Widespread and complex drought effects on vegetation physiology inferred from space

Area of Science:

• Earth and Environmental Sciences
• Ecology
• Plant Physiology

Background:

• Understanding vegetation's physiological response to drought at large scales is limited by observational data.
• Drought impacts ecosystem function, but the specific physiological mechanisms are not fully elucidated.

Purpose of the Study:

• To investigate vegetation physiological responses to drought using remote sensing and machine learning.
• To quantify the role of physiological changes (photosynthesis, evaporation, water content) in vegetation function under drought.
• To identify key drivers of vegetation physiological drought responses across diverse regions.

Main Methods:

• Utilized remotely sensed data to analyze vegetation physiological parameters like photosynthesis, evaporation, and water content.
• Employed a machine learning technique to isolate physiological drought responses from broader vegetation changes.
• Validated findings using simulations from a coupled soil-plant-atmosphere continuum and radiative transfer model.

Main Results:

• Vegetation functional decreases are primarily driven by physiological downregulation (stomatal conductance, light use efficiency), especially in arid regions.
• Physiological declines in wetter regions create a divergence between vegetation function and structure during severe drought.
• Aridity is the main factor controlling spatial patterns of physiological drought response, modulated by hydro-meteorological conditions and vegetation types.

Conclusions:

• Isolating vegetation physiological responses to drought is essential for understanding ecosystem feedbacks to climate change.
• The study highlights the critical role of physiological adjustments in ecosystem resilience and vulnerability to drought.
• Findings provide a more nuanced understanding of how different regions and vegetation types respond to water stress.