Legacy effects of climate extremes on deep soil water storage and water use efficiency across different land-use systems

Climate extremes, including multiyear droughts and extreme rainfall events, are projected to intensify, threatening the global water cycle and reducing agricultural productivity. Deep soil water storage plays a key role in buffering extremes, yet its influence on plant productivity and water use across land-use systems remains insufficiently understood. Here, we monitored soil moisture dynamics over three years and vegetation responses in a long-term field trial comprising five land-use types (two croplands: conventional & organic farming; three grasslands: intensive meadow, extensive meadow & pasture). The monitoring period captured both prolonged droughts and an extreme rainfall. We found strong legacy effects of past droughts on deep soil water storage (30–110 cm), which decoupled plant productivity from short-term climate fluctuations. Extensive grasslands exploited the deep soil water storage more efficiently than intensive grasslands and croplands, because of longer transpiration demand and higher interception caused by the perennial vegetation cover. In turn, water use efficiency increased with land-use intensity, driven by shorter growing periods in croplands and higher mowing frequency in intensive grasslands. Our findings highlight how land-use practices shape ecosystem responses to climate extremes and underscore the need to incorporate deep soil water dynamics into sustainable land-management strategies under future climate conditions.