Water Resilience of Aldina heterophylla (Fabaceae): An Endemic Tree from Amazonian White-Sand Forests Under Drought and Waterlogging Stress

Amazonian white-sand forests (campinarana) are highly specialized ecosystems characterized by nutrient-poor sandy soils and pronounced seasonal variation in water availability. Plant species inhabiting these environments are exposed to alternating periods of water deficit and soil saturation, which may strongly constrain recruitment and early establishment. Aldina heterophylla is an endemic tree species specialist in these habitats. This study evaluated seed germination, biomass allocation, anatomical traits, and early seedling responses of A. heterophylla under contrasting water regimes: control, partial flooding, and drought. Seedling performance was assessed after 50 and 100 days of treatment. After 50 days, flooded seedlings showed significantly greater root biomass than control plants, indicating short-term plastic adjustment to saturated soils. However, prolonged flooding induced chlorosis, necrosis, leaf abscission, and partial mortality. In contrast, drought-stressed seedlings developed leaf senescence but maintained 100% survival throughout the experiment. Morphological and physiological traits varied significantly over time among treatments, particularly leaf number, height, and chlorophyll dynamics. The results indicate that A. heterophylla seedlings are more tolerant to water deficit than to prolonged flooding, although they display adaptive responses to temporary soil saturation. These findings improve understanding of regeneration processes in Amazonian white-sand ecosystems and provide relevant information for conservation planning under increasing climatic extremes.