Contrasting precipitation seasonality influences evapotranspiration dynamics in water‐limited shrublands

Abstract

Water‐limited ecosystems occupy nearly 30% of the Earth, but arguably, the controls on their ecosystem processes remain largely uncertain. We analyzed six site years of eddy covariance measurements of evapotranspiration (ET) from 2008 to 2010 at two water‐limited shrublands: one dominated by winter precipitation (WP site) and another dominated by summer precipitation (SP site), but with similar solar radiation patterns in the Northern Hemisphere. We determined how physical forcing factors (i.e., net radiation (Rn), soil water content (SWC), air temperature (Ta), and vapor pressure deficit (VPD)) influence annual and seasonal variability of ET. Mean annual ET at SP site was 455 ± 91 mm yr−1, was mainly influenced by SWC during the dry season, by Rn during the wet season, and was highly sensitive to changes in annual precipitation (P). Mean annual ET at WP site was 363 ± 52 mm yr−1, had less interannual variability, but multiple variables (i.e., SWC, Ta, VPD, and Rn) were needed to explain ET among years and seasons. Wavelet coherence analysis showed that ET at SP site has a consistent temporal coherency with Ta and P, but this was not the case for ET at WP site. Our results support the paradigm that SWC is the main control of ET in water‐limited ecosystems when radiation and temperature are not the limiting factors. In contrast, when P and SWC are decoupled from available energy (i.e., radiation and temperature), then ET is controlled by an interaction of multiple variables. Our results bring attention to the need for better understanding how climate and soil dynamics influence ET across these globally distributed ecosystems.

Land–Atmosphere Exchange of Water and Heat in the Arid Mountainous Grasslands of Central Asia during the Growing Season

“…However, the P was markedly high in August compared to the ET. This phenomenon regarding the role of temperature and P on ET was similar to some findings in previous studies [45,46]. Monthly variations in the ET were closely related to vegetation growth during the growing period in this region; in 2013 and 2015, the ET rapidly increased with vegetation growth from April to July and reached its maximum value in July.…”

Seasonal divergence in the sensitivity of evapotranspiration to climate and vegetation growth in the Yellow River Basin, China

“…Recent research has revealed that interannual precipitation and temperature variations predominantly control variations in regional ET and hydrological cycles in many parts of these water‐limited regions [ Gao et al ., ; Goyal , ; Liu and Yang , ; K. Wang et al ., ]. Variations in other climate factors, such as soil moisture availability [ Villarreal et al ., ], solar radiation [ S. Y. Zhang et al ., ], vapor‐pressure deficits, and wind speed [ Burn and Hesch , ], also play an important role in mediating regional spatial and temporal ET patterns. In addition, changes in vegetation growth affect ET through their regulatory effects on land‐surface roughness, albedo, and water interception [ Shen et al ., ].…”

Optimizing an Environmental Observatory Network Design Using Publicly Available Data

“…On one side, MexFlux sites have contributed to synthesis studies to better understand the role of water‐limited ecosystems across North America (Biederman et al, ; Villarreal et al, ). On the other side, the lack of coordination on the distribution of MexFlux sites has resulted in a lack of representativeness for monitoring GPP and ET at the national level (Figures d and d and Table ).…”