DYNAMICS OF SAP FLOW IN RESPONSE TO FLOODING IN TREE SPECIES OF A LOWLAND FOREST, SANTARÉM-PARÁ
seasonality, water resistance, leaf area, tolerance, flood pulse.
Water is a determining factor in the establishment and permanence of trees in diferente environments. Its availability is closely linked to physiological processes in plants and the proper functioning of ecosystems, especially in floodplain forests, which are highly dynamic ecosystems subject to a flood pulse every year. Flooding cycles induce tree species present in this ecosystem to develop strategies that allow them to tolerate waterlogging, and these strategies are the result of combinations of different mechanisms. Therefore, this study aims to investigate how flooded and non-flooed conditions influence the dynamics of xylem sap flow in tree species from a floodplain forest in the Arapixuna District, Santarém, Pará. Three species that are frequently found and ecologically important for floodplain ecosystems were selected: Eugenia sp., Gustavia augusta L., and Laetia corymbulosa Spruce ex Benth. A sap flow sensor was installed in each species, and the flows were continuously inferred using the heat dissipation method and analyzed together with environmental variables and plant physiological variables. The results show that sap flow rates were lower during the flooded period and higher during the non-flooded periods. The species studied adopted different strategies to tolerate the water stress condition caused by soil saturation; these strategies are noticeable in the leaf morphoanatomy. Among the species studied, Eugenia sp. was the one that was best acclimated and adapted to the seasonal changes caused by the flood and drought cycles.