ORCID Profile
0000-0003-3935-9814
Current Organisation
The University of Auckland
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Publisher: Elsevier BV
Date: 28-04-2004
Publisher: Wiley
Date: 10-12-2007
DOI: 10.1111/J.1365-3040.2007.01771.X
Abstract: Stomata respond to increasing leaf-to-air vapour pressure difference (LAVPD) (D) by closing. The mechanism by which this occurs is debated. A role for feedback and peristomatal transpiration has been proposed. In this paper, we apply a recent mechanistic model of stomatal behaviour, and compare model and experimental data for the influence of increasing D on stomatal conductance. We manipulated cuticular conductance (g(c)) by three independent methods. First, we increased g(c) by using a solvent mixture applied to both leaf surfaces prior to determining stomatal responses to D second, we increased g(c) by increasing leaf temperature at constant D and third, we coated a small area of leaf with a light oil to decrease g(c). In all three experiments, experimental data and model outputs showed very close agreement. We conclude, from the close agreement between model and experimental data and the fact that manipulations of g(c), and hence cuticular transpiration, influenced g(s) in ways consistent with a feedback mechanism, that feedback is central in determining stomatal responses to D.
Publisher: Wiley
Date: 13-04-2013
DOI: 10.1002/HYP.9280
Publisher: Walter de Gruyter GmbH
Date: 2005
DOI: 10.1515/BOT.2005.031
Publisher: Elsevier BV
Date: 04-2004
Publisher: Copernicus GmbH
Date: 09-10-2020
Abstract: Abstract. Plant transpiration links physiological responses of vegetation to water supply and demand with hydrological, energy and carbon budgets at the land-atmosphere interface. However, despite being the main land evaporative flux at the global scale, transpiration and its response to environmental drivers are currently not well constrained by observations. Here we introduce the first global compilation of whole-plant transpiration data from sap flow measurements (SAPFLUXNET, sapfluxnet.creaf.cat/). We harmonised and quality-controlled in idual datasets supplied by contributors worldwide in a semi-automatic data workflow implemented in the R programming language. Datasets include sub-daily time series of sap flow and hydrometeorological drivers for one or more growing seasons, as well as metadata on the stand characteristics, plant attributes and technical details of the measurements. SAPFLUXNET contains 202 globally distributed datasets with sap flow time series for 2714 plants, mostly trees, of 174 species. SAPFLUXNET has a broad bioclimatic coverage, with woodland/shrubland and temperate forest biomes especially well-represented (80 % of the datasets). The measurements cover a wide variety of stand structural characteristics and plant sizes. The datasets encompass the period between 1995 and 2018, with 50 % of the datasets being at least 3 years long. Accompanying radiation and vapour pressure deficit data are available for most of the datasets, while on-site soil water content is available for 56 % of the datasets. Many datasets contain data for species that make up 90 % or more of the total stand basal area, allowing the estimation of stand transpiration in erse ecological settings. SAPFLUXNET adds to existing plant trait datasets, ecosystem flux networks and remote sensing products to help increase our understanding of plant water use, plant responses to drought and ecohydrological processes. SAPFLUXNET version 0.1.5 is freely available from the Zenodo repository ( 0.5281/zenodo.3971689, Poyatos et al., 2020a). The sapfluxnetr R package, designed to access, visualise and process SAPFLUXNET data is available from CRAN.
Publisher: Elsevier BV
Date: 05-2003
Publisher: Springer Science and Business Media LLC
Date: 06-09-2007
Publisher: Informa UK Limited
Date: 10-2007
Publisher: Elsevier BV
Date: 03-2011
Publisher: Elsevier BV
Date: 2005
Publisher: Elsevier BV
Date: 11-2003
Publisher: Copernicus GmbH
Date: 09-10-2020
Publisher: Copernicus GmbH
Date: 14-06-2021
DOI: 10.5194/ESSD-13-2607-2021
Abstract: Abstract. Plant transpiration links physiological responses of vegetation to water supply and demand with hydrological, energy, and carbon budgets at the land–atmosphere interface. However, despite being the main land evaporative flux at the global scale, transpiration and its response to environmental drivers are currently not well constrained by observations. Here we introduce the first global compilation of whole-plant transpiration data from sap flow measurements (SAPFLUXNET, sapfluxnet.creaf.cat/, last access: 8 June 2021). We harmonized and quality-controlled in idual datasets supplied by contributors worldwide in a semi-automatic data workflow implemented in the R programming language. Datasets include sub-daily time series of sap flow and hydrometeorological drivers for one or more growing seasons, as well as metadata on the stand characteristics, plant attributes, and technical details of the measurements. SAPFLUXNET contains 202 globally distributed datasets with sap flow time series for 2714 plants, mostly trees, of 174 species. SAPFLUXNET has a broad bioclimatic coverage, with woodland/shrubland and temperate forest biomes especially well represented (80 % of the datasets). The measurements cover a wide variety of stand structural characteristics and plant sizes. The datasets encompass the period between 1995 and 2018, with 50 % of the datasets being at least 3 years long. Accompanying radiation and vapour pressure deficit data are available for most of the datasets, while on-site soil water content is available for 56 % of the datasets. Many datasets contain data for species that make up 90 % or more of the total stand basal area, allowing the estimation of stand transpiration in erse ecological settings. SAPFLUXNET adds to existing plant trait datasets, ecosystem flux networks, and remote sensing products to help increase our understanding of plant water use, plant responses to drought, and ecohydrological processes. SAPFLUXNET version 0.1.5 is freely available from the Zenodo repository (0.5281/zenodo.3971689 Poyatos et al., 2020a). The “sapfluxnetr” R package – designed to access, visualize, and process SAPFLUXNET data – is available from CRAN.
Publisher: Wiley
Date: 05-2011
DOI: 10.1002/ECO.138
Publisher: Informa UK Limited
Date: 13-10-2017
Publisher: Oxford University Press (OUP)
Date: 21-06-2010
Abstract: Nocturnal fluxes may be a significant factor in the annual water budget of forested ecosystems. Here, we assessed sap flow in two co-occurring evergreen species (Eucalyptus parramattensis and Angophora bakeri) in a temperate woodland for 2 years in order to quantify the magnitude of seasonal nocturnal sap flow (E(n)) under different environmental conditions. The two species showed different diurnal water relations, demonstrated by different diurnal curves of stomatal conductance, sap flow and leaf water potential. The relative influence of several microclimatic variables, including wind speed (U), vapour pressure deficit (D), the product of U and D (UD) and soil moisture content, were quantified. D exerted the strongest influence on E(n) (r² = 0.59-0.86), soil moisture content influenced E(n) when D was constant, but U and UD did not generally influence E(n). In both species, cuticular conductance (G(c)) was a small proportion of total leaf conductance (G(s)) and was not a major pathway for E(n). We found that E(n) was primarily a function of transpiration from the canopy rather than refilling of stem storage, with canopy transpiration accounting for 50-70% of nocturnal flows. Mean E(n) was 6-8% of the 24-h flux across seasons (spring, summer and winter), but was up to 19% of the 24-h flux on some days in both species. Despite different daytime strategies in water use of the two species, both species demonstrated low night-time water loss, suggesting similar controls on water loss at night. In order to account for the impact of E(n) on pre-dawn leaf water potential arising from the influence of disequilibria between root zone and leaf water potential, we also developed a simple model to more accurately predict soil water potential (ψ(s)).
Publisher: CSIRO Publishing
Date: 2004
DOI: 10.1071/FP03194
Abstract: Convergence in leaf traits across biomes demonstrates generality in plant functioning. Relationships between hydraulic architecture and photosynthesis are less well studied. We investigated convergence in minimum leaf water potential (Ψmin), conductivity per sapwood area (ks), Huber value (Hv) and xylem embolism and photosynthesis in four habitats across two seasons (summer and winter) in the Sydney region in heathland, woodland (ridge-top), woodland (below-ridge) and mangrove. Seasonality strongly influenced all parameters in all habitats. Winter Ψmin values were lower than those for summer in the heathland and both woodland habitats but summer Ψmin values were lower than those for winter in the mangrove. Summer ks values were higher than winter values in all habitats, while Hv was higher in winter than summer for all habitats. Loss of conductance due to xylem embolism was larger in summer than winter in eight of 11 species. We also investigated relationships between the hydraulic parameters across habitats. There was a strong, significant inverse correlation between log-transformed Hv and log-transformed ks, which held across the seasons. There were significant inverse correlations between Ψmin and xylem embolism, which held within seasons but not across seasons. We found a strong, significant positive correlation between ks and Ψmin also within seasons but not across seasons and a significant negative correlation between xylem embolism and ks for winter but only a weak negative correlation between xylem embolism and ks for summer. We believe the seasonal patterns and relationships in hydraulic architecture and water relations are driven by the cost of efficient sapwood. This is demonstrated by the negative correlation between photosynthetic rate and ks in winter.
Publisher: Springer Science and Business Media LLC
Date: 17-06-2009
Publisher: Elsevier BV
Date: 09-2002
DOI: 10.1016/S0025-326X(01)00300-9
Abstract: This in situ study used photosynthetic activity (measured as chlorophyll a fluorescence) and photosynthetic pigment concentrations to assess the effect of copper, cadmium, lead and zinc on the seagrass Zostera capricorni. Custom-made portable in situ exposure (PIE) chambers were developed so seagrasses could be dosed within the meadow. Z capricorni was exposed to 0.1 and I mg l(-1) of metal solutions for 10 h. During this time and for the subsequent four-day recovery period, the effective quantum yield of photosystem II (PS II) (deltaF/Fm') was measured. While the results were variable, copper and zinc exposed s les had a depressed deltaF/Fm' during the exposure period. S les exposed to zinc recovered to pre-exposure levels but those exposed to copper did not. Cadmium and lead did not impact on the chlorophyll a fluorescence and the chlorophyll pigment data supported these findings. This study presents an innovative new application of chlorophyll a fluorescence stress assessment.
Publisher: Elsevier BV
Date: 06-2009
Publisher: Wiley
Date: 2009
DOI: 10.1002/ECO.63
Publisher: Informa UK Limited
Date: 19-10-2023
Publisher: Elsevier BV
Date: 2008
Publisher: Wiley
Date: 30-04-2010
DOI: 10.1002/HYP.7570
Publisher: Wiley
Date: 15-04-2011
Publisher: Springer Netherlands
Date: 2006
Publisher: Informa UK Limited
Date: 17-08-2023
Publisher: CSIRO Publishing
Date: 2008
DOI: 10.1071/FP08114
Abstract: Daily and seasonal patterns of tree water use were measured for the two dominant tree species, Angophora bakeri E.C.Hall (narrow-leaved apple) and Eucalyptus sclerophylla (Blakely) L.A.S. Johnson & Blaxell (scribbly gum), in a temperate, open, evergreen woodland using sap flow sensors, along with information about soil, leaf, tree and micro-climatological variables. The aims of this work were to: (a) validate a soil–plant–atmosphere (SPA) model for the specific site (b) determine the total depth from which water uptake must occur to achieve the observed rates of tree sap flow (c) examine whether the water content of the upper soil profile was a significant determinant of daily rates of sap flow and (d) examine the sensitivity of sap flow to several biotic factors. It was found that: (a) the SPA model was able to accurately replicate the hourly, daily and seasonal patterns of sap flow (b) water uptake must have occurred from depths of up to 3 m (c) sap flow was independent of the water content of the top 80 cm of the soil profile and (d) sap flow was very sensitive to the leaf area of the stand, whole tree hydraulic conductance and the critical water potential of the leaves, but insensitive to stem capacitance and increases in root biomass. These results are important to future studies of the regulation of vegetation water use, landscape-scale behaviour of vegetation, and to water resource managers, because they allow testing of large-scale management options without the need for large-scale manipulations of vegetation cover.
Publisher: Wiley
Date: 12-2015
DOI: 10.1890/150229
Publisher: American Association for the Advancement of Science (AAAS)
Date: 28-09-2022
Abstract: Deadwood is a large global carbon store with its store size partially determined by biotic decay. Microbial wood decay rates are known to respond to changing temperature and precipitation. Termites are also important decomposers in the tropics but are less well studied. An understanding of their climate sensitivities is needed to estimate climate change effects on wood carbon pools. Using data from 133 sites spanning six continents, we found that termite wood discovery and consumption were highly sensitive to temperature (with decay increasing .8 times per 10°C increase in temperature)—even more so than microbes. Termite decay effects were greatest in tropical seasonal forests, tropical savannas, and subtropical deserts. With tropicalization (i.e., warming shifts to tropical climates), termite wood decay will likely increase as termites access more of Earth’s surface.
Publisher: Springer Science and Business Media LLC
Date: 03-08-2007
Publisher: CSIRO Publishing
Date: 2005
DOI: 10.1071/BT04119
Abstract: This review aims to discuss ecosystem services, provide illustrative case studies at catchment and local scales and present future research needs. This review discusses the following: (1) Ecosystem services (ES) are those goods and services that are provided by or are attributes of ecosystems that benefit humans. Ex les of ES include the timber derived from a forest, the prevention of soil and coastal erosion by vegetation and the amelioration of dryland salinity through prevention of rises in the water table by trees. The provision of ES globally is in decline because of a lack of awareness of the total economic value of ES in the public, policy and political fora. (2) Providing a scientific understanding of the relationships among ecosystem structure, function and provision of ES, plus determining actual economic value of ES, are the central challenges to environmental scientists (including triple-bottom-line economists). (3) Some ES are widely dispersed throughout many different ecosystems. Carbon accumulation in trees and the contribution of bio ersity to ES provision are two ex les of highly dispersed attributes common to many ecosystems. In contrast, other ES are best considered within the context of a single defined ecosystem (although they may occur in other ecosystems too). Mangroves as ‘nursery’ sites for juvenile fish is one ex le. (4) Ex les of catchment-scale and local-scale provision of ES are discussed, along with future research issues for the nexus between ES and environmental sciences.
Publisher: Elsevier BV
Date: 06-2016
Publisher: CSIRO Publishing
Date: 2009
DOI: 10.1071/FP08114_CO
Publisher: CSIRO Publishing
Date: 2008
DOI: 10.1071/BT08079
Abstract: Trends in global soil moisture are needed to inform models of soil–plant–atmosphere interactions. Predawn leaf water potential (Ψpd), a surrogate for soil moisture and an index of plant water stress, has been routinely collected in Australian forests, woodlands and savannas, but the associated leaf area index (LAI) has seldom been available to enable the preparation of a Ψpd on LAI relationship. Following an analysis of Ψpd and MODIS LAI data from Australian forests, woodlands and savannas, we identified patterns in Ψpd which provide an understanding of the role of soil-moisture status in controlling LAI. In the savanna of northern Australia, the MODIS LAI product had a basal value of 0.96 during the dry season as compared with a mean value of 2.5 for the wet season. The dry season value is equivalent to the LAI of the tree component and corresponds with ground-truthed LAI. Ψpd is lowest (more negative) during the height of the dry season (late October) at −2.5 MPa, and highest (−0.1 MPa) during the wet season (early March). We present two models which predict Ψpd from the MODIS LAI product. These may be useful surrogates for studying trends in soil moisture in highly seasonal climates and may contribute to climate change research.
Publisher: CSIRO Publishing
Date: 2004
DOI: 10.1071/BT03123
Abstract: Seasonal comparisons of leaf water potential, root biomass, hydraulic architecture, xylem embolism and xylem dimensions were made for eight woody species in four erse habitats (mangroves, coastal heathland, ridge-top woodland and river-flat woodland). In most comparisons, pre-dawn and minimum leaf water potentials were lower in winter than in summer, a result attributed to lower rainfall and a smaller root biomass in winter than in summer. Branch hydraulic conductivities (per unit transverse area, sapwood area or leaf area) were generally larger in summer than in winter across all species in all habitats. An inverse relationship between Huber value and conductivity was observed across all four habitats. Increased solar radiation and evaporative demand in the summer was associated with an increased percentage loss of xylem conductance arising from embolism, compared with winter. These results are discussed in the context of patterns and relationships among water relations, microclimate and hydraulic architecture.
No related grants have been discovered for Cate Macinnis-Ng.