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Highlights • A new data-driven method is developed to partition ET based on the separation of soil and canopy conductances. • Magnitudes and trends in soil conductance, canopy conductance, E, and T:ET are consistent with physical understanding. • LAI only explained small variations of mean annual T:ET across sites. Abstract Separating evapotranspiration (ET) into evaporation (E) and transpiration (T) is challenging but key for a better understanding and prediction of the hydrological cycle and plant water use. In this study, flux data at 30 routine eddy-covariance sites were used to develop a new and simple method for ET partitioning based on the separation of soil and canopy conductances, with the main assumption that the latter is proportional to gross primary productivity (GPP). The result of T:ET across different plant functional types (PFTs) was consistent with recent modeling or empirical results. The mean annual T:ET was highest for evergreen needleleaf forests (0.75 ± 0.17), followed by croplands (0.62 ± 0.16) and grasslands (0.56 ± 0.15). The leaf area index (LAI) was shown to explain only small (20%) variations of mean annual T:ET across sites. However, at each site, the correlation of T:ET with LAI was strong at the seasonal scale, where T:ET increased nonlinearly with LAI. The results did not show significant relationship of T:ET with long-term mean precipitation across sites at multiyear timescales. However, the partitioned soil evaporation after each precipitation pulse is consistent with three-stage soil evaporation theory. This ET partitioning method is an objective assessment as it is mainly data-driven. The procedure to apply this method is also simple so it can be readily applied to global flux tower networks at different temporal and spatial scales, enabling continuous estimation of T:ET to monitor ecosystem dynamics and hydrological responses to environmental change. [ABSTRACT FROM AUTHOR]

Highlights • Global yield damages from surface ozone are calculated for wheat and soybeans. • Air temperature and plant water status are considered as co-factors. • Ozone damage depends on region and cultivar, ranging from 0 to 39% of harvest loss. • For wheat, Asia suffers from much higher losses than Europe or North America. Abstract Ozone pollution can severely diminish crop yields. Its damaging effects depend, apart from ozone concentration, on crop, cultivar, water status, temperature and CO 2 concentration. Previous studies estimating global yield loss from ozone pollution did not consider all of these co-factors and climate change impact studies on crop yields typically ignore ozone pollution. Here we introduce an ozone damage module for the widely used process-based crop model LPJmL. The implementation describes ozone uptake through stomata, internal detoxification and short- and long-term effects on productivity and phenology, dynamically accounting for all listed co-factors. Using this enhanced model we estimate historical global yield losses from ozone pollution for wheat and soybeans. We divide wheat into "Western" and "Asian" to account for higher ozone sensitivities in Asian types. We apply daily ozone concentrations obtained from six chemistry-transport models provided by the ACCMIP and HTAP2 projects. Our implementation of ozone damage follows expected dynamics, for example damage amplification under irrigation. The model is able to reproduce results from chamber and field studies. Historical ozone-induced losses between 2008 and 2010 vary between countries, and we estimate these between 2 and 10% of ozone-free yields for soybeans, between 0 and 27% for Western wheat and 4 and 39% for Asian wheat. Our study highlights the threat of ozone pollution for global crop production and improves over previous studies by considering co-factors of ozone damage. Uncertainties of our study include the extrapolation from rather few point observations to the globe, possible biases in ozone data, omission of sub-daily fluctuations in ozone concentration or stomatal conductance and the averaging of different cultivars across regions. We suggest performing further field-scale experimental studies of ozone effects on crops, as these are currently rare but would be particularly helpful to evaluate models and to estimate large-scale effects of ozone. [ABSTRACT FROM AUTHOR]

Reports on the annual effects of deficit irrigation regimes on olive trees are critical in shedding light on their impacts on water use, yield, and water productivity in distinct olive growing climate regions of the world. From the account of a four-year experiment, the aim of this work is to add insight into such effects on olive growing in southern Portugal. We worked with trees in an intensive 'Cobrançosa' orchard (300 trees ha-1) under full irrigation (FI) treatment and two regulated deficit irrigation (DI) treatments designed to replace around 70% and 50% of the FI water supply, respectively. Crop transpiration (T), irrigation water use (IWU), total water use (TWU), irrigation water use efficiency (IWUE), yield (Ya), and water productivity (WP) obtained from all treatments were analyzed, as well as their crop coefficients (Kc), simulated with the SIMDualKc software application for root zone and soil water balance based on the FAO dual crop coefficients. As expected, IWUE of the 50DI treatment was the highest among treatments, with 70DI being slightly lower. Ya showed alternate bearing with an "on-off" year sequence and was consistently higher for the 70DI treatment. WP (the ratio of Ya to IWU) values for the 70DI treatment were also consistently the highest among all treatments and years. The mean simulated Kc act values for 70DI and 50DI for the initial, mid-, and end-season compared well to the FAO56 Kc for olive crops. In general, to rank the irrigation treatments, 70DI presented the highest conversion efficiency among all treatments and years, providing a suitable DI alternative for our 'Cobrançosa' orchard. The 50DI treatment may be an attractive DI regime to undertake under scarce farm water resources or the expansion of olive hectares under water constraints. [ABSTRACT FROM AUTHOR]

Rising atmospheric CO 2 ( C a ) can increase tree radial growth by increasing intrinsic water-use efficiency (iWUE). However, the effects of age on the response remain unknown, particularly for forests in remote areas such as China’s Tianshan Mountains. Here, we assessed age-dependent growth trends of Picea schrenkiana using tree-ring data from low and high elevations and two detrending methods to detect robust long-term trends. We developed age-dependent relationships between basal area increment (BAI) and iWUE based on size-class isolation and separated the contributions of climate variables and iWUE to radial growth. The juvenile trees showed growth increases over time, versus growth reductions in two older age classes. An overall negative trend existed for combined data from all age classes and elevations. iWUE increased in response to increasing C a for trees in all age groups at low and high elevations, with higher values in near-mature and mature trees (100 yr < age ≤ 160 yr) at the lower sites. However, age affected radial growth and its responses to climate and iWUE. For juvenile trees (≤60 yr), BAI increased during the study period, temperature in May-July and iWUE all have positive effects on the radial growth with significantly high contribution variance from iWUE. The smaller hydraulic constraints in juvenile trees may permit higher photosynthetic rates, reduced climatic sensitivity, and increased growth by CO 2 fertilization. For older trees, BAI decreased, possibly due to stomatal closure caused by warmer temperatures and decreasing hydraulic efficiency with increasing tree age; thus, increased iWUE could not outweigh environmental stresses. The trees at high and low elevations responded consistently to environmental changes, but with different response intensity. Thus, climate and cambial age together determined whether increased iWUE could increase radial growth and the potential CO 2 fertilization effect. These age-dependent growth responses should be accounted for when assessing responses of forest dynamics to climate change. [ABSTRACT FROM AUTHOR]

In South Africa, the development of a plantation tree industry using fast-growing introduced species was accelerated by the limited extent of indigenous forests. However, concerns about the impacts of plantations on the country’s limited water resources has initiated forest hydrology research and subsequent regulation of the industry since 1972. The forestry industry’s continued efforts to sustainably meet fibre and timber demands for the country’s growing economy have prompted questions whether indigenous tree species can provide an additional low water-use form of forestry. Single-tree water use and water-use efficiencies of three indigenous species (Ilex mitis,Ocotea bullataandPodocarpus latifolius) and one introduced species (Pinus radiata) in the Southern Cape region of South Africa were quantified. The heat-pulse velocity method was used to collect hourly sap flow data over a 12-month period. Hourly weather and soil-water data were concurrently recorded and tree growth rates were determined for the year. Biophysical water-use efficiency was calculated as the ratio of utilisable biomass gained per volume of water transpired. Patterns of water use through the year were different for the different species.Pinus radiatahad higher transpiration volumes and water-use efficiency levels than the indigenous species. The most transpiringPinus radiatatree had a transpiration volume that was 4.7 times that of the most transpiring indigenous tree. Indigenous species’ relatively lower water-use efficiencies were more a consequence of slow growth rates and not high water-use rates, which could be attributed to competition for resources in the dense indigenous forest. Potential implications for further hydrological research on the development of water-use-efficient tree production systems are discussed. [ABSTRACT FROM PUBLISHER]

Current models used for predicting vegetation responses to climate change are often guided by the dichotomous needs to resolve either (i) internal plant water status as a proxy for physiological vulnerability or (ii) external water and carbon fluxes and atmospheric feedbacks. Yet, accurate representation of fluxes does not always equate to accurate predictions of vulnerability. We resolve this discrepancy using a hydrodynamic framework that simultaneously tracks plant water status and water uptake. We couple a minimalist plant hydraulics model with a soil moisture model and, for the first time, translate rainfall variability at multiple timescales - with explicit descriptions at daily, seasonal, and interannual timescales - into a physiologically meaningful metric for the risk of hydraulic failure. The model, parameterized with measured traits from chaparral species native to Southern California, shows that apparently similar transpiration patterns throughout the dry season can emerge from disparate plant water potential trajectories, and vice versa. The parsimonious set of parameters that captures the role of many traits across the soil-plant-atmosphere continuum is then used to establish differences in species sensitivities to shifts in seasonal rainfall statistics, showing that co-occurring species may diverge in their risk of hydraulic failure despite minimal changes to their seasonal water use. The results suggest potential shifts in species composition in this region due to species-specific changes in hydraulic risk. Our process-based approach offers a quantitative framework for understanding species sensitivity across multiple timescales of rainfall variability and provides a promising avenue toward incorporating interactions of temporal variability and physiological mechanisms into drought response models. [ABSTRACT FROM AUTHOR]

Water scarcity and increasing water use in many socioeconomic sectors lead to an urgent need to improve irrigation management, especially in arid and semiarid areas, such as southeast Spain. For this reason, we studied, during 3 years, the possibility of scheduling regulated deficit irrigation (RDI) using maximum daily shrinkage (MDS) measurements on peach trees [ Prunus persica (L.) Batsch cv. 'Catherine'] in Murcia (Spain). Three irrigation treatments were established: a control treatment (C), irrigated above the estimated crop water requirements, and two treatments based on measurements of maximum daily trunk shrinkage signal intensity (MDS SI), namely a precision treatment (C) using a threshold value of MDS SI = 1 during all the period and a RDI treatment using MDS SI = 1 all the period except for stage II and post-harvest where MDS SI = 2. The low coefficients of variation for MDS SI indicated that this information was sufficient to adjust the irrigation schedule to maintain MDS SI close to the selected threshold values. Maintaining the MDS SI close to unity throughout the growing season allowed us to estimate peach water requirements (ET). The RDI treatment significantly reduced pruning weight, but no differences were found in terms of reproductive growth and yield. Moreover, RDI increased water productivity and fruit quality, since soluble solids content and maturity index were higher in the RDI treatment compared to C and C. This study demonstrated that irrigation scheduling in peach trees based exclusively on MDS SI was feasible without detrimental effects on yield and fruit quality. [ABSTRACT FROM AUTHOR]

Fertilization increases productivity in Eucalyptus plantations, but losses in productivity associated with soil fertility continue at operational scales. In this study, we evaluated the fertilization response (FR), light use efficiency (LUE) and growth efficiency (GE), i.e., the amount of wood biomass accumulated per unit of light absorbed (LUE) and per unit of leaf area index of Eucalyptus plantations. We used a "twin plot" approach, with 161 blocks representing 52,700 ha of planted forests that spanned a broad range of edaphoclimatic conditions in southeastern Brazil. The normal plots (NP) were part of a permanent inventory network, whereas the twin plots (TP) received extra high levels of fertilization and extra weed control after fertilization. The intensive management (twin plots) led to a large increase of 5.3 Mg· ha–1· year–1 of wood increment. The region without dry periods and with soils with high clay content was most responsive to fertilization, with a 15% increment in the LUE and 10% increase in the GE of the TPs compared with those of the NPs. Our results suggested that water availability was the primary element affecting productivity and potential response to fertilization. With this information, decisions can be made on which regions should receive priority fertilization investments. However, more research is required to determine the most limiting nutrient in each type of environment. [ABSTRACT FROM AUTHOR]

We assessed growth and physiological responses of Eucalyptus and Corymbia species to water limitation aiming to widen possibilities for plantations in dry climatic conditions. We selected 16 taxa: 4 Corymbia and 12 Eucalyptus species from the Subgenera Symphyomyrtus. Seedlings were evaluated from 100 to 170 days after sowing. Growth and physiological traits showed significant differences among taxa and between two levels of water availability. Water limitation significantly impacted biomass production and physiological characteristics, however in different levels. Leaf area and biomass production decreased 15%–48% under water limitation among taxa. Eucalyptus moluccana, CCV 2, and VM1 (drought tolerant clone) showed the largest decrease in leaf area. Transpiration across taxa decreased 30%–57% and photosynthesis 14%–48% under water limited condition. Taxa from cold environments were less responsive in leaf area reduction under water limitation, and taxa from Exsertaria section showed lower reduction in photosynthesis (E. camaldulensis showed the lowest reduction). Responses to water limitation are related to the environment of origin. E. molucana, the only Adnataria species from a high precipitation region (>1500 mm year–1), was one of the most sensitive in reduction of biomass production, different behavior from the other Adnataria species, originated in regions with rainfall <750 mm year–1. Water limitation increased leaf-level water use efficiency by 18% on average, 8% in E. longirostrata, and 28% in E. camaldulensis, E. brassiana, and E. crebra. Growth and physiological responses observed show the potential of different eucalypts taxa to tolerate water limited environments. [ABSTRACT FROM AUTHOR]

Correlation analysis provides useful information for basis of selection for trait like pod and seed yield. Seed yield is the most economic as well as very complex character in nature because it is governed by polygene and greatly influenced by environmental factors. The estimate of genotypic correlation coefficients in general higher than their corresponding phenotypic correlations indicating strong inherent association among the traits. Pod yield in groundnut is a complex and depends upon the interplay of number of components attributes. Primary yield components of groundnut viz., pod size, sound mature kernels, shelling percentage, 100 kernel weight, kernel yield and number of mature pods per plant showed positive correlation with each other and with pod yield. A clear picture of contribution of each component is the final expression of character would emerge through the study of correlation and causation of path concept revealing different ways in which component attributes influence the complex traits. Path coefficient analysis helps in formulating the selection criteria based on these direct and indirect effects. In order to achieve the goal of increased production by increasing the yield potential of crop, knowledge of direction and magnitude of association between various traits is essential for plant breeders. [ABSTRACT FROM AUTHOR]

Increasing water abstraction is severely degrading the world’s wetlands, which is frequently reflected in the condition of flood dependent organisms. Understanding minimum requirements under which thresholds are crossed from desired to undesired states can improve managing for resilience and avoid catastrophic ecological consequences. The Macquarie Marshes, a Ramsar-listed wetland in eastern Australia is located in a catchment with a long history of water resource development. It is also a catchment in which there has been a strong focus on wetland recovery using environmental flows. We investigated changes in the condition of 212 river red gum trees ( Eucalyptus camaldulensis ), a long-lived flood dependent species, at 17 sites, over 18 years (1993–2011). Four variables were measured for each tree: crown density, crown size, dead branches and epicormic growth. More than half (56.13%, 119) of the healthy trees first measured in 1993, showed no signs of life by 2011. Using historic inundation mapping, we identified that condition declined with reduced flooding. The probability of inundation in the previous five years had the strongest explanatory power, with strong increasing threshold responses of persistence and recovery associated with probabilities of flooding exceeding 5 years in the previous 10 years. We extended our modelling to the river red gum forests of the Macquarie Marshes floodplain, showing that 37% of the area had a predicted survival probability lower than P = 0.6 while similar probabilities were present in only 12% of the area within the Macquarie Marshes Nature Reserve. The condition of river red gum forests, using the relationships identified, provide a useful measure of ecosystem health, particularly if extended to understanding of reproduction, germination and recruitment in relation to different scenarios for environmental flows. Embedding such a monitoring strategy in an adaptive management framework provides considerable promise for ongoing learning and improvement of management, not just for river red gums but also other indicators. There is a possibility that the current poor ecological condition of the Macquarie Marshes can be redressed with increased environmental flows restoring some of the river red gum forests that are a key characteristic of the wetland. [ABSTRACT FROM AUTHOR]

Within-canopy gradients of leaf functional traits have been linked to both light availability and vertical gradients in leaf water potential. While observational studies can reveal patterns in leaf traits, within-canopy experimental manipulations can provide mechanistic insight to tease apart multiple interacting drivers. Our objectives were to disentangle effects of height and light environment on leaf functional traits by experimentally shading branches along vertical gradients within a sugar maple ( Acer saccharum) forest. Shading reduced leaf mass per area (LMA), leaf density, area-based leaf nitrogen (N), and carbon:nitrogen (C:N) ratio, and increased mass-based leaf nitrogen (N), highlighting the importance of light availability on leaf morphology and chemistry. Early in the growing season, midday leaf water potential (Ψ), LMA, and N were driven primarily by height; later in the growing season, light became the most important driver for LMA and N. Carbon isotope composition (δC) displayed strong, linear correlations with height throughout the growing season, but did not change with shading, implying that height is more influential than light on water use efficiency and stomatal behavior. LMA, leaf density, N, C:N ratio, and δC all changed seasonally, suggesting that leaf ageing effects on leaf functional traits are equally as important as microclimatic conditions. Overall, our results indicate that: (1) stomatal sensitivity to vapor pressure deficit or Ψ constrains the supply of CO to leaves at higher heights, independent of light environment, and (2) LMA and N distributions become functionally optimized through morphological acclimation to light with increasing leaf age despite height-related constraints. [ABSTRACT FROM AUTHOR]

Understanding the regulation of water use at the whole-tree scale is critical to advancing the utility of physiological ecology, for example in its role in predictive hydrology of forested catchments. For three eucalypt species that dominate high-elevation catchments in south-eastern Australia, we examined if whole-tree water use could be related to three widely discussed regulators of water use: stomatal anatomy, sensitivity of stomata [i.e. stomatal conductance ( g)] to environmental influences, and sapwood area. While daily tree water use varied sixfold among species, sap velocity and sapwood area varied in parallel. Combined, stomatal structure and physiology could not explain differences in species-specific water use. Species which exhibited the fastest ( Eucalyptus delegatensis) and slowest ( Eucalyptus pauciflora) rates of water use both exhibited greater capacity for physiological control of g [indicated by sensitivity to vapour pressure deficit (VPD)] and a reduced capacity to limit g anatomically [indicated by greater potential g ( g)]. Conversely, g was insensitive to VPD and g was lowest for Eucalyptus radiata, the species showing intermediate rates of water use. Improved knowledge of stomatal anatomy will help us to understand the capacity of species to regulate leaf-level water loss, but seems likely to remain of limited use for explaining rates of whole-tree water use in montane eucalypts at the catchment scale. [ABSTRACT FROM AUTHOR]

Mixtures can be more productive than monocultures and may therefore use more water, which may make them more susceptible to droughts. The species interactions that influence growth, transpiration and water-use efficiency (WUE, tree growth per unit transpiration) within a given mixture vary with intra- and inter-annual climatic variability, stand density and tree size, but these effects remain poorly quantified. These relationships were examined in mixtures and monocultures of Eucalyptus globulus Labill. and Acacia mearnsii de Wildeman. Growth and transpiration were measured between ages 14 and 15 years. All E. globulus trees in mixture that were growing faster than similar sized trees in monocultures had higher WUE, while trees with similar growth rates had similar WUE. By the age of 14 years A. mearnsii trees were beginning to senesce and there were no longer any relationships between tree size and growth or WUE. The relationship between transpiration and tree size did not differ between treatments for either species, so stand-level increases in transpiration simply reflected the larger mean tree size in mixtures. Increasing neighbourhood basal area increased the complementarity effect on E. globulus growth and transpiration. The complementarity effect also varied throughout the year, but this was not related to the climatic seasonality. This study shows that stand-level responses can be the net effect of a much wider range of individual tree-level responses, but at both levels, if growth has not increased for a given species, it appears unlikely that there will be differences in transpiration or WUE for that species. Growth data may provide a useful initial indication of whether mixtures have higher transpiration or WUE, and which species and tree sizes contribute to this effect. [ABSTRACT FROM AUTHOR]

Leaf morphological and physiological traits of Abies faxoniana growing in a natural forest along an altitudinal gradient were measured with the aim to identify the central mechanism for the marked variation in foliar δC determined by an isotope ratio mass spectrometer. There is a unimodal pattern of plant functional traits in these temperate and semi-humid areas. Stomatal parameters, specific leaf area, and C/N ratio increased, whereas C, N and δC values decreased with increasing altitude below 3000 m a.s.l.. In contrast, they exhibited opposite trends above 3000 m a.s.l.. Our results demonstrated that high-altitude plants achieve higher water use efficiency (WUE) at the expense of decreasing nitrogen use efficiency (NUE), whereas plants at 3000 m can maintain a relatively higher NUE but a lower WUE. Such intra-specific differences in the trade-off between NUE and WUE may partially explain the altitudinal distribution of the plants in relation to moisture and nutrient availability. Our results clearly indicate that the functional relations between nutritional status and the structure of leaves are responsible for the altitudinal variations associated with δC. The pivotal role of specific leaf area in regulating plant adaptive responses provides a potential physiological mechanism for the observed growth advantage of populations occupying the medium altitude. These adaptive responses to altitudinal gradients showed that an altitude of approximately 3000 m a.s.l. is the optimum distribution zone for A. faxoniana, allowing the most vigorous growth and metabolism. These results improve our understanding of the various roles of environmental and biotic variables upon δC dynamics and provide useful information for subalpine coniferous forest management. [ABSTRACT FROM AUTHOR]

Highlights: [•] We measured assimilation and transpiration simultaneously in whole orange canopies. [•] Water stress induces a non-significant increase in instant water use efficiency. [•] Water stress plants show higher water use efficiency at daily time scale. [•] The effect on daily WUE is due to different transpiration pattern under water stress. [•] Overall effect of water stress on water use efficiency resulted moderate in orange. [ABSTRACT FROM AUTHOR]

Field spectroscopy was tested in predicting water stress induced byThaumastocoris peregrinusinfestations, a pest which is causing significant damage to eucalypt plantations internationally. Water indices and known water absorption bands calculated from hyperspectral field reflectance were input into a neural network algorithm to predict plant water content (PWC) and equivalent water thickness (EWT). The integrated approach involving field spectral data and neural networks predicted PWC and EWT with correlation coefficients of 0.88 and 0.71 on independent test datasets. The results indicate the potential of high-resolution field spectral data in detecting the early stages of insect infestation due to physiological changes that alter water content. [ABSTRACT FROM PUBLISHER]

The Jinping cascade project on the Yalong River consists of the Jinping I and the Jinping II hydropower stations, in which the Jinping II hydropower station is a diversion-type hydropower station. There is a 119-km-long water-reduced reach between the lock site and a factory site. For the sustainable development of the watershed ecosystem health, a prescribed amount of water to support the ecosystem, called the process volume of ecological water requirements, should be discharged periodically to reduce the eco-environmental stress on the river channels. This article presents calculations of eco-scheduling of the Jinping cascade project under the given constraints of quantitatively analyzing and calculating the eco-flow process in a water-reduced reach. Comparative analysis has been carried out to search for the best scheduling scheme by using utility function theory. [ABSTRACT FROM PUBLISHER]

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Seven criteria (water requirement, water temperature, soil texture, terrain slope, potential farm gate sales, availability of farm inputs, and access to local and regional markets) were analyzed to determine site suitability for tilapia and clarias farming in Uganda. Crisp and fuzzy approaches of criterion classification were implemented using GIS, and the results were compared. There was a statistically significant difference between maps generated by crisp and fuzzy approaches. For both the crisp and the fuzzy approaches, over 98% of the land was classified as moderately suitable or suitable. Overall, the crisp method classified 16,322 hectares (0.09%) as very suitable compared to zero hectares (0%) by the fuzzy method. Simultaneously, the crisp method gave 297,344 hectares (1.96%) as unsuitable compared to 168,592 hectares (0.96%) by the fuzzy method. Of the 138 surveyed fishponds that were operational, the crisp method classified 71% as suitable and 29% as moderately suitable, while the fuzzy method classified 71.7% as suitable and 28.3% as moderately suitable. [ABSTRACT FROM AUTHOR]

Conventionally, increment cores collected at breast height (1.4 m) have been used to measure wood properties of standing loblolly pine ( Pinus taeda L.) trees. This height has been used because of the ease of sampling and cost involved in extracting the cores. In this study, the efficacy of a breast-height core to represent whole-tree specific gravity (SG) and moisture content (MC) was examined. The sampling height that best represents whole-tree SG and MC was identified using the correlation between volume-weighted whole-tree SG and MC with SG and MC measurements collected at different heights within a tree. We found a high correlation between observed whole-disk SG and MC with volume-weighted whole-tree SG and MC at most sampling heights. The strength of the correlation followed a skewed parabolic curve form for both wood properties. The strongest correlations were observed between 4.6 and 6.1 m, with marginally lower correlations at the base of the tree, and the weakest correlations were observed towards the tip of the tree. In addition, it was found that the number of stands and trees that need to be sampled to achieve a certain accuracy in overall mean whole-tree SG and MC was greater if breast height was used as a sampling height compared with the most representative sampling heights identified (4.6 m for SG and 6.1 m for MC). [ABSTRACT FROM AUTHOR]

1. Tree plantations play an important role in meeting the growing demand for wood, but there is concern about their high rates of water use. Recent approaches to reforestation in the tropics involve the establishment of multispecies plantations, but few studies have compared water use in mixed vs. monospecific stands. 2. We hypothesized that tree species diversity enhances stand transpiration. Tree water use rates were estimated in monocultures ( n = 5), two-species mixtures ( n = 3), three-species mixtures ( n = 3) and five-species mixtures ( n = 4). Sap flux densities were monitored with thermal dissipation probes in 60 trees for 1 year in a 7-year-old native tree plantation in Panama. We also estimated changes in the amount of wood produced per unit water transpired (i.e. water use efficiency, WUEwood). 3. Annual stand transpiration rates in two-/three-species mixtures (464 ± 271 mm year−1) and five-species mixtures (900 ± 76 mm year−1) were 14% and 56% higher than those of monocultures (398 ± 293 mm year−1), respectively. Trees growing in mixtures had larger diameters, conductive sapwood and basal area than those in monocultures, which partly explained the enhanced stand transpiration in mixtures. 4. The five-species mixtures maintained equally high stand transpiration rates during wet (2·64 ± 0·30 mm day−1) and dry seasons (2·51 ± 0·21 mm day−1), whereas monocultures and two-species mixtures had significantly lower transpiration rates during the dry season, because of the presence of dry season deciduous species. 5. The WUEwood of the five-species mixtures (2·1 g DM kg−1 H2O) was about half that of either monocultures, two- or three-species mixtures. 6. The comparably high stand transpiration rates in the five-species plots may arise from enhanced vegetation-atmosphere-energy exchange through higher canopy roughness and/or complementary use of soil water. 7. Synthesis and applications. Stand transpiration increased linearly with tree species richness and basal area in monocultures, two- and three-species mixtures, but the ratio of stand transpiration to basal area was larger for five-species mixtures. In conclusion, species selection and consideration of species richness and composition is crucial in the design of plantations to maximize wood production while conserving water resources. [ABSTRACT FROM AUTHOR]

Abstract: Water is the principal limiting resource in Australian broadacre farming, and the efficiency with which farmers use water to produce various products is a major determinant both of farm profit and of a range of natural resource management (NRM) outcomes. We propose a conceptual framework based on multiple water use efficiencies (WUEs) that can be used to gain insight into high-level comparisons of the productivity and sustainability of alternative farming practices across temporal and spatial scales. The framework is intended as a data aggregation and presentation device. It treats flows of water, biomass and money in a mixed farming system; economic inefficiencies in these flows are tracked as they are associated with a range of NRM indicators. We illustrate the use of the framework, and its place in a larger research programme, by employing it to synthesise the results from a set of modelling analyses of the effect of land use choices on long-term productivity and a range of NRM indicators (frequency of low ground cover, deep drainage, N leaching rates and rate of change in surface soil organic carbon). The analyses span scales from single paddocks and years to whole farms and have been carried out with the APSIM and GRAZPLAN biophysical simulation models and the MIDAS whole-farm economic model. In single wheat crops in one study, different land uses in preceding years affect grain yield primarily by affecting the harvest index. When the scale changes to cropping rotations, the critical factor affecting overall water use efficiency is found to be the proportion of stored soil water that is transpired by crops. When ordinated in terms of their water use efficiencies, a set of 45 modelled rotation sequences at another location are differentiated mainly by the proportion of pasture in the rotation; when rotations are ordinated using key NRM indicators, the proportion of lucerne pasture is the main distinguishing factor. Finally, we show that for whole crop-livestock farms at three different locations across southern Australia, the pattern of water use efficiencies in the most profitable farming systems changes in similar ways as cropping proportion is altered. At this scale, land use choices affect multiple water use efficiency indices simultaneously and commodity prices determine the balance of the resulting economic tradeoffs. Limitations to the use of the WUE framework arising from its relative simplicity are discussed, as are other areas of farming systems research and development to which it can be applied. [Copyright &y& Elsevier]

Abstract: As a sustainable biofuel feedstock, marine algae have superior aspects to terrestrial biomass such as less energy and water requirement for cultivation, higher CO2 capture capacity, and negligible lignin content. In this study, various marine algae were tested for fermentative hydrogen production (FHP). Among them, Laminaria japonica exhibited the best performance, showing the highest H2 yield of 69.1mL H2/g CODadded. It was attributed to its high carbohydrate content and main constituents of polysaccharides, laminarin and alginate, which were found to posses higher H2 production potential than agar and carrageenan. To enhance the H2 production from L. japonica, thermal pretreatment was applied at various conditions. At 170°C and 20min, H2 yield was maximized to 109.6mL H2/g CODadded. The experimental results suggested that marine algae, especially L. japonica, could be used for FHP, and future works would be focused on gaining more energy from the H2 fermentation effluent. [ABSTRACT FROM AUTHOR]

Abstract: In a cacao agroforest with Gliricidia shade trees we studied the effects of experimentally reduced throughfall on tree sap flux densities and soil water budget. The objectives of our study were: (1) to identify the response of cacao and Gliricidia sap flux densities to reduced soil water availability, and (2) to analyze the changes in stand level soil water partitioning, measured as changes in transpiration, drainage and soil moisture storage under reduced throughfall. The study was conducted in Sulawesi, Indonesia at a site where ambient precipitation was 2841mmyr−1. The research site was subdivided into three control plots and three plastic roof plots in which net precipitation was reduced by 71% through the use of a sub-canopy roof for 13 months, to create rainfall conditions similar to an extended El Niño event. The two species differed in their sap flux response to declining soil water content. Daily Gliricidia sap flux declined at higher soil water contents than cacao, while Gliricidia sap flux declined in response to all levels of vapor pressure deficit (VPD) and cacao only responded to high levels of VPD. Average monthly sap flux densities of cacao and Gliricidia in the roof plots decreased linearly with decreasing soil water content reaching a maximum reduction of 21% (cacao) and 29% (Gliricidia) as compared to control plots. Cacao withdrew water mainly from the topsoil where small amounts of throughfall entering gaps in the roof frequently rewetted the soil. Therefore the competition between the two species for water resources during long periods with only little precipitation was low or in favor of cacao. Average daily stand transpiration was 1.3mm in roof plots and 1.5mm in control plots. Measured soil water contents were simulated satisfactorily by the application of a one-dimensional soil water model based on Richards unsaturated flow equation. The model suggested that drainage amounted to 1554mmyr−1 in control plots. Drainage in roof plots was greatly reduced, totaling 299mmyr−1. Soil moisture storage in the control underwent minor variations while it was heavily reduced in roof plots. Drainage in roof plots was a large driver of changes in soil moisture storage especially in deeper soil layers while precipitation and root water uptake were the main influencing factors for the topsoil. Deep root water uptake seemed to play a minor role in this experiment. Despite the strong reduction in net precipitation, declines in stand transpiration were moderate, suggesting that the stand did not react sensitively to the reduced throughfall scenario. [Copyright &y& Elsevier]

Plantation forests not only impact carbon and water cycles, but also affect biodiversity, livelihoods, and shape regional economies. Each of these impacts differs across varying scales of analysis. This paper illustrates how forest, climate change and hydrology debates play out in the context of the forest plantations of Australian black wattle ( Acacia mearnsii) in the upper Palni hills of southern India. We outline the contradictory perspectives of different local groups regarding the impact of plantations on catchment hydrology and water availability, and examine these in relation to changes in the regional economy and rainfall patterns. Our analysis indicates that changes in these two factors have played a more significant role than existing wattle plantations in affecting local and regional water availability. We suggest that ongoing debates regarding forest plantation–hydrology–climate change relationships need to broaden their scope to include changes in regional rainfall patterns and shifts in regional economic activity. This approach is likely to provide a more realistic assessment of plantation forests in a dynamic regional context, and offer more resilient strategies for regional landscape and catchment management under conditions of high variability in rainfall patterns. [ABSTRACT FROM AUTHOR]

Abstract: Sustainable management of water resources allocated to palm crops requires reliable tools for measuring palm water use. Thermometric sap flow methods developed for woody dicot plants hold great potential for use in palms, but there have been few investigations to determine whether such methods can be used successfully in ‘woody’ monocots. Here, we evaluate two sap flow methods for measuring whole-plant water use by potted cocos palms (Syagrus romanzoffiana): the Heat Ratio Method (HRM) and the Compensation Heat Pulse Method (CHPM). Measurements of whole-plant water use from the HRM and the CHPM were compared to gravimetric measurements acquired from an electronic balance. Of the two methods, the HRM gave the most accurate results and it most precisely described patterns of transpiration with respect to environmental conditions and leaf morphology. Estimates of total daily water use from the HRM and the balance were highly correlated (R 2 =0.92; P <0.0001) and very near to a 1:1 relationship—an excellent result given the potential for error associated with each method. As expected, the CHPM was seriously limited at low flow rates, but it agreed well with the HRM at higher flow rates (heat pulse velocity >4cmh−1). Anatomical investigations revealed that vascular bundles in measured palm fronds were evenly distributed and the distance between bundles was comparable in scale to the diameter of probes of HRM sensors, and most likely an order of magnitude smaller than the probable zone of thermal influence for HRM measurements. This contention was supported by results of mathematical modeling suggesting that HRM heat pulse velocities in palm-like sapwood remain largely unaffected by increases in heterogeneity caused by larger xylem vessels and wider interstitial tissues. Although wounding models for heat pulse sap flow methods have not historically catered for the effects of discrete vascular bundles, they are sufficiently approximate given our empirical validations, and we conclude that palm sapwood is thermally homogenous enough for the HRM and the CHPM to be used without modification. Overall, we present strong evidence that heat pulse methods such as the HRM and the CHPM can be used successfully in woody monocots. Finally, we note that the CHPM is likely to perform better in cases of very high flow rates, while the HRM provides more comprehensive monitoring of the usual range of flow rates including at night, early morning and during water deficit. [Copyright &y& Elsevier]

The article attempts to investigate the impact of harvesting Pinus radiata to streamflows in Canobolas State forest, New South Wales. It mentions that the streamflows were measured in terms of their water levels in the two Pinus radiata plantation watersheds and compared its levels to a eucalyptus forest watershed in the said state forest from 1999 up to 2007. Accordingly, streamflows of these two plantations increased for the first three years of tests after the harvesting of Pinus radiata. Moreover, there is a further significant increase of streamflows after the three-year tests regardless of the forest conditions and stormflow interventions.

Abstract: Urban agriculture (UA) in Khartoum, Sudan, contributes to meeting the increasing food demand of the city''s rapidly growing population, but its spatial extent, development over time and resource consumption are unknown. To fill this knowledge gap, we analyzed scenes captured by Landsat satellites in 1972, 1987 and 2000. For each dataset, we calculated the Normalized Difference Vegetation Index (NDVI) and classified all grid cells with NDVI values higher than one standard deviation above the mean as vegetated land. We also quantified agricultural vegetation on aerial photographs taken in 1958 and on a recent Google Earth image. The built-up area of the city was estimated for each point in time. Based on these spatial estimates, we computed water consumption by UA based on geographic, temporal and climatic datasets and official data on the cropping patterns of Khartoum State, using the Penman–Monteith equation to estimate crop water demands, and assuming a water use efficiency of 0.56. Urban agriculture increased from 8751ha in 1972 to 13,249ha today. In the municipal core zone, UA decreased from 4799ha in 1958 to 2869ha today. Along the Nile, UA persisted through time, whereas many urban irrigation schemes have been pushed into the periphery. The built-up area increased strongly and today exceeds the UA area 5.5-fold. Estimated crop water demand on UA land increased from 241 to 365 millionm3 year−1 between 1972 and today. [Copyright &y& Elsevier]

Abstract  The aim of this research was to determine whether exogenous abscisic acid (ABA) applied immediately after ex vitro transfer of in vitro grown plants can improve their acclimatization. Tobacco (Nicotiana tabacum L.) plantlets were transferred into pots with Perlite initially moistened either by water or 50 µM ABA solution and they were grown under low (LI) or high (HI) irradiance of 150 and 700 µmol m−2 s−1, respectively. Endogenous content of ABA in tobacco leaves increased considerably after ABA application and even more in plants grown under HI. Stomatal conductance, transpiration rate and net photosynthetic rate decreased considerably 1 d after ex vitro transfer and increased thereafter. The gas exchange parameters were further decreased by ABA application and so wilting of these plants was limited. Chlorophyll (a) and β-carotene contents were higher in ABA-treated plants, but the content of xanthophyll cycle pigments was not increased. However, the degree of xanthophyll cycle pigments deepoxidation was decreased what also suggested less stress in ABA-treated plants. No dramatic changes in most chlorophyll a fluorescence parameters after ex vitro transfer suggested that the plants did not suffer from restriction of electron transport or photosystem damage. [ABSTRACT FROM AUTHOR]

Abstract: Tree plantations have developed a reputation for excessive water use, with age commonly used as an explanatory variable to predict water loss – but many factors have the potential to affect plantation water use, and few of these alternatives have been considered. Changes in forest cover may be correlated with other environmental changes that may affect precipitation, transpiration, and runoff, indicating that more thorough investigation is required in both field and simulation studies. Several factors influencing water use by plantations are amenable to management control, so there is scope to design and manage forest plantations deliberately for water use efficiency. Research is needed to elucidate the relative contributions of forests and grasslands to atmospheric moisture; the influence of vegetation on the distribution of rainfall; the effect of air turbulence from plantation edges, firebreaks and streamlines; the potential to modify atmospheric coupling of forest plantations through plantation design, including the use of mixed species plantations, and by softening hard edges by thinning and pruning plantation edges. [Copyright &y& Elsevier]

The bio-drainage commercial forestry strategy was applied in five plots in the Yizre'el Valley, northern Israel, to evaluate the hydrological and salinity impacts of eucalypt plantations. Each plot contained a mix of 11 selected eucalyptus species/ecotypes, Two plots (Nahalal and Genigar), representing the two extreme waterlogging/salinity conditions in the valley, were selected for in-depth monitoring over a 10-year period to assess the likely environmental improvement through bio-drainage. Despite impressive growth rates of genetically improved Eucalyptus camaldulensis in the year-round waterlogged, slightly saline Nahalal site (650 mm annual rainfall), the water uptake by the trees was insufficient to control the rising water table caused by excessive water inputs, both natural and human. In the more saline, alkaline and drier Genigar plot (450 mm annual rainfall), where rainfall is the only water input, the ground water dropped to below 3 m from soil surface in the fourth year after planting, i.e. deeper than the adjacent ground water levels. Both sites showed appreciable rise in wells that penetrated the 3- to 4-m confining layer. The 10-year salinity (EC) trend of the top layer in Nahalal varied because the drainage was limited by the positive water balance and the above-average spells of dry winters. In and below the 4 m deep layer the EC remained below 1-5 dS m-1 throughout the entire 10-year study. The last EC measurement, taken in 2003, showed values not higher than 4 dS m-1 throughout the 6 m soil profile. In Genigar, there was significant leaching of salts from the top layer (1 m) during the 9-year monitoring period, but recently a salts 'bulge' was gradually developed in the 1-5 m strata indicating that the expected downward movement of leached salts was impeded by the 3-4 m deep low-permeability clayey layer that lies over a coarser, far more conductive and notably confined layer, which leads to a perched water body. The last EC measurement at the end of 2003 showed a maximum value of 5.5 dS m-1 at 3 m depth. No signs of tree stress were observed in either site, at any soil depth during the 10 years of monitoring. Theoretical considerations do not support the hypothesis that there would be a fatal long-term accumulation of salts in the root zone. The Israeli experience has shown that the bio-drainage technique can effectively lower a shallow water table and reverse salinity trends, provided that the overall water balance is negative. i.e. that the water inputs match the water use by the tree plantation and local drainage characteristics. However, the rate of improvement of the hydraulic, salinity, sodicity and soil physical properties is site specific. Excess fresh water inputs into the plantation, although they create waterlogging conditions, supply unlimited water to the trees, which, in turn, show exceptional growth rates, with usable commercial value. [ABSTRACT FROM AUTHOR]

This field study examined the ecophysiological responses of three tree species to salinity in the Austin Bay Nature Reserve, adjacent to the Peel-Harvey Estuary in Western Australia (115°46′ E 32°37′ S). The area is at increased risk of flooding with saline water during storm surges due to the construction of a channel between the estuary and Indian Ocean in 1994. Banksia attenuata R.Br. occurs on small sandy ridges adjacent to a seasonal wetland, while Melaleuca cuticularis Labill. and Casuarina obesa Miq. occur in a seasonally flooded wetland. Landscape position determined exposure to salinity, with M. cuticularis and C. obesa experiencing high soil and groundwater salinity during summer (electrical conductivity, EC, up to 70 dS m−1) while B. attenuata was not exposed to soil or groundwater with EC greater than 20 dS m−1. B. attenuata had relatively stable leaf water status throughout the year and did not osmotically adjust as root-zone salinity increased. By contrast, M. cuticularis and C. obesa had large variation in stem water potential and exhibited osmotic adjustment during summer. Whereas the sap flow rates of M. cuticularis and C. obesa remained high throughout the year, sap flow of B. attenuata decreased during summer which may have limited uptake of salt. The three species also exhibited differences in traits associated with tissue-level salt tolerance, as M. cuticularis and C. obesa produced compatible organic solutes (methyl proline in M. cuticularis and proline in C. obesa), whereas B. attenuata did not. The distributions of these species within the Austin Bay Nature Reserve are determined in part by their tolerance to salinity, which will influence their responses to hydrological disturbance. [ABSTRACT FROM AUTHOR]

An investigation was made into the effects of long- and short-term water stress on the growth and water relations of species of Acacia belonging to four major sections of the subgenus Phyllodineae; the bipinnate-leaved Botrycephalae and the phyllodinous Juliflorae, Phyllodineae and Plurinerves. The germplasm was collected from sites within a narrow rainfall band [700–800 mm mean annual rainfall (m.a.r.)]. Shoot and root mass were significantly decreased in three of the four sections by water stress. The exception was the Juliflorae that showed a conservative growth strategy. A high root/shoot ratio is associated with tolerance to arid or semiarid environments, however, the highest root/shoot ratio was found for the temperate Botrycephalae. Measurements were made of the capacity for active and partial osmoregulation. All sections showed a biphasic response to drought stress for natural logarithm plots of relative water content (RWC) vs. osmotic potential in one or both experiments. This pattern of response has previously only been reported in a few plant species. Osmotic adjustment (OA) ranged from 1.6 MPa for the Botrycephalae to 3.4 MPa for Juliflorae at RWC of 60%. Active osmoregulation in the second phase was lower for the Botrycephalae and Phyllodineae than for the Juliflorae and Plurinerves. Although the germplasm was collected within a narrow and relatively high m.a.r. band, the sections with arid and semiarid relatives (Juliflorae and Plurinerves) still retained a higher degree of xeromorphic character and drought tolerance as determined by the growth responses and the higher capacity for OA. [ABSTRACT FROM AUTHOR]

Water relations of Engelmann spruce (Picea engelmannii Parry) and subalpine fir (Abies lasiocarpa (Hook.) Nutt.) trees growing at an elevation of 3230 m on Mt. Evans, Colorado, USA, were studied during the winters of 1995–1996 and 1996–1997. During both winters, current-year and 1-year-old shoots were collected weekly and their relative water contents (RWC) determined. Measured meteorological parameters were used in a conifer winter water relations model, WINWAT, to simulate changes in shoot RWC of P. engelmannii and A. lasiocarpa during the winter. The model failed to predict shoot RWCs in 1996–1997 when calibrated with 1995–1996 data. The cold early summer of 1995 inhibited xylem formation, which appears to have caused lower rates of water recharge to the needles during the 1995–1996 winter than during the 1996–1997 winter. We conclude that summer climate strongly affects winter water relations in these subalpine species, and that changes in both summer and winter climate must be considered when predicting future ranges of these species. [ABSTRACT FROM PUBLISHER]