Climate and landscape context drive the functional composition of young tropical forests

Résumé fourni par la source

Human-modified tropical landscapes are mosaics of farmland, young regrowing forests, and old-growth forests. These fragmented landscapes are hotter and drier than forested landscapes and, combined with climate change, may lead to shifts in forest community composition. We asked how macroclimate and surrounding landscape shape community-level drought strategies of young regrowing secondary forests. We assessed community composition of 37 young secondary dry and wet forests in Ghana during the first 3 years of succession, collected drought-related leaf and stem traits of their pioneer species, and quantified surrounding landscape cover within an 800-m radius around each plot. Macroclimate had the strongest influence on community drought strategies. Dry forest communities avoided drought through leaf shedding, delayed drought through small compound leaves that reduce heat load, and tolerated drought through dense wood and slow-wilting leaves that both help maintain function during drought stress. Wet forest communities showed the opposite suite of traits, reflecting prioritization of fast growth under high water availability. Landscape context reinforced different forest recovery trajectories by further shaping community traits. Agricultural cover reduced community wood density in the dry forest, whereas it increased wood density in the wet forest and tended to increase drought traits such as small, compound, and deciduous leaves. Surrounding secondary forest cover promoted fast-growing species with acquisitive leaves and low leaf mass per area in the dry forest, likely due to increased propagule pressure of pioneer species. Greater surrounding old-growth cover increased leaf dry matter content in the wet forest, supporting the recruitment of conservative, shade-tolerant late-successional species. Macroclimate, landscape context, and their interaction thus jointly shape community functional composition and drought strategies of regrowing forests.

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