资源环境科技发展态势分析平台

Understanding daytime (ET_D) and nighttime (ET_N) evapotranspiration is critical for accurately evaluating terrestrial water and carbon cycles. However, unlike ET_D, the factors influencing ET_N remain poorly understood. Here, long-term ET_D and ET_N data from five FLUXNET sites along a climate gradient in Northern Australia were analyzed to compare their responses to environmental drivers at different temporal scales. We found that (1) across the sites, mean annual ET_N/ET_D ( / ) ranged between 5.1% and 11.7%, which was mainly determined by variations. Particularly, vegetation and meteorological variables mostly controlled , while was largely related to air temperature and net radiation (Rn) due to lower nighttime atmospheric water demands; (2) At individual sites, ET_D and ET_N exhibited higher correlations with meteorological and vegetation variables at monthly timescales than at annual timescales. Monthly ET_D and ET_N were also strongly coupled, especially under drier climatic conditions. At daily timescales, leaf area index and soil water content (SWC) controlled ET_D with SWC being more important at drier sites; whereas, SWC was the dominant factor controlling ET_N. At half-hourly timescales, the boosted regression tree method quantitively showed that ET_D and ET_N were controlled by Rn and SWC, respectively. Overall, the results showed that ET_N was less responsive to environmental variables, illustrating that ET_D and ET_N responded differently to diverse climate regimes and ecosystems at varying temporal scales. These findings provide a critical evaluation for contrasting ET_D and ET_N interactions in constantly changing environments, which has important implications for ecosystem water balance and land surface processes modeling.

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