How multiple factors control evapotranspiration in North America evergreen needleleaf forests

Abstract

Identifying the factors dominating ecosystem water flux is a critical step for predicting evapotranspiration (ET). Here, the fuzzy rough set with binary shuffled frog leaping (BSFL-FRSA) was used to identify both individual factors and multi-factor combinations that dominate the half-hourly ET variation at evergreen needleleaf forests (ENFs) sites across three different climatic zones in the North America. Among 21factors, air temperature (TA), atmospheric CO2 concentration (CCO2), soil temperature (TS), soil water content (SWC) and net radiation (NETRAD) were evaluated as dominant single factors, contributed to the ET variation averaged for all ENF sites by 48%, 36%, 32%, 18% and 13%, respectively. While the importance order would vary with climatic zones, and TA was assessed as the most influential factor at a single climatic zone level, counting a contribution rate of 54.7%, 49.9%, and 38.6% in the subarctic, warm summer continental, and Mediterranean climatic zones, respectively. In view of impacts of each multi-factors combination on ET, both TA and CCO2 made a contribution of 71% across three climate zones; the combination of TA, CCO2 and NETRAD was evaluated the most dominant at Mediterranean and subarctic ENF sites, and the combination of TA, CCO2 and TS at warm summer continental sites. Our results suggest that temperature was most critical for ET variation at the warm summer continental ENF.