Lackey, Russell , Schwilk, Dylan .
Oak Vulnerability to Xylem Cavitation in a Sky Island Mountain Range.
In arid and semi-arid systems,differences in water-use strategies are recognized as important drivers of niche differentiation. The arid and semi-arid American Southwest is expected to see longer, more severe droughts, but our ability to predict species responses to such change is hampered by gaps in our current understanding of the interactions among drought and temperature stress(both high temperatures and freezing stress). When dealing with climate change and warming temperatures, an often overlooked but potentially important determining factor in niche differentiation of species in these systems is freezing stress; freezing combined with droughtmay lead to freeze-thaw induced xylem embolism. The objective of this study was to determine the variation across species of leaf traits and hydraulic functional traits and to determine their relationships to environmental variables. We approached this by conducting a comparative study of water use strategies among coexisting tree species from a single genera that differ in micro habitat preferences along elevation and soil characteristic gradients in a desert mountain range. Measuring vulnerability to water stress induced cavitation has emerged as one of the most powerful ways in which to assess drought tolerance and determine trade-offs between safety and efficacy of water movement. Detailed xylem functional traits were collected on five oak (Quercus: Fagaceae) species in the Nature Conservancy's Davis Mountain Preserve. Vulnerability to cavitation curves were produced using centrifugal methods. We measured leaf functional traits including minimal seasonal water potentials, leaf gas exchange measurements and leaf mass per area. Environmental variable measurements were also obtained for this preserve to model temperature and soil moisture variation across topography and through time. The combination of environmental, existing plant community structure and plant functional trait information will serve as a valuable starting point in determining future optimal species distributions under climate change. Results show strong differences across species in susceptibility to xylem embolism. Temperature data shows that lower elevations experience more freezing events and higher daily temperature ranges than do higher locations. The data suggest that future distribution shifts maybe much more complex than originally thought and may result in the downward movement of some freezing susceptible species.
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1 - Texas Tech University, Biological Sciences, Box 43131 , Box 43131, Lubbock, Texas, 79409, United States
2 - Texas Tech University, Biological Sciences, Texas Tech University, Department of Biological Sciences, Box 43131, Lubbock, Texas, 79409, United States
Presentation Type: Oral Paper:Papers for Sections
Location: Union B/Hyatt
Date: Tuesday, July 10th, 2012
Time: 2:00 PM