Increase in plant reliance on past precipitation associated with greening and drying
摘要
Water is indispensable for life on Earth. Plants use water either from recent precipitation (within a month) or from past precipitation stored in deeper soil (PP; at least a month ago) to maintain metabolism and growth. It is widely known that plants tend to rely more on PP to buffer against short-term rainfall deficits. However, how this reliance has changed in response to global change remains unclear. Here we develop a novel framework to estimate temporal changes in plant reliance on PP during the past four decades. Observational data reveal that 42% of tropical and subtropical natural ecosystems have experienced a significant increase in plant reliance on PP over the period 1982–2021 (P < 0.05). Such an increase is consistent with greening during the late growing season in drylands and drying during the wet-to-dry transitional period in non-drylands, when short-term precipitation fails to meet plant water demand. Adaptive changes in root depth and species composition may further facilitate this change in PP reliance, especially in drylands. Our study highlights the importance of PP in ecosystem functioning and implies an increasing ecosystem resilience to climate variability.