Water Availability Impacts on Evapotranspiration Partitioning

Knowing how evapotranspiration (ET) is mediated by abiotic and biotic pathways essential to understanding water affects ecosystem productivity. Recent studies have investigated the average transpiration fraction (T/ET) across sites biomes, but temporal variability of partitioning its controls are less understood. Here, we examine availability may regulate seasonal interannual ET partitioning. To do this, leveraged four techniques long-term (14 years) eddy-flux records from a semiarid grassland riparian woodland site in southeastern Arizona USA that share same climate differ table depth. T/ET was sensitive changes over space time as evidenced consistently lower more variable at grassland, where vegetation does not access groundwater. Seasonally, pronounced dry foresummer depression rainfall-dependent resulted bimodal distribution. In contrast, unimodally distributed groundwater-dependent woodland, high levels were maintained throughout both wet summer periods. Annual closely tracked quantified ET, whereas evaporation nearly constant. All methods yielded similar patterns T/ET, although they differed approximately 5 10% magnitude. At sites, most correlated plant metrics (photosynthesis, leaf area index) surface moisture variables (soil moisture, precipitation). However, substantial differences between monthly annual correlations demonstrate on year. These results provide novel insights into effects illuminate mechanisms regulating terrestrial carbon exchange.