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Parkinson’s disease is the second most common neurological disorder after dementia in Australia (Deloitte, 2015). The complexities of caring for a person with Parkinson’s disease highlights the need for Parkinson’s disease and movement disorder nurse specialists (PDMDNS) (Bramble, Carroll, & Rossiter, 2018). The Australasian Neuroscience Nurses Association’s (ANNA) Movement Disorder Chapter (MDC) aims to implement an annual demographic survey over the next 10 years to capture the characteristics of the PDMDNS cohort, identify gaps in service provision and aid the workforce planning through useful and influential data. The results of this survey were able to highlight the geographical areas that are underserviced, the diverse employment opportunities available and the issues around financial funding for PDMDNS positions in Australia.

This study aimed to investigate the cost-effectiveness of preimplantation genetic diagnosis (PGD) for the reproductive choices of patients with heritable retinoblastoma. The study modelled the costs of three cycles of in-vitro fertilization (IVF) and PGD across all uptake rates of PGD, number of children affected with retinoblastoma at each uptake rate and the estimated quality-adjusted life years (QALYs) gained. Cost-effectiveness analysis was conducted from the Australian public healthcare perspective. The intervention was the use of three cycles (one fresh and two frozen) of IVF and PGD with the aim of live births unaffected by the retinoblastoma phenotype. Compared with the standard care pathway (i.e. natural pregnancy), IVF and PGD resulted in a cost-saving to 18 years of age of AUD$2,747,294 for a base case of 100 couples with an uptake rate of 50%. IVF and PGD resulted in fewer affected (n = 56) and unaffected (n = 78) live births compared with standard care (71 affected and 83 unaffected live births), and an additional 0.03 QALYs per live birth. This modelling suggests that the use of IVF and PGD to achieve an unaffected child for patients with heritable retinoblastoma resulted in an overall cost-saving. There was an increase in QALYs per baby across all uptake rates. However, in total, fewer babies were born following the IVF and PGD pathway.

© 2019 The Authors. Ecology and Evolution published by John Wiley & Sons Ltd. Drought-induced tree mortality is expected to increase in future climates with the potential for significant consequences to global carbon, water, and energy cycles. Xylem embolism can accumulate to lethal levels during drought, but species that can refill embolized xylem and recover hydraulic function may be able to avoid mortality. Yet the potential controls of embolism recovery, including cross-biome patterns and plant traits such as nonstructural carbohydrates (NSCs), hydraulic traits, and nocturnal stomatal conductance, are unknown. We exposed eight plant species, originating from mesic (tropical and temperate) and semi-arid environments, to drought under ambient and elevated CO 2 levels, and assessed recovery from embolism following rewatering. We found a positive association between xylem recovery and NSCs, and, surprisingly, a positive relationship between xylem recovery and nocturnal stomatal conductance. Arid-zone species exhibited greater embolism recovery than mesic zone species. Our results indicate that nighttime stomatal conductance often assumed to be a wasteful use of water, may in fact be a key part of plant drought responses, and contribute to drought survival. Findings suggested distinct biome-specific responses that partially depended on species climate-of-origin precipitation or aridity index, which allowed some species to recover from xylem embolism. These findings provide improved understanding required to predict the response of diverse plant communities to drought. Our results provide a framework for predicting future vegetation shifts in response to climate change.

Xylem sap velocity of two dominant tree species, Eucalyptus crebra F. Muell. and Callitris glaucophylla J. Thompson & L.A.S. Johnson, in a native remnant forest of eastern Australia was measured in winter and summer during a prolonged (> 12 months) and extensive drought. The influence of vapour pressure deficit (VPD) and solar radiation levels on the velocity of sap was determined. Pronounced hysteresis in sap velocity was observed in both species as a function of VPD and solar radiation. However, the rotation of the hysteresis curve was clockwise for the response of sap velocity to VPD but anti-clockwise in the response of sap velocity to radiation levels. A possible reason for this difference is discussed.The degree of hysteresis (area bounded by the curve) was larger for the VPD response than the response to solar radiation and also varied with season. A simple linear model was able to predict sap velocity from knowledge of VPD and solar radiation in winter and summer. The consistent presence of hysteresis in the response to sap velocity to VPD and solar radiation suggests that large temporal and spatial models of vegetation water use may require some provision for the different responses of sap velocity, and hence water use, to VPD and solar radiation, between morning and afternoon and between seasons.

Objective Childhood cancer can have short- and long-term impacts on parents' finances and employment. It is important to understand how families adjust to the financial and employment changes caused by childhood cancer, the ongoing impacts after treatment completion, and which families need more targeted support. Qualitative research is necessary to facilitate an in-depth understanding of the employment and financial impacts on families and to capture parents' complex and nuanced experiences and perspectives. Methods We interviewed 56 parents of childhood cancer survivors (M = 2.13 years after treatment completion; 89% mothers) using the vocational and financial impact section of the Psychosocial Adjustment to Illness Scale-Carer Interview Form. We analyzed interviews using content analysis. Results Parents reported multiple sources of financial toxicity including travel to and from the hospital and needing to reduce their working hours during their child's cancer treatment. Workplace flexibility was an important factor to protect against unwanted vocational changes. After treatment completion, families living in low socioeconomic areas commonly reported ongoing financial difficulties. Mothers, particularly those who were on maternity leave when their child was diagnosed with cancer, reported ongoing employment impacts including unemployment. Conclusions Clinical staff including social workers could more consistently assess families' financial distress and refer to professional services who can offer guidance for financial decision-making as standard care. Flexible workplace agreements appear important for parents of children with cancer. Our findings can assist organizations to understand that cancer-related disruptions are likely to continue after treatment completion, and therefore should offer benefits to parents where possible.

This study models the economic costs of informal caring for people with back pain, using a microsimulation model, Care&WorkMOD, from 2015 to 2030. Care&WorkMOD was based on 3 national Australian Surveys of Disability, Ageing and Carers (2003, 2009, 2012) data sets for individuals aged 15 to 64 years. Estimated national income loss due to caring for people with back pain was AU$258 million in 2015, increasing to $398 million in 2030 (54% increase). Lost income tax revenue to the Australian government due to informal care of people with back pain was estimated to be AU$78 million in 2015, increasing to AU$118 million in 2030 (50% increase), and additional welfare payments were estimated to rise from $132 million in 2015 to AU$180 in 2030 (36% increase). Larger growth in lost income, compared with the increase in welfare payments, means that there would be an increasing income gap between those out of the labour force providing informal care and noncarers who are in the labour force, leading to increased inequality. Informal carers are defined as providers of informal, unpaid assistance to someone with a health condition, for at least 6 months. Informal carers of people with back pain who are out of the labour force incur substantial economic costs. Furthermore, back pain is a large economic burden on national governments. Policies addressing back pain prevention and treatment, and supporting carers, may offset government welfare expenditure, while improving the socioeconomic well-being of carers and patients.

The terrestrial biosphere regulates climate through carbon, water, and energy exchanges with the atmosphere. Land-surface models estimate plant transpiration, which is actively regulated by stomatal pores, and provide projections essential for understanding Earth's carbon and water resources. Empirical evidence from 204 species suggests that significant amounts of water are lost through leaves at night, though land-surface models typically reduce stomatal conductance to nearly zero at night. Here, we test the sensitivity of carbon and water budgets in a global land-surface model, the Community Land Model (CLM) version 4.5, to three different methods of incorporating observed nighttime stomatal conductance values. We find that our modifications increase transpiration by up to 5 % globally, reduce modeled available soil moisture by up to 50 % in semi-arid regions, and increase the importance of the land surface in modulating energy fluxes. Carbon gain declines by up to ∼ 4 % globally and > 25 % in semi-arid regions. We advocate for realistic constraints of minimum stomatal conductance in future climate simulations, and widespread field observations to improve parameterizations.

This review discusses the evolution of microsimulation models in health over the past three decades. We focus on three aspects of health microsimulation. First, we describe the origins and applications of health microsimulation, including how early research challenged early methodologies and led to the development of more rigorous models. We describe limitations of early means-based models and how more detailed methods, which are based on health-specific input data, overcame many of the early data shortfalls and assumptions. Second, we discuss the global expansion of applications of microsimulation to health over the last ten years. Many health microsimulation models have focussed on health expenditure, the ageing population, diabetes, mortality modelling, and spatial models. Health models over the past few decades have expanded to many countries including Canada, Africa, the United States, the UK, Sweden, the Netherlands, New Zealand and Australia. Finally, we describe future developments, including emerging research fields for microsimulation and health and how the early development of health microsimulation models provides important lessons for emerging applications. These include the emerging field of genomics and precision medicine, and the diagnosis and treatment of childhood cancers and rare diseases. We suggest research directions, including the need for good data to avoid model errors, and highlight some pitfalls to avoid.

We developed a microsimulation model, Care & WorkMOD, to estimate the economic costs of early exit from the labour force, both for informal carers and the government, from 2015 to 2030. In this paper, we describe the methods used to create the model Care & WorkMOD, and the sources of data and model assumptions. Care & WorkMOD is based on the unit record data of people aged 15-64 years in the three Australian Bureau of Statistics (ABS) Surveys of Disability, Ageing and Carers (SDAC) 2003, 2009 and 2012. Population and the labour force projections from the 2015 Intergenerational Report and the outputs of an Australian microsimulation model APPSIM were used for the static aging of the base data to every five years from 2015 to 2030. The 2015 output dataset of another microsimulation model STINMOD was linked with Care & WorkMOD base data using synthetic matching. The matching process has added data on further economic variables from STINMOD into Care & WorkMOD, which are not available in SDACs. Economic data were indexed based on long-term trends on economic variables to capture the projected economic growth from 2015 to 2030. Care & WorkMOD can provide the long-term estimates of the lost labour productivity due to informal caring responsibilities and the related economic burden both at the individual and national level, and has the potential to "fill the gaps" in the current body of evidence on the costs of chronic diseases, particularly related to informal carers.

BackgroundIntellectual disability and autism spectrum disorder (ASD) influence the interactions of a person with their environment and generate economic and socioeconomic costs for the person, their family and society.AimsTo estimate costs of lost workforce participation due to informal caring for people with intellectual disability or autism spectrum disorders by estimating lost income to individuals, lost taxation payments to federal government and increased welfare payments.MethodWe used a microsimulation model based on the Australian Bureau of Statistics' Surveys of Disability, Ageing and Carers (population surveys of people aged 15–64), and projected costs of caring from 2015 in 5-year intervals to 2030.ResultsThe model estimated that informal carers of people with intellectual disability and/or ASD in Australia had aggregated lost income of AU$310 million, lost taxation of AU$100 million and increased welfare payments of AU$204 million in 2015. These are projected to increase to AU$432 million, AU$129 million and AU$254 million for income, taxation, and welfare respectively by 2030. The income gap of carers for people with intellectual disability and/or ASD is estimated to increase by 2030, meaning more financial stress for carers.ConclusionsInformal carers of people with intellectual disability and/or ASD experience significant loss of income, leading to increased welfare payments and reduced taxation revenue for governments; these are all projected to increase. Strategic policies supporting informal carers wishing to return to work could improve the financial and psychological impact of having a family member with intellectual disability and/or ASD.Declaration of interestNone.

Ecophysiological studies of remnant woodlands in saline environments are scarce. We investigated seasonal fluctuations in soil water and salinity together with leaf and branch traits (area-based maximum assimilation (Amax), foliar nitrogen, specific leaf area (SLA) and Huber value (Hv)) and sap velocities of Eucalyptus macrorhyncha at four semi-arid sites in south-eastern Australia. Summer and winter soil salinities (10 cm depth) were 15–35 dS m−1 and 8–10 dS m−1 respectively. Gravimetric soil water content in the upper 20 cm was 2–5% in summer and 7–23% in winter, resulting in a significant inverse correlation between soil water and soil salinity. We found significant correlations between soil conditions and plant traits and function across seasons. Soil water content was significantly correlated with foliar N, SLA, Hv and maximum sap velocity while soil salinity was significantly correlated with Amax, Hv and maximum sap velocity. Correlations indicate co-variation of soil conditions and plant physiology in response to environmental conditions such as solar radiation and vapour pressure deficit (D). E. macrorhyncha tolerates the dual stresses of high salinity and low soil water during summer. While the plants appeared unhealthy, our data show that remnant vegetation can remain functional even in close proximity to saline scalds.

© 2018, The Ecological Society of Japan. Understanding which species are able to recover from drought, under what conditions, and the mechanistic processes involved, will facilitate predictions of plant mortality in response to global change. In response to drought, some species die because of embolism-induced hydraulic failure, whilst others are able to avoid mortality and recover, following rehydration. Several tree species have evolved strategies to avoid embolism, whereas others tolerate high embolism rates but can recover their hydraulic functioning upon drought relief. Here, we focus on structures and processes that might allow some plants to recover from drought stress via embolism reversal. We provide insights into how embolism repair may have evolved, anatomical and physiological features that facilitate this process, and describe possible trade-offs and related costs. Recent controversies on methods used for estimating embolism formation/repair are also discussed, providing some methodological suggestions. Although controversial, embolism repair processes are apparently based on the activity of phloem and ray/axial parenchyma. The mechanism is energetically demanding, and the costs to plants include metabolism and transport of soluble sugars, water and inorganic ions. We propose that embolism repair should be considered as a possible component of a ‘hydraulic efficiency-safety’ spectrum. We also advance a framework for vegetation models, describing how vulnerability curves may change in hydrodynamic model formulations for plants that recover from embolism.

Relatively anisohydric species are predicted to be more predisposed to hydraulic failure than relatively isohydric species, as they operate with narrower hydraulic safety margins. We subjected co-occurring anisohydric Juniperus monosperma and isohydric Pinus edulis trees to warming, reduced precipitation, or both, and measured their gas exchange and hydraulic responses. We found that reductions in stomatal conductance and assimilation by heat and drought were more frequent during relatively moist periods, but these effects were not exacerbated in the combined heat and drought treatment. Counter to expectations, both species exhibited similar gs temporal dynamics in response to drought. Further, whereas P. edulis exhibited chronic embolism, J. monosperma showed very little embolism due to its conservative stomatal regulation and maintenance of xylem water potential above the embolism entry point. This tight stomatal control and low levels of embolism experienced by juniper refuted the notion that very low water potentials during drought are associated with loose stomatal control and with the hypothesis that anisohydric species are more prone to hydraulic failure than isohydric species. Because direct association of stomatal behaviour with embolism resistance can be misleading, we advocate consideration of stomatal behaviour relative to embolism resistance for classifying species drought response strategies.

Climate change is expected to drive increased tree mortality through drought, heat stress, and insect attacks, with manifold impacts on forest ecosystems. Yet, climate-induced tree mortality and biotic disturbance agents are largely absent from process-based ecosystem models. Using data sets from the western USA and associated studies, we present a framework for determining the relative contribution of drought stress, insect attack, and their interactions, which is critical for modeling mortality in future climates. We outline a simple approach that identifies the mechanisms associated with two guilds of insects - bark beetles and defoliators - which are responsible for substantial tree mortality. We then discuss cross-biome patterns of insect-driven tree mortality and draw upon available evidence contrasting the prevalence of insect outbreaks in temperate and tropical regions. We conclude with an overview of tools and promising avenues to address major challenges. Ultimately, a multitrophic approach that captures tree physiology, insect populations, and tree-insect interactions will better inform projections of forest ecosystem responses to climate change.

Broad-scale forest die-off associated with drought and heat has now been reported from every forested continent, posing a global-scale challenge to forest management. Climate-driven die-off is frequently compounded with other drivers of tree mortality, such as altered land use, wildfire, and invasive species, making forest management increasingly complex. Facing similar challenges, rangeland managers have widely adopted the approach of developing conceptual models that identify key ecosystem states and major types of transitions between those states, known as "state-and-transition models" (S&T models). Using expert opinion and available research, the development of such conceptual S&T models has proven useful in anticipating ecosystem changes and identifying management actions to undertake or to avoid. In cases where detailed data are available, S&T models can be developed into probabilistic predictions, but even where data are insufficient to predict transition probabilities, conceptual S&T models can provide valuable insights for managing a given ecosystem and for comparing and contrasting different ecosystem dynamics. We assembled a synthesis of 14 forest die-off case studies from around the globe, each with sufficient information to infer impacts on forest dynamics and to inform management options following a forest die-off event. For each, we developed a conceptual S&T model to identify alternative ecosystem states, pathways of ecosystem change, and points where management interventions have been, or may be, successful in arresting or reversing undesirable changes. We found that our diverse set of mortality case studies fit into three broad classes of ecosystem trajectories: (1) single-state transition shifts, (2) ecological cascading responses and feedbacks, and (3) complex dynamics where multiple interactions, mortality drivers, and impacts create a range of possible state transition responses. We integrate monitoring and management goals in a framework aimed to facilitate development of conceptual S&T models for other forest die-off events. Our results highlight that although forest die-off events across the globe encompass many different underlying drivers and pathways of ecosystem change, there are commonalities in opportunities for successful management intervention. Fil: Cobb, Richard C.. California State Polytechnic University. Natural Resources Management & Environmental Sciences Department; Estados Unidos Fil: Ruthrof, Katinka X.. Botanic Gardens And Parks Authority; Australia. Murdoch University. School of Veterinary and Life Sciences; Australia Fil: Breshears, David D.. University of Arizona. School of Natural Resources and the Environment, and Department of Ecology and Evolutionary Biology; Estados Unidos Fil: Lloret, Francisco. Consejo Superior de Investigaciones Científicas. Centre de Recerca Ecológica I Aplicacions Forestals; España Fil: Aakala, Tuomas. University of Helsinki. Department of Forest Sciences; Finlandia Fil: Adams, Henry D.. Oklahoma State University. Department of Plant Biology, Ecology, and Evolution; Estados Unidos Fil: Anderegg, William R. L.. University of Utah. Department of Biology; Estados Unidos Fil: Ewers, Brent E.. University of Wyoming. Department of Botany and Program in Ecology and Wyoming EPSCoR; Estados Unidos Fil: Galiano, Lucía. Lliçà d’Amunt; España Fil: Grcunzweig, Jose M.. The Hebrew University of Jerusalem. Faculty of Agriculture, Food and Environment; Israel Fil: Hartmann, Henrik. Max‐Planck Institute for Biogeochemistry. Department of Biogeochemical Processes; Alemania Fil: Huang, Cho-ying. National Taiwan University; República de China. National Taiwan University. Department of Geography; República de China Fil: Klein, Tamir. Weizmann Institute Of Science Israel; Israel Fil: Kunert, Norbert. University of Freiburg; Alemania Fil: Kitzberger, Thomas. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina Fil: Landhäusser, Simon M.. University of Alberta. Department of Renewable Resources; Canadá Fil: Levick, Shaun. Max‐Planck Institute for Biogeochemistry. Department of Biogeochemical Processes; Alemania. Charles Darwin University. Research Institute for the Environment and Livelihoods; Australia Fil: Preisler, Yakir. The Hebrew University of Jerusalem. Robert H. Smith Faculty of Agriculture, Food and Environment; Israel. Weizmann Institute of Science. Department of Earth and Planetary Science; Israel Fil: Suarez, Maria Laura. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina Fil: Trotsiuk, Volodymyr. Czech University of Life Sciences Prague. Faculty of Forestry and Wood Sciences; República Checa Fil: Zeppel, Melanie J. B.. University of Sydney. Faculty of Pharmacy; Australia

© The Author 2017. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com. Water resources and their management present social, economic and environmental challenges, with demand for human consumptive, industrial and environmental uses increasing globally. However, environmental water requirements, that is, the allocation of water to the maintenance of ecosystem health, are often neglected or poorly quantified. Further, transpiration by trees is commonly a major determinant of the hydrological balance of woodlands but recognition of the role of groundwater in hydrological balances of woodlands remains inadequate, particularly in mesic climates. In this study, we measured rates of tree water-use and sapwood 13C isotopic ratio in a mesic, temperate Eucalypt woodland along a naturally occurring gradient of depth-to-groundwater (DGW), to examine daily, seasonal and annual patterns of transpiration. We found that: (i) the maximum rate of stand transpiration was observed at the second shallowest site (4.3 m) rather than the shallowest (2.4 m); (ii) as DGW increased from 4.3 to 37.5 m, stand transpiration declined; (iii) the smallest rate of stand transpiration was observed at the deepest (37.5 m) site; (iv) intrinsic water-use efficiency was smallest at the two intermediate DGW sites as reflected in the Δ13C of the most recently formed sapwood and largest at the deepest and shallowest DGW sites, reflecting the imposition of flooding at the shallowest site and the inaccessibility of groundwater at the deepest site; and (v) there was no evidence of convergence in rates of water-use for co-occurring species at any site. We conclude that even in mesic environments groundwater can be utilized by trees. We further conclude that these forests are facultatively groundwater-dependent when groundwater depth is

[Departement_IRSTEA]Territoires [TR1_IRSTEA]SEDYVIN; International audience; Widespread tree mortality associated with drought has been observed on all forested continents and global change is expected to exacerbate vegetation vulnerability. Forest mortality has implications for future biosphere–atmosphere interactions of carbon, water and energy balance, and is poorly represented in dynamic vegetation models. Reducing uncertainty requires improved mortality projections founded on robust physiological processes. However, the proposed mechanisms of drought-induced mortality, including hydraulic failure and carbon starvation, are unresolved. A growing number of empirical studies have investigated these mechanisms, but data have not been consistently analysed across species and biomes using a standardized physiological framework. Here, we show that xylem hydraulic failure was ubiquitous across multiple tree taxa at drought-induced mortality. All species assessed had 60% or higher loss of xylem hydraulic conductivity, consistent with proposed theoretical and modelled survival thresholds. We found diverse responses in non-structural carbohydrate reserves at mortality, indicating that evidence supporting carbon starvation was not universal. Reduced non-structural carbohydrates were more common for gymnosperms than angiosperms, associated with xylem hydraulic vulnerability, and may have a role in reducing hydraulic function. Our finding that hydraulic failure at drought-induced mortality was persistent across species indicates that substantial improvement in vegetation modelling can be achieved using thresholds in hydraulic function

Total daily water use is a key factor influencing the growth of many terrestrial plants, and reflects both day-time and nocturnal water fluxes. However, while nocturnal sap flow (En) and stomatal conductance (gs,n) have been reported across a range of species, ecosystems and microclimatic conditions, the regulation of these fluxes remains poorly understood. Here, we present a framework describing the role of abiotic and biotic factors in regulating En and gs,n highlighting recent developments in this field. Across ecosystems, En and gs,n generally increased with increasing soil water content and vapor pressure deficit, but the interactive effects of these factors and the potential roles of wind speed and other abiotic factors remain unclear. On average, gs,n and En are higher in broad-leaved compared with needle-leaved plants, in C3 compared with C4 plants, and in tropical compared with temperate species. We discuss the impacts of leaf age, elevated [CO2] and refilling of capacitance on night-time water loss, and how nocturnal gs,n may be included in vegetation models. Younger leaves may have higher gs,n than older leaves. Embolism refilling and recharge of capacitance may affect sap flow such that total plant water loss at night may be less than estimated solely from En measurements. Our estimates of gs,n for typical plant functional types, based on the published literature, suggest that nocturnal water loss may be a significant fraction (10-25%) of total daily water loss. Counter-intuitively, elevated [CO2] may increase nocturnal water loss. Assumptions in process-based ecophysiological models and dynamic global vegetation models that gs is zero when solar radiation is zero are likely to be incorrect. Consequently, failure to adequately consider nocturnal water loss may lead to substantial under-estimation of total plant water use and inaccurate estimation of ecosystem level water balance.

Responses of transpiration (E c) to rain pulses are presented for two semiarid tree species in a stand of Pinus tabulaeformis and Robinia pseudoacacia. Our objectives are to investigate (1) the environmental control over the stand transpiration after rainfall by analyzing the effect of vapor pressure deficit (VPD), soil water condition, and rainfall on the post-rainfall E c development and recovery rate, and (2) the species responses to rain pulses and implications on vegetation coverage under a changing rainfall regime. Results showed that the sensitivity of canopy conductance (G c) to VPD varied under different incident radiation and soil water conditions, and the two species exhibited the same hydraulic control (−dG c/dlnVPD to G cref ratio) over transpiration. Strengthened physiological control and low sapwood area of the stand contributed to low E c. VPD after rainfall significantly influenced the magnitude and time series of post-rainfall stand E c. The fluctuation of post-rainfall VPD in comparison with the pre-rainfall influenced the E c recovery. Further, the stand E c was significantly related to monthly rainfall, but the recovery was independent of the rainfall event size. E c enhanced with cumulative soil moisture change (ΔVWC) within each dry–wet cycle, yet still was limited in large rainfall months. The two species had different response patterns of post-rainfall E c recovery. E c recovery of P. tabulaeformis was influenced by the pre- and post-rainfall VPD differences and the duration of rainless interval. R. pseudoacacia showed a larger immediate post-rainfall E c increase than P. tabulaeformis did. We, therefore, concluded that concentrated rainfall events do not trigger significant increase of transpiration unless large events penetrate the deep soil and the species differences of E c in response to pulses of rain may shape the composition of semiarid woodlands under future rainfall regimes.

Global vegetation models are used to estimate water and carbon fluxes in current and future climates. To accurately estimate these fluxes, it is crucial to incorporate tree processes, such as transpiration. Some models accurately predict fluxes in well-watered conditions; however, our ability to predict responses of trees when water availability is limited remains restricted. Including mechanistic responses of trees during drought in models will improve estimates of water and carbon fluxes. Estimating water fluxes over large spatial scales may be calculated by combining (1) remotely sensed estimates of evapotranspiration with (2) knowledge of whether tree water use for a particular forest type or plant functional type follows universal scaling rules. There is little knowledge of whether universal scaling rules apply to water-limited ecosystems. This review examines ‘convergence’ in relationships among tree water use, leaf area, and tree size, using Australian broad-leaved evergreen vegetation as a case study. Broad-leaved evergreen is a plant functional type commonly used in global vegetation models. If convergence is observed among leaf area and water use relationships for different species within this plant functional type, this would provide a powerful tool for scaling ecohydrological processes. This work tests the hypothesis that tree water use (Q) converges along a common relationship with leaf area for a continent-wide range of species (n = 21), spanning a 100-fold difference in size across broad-leaved evergreens, including Acacia, Corymbia, and Eucalyptus as well as Callitris. Remarkably, the slope of the relationship between tree water use and leaf area was similar for the broad-leaved evergreen genus, Eucalyptus, despite different slopes in relationships among diameter at breast height, leaf area, sapwood area, and Q. Realistic modelling of water and carbon fluxes requires an understanding of physiological mechanisms influencing Q, for each plant functional type, and for these mechanisms to be incorporated into vegetation models. Copyright © 2013 John Wiley & Sons, Ltd.

System dynamics (SD) is one of the most suitable methods available to simulate and quantify the behaviour of complex systems due to it non-linear, multivariable, information feedback and temporally changing characteristics. This paper has improved on Khan et al.'s established model (see Khan et al. (2009) ‘Analyzing complex behavior of hydrological systems through a system dynamics approach’, Environmental Modeling & Software24, 1363–1372) by adding water production functions for three main crops (winter wheat, summer maize and cotton) based on soil water balance at the field level. Conclusions based on the simulation were as follows. (1) The model could simulate the dynamics of water balance components of winter wheat and summer maize relatively accurately through testing and validation. (2) Two to four irrigations were needed for the water-use requirement for winter wheat and summer maize when irrigation level was 75 mm each time. Cotton did not need to be irrigated except for the addition of 60 mm pre-sowing water. (3) Exploiting groundwater as far as possible and taking measures to reduce soil evaporation and at the same keeping irrigation unchanged was one of the best ways for sustainable utilization of water resources in the upper reaches of the Panzhuang District. (4) Water-use efficiencies were consistent with the regions' measured results showing that the model could simulate the water cycle in the field comparatively accurately.

Fire weather indices have been widely applied to predict fire risk in many regions of the world. The objectives of this study were to establish fire risk probability models based on fire indices over different climatic regions in China. We linked the indices adopted in Canadian, US, and Australia with location, time, altitude, vegetation and fire characteristics during 1998–2007 in four regions using semi— parametric logistic (SPL) regression models. Different combinations of fire risk indices were selected as explanatory variables for specific regional probability model. SPL regression models of probability of fire ignition and large fire events were established to describe the non—linear relationship between fire risk indices and fire risk probabilities in the four regions. Graphs of observed versus estimated probabilities, fire risk maps, graphs of numbers of large fire events were produced from the probability models to assess the skill of these models. Fire ignition in all regions showed a ...

A modified Jarvis–Stewart model of canopy transpiration (Ec) was tested over five ecosystems differing in climate, soil type and species composition. The aims of this study were to investigate the model's applicability over multiple ecosystems; to determine whether the number of model parameters could be reduced by assuming that site-specific responses of Ec to solar radiation, vapour pressure deficit and soil moisture content vary little between sites; and to examine convergence of behaviour of canopy water-use across multiple sites. This was accomplished by the following: (i) calibrating the model for each site to determine a set of site-specific (SS) parameters, and (ii) calibrating the model for all sites simultaneously to determine a set of combined sites (CS) parameters. The performance of both models was compared with measured Ec data and a statistical benchmark using an artificial neural network (ANN). Both the CS and SS models performed well, explaining hourly and daily variation in Ec. The SS model produced slightly better model statistics [R2 = 0.75–0.91; model efficiency (ME) = 0.53–0.81; root mean square error (RMSE) = 0.0015–0.0280 mm h-1] than the CS model (R2 = 0.68–0.87; ME = 0.45–0.72; RMSE = 0.0023–0.0164 mm h-1). Both were highly comparable with the ANN (R2 = 0.77–0.90; ME = 0.58–0.80; RMSE = 0.0007–0.0122 mm h-1). These results indicate that the response of canopy water-use to abiotic drivers displayed significant convergence across sites, but the absolute magnitude of Ec was site specific. Period totals estimated with the modified Jarvis–Stewart model provided close approximations of observed totals, demonstrating the effectiveness of this model as a tool aiding water resource management. Analysis of the measured diel patterns of water use revealed significant nocturnal transpiration (9–18% of total water use by the canopy), but no Jarvis–Stewart formulations are able to capture this because of the dependence of water-use on solar radiation, which is zero at night. Copyright © 2012 John Wiley & Sons, Ltd.

Nocturnal water flux has been observed in trees under a variety of environmental conditions and can be a significant contributor to diel canopy water flux. Elevated atmospheric CO(2) (elevated [CO(2)]) can have an important effect on day-time plant water fluxes, but it is not known whether it also affects nocturnal water fluxes. We examined the effects of elevated [CO(2)] on nocturnal water flux of field-grown Eucalyptus saligna trees using sap flux through the tree stem expressed on a sapwood area (J(s)) and leaf area (E(t)) basis. After 19 months growth under well-watered conditions, drought was imposed by withholding water for 5 months in the summer, ending with a rain event that restored soil moisture. Reductions in J(s) and E(t) were observed during the severe drought period in the dry treatment under elevated [CO(2)], but not during moderate- and post-drought periods. Elevated [CO(2)] affected night-time sap flux density which included the stem recharge period, called 'total night flux' (19:00 to 05:00, J(s,r)), but not during the post-recharge period, which primarily consisted of canopy transpiration (23:00 to 05:00, J(s,c)). Elevated [CO(2)] wet (EW) trees exhibited higher J(s,r) than ambient [CO(2)] wet trees (AW) indicating greater water flux in elevated [CO(2)] under well-watered conditions. However, under drought conditions, elevated [CO(2)] dry (ED) trees exhibited significantly lower J(s,r) than ambient [CO(2)] dry trees (AD), indicating less water flux during stem recharge under elevated [CO(2)]. J(s,c) did not differ between ambient and elevated [CO(2)]. Vapour pressure deficit (D) was clearly the major influence on night-time sap flux. D was positively correlated with J(s,r) and had its greatest impact on J(s,r) at high D in ambient [CO(2)]. Our results suggest that elevated [CO(2)] may reduce night-time water flux in E. saligna when soil water content is low and D is high. While elevated [CO(2)] affected J(s,r), it did not affect day-time water flux in wet soil, suggesting that the responses of J(s,r) to environmental factors cannot be directly inferred from day-time patterns. Changes in J(s,r) are likely to influence pre-dawn leaf water potential, and plant responses to water stress. Nocturnal fluxes are clearly important for predicting effects of climate change on forest physiology and hydrology.

A soil–plant–atmosphere model was used to estimate gross primary productivity (GPP) and evapotranspiration (ET) of a tropical savanna in Australia. This paper describes model modifications required to simulate the substantial C4 grass understory together with C3 trees. The model was further improved to include a seasonal distribution of leaf area and foliar nitrogen through 10 canopy layers. Model outputs were compared with a 5-year eddy covariance dataset. Adding the C4 photosynthesis component improved the model efficiency and root-mean-squared error (RMSE) for total ecosystem GPP by better emulating annual peaks and troughs in GPP across wet and dry seasons. The C4 photosynthesis component had minimal impact on modelled values of ET. Outputs of GPP from the modified model agreed well with measured values, explaining between 79% and 90% of the variance and having a low RMSE (0.003–0.281 g C m � 2 day � 1 ). Approximately, 40% of total annual GPP was contributed by C4 grasses. Total (trees and grasses) wet season GPP was approximately 75–80% of total annual GPP. Light-use efficiency (LUE) was largest for the wet season and smallest in the dry season and C4 LUE was larger than that of the trees. A sensitivity analysis of GPP revealed that daily GPP was most sensitive to changes in leaf area index (LAI) and foliar nitrogen (Nf) and relatively insensitive to changes in maximum carboxylation rate (Vcmax), maximum electron transport rate (Jmax) and minimum leaf water potential (cmin). The modified model was also able to represent daily and seasonal patterns in ET, (explaining 68–81% of variance) with a low RMSE (0.038–0.19 mm day � 1 ). Current values of Nf, LAI and other parameters appear to be colimiting for maximizing GPP. By manipulating LAI and soil moisture content inputs, we show that modelled GPP is limited by light interception rather than water availability at this site.

Climate change is highly likely to impact on forest productivity over the next century. The direction and magnitude of change are uncertain because many factors are changing simultaneously, such as atmospheric composition, temperature, rainfall, and land use. Simulation models have been widely used to estimate how these interacting factors might combine to alter forest productivity. Such studies have used many different types of models with different underlying assumptions. To evaluate predictions made by such studies, it is essential to understand the type of modelandtheassumptionsused.Inthisarticle,weprovideachecklistforusewhen evaluating modeled estimates of climate change impacts on forest productivity. The checklist highlights the assumptions that we believe are critical in determining model outcomes. Models are classified into different general types, and assumptions relating to effects of atmospheric CO2 concentration, temperature, water availability, nutrient cycling, and disturbance are discussed. Our main aim is to provide a guide to enable correct interpretation of model projections. The article alsochallengesmodelerstoimprovethequalityofinformationprovidedabouttheir model assumptions.  2011 John Wiley & Sons, Ltd. WIREs Clim Change2011 DOI: 10.1002/wcc.108

Summary Revegetation to restore hydrological function to highly disturbed landscapes used for waste disposal or mining is often constrained by the initial low rates of water-use during the early phases of the developing vegetation. This problem is especially pronounced for revegetation that relies on trees due to their prolonged lead-time to achieve canopy closure. Initial low rates of water-use can however be overcome if a groundcover of quick-growing herbaceous species is planted first. To demonstrate the significance of groundcover in the early phase of revegetation, we undertook an energy balance analysis using the Bowen ratio technique for a juvenile plantation growing over a heavy groundcover of herbaceous species on a waste disposal site in 2006/2007 and 2007/2008. Latent heat flux (λE) from the landscape (trees plus groundcover and soil) fluctuated widely between 0.5 and 22 MJ m−2 d−1 and accounted for between 60% and 90% of available energy at the site; this percentage exceeded 100% during periods with significant advection. The latent heat emanating from the tree canopy (λEc), derived from sapflow measurements in the trees, accounted for only between 4% and 18% of daily λE with the balance arising from the groundcover that intercepted more than 90% of incident solar radiation. The λEc was mostly smaller than the net radiation intercepted by the tree canopy (Rnc) with the excess energy expended by the canopy as sensible heat (Hc), which accounted for up to 18% of bulk sensible heat from the landscape. The λE expressed as ET was in excess (114%) of rainfall in the relatively dry first growing (September–May) season, when rainfall was only 87% of the long-term average. It was, however, smaller (80%) than rainfall during the second season, when the annual rainfall was close to the long-term average. We used these data to develop an empirical model for predicting λE from soil–water content and the prevailing evaporative demand.

Accurately quantifying evapotranspiration (ET) is essential for modelling regional-scale ecosystem water balances. This study assembled an ET data set estimated from eddy flux and sapflow measurements for 13 ecosystems across a large climatic and management gradient from the United States, China, and Australia. Our objectives were to determine the relationships among monthly measured actual ET (ET), calculated FAO-56 grass reference ET (ETo), measured precipitation (P), and leaf area index (LAI)—one associated key parameter of ecosystem structure. Results showed that the growing season ET from wet forests was generally higher than ETo while those from grasslands or woodlands in the arid and semi-arid regions were lower than ETo. Second, growing season ET was found to be converged to within ± 10% of P for most of the ecosystems examined. Therefore, our study suggested that soil water storage in the nongrowing season was important in influencing ET and water yield during the growing season. Lastly, monthly LAI, P, and ETo together explained about 85% of the variability of monthly ET. We concluded that the three variables LAI, P, and ETo, which were increasingly available from remote sensing products and weather station networks, could be used for estimating monthly regional ET dynamics with a reasonable accuracy. Such an empirical model has the potential to project the effects of climate and land management on water resources and carbon sequestration when integrated with ecosystem models. Copyright © 2010 John Wiley & Sons, Ltd.

Revegetation is critical to restoring hydrological function on waste disposal sites in order to minimize runoff and drainage and safeguard the water quality of the catchment. In this study, we determined the components of soil–water balance between late 2006 and the end of 2008 for three vegetation types established over sites used for waste disposal: (i) a juvenile plantation of mixed Australian woody species; (ii) a block of mixed tree seedlings; (iii) and an ungrazed grass pasture. These were compared against a nearby natural woodland taken as an analogue of a pre-existing hydrological state. Evapotranspiration (ET) was the major component of the soil–water balance in all the four vegetation types. In the plantation and woodland, ET accounted for 60–93% of the annual rainfall compared to 44–88% in the grass and seedling blocks. While the balance of rainfall was largely lost to runoff in the plantation and the woodland, it was split almost equally between runoff and drainage in the other two vegetation covers. The plantation maintained parity in its ET with woodland due to groundcover that contributed at least 70% of the water use, while seasonal growth and periodic mowing reduced ET from the grass. Over the 2 years, the height of the deep (¾19 m above sea level) water table under the plantation and grass declined by an average of 0Ð3 m, while it rose by a similar magnitude in the woodland. The height of the shallow water table (¾8 m above sea level) showed no consistent change. We conclude that, with a good groundcover of mixed herbaceous species, a juvenile plantation can restore hydrological function and minimize deep recharge of a waste disposal site to the status of that under a pre-existing undisturbed woodland. Copyright  2010 John Wiley & Sons, Ltd.

Data on the distribution of root biomass are critical to understanding the ecophysiology of vegetation communities. This is particularly true when models are applied to describe ecohydrology and vegetation function. However, there is a paucity of such information across continental Australia. We quantified vertical and horizontal root biomass distribution in a woodland dominated by Angophora bakeri and Eucalyptus sclerophylla on the Cumberland Plains near Richmond, New South Wales. The site was characterised by a duplex (texture contrast) soil with the A horizon (to 70 cm) consisting of loamy sand and the B horizon (to > 10 m) consisting of sandy clay. The topsoil had a smaller bulk density, a smaller water holding capacity but a larger organic component and a larger hydraulic conductivity in comparison to the subsoil. Root biomass was sampled to 1.5 m depth and declined through the soil profile. Whilst total biomass in the B horizon was relatively small, its contribution to the function of the trees was highly significant. Coarse roots accounted for approximately 82% of the root mass recovered. Lateral distribution of fine roots was generally even but coarse roots were more likely to occur closer to tree stems. Variation in tree diameter explained 75% of the variation in total below-ground biomass. The trench method suggested the belowground biomass was 6.03 ± 1.21 kg m−2 but this method created bias towards sampling close to tree stems. We found that approximately 68% of root material was within a 2 m radius of tree stems and this made up 54% of the total number of samples but in reality, only approximately 5 to 10% of the site is within a 2 m radius of tree stems. Based on these proportions, our recalculated belowground biomass was 2.93 ± 0.59 kg m−2. These measurements provide valuable data for modeling of ecosystem water use and productivity.

SUMMARY The responses of canopy conductance to variation in solar radiation, vapour pressure deficit and soil moisture have been extensively modelled using a Jarvis–Stewart (JS) model. Modelled canopy conductance has then often been used to predict transpiration using the Penman–Monteith (PM) model. We previously suggested an alternative approach in which the JS model is modified to directly estimate transpiration rather than canopy conductance. In the present study we used this alternative approach to model tree water fluxes from an Australian native forest over an annual cycle. For comparative purposes we also modelled canopy conductance and estimated transpiration via the PM model. Finally we applied an artificial neural network as a statistical benchmark to compare the performance of both models. Both the PM and modified JS models were parameterised using solar radiation, vapour pressure deficit and soil moisture as inputs with results that compare well with previous studies. Both models performed comparably well during the summer period. However, during winter the PM model was found to fail during periods of high rates of transpiration. In contrast, the modified JS model was able to replicate observed sapflow measurements throughout the year although it too tended to underestimate rates of transpiration in winter under conditions of high rates of transpiration. Both approaches to modelling transpiration gave good agreement with hourly, daily and total sums of sapflow measurements with the modified JS and PM models explaining 87% and 86% of the variance, respectively. We conclude that these three approaches have merit at different time-scales.

SummaryThis study was undertaken to obtain an increased understanding of how current water management practices affect fruit yield in olives (Olea europaea L.) in Australian groves, in order to identify opportunities for improvement. We assessed the relationships between seasonal water supply and fruit yield on a range of olive groves that were either irrigated or rain-fed. All the groves experienced inadequate water supply at the start of the season until early Summer (December). This limited the transpiration (T) component of evapotranspiration (ET) and certainly constrained fruit yield. Seasonal averages for the crop coefficient (Kc) ranged between 0.30 for the lightly irrigated groves, to 0.40 for the well-irrigated groves, but fluctuated during the season from as high as 0.7 during wet periods to as low as 0.2 during extended dry periods. Peak rates for daily T in Summer ranged from 1.0 mm (53 l d–1 tree–1) for the rain-fed grove, to 4.0 mm (196 l d–1 tree–1) for groves that were regularly irrigated....

Summary Daily and annual rates of stand transpiration in a drought year and a non-drought year are compared in order to understand the adaptive responses of a remnant woodland to drought and predict the effect of land use change. Two methods were used to estimate stand transpiration. In the first, the ratio of sap velocity of a few trees measured for several hundred days to the mean sap velocity of many trees measured during brief sampling periods (generally 6–7 trees for 5 or 6 days), called the E sv method is used to scale temporally from the few intensive study periods. The second method used was the Penman–Monteith (P–M) equation (called the E PM method). Weather variables and soil moisture were used to predict canopy conductance, which in turn was used to predict daily and annual stand transpiration. Comparisons of daily transpiration estimated with the two methods showed larger values for the E PM method during a drought year and smaller values for the E PM when the rainfall was above average. Generally, though, annual estimates of stand transpiration were similar using the two methods. The E sv method produced an estimate of 318 mm (61% of rainfall) in the drought year and 443 mm (42%) in the year having above average rainfall. The E PM method estimated stand transpiration as 379 mm (73%) and 398 mm (37%), respectively, for the two years. Both estimates of annual stand transpiration demonstrated that the remnant forest showed resilience to an extreme and long-term drought. More importantly, the annual estimates showed that in dry years a larger proportion of rainfall was used as transpiration, and groundwater recharge was absent but in years with above average rainfall recharge was significantly increased. Changes in leaf area index were minimal between years and changes in stomatal conductance were the dominant mechanism for adapting to the drought. The remnant forest rapidly responded to increased water availability after the drought through a new flush of leaves and increased stomatal conductance.

The terrestrial biosphere regulates climate through carbon, water, and energy exchanges with the atmosphere. Land surface models estimate plant transpiration, which is actively regulated by stomatal pores, and provide projections essential for understanding Earth's carbon and water resources. Empirical evidence from 204 species suggests that significant amounts of water are lost through leaves at night, though land surface models typically reduce stomatal conductance to nearly zero at night. Here, we apply observed nighttime stomatal conductance values to a global land surface model, to better constrain carbon and water budgets. We find that our modifications increase transpiration up to 5 % globally, reduce modeled available soil moisture by up to 50 % in semi-arid regions, and increase the importance of the land surface on modulating energy fluxes. Carbon gain declines up to ~ 4 % globally and > 25 % in semi-arid regions. We advocate for realistic constraints of minimum stomatal conductance in future climate simulations, and widespread field observations to improve parameterizations.

Sudden and widespread forest die-back and die-off (e.g., Huang & Anderegg, 2012) and increased mortality rates (e.g., Peng et al., 2011) in many forest ecosystems across the globe have been linked to drought and elevated temperatures (Allen et al., 2010, Fig. 1). Furthermore, these observations have caused a focus on the physiological mechanisms of drought-induced tree mortality (e.g. McDowell et al., 2008) and many studies, both observational and manipulative, have been carried out to explain tree death during drought from a physiological perspective.

Heterogeneity in water availability acts as an important driver of variation in plant structure and function. Changes in hydraulic architecture represent a key mechanism by which adaptation to changes in water availability can be expressed in plants. The aim of this study was to investigate whether differences in depth-to-groundwater influence the hydraulic architecture of Eucalyptus trees in remnant woodlands within mesic environments. Hydraulic architecture of trees was examined in winter and summer by measuring the following traits: Huber value (HV: the ratio between sapwood area and leaf area), branch hydraulic conductivity (leaf and sapwood area specific), sapwood density, xylem vulnerability (P50 and Pe) and hydraulic safety margins across four sites where depth-to-groundwater ranged from 2.4 to 37.5 m. Huber value increased significantly as depth-to-groundwater increased. Neither sapwood density nor branch hydraulic conductivity (sapwood and leaf area specific) varied significantly across sites. Xylem vulnerability to embolism (represented by P50 and Pe) in both seasons was significantly and negatively correlated with depth-to-groundwater. Hydraulic safety margins increased with increasing depth-to-groundwater and therefore trees growing at sites with deeper water tables were less sensitive to drought induced embolism. These results showed plasticity in some, but not all, hydraulic traits (as reflected in HV, P50, Pe and hydraulic safety margin) in response to increase in depth-to-groundwater in a mesic environment.

Quantifying water use of native vegetation is an important contribution to understanding landscape ecohydrology. Few studies provide long-term (more than one growing season) estimates of water use and even fewer quantify interseasonal and interannual variation in transpiration. Globally, changes in land use are significantly altering landscape ecohydrology, resulting in problems such as dryland salinity and excessive groundwater recharge. Estimating stand water use is complex in multispecies forests, due to the differences in relationships among sapwood area, basal area and tree size for co-occurring species. In this article, we examine seasonal and interannual variation in transpiration rate of the tree canopy of two co-occurring species (a conifer Callitris glaucophylla J. Thompson & L.A.S. Johnson and a broad-leaved Eucalyptus crebra F. Muell.) in an open woodland in eastern Australia. Evapotranspiration of understorey species was measured using an open-top chamber, and tree water use was measured using heat-pulse sap flow sensors. Annual stand transpiration was 309 mm in 2003, a year of below average rainfall, and 629 mm in 2004, a year with higher-than-average rainfall. Despite an almost doubling (522 vs. 1062 mm) of annual rainfall between 2003 and 2004, annual tree water use remained a constant fraction (59%) of rainfall, indicative of compensatory mechanisms linking annual rainfall, leaf area index and tree water use. Deep drainage was estimated to be 4% of rainfall (20.8 mm) in 2003 and 2% (21.2 mm) in 2004, indicating that this native woodland was able to minimize deep drainage despite large interannual variability in rainfall.

The leaf area index (LAI) product from the Moderate Resolution Imaging Spectroradiometer (MODIS) is important for monitoring and modelling global change and terrestrial dynamics at many scales. The algorithm relies on spectral reflectances and a six biome land cover classification. Evaluation of the specific behaviour and performance of the product for regions of the globe such as Australia are needed to assist with product refinement and validation. We made an assessment of Collection 4 of the MODIS LAI product using four approaches: (a) assessment against a continental scale Structural Classification of Australian Vegetation (SCAV); (b) assessment against a continental scale land use classification (LUC); (c) assessment against historical field-based measurement of LAI collected prior to the Terra Mission; and (d) direct comparison of MODIS LAI with coincident field measurements of LAI, mostly from hemispherical photography. The MODIS LAI product produced a wide variety of geographically and structurally specific temporal response profiles between different classes and even for sub-groups within classes of the SCAV. Historical and concurrent field measurements indicated that MODIS LAI was giving reasonable estimates for LAI for most cover types and land use types, but that major overestimation of LAI occurs in some eastern Australian open forests and woodlands. The six biome structural land cover classification showed some significant deviations in class allocation compared to the SCAV particularly where grasslands are allocated to shrubland, savanna woodlands are allocated to shrubland, savanna and broadleaf forest, and open forests are allocated to savanna and broadleaf forest. The land cover and LAI products could benefit from some additional examination of Australian data addressing the structural representation of Eucalypt canopies in the “space of canopy realisation” for savanna and broadleaf forest classes.

Summary We used digital map overlays in a geographical information system (GIS) toquantify the potential impact of dryland salinity on the threatened flora and fauna of NewSouth Wales (NSW). Geographical areas of conservation priority were identified based onrichness of threatened species with distribution records overlapping dryland salinity. Twoalternative schemes – Interim Biogeographical Regionalization for Australia (regions) andcatchment boundaries (catchments) – were used to subdivide NSW. Sydney Basin, NorthCoast and South-western Slopes regions – and Hunter, Sydney, Macquarie, Murrumbidgeeand Lachlan catchments – were identified as priority areas with more than 10 salinity-overlap species present. Five threatened plant species were identified as priority speciesdue to more than half of their known distributions overlapping areas of dryland salinity.Threatened animal species of most concern had 10–50% of their records overlapping areasof dryland salinity. Our findings demonstrate that landscape exposure to dryland salinityshould be used in conjunction with total richness of threatened species for prioritizing con-servation of geographical areas with respect to the potential impact of dryland salinity onthreatened species.Key wordsbiodiversity, conservation, dryland salinity, geographical information system,threatened species.

Relatively anisohydric species are predicted to be more predisposed to hydraulic failure than relatively isohydric species, as they operate with narrower hydraulic safety margins. We subjected co-occurring anisohydric Juniperus monosperma and isohydric Pinus edulis trees to warming, reduced precipitation, or both, and measured their gas exchange and hydraulic responses. We found that reductions in stomatal conductance and assimilation by heat and drought were more frequent during relatively moist periods, but these effects were not exacerbated in the combined heat and drought treatment. Counter to expectations, both species exhibited similar gs temporal dynamics in response to drought. Further, whereas P. edulis exhibited chronic embolism, J. monosperma showed very little embolism due to its conservative stomatal regulation and maintenance of xylem water potential above the embolism entry point. This tight stomatal control and low levels of embolism experienced by juniper refuted the notion that very low water potentials during drought are associated with loose stomatal control and with the hypothesis that anisohydric species are more prone to hydraulic failure than isohydric species. Because direct association of stomatal behaviour with embolism resistance can be misleading, we advocate consideration of stomatal behaviour relative to embolism resistance for classifying species drought response strategies.

Many species have the ability to resprout vegetatively after a substantial loss of biomass induced by environmental stress, including drought. Many of the regions characterised by ecosystems where resprouting is common are projected to experience more frequent and intense drought during the 21st Century. However, in assessments of ecosystem response to drought disturbance there has been scant consideration of the resilience and post-drought recovery of resprouting species. Systematic differences in hydraulic and allocation traits suggest that resprouting species are more resilient to drought-stress than nonresprouting species. Evidence suggests that ecosystems dominated by resprouters recover from disturbance more quickly than ecosystems dominated by nonresprouters. The ability of resprouters to avoid mortality and withstand drought, coupled with their ability to recover rapidly, suggests that the impact of increased drought stress in ecosystems dominated by these species may be small. The strategy of resprouting needs to be modelled explicitly to improve estimates of future climate-change impacts on the carbon cycle, but this will require several important knowledge gaps to be filled before resprouting can be properly implemented.

BackgroundAbies faxonianais the dominant plant species of the forest ecosystem on the eastern edge of Qinghai-Tibet Plateau, where the treeline is strongly defined by climate. The tree-ring chronologies and age structure ofAbies faxonianawere developed in the treeline ecotones on the northwestern and southeastern aspects of the Min Mountains in the Wanglang Nature Reserve to examine the treeline dynamics of recent decades in response to climate change.ResultsOn the northwestern aspect, correlation analysis showed that the radial growth was significantly and positively correlated with precipitation in current January and monthly mean temperature in current April, but significantly and negatively correlated with monthly mean temperature in previous August. On the southeastern aspect, the radial growth was significantly negatively correlated with monthly mean temperature in previous July and August.ConclusionsThe different responses of radial growth to climatic variability on both the aspects might be mainly due to the micro-environmental conditions. The recruitment benefited from the warm temperature in current April, July and September on the northwestern aspect. The responses of radial growth and recruitment to climatic variability were similar on the northwestern slope. Recruitment was greatly restricted by competition with dense bamboos on the southeastern aspect.

Production and distribution of fine roots (≤2.0 mm diameter) are central to belowground ecological processes. This is especially true where vegetation serves as a pump to prevent saturation of soil and possible drainage of excess water into or from potentially toxic waste material stored underground or in mounds aboveground. In this study undertaken near Sydney in Australia, we determined fine root biomass and evapotranspiration (ET) on a waste disposal site restored with either a 15-year-old grass sward or plantations of mixed woody species that were either 5 years old (plantation-5) with a vigorous groundcover of pasture legumes and grasses, or 3 years old (plantation-3) with sparse groundcover. These sites were compared with nearby remnant woodland; all four were located within 0.5-km radius at the same site. Ranking of fine root biomass was in the order woodland (12.3 Mg ha -1) > plantation-5 (8.3 Mg ha -1) > grass (4.9 Mg ha -1) > plantation-3 (1.2 Mg ha -1) and was not correlated with nutrient contents in soil or plants, but reflected the form and age of the vegetation covers. Trends in root length density (RLD) and root area index (RAI) followed those in root biomass, but the differences in RAI were larger than those in biomass amongst the vegetation covers. Annual ET in the dry year of 2009 was similar in the three woody vegetation covers (652-683 mm) and was at least 15% larger than for the grass (555 mm), which experienced restrained growth in winter and periodic mowing. This resulted in drainage from the grass cover while there was no drainage from any of the woody vegetation covers. In plantation-5, root biomass, RAI and RLD were reduced in the rain shadow side of the tree rows. Similarly, the amount and depth of rooting in the groundcover were reduced close to the trees compared to midway between rows. Differences in the root variables were larger than those in ET, which suggested that more roots were produced than were needed for water uptake and/or presence of considerable amounts of necromass. We conclude that vegetation covers, such as plantation-5 consisting of widely spaced trees and a heavy groundcover containing winter-active pasture legumes, will promote year-round water-use with a reduced risk of deep rooting that could breach buried wastes. This function could be sustained through progressive thinning of trees to account for not more than 25% of the whole canopy cover; this will minimize competition for limited soil-water and thereby constrain deep rooting as vegetation ages and attains climax. © 2011 Springer Science+Business Media, LLC.

The response of nocturnal stomatal conductance (g(s,n)) to rising atmospheric CO(2) concentration ([CO(2)]) is currently unknown, and may differ from responses of daytime stomatal conductance (g(s,d)). Because night-time water fluxes can have a significant impact on landscape water budgets, an understanding of the effects of [CO(2)] and temperature on g(s,n) is crucial for predicting water fluxes under future climates. Here, we examined the effects of [CO(2)] (280, 400 and 640 μmol mol(-1)), temperature (ambient and ambient + 4°C) and drought on g(s,n,) and g(s,d) in Eucalyptus sideroxylon saplings. g(s,n) was substantially higher than zero, averaging 34% of g(s,d). Before the onset of drought, g(s,n) increased by 85% when [CO(2)] increased from 280 to 640 μmol mol(-1), averaged across both temperature treatments. g(s,n) declined with drought, but an increase in [CO(2)] slowed this decline. Consequently, the soil water potential at which g(s,n) was zero (Ψ(0)) was significantly more negative in elevated [CO(2)] and temperature treatments. g(s,d) showed inconsistent responses to [CO(2)] and temperature. g (s,n) may be higher in future climates, potentially increasing nocturnal water loss and susceptibility to drought, but cannot be predicted easily from g(s,d). Therefore, predictive models using stomatal conductance must account for both g(s,n) and g(s,d) when estimating ecosystem water fluxes.

Woody thickening is a global phenomenon that influences landscape C density, regional ecohydrology and biogeochemical cycling. The aim of the work described here is to test the hypothesis that increased atmospheric CO2 concentration, with or without photosynthetic acclimation, can increase gross primary production (GPP) and that this can explain woody thickening. We examine mechanisms underlying the response of GPP and highlight the importance of changes in soil water content by applying a detailed soil–plant–atmosphere model. Through this model, we show that CO2 enrichment with decreased or increased D and photosynthetic acclimation results in decreased canopy water use because of reduced gs. The decline in water use coupled with increased photosynthesis resulted in increased GPP, water-use efficiency and soil moisture content. This study shows that this is a valid mechanism for GPP increase because of CO2 enrichment coupled with either a decrease or an increase in D, in water-limited environments. We also show that a large increase in leaf area index could be sustained in the future as a result of the increased soil moisture content arising from CO2 enrichment and this increase was larger if D decreases rather than increases in the future. Large-scale predictions arising from this simple conceptual model are discussed and found to be supported in the literature. We conclude that woody thickening in Australia and probably globally can be explained by the changes in landscape GPP and soil moisture balance arising principally from the increased atmospheric CO2 concentration. Copyright © 2010 John Wiley & Sons, Ltd.