Disentangling hydroclimatic and irrigation controls on vegetation photosynthesis variability in India

A high-resolution satellite-derived solar-induced chlorophyll fluorescence (SIF) data product is used to investigate the roles of climatic variability and irrigation in modulating photosynthetic activity across India (2001–2020). This study establishes that hydroclimatic variations primarily govern the large-scale photosynthesis variability in India. Year-to-year variations in the irrigated area are influenced by climatic variability, particularly through changes in surface water availability for irrigation. The irrigated area does not exhibit a significant independent contribution to interannual SIF variability beyond the influence of rainfall variability at the annual scale. Rainfall exerts the dominant lagged (1-month) control on interannual SIF anomalies, while soil moisture and air temperature exert their strongest influence concurrently. These prominent hydroclimatic controls on vegetation productivity are further evaluated using an artificial neural network (ANN). The ANN reproduces photosynthesis variability with robust skill in croplands ( R 2 ensemble =0.62) and deciduous forests ( R 2 ensemble =0.60). Simulations align more closely with observations during the summer monsoon over croplands, whereas deciduous forests exhibit improved agreement during the post-monsoon season. Feature importance analysis reveals soil moisture as the dominant control (∼58%), with a more pronounced delayed rainfall influence in deciduous forests (32.7%) compared to croplands (23.6%). Air temperature exerts a comparatively greater influence in croplands (17.6%) than in deciduous forests (8.9%). A significant upward trend in all-India SIF (0.0014 Wm −2 μm −1 sr −1 ) is observed, coinciding with rapid expansion of the irrigated area (1013.56 ha yr⁻¹), largely associated with subsurface irrigation sources (∼63%). These findings enhance vegetation variability predictions in India and highlight the critical role of water resource management in sustaining agricultural productivity under a changing monsoon regime.