The relative role of soil moisture and vapor pressure deficit in affecting the Indian vegetation productivity

Atmospheric aridity (vapor pressure deficit, VPD) and soil moisture (SM) deficit limit plant photosynthesis and, thus, affect vegetation carbon uptake. The strong correlation between SM and VPD makes it challenging to delineate their relative contributions to regional vegetation productivity. Addressing this gap is vital to understand the future trajectory of plant productivity in India-the second-highest contributor to global greening. Here, we separate the controls of SM and VPD on the Indian vegetation using statistical and causal analysis. We found that vegetation productivity in India is primarily controlled by SM limitation (87.66% of grids) than VPD limitation (12.34% of grids). Vegetation has a varying association with SM and VPD across different agroecological regions in India. The negative impact of VPD on vegetation carbon uptake is not visible in high-rainfall areas of India. These findings advance our understanding of vegetation dynamics under regional dryness stress and can enhance dynamic vegetation model estimates for India under changing climate scenarios.

Automated summary

Atmospheric aridity and soil moisture deficit have different impacts on vegetation productivity in India, with soil moisture being the primary limiting factor. The association between vegetation and atmospheric aridity varies across different agroecological regions in India. These findings contribute to our understanding of vegetation dynamics under regional dryness stress and can improve dynamic vegetation model estimates for India in a changing climate.