Drought impact on tree productivity: Varying roles of tree size and structural diversity in 18 woody species along gradients of slow-fast growth strategies

Abstract

Previous studies have shown significant variation in drought effects on forest productivity, potentially linked to differing structural attributes among forest ecosystems. However, the influences of tree size and structural diversity, especially across different species, remain poorly understood. We analyzed large-scale forest survey data to examine the interactive effects of structural attributes and drought on the growth of 18 dominant species in southcentral U.S. forests. Additionally, we explored five functional traits to understand their association with these effects. Our findings reveal species-specific responses to the interactive effects of drought with tree height and structural diversity on tree growth, ranging from negative (amplifying) to positive (mitigating). Greater tree height had more pronounced mitigating effects in species with a slow growth strategy, characterized by short maximum heights and high leaf dry mass. Greater structural diversity also mitigated drought effects, particularly in species with low specific leaf area, leaf nitrogen content, and deeper rooting. Our study provides insights for projecting and managing forest productivity under drought by considering the forest structures and species-specific growth strategies.