Sequía experimental en plántulas en un claro y en el sotobosque de un bosque de niebla, Veracruz, México

Abstract

Background and Aims: Droughts induced by climate change are expected to affect tropical cloud forests. As functional traits are useful indicators of plant species performance, this study aimed to determine the effect of light environment and drought on leaf area (LA), specific leaf area (SLA), chlorophyll content, leaf thickness and toughness, survival and relative growth rate (RGR) of seedlings in forest understory and gap. Methods: In a cloud forest from Veracruz, Mexico, rainout shelters to simulate drought in the forest understory and gap were used. Leaf area, SLA, chlorophyll content, leaf thickness and toughness, survival, and RGR in Eugenia capuli (shade-tolerant understory tree), Liquidambar styraciflua (intermediate shade-tolerant canopy tree), and Trema micranthum (pioneer tree that colonizes gaps) in understory-control and -drought, and gap-control and -drought were measured. Key results: Leaf area increased with drought in E. capuli in gaps and decreased in L. styraciflua in both light environments. Chlorophyll content was similar between water treatments for E. capuli and L. styraciflua in the understory. Leaf thickness and toughness differed with drought for E. capuli and L. styraciflua in the gap. Leaf traits of T. micranthum tended to change in understory and not in gap. Overall, the highest survival occurred in gap. Eugenia capuli displayed the highest and similar survival across treatments. Liquidambar styraciflua displayed higher survival in gap-drought, and T. micranthum in gap conditions. Eugenia capuli had the highest RGR in understory, whereas T. micranthum has the highest RGR in gap. Conclusions: Plant functional traits of E. capuli and L. styraciflua seedlings responded to moderate drought more in gap than in understory. The results suggest that functional traits of intermediate and shade-tolerant species may shift less under a moderate drought than those of a pioneer tree, as long as the forest light environment is maintained.

Research History of Forest Gap as Small-Scale Disturbances in Forest Ecosystems

“…Natural regeneration is delayed by changes in the forest microclimate and nutrient cycling [204], providing an important mechanism for the regeneration of bryophytes and canopy species that dominate the early successional stages of secondary forests [209]. Resource heterogeneity helps to maintain diversity in the understory community by allowing more typical early-successional community species to coexist with late-successional community species, and the functional traits of intermediate and shade-tolerant species are likely to shift less than those of pioneer trees under moderate drought conditions [210], as long as the forest light environment is maintained [211]. Light availability and other climate factors combine to influence species ranges at sensitive scales, and in general, climate is a major predictor of adult tree distributions.…”