Abstract
Successful management of forest systems requires a deeper understanding of the role of ecophysiological traits in enabling adaptation to high temperature and water deficit under current and anticipated changes in climate. A key attribute of leaf water relations is the water potential at zero turgor (πtlp), because it defines the operating water potentials over which plants actively control growth and gas exchange. This study examines the drivers of variation in πtlp with respect to species climate of origin and habitat water availability. We compiled a water relations database for 174 woody species occupying clearly delineated gradients in temperature and precipitation across the Australian continent. A significant proportion of the variability in πtlp (~35%) could be explained by climatic water deficit and its interaction with summertime maximum temperature, demonstrating the strong selective pressure of aridity and high temperature in shaping leaf water relations among Australian species. Habitat water availability (midday leaf water potential), was also a significant predictor of πtlp (R2 = 0.43), highlighting the importance of species ecohydrologic niche under a set of climatic conditions. Shifts in πtlp in response to both climatic and site-based drivers of water availability emphasises its adaptive significance and its suitability as a predictor of plant performance under future climatic change.
Highlights
IntroductionPredicted increases in extremes such as drought events and heat waves, in conjunction with long-term changes in water availability (increasing or decreasing) and temperature regimes (increasing) will potentially drive significant changes in forest productivity
Predicted increases in extremes such as drought events and heat waves, in conjunction with long-term changes in water availability and temperature regimes will potentially drive significant changes in forest productivity
The bulk of the species within the database were derived from climates with mean annual precipitation (MAP) < 1000 mm and mean annual temperature (MAT) > 10 °C, reflecting the relatively dry and warm climates experienced across much of the Australian landscape
Summary
Predicted increases in extremes such as drought events and heat waves, in conjunction with long-term changes in water availability (increasing or decreasing) and temperature regimes (increasing) will potentially drive significant changes in forest productivity. Successful management of existing or new forests to deliver a range of commodities and environmental services under these conditions must include careful consideration of species capacity to absorb future climatic disturbances and adapt to future climate regimes. This requires a deeper understanding of the role of ecophysiological traits in enabling adaptation of species and genotypes to high temperature and water deficit. Plants actively accumulate solutes in order to lower their osmotic potential during water deficit, thereby sustaining turgor and prolonging water uptake [6]. Pressure-volume relationships are routinely used to estimate these key parameters of leaf physiology [7] and are often interpreted as indicators of species drought tolerance i.e., the ability to maintain physiological function at low water status [8,9]
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