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作者 Ambrose, Anthony Ray
書名 Effects of climate and water stress on physiological performance in California's redwoods
國際標準書號 9781124029160
book jacket
說明 161 p
附註 Source: Dissertation Abstracts International, Volume: 71-06, Section: B, page: 3523
Adviser: Todd E. Dawson
Thesis (Ph.D.)--University of California, Berkeley, 2009
The physiology of trees is strongly influenced by environmental conditions. However, our understanding of how changes in tree size affect their response to the environment remains limited. This dissertation examines the effects of climate and water stress on physiological performance in different-sized coast redwood (Sequoia sempervirens) and giant sequoia ( Sequoiadendron giganteum) trees in both greenhouse and field settings
When exposed to soil water stress and high vapour pressure deficit (VPD), S. giganteum saplings maintained higher leaf water potentials (Psi) and gas exchange rates than S. sempervirens saplings. S. giganteum saplings also maintained higher leaf gas exchange rates at a given leaf Psi and VPD, but also exhibited greater stomatal sensitivity to decreasing Psi and increasing VPD. Variation in leaf soluble sugar carbon isotope discrimination (Delta13C) and leaf water oxygen isotope enrichment (Delta18O) in saplings was related to differences in gas exchange rates and VPD. Taller trees have lower leaf Psi than shorter trees due to greater effects of gravity and friction on water transport. Variation in Delta13C and Delta18O along vertical gradients in mature trees of different height was related to changes in leaf Psi, leaf gas exchange capacity, leaf structure, and canopy microclimate. Adjustments in treetop branch water transport capacity and cavitation vulnerability partially compensated for lower leaf Psi in taller trees. Despite these adjustments, increasing leaf mass per unit area (LMA) led to decreasing mass-based gas exchange rates with height. Species-level differences in LMA, wood density, and area-based gas exchange rates constrained other structural and physiological responses to increased height. Treetop transpiration and stomatal conductance also decreased with increasing height in S. sempervirens, although shorter trees exhibited greater stomatal sensitivity to increasing VPD than taller trees
These results reveal that the two redwood species exhibit fundamental differences in their physiological response to climate and water stress that reflects contrasting environmental conditions in their native habitat. They also suggest that the physiological response of redwoods to climate change will vary with tree size and age, and that the combined analysis of Delta 13C and Delta18O can be useful for examining climate and water stress effects on physiological performance in redwoods
School code: 0028
Host Item Dissertation Abstracts International 71-06B
主題 Climate Change
Biology, Plant Physiology
0404
0817
Alt Author University of California, Berkeley
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