H51D-0639:
Global Synthesis of Vegetation Control on Evapotranspiration Partition
Friday, 19 December 2014
Lixin Wang, Indiana University Purdue University Indianapolis, Indianapolis, IN, United States, Stephen P Good, University of Utah, Salt Lake City, UT, United States and Kelly K Caylor, Princeton Univ-E-Quad, Princeton, NJ, United States
Abstract:
Evapotranspiration (ET) is an important component of the global hydrological cycle, and is comprised of evaporation (E) and transpiration (T). To what extent T/ET ratios are controlled by vegetation and how to explain the global-scale T/ET variations are not clear. This hinders our predictions of future hydrological changes since vegetation provides a strong feedback to water cycling. We synthesized all the published papers that experimentally quantified at least two of three ET components and measured leaf area index (LAI) simultaneously. Non-linear relationships between T/ET and LAI are identified for both the overall dataset as well as agricultural and natural data subsets. Large variations in T/ET occur across all LAI ranges, with wider variability in T/ET at lower LAI levels. We find that for a given LAI amount, higher T/ET ratios occur latter in the growing season. We developed a function relating T/ET ratios to the growing stage relative to the timing of peak LAI. These two parameters, LAI and growing stage, collectively explained 43% of the variations in the global T/ET dataset, providing a new way to interpret and model the global T/ET variability.
