Trees remember drought: canopy adjustments boost spruce drought resistance while wet history hinders Swiss pines

Plant Biology researchers in Germany report that trees carry a memory of past water availability that shapes their drought responses. In a large Munich-area study, an artificial drought imposed on Norway spruce (Picea abies) and European beech (Fagus sylvatica) reduced leaf area and needle density, enabling trees to conserve water. Three years after the drought ended, spruce with drought history showed less physiological stress during a new drought than well-watered controls, indicating a lasting canopy-based water-saving strategy. Beech nearby also benefited from the spruce’s reduced canopy. In contrast, a Swiss Scots pine experiment found that previously irrigated trees under drought stress performed worse than drought-experienced trees, suggesting a wet-history memory can increase drought vulnerability. The findings highlight species-specific memory effects and caution against uniform expectations of forest responses to climate change. Author: Plant Biology.