Balanço hídrico em espécies florestais representativas da Mata Atlântica

Abstract

Understanding the capacity of Atlantic Forest vegetation to maintain the soil-vegetation- atmosphere dynamic is crucial, given the challenges faced by Brazilian biomes due to

deforestation and prolonged drought periods, especially in the Southeast of the country. The aim of this study is to evaluate the water balance behavior in forest species of the Atlantic Forest, in a remnant of the Montane Semideciduous Seasonal Forest (FESM), located in Lavras, Minas Gerais. Soil moisture monitoring was conducted at 7 points within the remnant, and hydrological variables such as gross precipitation (GR), canopy interception (C), effective precipitation (EP), as well as above-ground biomass (AGB) estimation, root biomass (BR) sampling, and soil hydrological properties along the profile down to 1.80 m were assessed. The results revealed a vertical concentration of BR, with a higher mass in the superficial soil layers (0-60 cm), gradually decreasing with depth. Finer roots (< 2 mm) dominate in the upper layers, playing essential roles in water absorption and nutrient cycling, while intermediate thick roots (5 – 50 mm) are more abundant in deeper layers. In the tree-specific water balance, the rainfall pattern and the morphological characteristics of the plants influenced the values of ET, EP, and C. Canopy interception followed the EP regime, being more intense in the middle of the dry season. The highest EP values were observed in Miconia willdenowii, while the lowest were in Xylopia brasiliensis. For C, the highest and lowest values were observed in Xylopia brasiliensis. Water storage in the root zone showed a declining trend throughout the period at all monitored points, with fluctuations influenced by rainfall events, with the highest values observed at sites with Miconia willdenowii. ET was highest in June for most trees, while April, July, and September were the most critical months for some trees. The species Miconia willdenowii and Copaifera langsdorffii presented the highest ET values. AGB was influenced by the diameter at breast height (DBH), showing a stronger correlation with C than with ET. In the soil profile, soil moisture showed a declining trend throughout the monitoring period, with the superficial layer showing lower moisture compared to deeper layers. Temporal variations (CVt) of soil moisture were more evident at depths of 20 cm and 140 cm, influenced by rainfall events and the water demand of trees. Spatial variations (CVs) stabilized with increasing depth, while the greatest variability was observed in the superficial layer (0-20 cm). The Temporal Stability Index (TSI) indicated greater stability at the point with Blepharocalyx salicifolius. This study highlights the critical importance of soil water and evapotranspiration loss in tropical forest ecosystems, especially under drought conditions, allowing the identification of species that can be more successfully used in the recovery of degraded areas.