Influência de variáveis biométricas de espécies florestais na interceptação pluvial da floresta urbana tropical

Abstract

Urban forests are important water regulators as they reduce the overload on water reservoirs, decreasing the intensity of floods. Trees retain rainwater and aid in the gradual penetration of water into the soil, making them important for water regulation in urban areas. This ability varies according to the biometric characteristics of each species and individual, with the majority of variables related to the canopy. To quantify and classify the benefits of urban forests as a tool for water regulation, a thorough study of the services provided by trees is necessary. In this sense, the present research aimed to evaluate the influence of biometric variables of individuals of Senna siamea and Paubrasilia echinata on rainwater interception. The hypothesis tested was that there is a significant difference in the volume of water intercepted by the species according to their different biometric patterns conferred by morphological, dendrometric, and morphometric variables. To test the hypothesis, individuals of both species present in the tropical urban forest of Recife - PE were selected. The selection of trees was based on criteria such as size, age, health, and geographical location. The morphological, dendrometric, and morphometric variables of each selected tree were measured, as well as the volume of water intercepted by the trees during rainfall events. The results were discussed in relation to the formulated hypothesis, with the identification of significant differences found between the studied variables. Thus, it was observed that the rates of rainwater interception between the two species were above 50% in most events. In a comparative nature, the species P. echinata showed slightly higher rainwater interception than the species S. siamea in almost all events. The average interception of the P. echinata group (55.99%) was higher than that of the S. siamea group (46.97%). These results indicate that the P. echinata species may have a greater capacity for rainwater interception than the S. siamea species. It was evaluated that the intensity of the rain directly affected the rainwater interception of both species. In events with lower rainfall intensity (0.3mm/h), the average percentages of interception of the species were higher (85.5%), being (84%) for P.echinata and (87%) for S.siamea, while in events with higher rainfall intensity (8.5mm/h), the average percentages of interception were lower (36%), being (41.3%) for P.echinata and (30.83%) for S.siamea. For P. echinata, the Spearman correlation revealed that the canopy proportion presented a significant positive correlation with the average interception (0.76), while the canopy shape and coverage index presented negative correlations (-0.71). For P. echinata, individuals with larger proportions of more rounded and less branched canopies were related to higher rainwater interception. Other evaluated variables did not present a significant correlation with the average interception. For S. siamea, it was found that the study did not find a significant correlation at 5% between rainwater interception and the evaluated biometric variables, suggesting the need to increase the sample size and thus improve the precision of the estimates and increase the statistical power of the test. However, it is important to highlight that correlation does not imply causality between variables. It was observed that individuals of S. siamea from the sample have morphological characteristics that can favor greater canopy coverage and, consequently, greater potential for the provision of ecosystem services when well developed, but are suffering from excessive prunning.