Drought Resistance of Tropical Tree Seedlings

Pronounced changes of rainfall patterns, including more frequent and intense drought, are projected for the tropics. Seedlings are especially vulnerable to drought and provide the template for future forest composition. My colleagues and I combined observational, experimental, and mechanistic approaches to quantify drought effects on seedlings in the Barro Colorado Nature Monument and its implications for species distributions. We quantified seedling drought resistance experimentally as survival in dry relative to irrigated conditions in the forest understory, revealing tremendous variation across species that cooccur on Barro Colorado Island. Differences of dehydration tolerance and associated mechanisms, especially the turgor loss point, govern this interspecific variation. Drought resistance drives seedling survival and growth responses to temporal and spatial variation of soil moisture and plays a significant role in shaping differences in species distribution and diversity patterns.