Soil moisture variation drives canopy water content dynamics across the western U.S.

Drought stress is a major contributing factor to plant mortality across the globe. effects are often studied at local scale, but recent advances in remote sensing allow for observations of water status broad geographic scales. The vegetation optical depth (VOD) derived from satellite-based surface microwave emission has been shown be sensitive canopy content, which increasingly recognized as an important indicator relations and incipient plants. We develop index quantifies normalized difference between night- daytime diurnal VOD retrievals (nVODr) apply it western U.S. determine relative sensitivity plants variations supply (soil moisture) atmospheric demand (vapor pressure deficit -VPD). Canopy content dynamics were most soil moisture variation intermediate climatic deficits where tree cover transitions grass cover. These areas transitional climate zones occur ecotones forest non-forest both VPD variation. Our results suggest that semi-arid likely see proximal impacts drought planet warms.