Evapotranspiration Profiles and Trends in Seasonally Dry and Seasonally Humid Tropical Forests

ABSTRACT Evapotranspiration (ET) is the sum of evaporation and plant transpiration. In Brazil, climatic (humid and semiarid) and biogeographic (e.g., Atlantic Forest—humid and Caatinga—seasonally dry) contrasts influence ET dynamics. This study analyses the spatial and temporal profiles and trends of ET in seasonally humid (Atlantic Forest) and seasonally dry (Caatinga) biomes. Monthly actual ET data (MOD16 Product), precipitation data (INMET) and land cover data (MapBiomas Brazil) from 2001 to 2020 were used. The spatiotemporal characterisation was performed for the dry and rainy quarters and annually. Hypothesis tests (Mann–Kendall, Sen's slope estimator and Pettitt) were applied. Results showed that ET gradually decreases from east (Atlantic Forest) to west (Caatinga) and is consistently higher during the rainiest quarter. On an annual scale, the average accumulated ET is 827.9 mm/year, ranging from 182.6 mm/year (Caatinga) to 2225.9 mm/year (Atlantic Forest). We found that in years/months with higher ET values, rainfall was above average. In other words, ET is positively correlated with precipitation ( r = 0.20–0.67), with 5% statistical significance. Significant trends ( p < 0.05) in ET were identified, with opposing patterns. In the southeastern Atlantic Forest, reductions of up to −15 mm/year predominated. In the Caatinga biome, 97.9% of the areas with trends exhibited decreasing ET, indicating an association with deforested regions. On the other hand, some isolated areas in both biomes presented localised increases in ET. We can conclude that ET variations/trends are important indicators of moisture availability and the impacts of improper land management (deforestation). Therefore, a need exists for public policies aimed at vegetation conservation, sustainable water resource management, and the planning of adaptation strategies.