Adaptive responses of a tree species from rainforests to the progression of semi-arid conditions of dry forests: Rainfall simulation experiment

Climate change threatens plant survival, requiring effective adaptive responses. Projections indicate that tropical rainforests will face drier conditions, resembling seasonally dry forests, highlighting the need to understand plant adaptations. In this context, this study evaluated the growth, anatomical traits, and survival of Schinus terebinthifolius seedlings, a species typical of rainforests, under three simulated precipitation regimes representative of seasonally dry forests: rainy years (>833 mm), median years (>433 and < 833 mm) and dry years (<433 mm), with 40 replicates per treatment. The seedling responses were monitored over the course of one year, encompassing the rainy and dry seasons typical of seasonally dry forests, under three possible climatic scenarios. Growth rates and leaf production were higher in rainy years. During the dry season, plants exhibited aerial system loss, diameter reduction, and leaf shedding. Precipitation did not significantly affect root biomass in the rainy and dry years’ treatments, survival in rainy years, or root-to-shoot ratio in dry years. In treatment of the median years, precipitation significantly influenced all measured variables. The physiological and anatomical responses of the species to projected climatic conditions for seasonally dry forests include reductions in leaf area and dry mass, accompanied by an increased frequency of smaller xylem vessels. These observed adjustments suggest that some individuals may still survive the advanced semi-arid climatic conditions of seasonally dry forests. These findings confirm the theory of a possible floristic convergence between humid and dry forests, with similar functional traits, whose occurrence will be directly linked to interannual precipitation variability.