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"Water relations"
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Water conflict : economics, politics, law and Palestinian-Israeli water resources
A study of the conflict over the natural water resources of geographic Palestine. The author focuses on both the scarcity and commonality of the water resources in order to demonstrate why water has become one of the most contentious issues between Israel and the Palestinians. He discusses how the principles of equitable utilization and joint management of common water resources can be achieved and can enhance the prospects for reducing conflict over water, and may ultimately contribute to overall Israeli-Palestinian cooperation. Includes several maps and charts which detail the area's water resources. Annotation copyrighted by Book News, Inc., Portland, OR.
Book
How do stomata respond to water status?
Stomatal responses to humidity, soil moisture and other factors that influence plant water status are critical drivers of photosynthesis, productivity, water yield, ecohydrology and climate forcing, yet we still lack a thorough mechanistic understanding of these responses. Here I review historical and recent advances in stomatal water relations. Clear evidence now implicates a metabolically mediated response to leaf water status (‘hydroactive feedback’) in stomatal responses to evaporative demand and soil drought, possibly involving abscisic acid production in leaves. Other hypothetical mechanisms involving vapor and heat transport within leaves may contribute to humidity, light and temperature responses, but require further theoretical clarification and experimental validation. Variation and dynamics in hydraulic conductance, particularly within leaves, may contribute to water status responses. Continuing research to fully resolve mechanisms of stomatal responses to water status should focus on several areas: validating and quantifying the mechanism of leaf-based hydroactive feedback, identifying where in leaves water status is actively sensed, clarifying the role of leaf vapor and energy transport in humidity and temperature responses, and verifying foundational but minimally replicated results of stomatal hydromechanics across species. Clarity on these matters promises to deliver modelers with a tractable and reliable mechanistic model of stomatal responses to water status.
Journal Article
Climate and functional traits jointly mediate tree water-use strategies
Tree water use is central to plant function and ecosystem fluxes. However, it is still unknown how organ-level water-relations traits are coordinated to determine whole-tree water-use strategies in response to drought, and whether this coordination depends on climate.
Here we used a global sap flow database (SAPFLUXNET) to study the response of water use, in terms of whole-tree canopy conductance (G), to vapour pressure deficit (VPD) and to soil water content (SWC) for 142 tree species. We investigated the individual and coordinated effect of six water-relations traits (vulnerability to embolism, Huber value, hydraulic conductivity, turgor-loss point, rooting depth and leaf size) on water-use parameters, also accounting for the effect of tree height and climate (mean annual precipitation, MAP).
Reference G and its sensitivity to VPD were tightly coordinated with water-relations traits rather than with MAP. Species with efficient xylem transport had higher canopy conductance but also higher sensitivity to VPD. Moreover, we found that angiosperms had higher reference G and higher sensitivity to VPD than did gymnosperms.
Our results highlight the need to consider trait integration and reveal the complications and challenges of defining a single, whole-plant resource use spectrum ranging from ‘acquisitive’ to ‘conservative’.
Journal Article
The value of wet leaves
An often-overlooked feature of all plants is that their leaf surfaces are wet for significant periods over their lifetimes. Leaf wetting has a number of direct and indirect effects on plant function from the scale of the leaf to that of the ecosystem. The costs of leaf wetting for plant function, such as the growth of pathogens and the leaching of nutrients, have long been recognized. However, an emerging body of research has also begun to demonstrate some very clear benefits. For instance, leaf wetting can improve plant–water relations and lead to increased photosynthesis. Leaf wetting may also lead to synergistic effects on plant function, such as when leaf water potential improvements lead to enhanced growth that does not occur when plant leaves are dry. We identify important reasons why leaf wetting can be critical for plant sciences to not only acknowledge, but also directly address, in future research. To do so, we provide a framework for the consideration of the relative balance of the various costs and benefits resulting from leaf wetting, as well as how this balance may be expected to change given projected scenarios of global climate change in the future.
Journal Article
Greater focus on water pools may improve our ability to understand and anticipate drought-induced mortality in plants
Drought-induced tree mortality has major impacts on ecosystem carbon and water cycles, and is expected to increase in forests across the globe with climate change. A large body of research in the past decade has advanced our understanding of plant water and carbon relations under drought. However, despite intense research, we still lack generalizable, cross-scale indicators of mortality risk. In this Viewpoint, we propose that a more explicit consideration of water pools could improve our ability to monitor and anticipate mortality risk. Specifically, we focus on the relative water content (RWC), a classic metric in plant water relations, as a potential indicator of mortality risk that is physiologically relevant and integrates different aspects related to hydraulics, stomatal responses and carbon economy under drought. Measures of plant water content are likely to have a strong mechanistic link with mortality and to be integrative, threshold-prone and relatively easy to measure and monitor at large spatial scales, and may complement current mortality metrics based on water potential, loss of hydraulic conductivity and nonstructural carbohydrates. We discuss some of the potential advantages and limitations of these metrics to improve our capacity to monitor and predict drought-induced tree mortality.
Journal Article
Pachamama politics : campesino water defenders and the anti-mining movement in Andean Ecuador
\"Pachamama Politics examines how campesinos came to defend their community water sources from gold mining upstream and explains why Ecuador's \"pink tide\" government came under fire by Indigenous and environmental rights activists\"-- Provided by publisher.
BOOK
Review: Safe and sustainable groundwater supply in China
Exploitation of groundwater has greatly increased since the 1970s to meet the increased water demand due to fast economic development in China. Correspondingly, the regional groundwater level has declined substantially in many areas of China. Water sources are scarce in northern and northwestern China, and the anthropogenic pollution of groundwater has worsened the situation. Groundwater containing high concentrations of geogenic arsenic, fluoride, iodine, and salinity is widely distributed across China, which has negatively affected safe supply of water for drinking and other purposes. In addition to anthropogenic contamination, the interactions between surface water and groundwater, including seawater intrusion, have caused deterioration of groundwater quality. The ecosystem and geo-environment have been severely affected by the depletion of groundwater resources. Land subsidence due to excessive groundwater withdrawal has been observed in more than 50 cities in China, with a maximum accumulated subsidence of 2–3 m. Groundwater-dependent ecosystems are being degraded due to changes in the water table or poor groundwater quality. This paper reviews these changes in China, which have occurred under the impact of rapid economic development. The effects of economic growth on groundwater systems should be monitored, understood and predicted to better protect and manage groundwater resources for the future.
Journal Article