years after nutrient addition, while enhanced extinction continued throughout the first decade. Synthesis . Our results indicate a high rate of colonizations and extinctions underlying the richness of ambient communities and that nutrient enhancement drives overall declines in ersity primarily by exclusion of previously established species. Moreover, enhanced extinction continues over long time‐scales, suggesting continuous, long‐term community responses and a need for long‐term study to fully realize the extinction impact of increased nutrients on grassland composition.
Publisher: Wiley
Date: 23-09-2023
Publisher: Wiley
Date: 24-10-2022
DOI: 10.1111/ELE.14126
Abstract: Global change drivers, such as anthropogenic nutrient inputs, are increasing globally. Nutrient deposition simultaneously alters plant bio ersity, species composition and ecosystem processes like aboveground biomass production. These changes are underpinned by species extinction, colonisation and shifting relative abundance. Here, we use the Price equation to quantify and link the contributions of species that are lost, gained or that persist to change in aboveground biomass in 59 experimental grassland sites. Under ambient (control) conditions, compositional and biomass turnover was high, and losses (i.e. local extinctions) were balanced by gains (i.e. colonisation). Under fertilisation, the decline in species richness resulted from increased species loss and decreases in species gained. Biomass increase under fertilisation resulted mostly from species that persist and to a lesser extent from species gained. Drivers of ecological change can interact relatively independently with ersity, composition and ecosystem processes and functions such as aboveground biomass due to the in idual contributions of species lost, gained or persisting.
Publisher: Wiley
Date: 12-03-2020
DOI: 10.1111/GEB.13092
Publisher: Springer Science and Business Media LLC
Date: 15-05-2020
Publisher: Wiley
Date: 04-2020
DOI: 10.1111/GEB.13094
Publisher: Wiley
Date: 09-07-2021
DOI: 10.1111/ELE.13838
Abstract: The effects of altered nutrient supplies and herbivore density on species ersity vary with spatial scale, because coexistence mechanisms are scale dependent. This scale dependence may alter the shape of the species–area relationship (SAR), which can be described by changes in species richness ( S ) as a power function of the s le area ( A ): S = cA z , where c and z are constants. We analysed the effects of experimental manipulations of nutrient supply and herbivore density on species richness across a range of scales (0.01–75 m 2 ) at 30 grasslands in 10 countries. We found that nutrient addition reduced the number of species that could co‐occur locally, indicated by the SAR intercepts (log c ), but did not affect the SAR slopes ( z ). As a result, proportional species loss due to nutrient enrichment was largely unchanged across s ling scales, whereas total species loss increased over threefold across our range of s ling scales.
Publisher: American Association for the Advancement of Science (AAAS)
Date: 23-03-2012
Abstract: Pan et al . claim that our results actually support a strong linear positive relationship between productivity and richness, whereas Fridley et al . contend that the data support a strong humped relationship. These responses illustrate how preoccupation with bivariate patterns distracts from a deeper understanding of the multivariate mechanisms that control these important ecosystem properties.
Publisher: Wiley
Date: 22-11-2021
DOI: 10.1002/ECE3.8266
Abstract: Biotic and abiotic factors interact with dominant plants—the locally most frequent or with the largest coverage—and nondominant plants differently, partially because dominant plants modify the environment where nondominant plants grow. For instance, if dominant plants compete strongly, they will deplete most resources, forcing nondominant plants into a narrower niche space. Conversely, if dominant plants are constrained by the environment, they might not exhaust available resources but instead may ameliorate environmental stressors that usually limit nondominants. Hence, the nature of interactions among nondominant species could be modified by dominant species. Furthermore, these differences could translate into a disparity in the phylogenetic relatedness among dominants compared to the relatedness among nondominants. By estimating phylogenetic dispersion in 78 grasslands across five continents, we found that dominant species were clustered (e.g., co‐dominant grasses), suggesting dominant species are likely organized by environmental filtering, and that nondominant species were either randomly assembled or overdispersed. Traits showed similar trends for those sites ( %) with sufficient trait data. Furthermore, several lineages scattered in the phylogeny had more nondominant species than expected at random, suggesting that traits common in nondominants are phylogenetically conserved and have evolved multiple times. We also explored environmental drivers of the dominant/nondominant disparity. We found different assembly patterns for dominants and nondominants, consistent with asymmetries in assembly mechanisms. Among the different postulated mechanisms, our results suggest two complementary hypotheses seldom explored: (1) Nondominant species include lineages adapted to thrive in the environment generated by dominant species. (2) Even when dominant species reduce resources to nondominant ones, dominant species could have a stronger positive effect on some nondominants by ameliorating environmental stressors affecting them, than by depleting resources and increasing the environmental stress to those nondominants. These results show that the dominant/nondominant asymmetry has ecological and evolutionary consequences fundamental to understand plant communities.
Publisher: Springer Science and Business Media LLC
Date: 31-03-2023
DOI: 10.1038/S41467-023-37395-Y
Abstract: Plant productivity varies due to environmental heterogeneity, and theory suggests that plant ersity can reduce this variation. While there is strong evidence of ersity effects on temporal variability of productivity, whether this mechanism extends to variability across space remains elusive. Here we determine the relationship between plant ersity and spatial variability of productivity in 83 grasslands, and quantify the effect of experimentally increased spatial heterogeneity in environmental conditions on this relationship. We found that communities with higher plant species richness (alpha and gamma ersity) have lower spatial variability of productivity as reduced abundance of some species can be compensated for by increased abundance of other species. In contrast, high species dissimilarity among local communities (beta ersity) is positively associated with spatial variability of productivity, suggesting that changes in species composition can scale up to affect productivity. Experimentally increased spatial environmental heterogeneity weakens the effect of plant alpha and gamma ersity, and reveals that beta ersity can simultaneously decrease and increase spatial variability of productivity. Our findings unveil the generality of the ersity-stability theory across space, and suggest that reduced local ersity and biotic homogenization can affect the spatial reliability of key ecosystem functions.
Publisher: Wiley
Date: 29-08-2016
DOI: 10.1111/JVS.12450
Publisher: Springer Science and Business Media LLC
Date: 15-07-0001
DOI: 10.1038/NCOMMS8710
Abstract: Exotic species dominate many communities however the functional significance of species’ biogeographic origin remains highly contentious. This debate is fuelled in part by the lack of globally replicated, systematic data assessing the relationship between species provenance, function and response to perturbations. We examined the abundance of native and exotic plant species at 64 grasslands in 13 countries, and at a subset of the sites we experimentally tested native and exotic species responses to two fundamental drivers of invasion, mineral nutrient supplies and vertebrate herbivory. Exotic species are six times more likely to dominate communities than native species. Furthermore, while experimental nutrient addition increases the cover and richness of exotic species, nutrients decrease native ersity and cover. Native and exotic species also differ in their response to vertebrate consumer exclusion. These results suggest that species origin has functional significance, and that eutrophication will lead to increased exotic dominance in grasslands.
Publisher: Wiley
Date: 02-2011
DOI: 10.1111/J.1461-0248.2010.01584.X
Abstract: Many ecosystems worldwide are dominated by introduced plant species, leading to loss of bio ersity and ecosystem function. A common but rarely tested assumption is that these plants are more abundant in introduced vs. native communities, because ecological or evolutionary-based shifts in populations underlie invasion success. Here, data for 26 herbaceous species at 39 sites, within eight countries, revealed that species abundances were similar at native (home) and introduced (away) sites - grass species were generally abundant home and away, while forbs were low in abundance, but more abundant at home. Sites with six or more of these species had similar community abundance hierarchies, suggesting that suites of introduced species are assembling similarly on different continents. Overall, we found that substantial changes to populations are not necessarily a pre-condition for invasion success and that increases in species abundance are unusual. Instead, abundance at home predicts abundance away, a potentially useful additional criterion for biosecurity programmes.
Publisher: Wiley
Date: 28-11-2015
DOI: 10.1111/ELE.12381
Abstract: Aboveground-belowground interactions exert critical controls on the composition and function of terrestrial ecosystems, yet the fundamental relationships between plant ersity and soil microbial ersity remain elusive. Theory predicts predominantly positive associations but tests within single sites have shown variable relationships, and associations between plant and microbial ersity across broad spatial scales remain largely unexplored. We compared the ersity of plant, bacterial, archaeal and fungal communities in one hundred and forty-five 1 m(2) plots across 25 temperate grassland sites from four continents. Across sites, the plant alpha ersity patterns were poorly related to those observed for any soil microbial group. However, plant beta ersity (compositional dissimilarity between sites) was significantly correlated with the beta ersity of bacterial and fungal communities, even after controlling for environmental factors. Thus, across a global range of temperate grasslands, plant ersity can predict patterns in the composition of soil microbial communities, but not patterns in alpha ersity.
Publisher: American Association for the Advancement of Science (AAAS)
Date: 29-01-2016
Abstract: Fraser et al . (Reports, 17 July 2015, p. 302) report a unimodal relationship between productivity and species richness at regional and global scales, which they contrast with the results of Adler et al . (Reports, 23 September 2011, p. 1750). However, both data sets, when analyzed correctly, show clearly and consistently that productivity is a poor predictor of local species richness.
Publisher: American Association for the Advancement of Science (AAAS)
Date: 23-09-2011
Abstract: Standardized s ling from many sites worldwide was used to address an important ecological problem.
Publisher: Cold Spring Harbor Laboratory
Date: 17-04-2023
DOI: 10.1101/2023.04.16.537045
Abstract: Eutrophication usually impacts bio ersity, species composition, and functioning of grassland communities. Whether such effects propagate to influence the stability of these community aspects is unknown. Using standardized experiments across 55 global grasslands, we quantified the effects of nutrient addition on five stability facets (i.e., temporal invariability and resistance during and recovery after dry and wet growing seasons) for three community aspects (i.e., aboveground biomass, community composition, and species richness). Nutrient addition reduced the temporal invariability and resistance of species richness and community composition, but not biomass, during dry and wet growing seasons. Temporal invariability and resistance during, but not recovery after, dry and wet growing seasons were strongly positively correlated in both ambient and eutrophic conditions. This indicates that maintaining and restoring the stability of plant communities requires increasing resistance rather than recovery. Harnessing the complexity of ecological stability provides new insights for grassland ecosystem sustainability in a changing world.
Publisher: Wiley
Date: 2015
DOI: 10.1890/14-1902.1.SM
Publisher: Springer Science and Business Media LLC
Date: 05-05-2023
DOI: 10.1038/S41467-023-37194-5
Abstract: Causal effects of bio ersity on ecosystem functions can be estimated using experimental or observational designs — designs that pose a tradeoff between drawing credible causal inferences from correlations and drawing generalizable inferences. Here, we develop a design that reduces this tradeoff and revisits the question of how plant species ersity affects productivity. Our design leverages longitudinal data from 43 grasslands in 11 countries and approaches borrowed from fields outside of ecology to draw causal inferences from observational data. Contrary to many prior studies, we estimate that increases in plot-level species richness caused productivity to decline: a 10% increase in richness decreased productivity by 2.4%, 95% CI [−4.1, −0.74]. This contradiction stems from two sources. First, prior observational studies incompletely control for confounding factors. Second, most experiments plant fewer rare and non-native species than exist in nature. Although increases in native, dominant species increased productivity, increases in rare and non-native species decreased productivity, making the average effect negative in our study. By reducing the tradeoff between experimental and observational designs, our study demonstrates how observational studies can complement prior ecological experiments and inform future ones.
Publisher: Springer Science and Business Media LLC
Date: 20-01-2021
DOI: 10.1038/S41467-021-20985-Z
Abstract: A Correction to this paper has been published: 0.1038/s41467-021-20985-z.
Location: United States of America
Location: United States of America
Location: United States of America
Start Date: 07-2020
End Date: 12-2024
Amount: $360,000.00
Funder: Australian Research Council
View Funded Activity