Lebrija-Trejos Edwin, Hernández Andrés, Wright S Joseph
Department of Biology and Environment, University of Haifa-Oranim, Kiryat Tiv'on, Israel.
Smithsonian Tropical Research Institute, Balboa Ancón, Panama.
Nature. 2023 Mar;615(7950):100-104. doi: 10.1038/s41586-023-05717-1. Epub 2023 Feb 15.
Tropical tree diversity increases with rainfall. Direct physiological effects of moisture availability and indirect effects mediated by biotic interactions are hypothesized to contribute to this pantropical increase in diversity with rainfall. Previous studies have demonstrated direct physiological effects of variation in moisture availability on tree survival and diversity, but the indirect effects of variation in moisture availability on diversity mediated by biotic interactions have not been shown. Here we evaluate the relationships between interannual variation in moisture availability, the strength of density-dependent interactions, and seedling diversity in central Panama. Diversity increased with soil moisture over the first year of life across 20 annual cohorts. These first-year changes in diversity persisted for at least 15 years. Differential survival of moisture-sensitive species did not contribute to the observed changes in diversity. Rather, negative density-dependent interactions among conspecifics were stronger and increased diversity in wetter years. This suggests that moisture availability enhances diversity indirectly through moisture-sensitive, density-dependent conspecific interactions. Pathogens and phytophagous insects mediate interactions among seedlings in tropical forests, and many of these plant enemies are themselves moisture-sensitive. Changes in moisture availability caused by climate change and habitat degradation may alter these interactions and tropical tree diversity.
热带树木的多样性随降雨量增加。水分可利用性的直接生理效应以及由生物相互作用介导的间接效应被认为是导致这种热带地区多样性随降雨增加的原因。以往的研究已经证明了水分可利用性变化对树木生存和多样性的直接生理效应，但水分可利用性变化通过生物相互作用对多样性的间接效应尚未得到证实。在这里，我们评估了巴拿马中部水分可利用性的年际变化、密度依赖相互作用的强度与幼苗多样性之间的关系。在20个年度队列中，幼苗在生命的第一年，其多样性随土壤湿度增加。这些第一年的多样性变化至少持续了15年。对水分敏感物种的差异存活并不是观察到的多样性变化的原因。相反，同种个体之间的负密度依赖相互作用在较湿润年份更强，且增加了多样性。这表明水分可利用性通过对水分敏感的、依赖密度的同种相互作用间接提高了多样性。病原体和植食性昆虫介导热带森林中幼苗之间的相互作用，而且这些植物敌人中的许多本身对水分敏感。气候变化和栖息地退化引起的水分可利用性变化可能会改变这些相互作用以及热带树木的多样性。
