INTERCEPTAÇÃO PLUVIOMÉTRICA NA FLORESTA OMBRÓFILA MISTA

Abstract

The process of interception of rainwater by forests is a few understood factor in the continental hydrological cycle, but it promotes important environmental services. The water flow of a region is related to the process of interception of rainwater by the treetops. This process, characterized as forest interception of precipitation, is of great importance for the balance of watersheds, as it distributes and conditions the water, favoring the process of infiltration and recharge of shallow aquifers, reducing the surface flow. Forest interception is understood as the return of precipitated water to the atmosphere during or shortly after precipitation. The objective of the present text was to study the modeling process, together with remote sensing techniques, with the purpose of generating information about the dynamics of Forest Interception in a mixed Ombrophilous Forest environment. Methods used to estimate forest interception, its components and definitions. The focus was on models applicable to the Mixed Ombrophylous Forest with Araucaria with the observation of the climatic profile of the region of occurrence of this forest typology. Remote sensing techniques were applied to verify the occurrence conditions of the dominant species Araucaria angustifolia (Bert.) O. Kuntze. Rainfall monitoring was conducted by a hydrological year, under various forest cover conditions. Methodology consisted of a bibliographical analysis of the use of the different models to calculate Forest Interception and its variables. The local climatic profile was obtained with the analysis of data of surface meteorological stations, and the influence of the vegetation on the precipitation was observed in 102 collection points with rain gauges. Volumes, frequencies and rainfall times under different forest canopy covers were obtained and compared with their expression in high resolution remote sensor images. The location of individuals of the dominant species (Araucaria) used for inferences related to their influence on the rainfall profile of the internal precipitation. Result obtained was the verification that the Rutter and Gash models are the most used for the estimation of forest interception. The climatic analysis in the region of the Mixed Ombrophilous Forest revealed a profile of frequent precipitations with a predominance of low intensity events, with intense rainfall mainly during the summer. The monitoring of the internal precipitation consisted in the installation of pluviometers, in 102 points distributed in an area of 3 ha of Mixed Ombrobile Forest, monitored during 365 days. The observed result was a decrease profile of the interceptor factor by the canopy, as the precipitation intensity increases. On average, interception was 13.8%. Rainfall was measured at hourly frequency, with lower rainfall intensity (<3 mm/h), with lower rainfall events (<40 mm/h). Internal precipitation time is 34.6% higher than the external rainfall, probably due to the drip factor. Monitoring of the process of Forest Interception in isolated trees allowed to observe that the Araucaria forms an additional layer of canopy on the forest. Precipitation data, integrated the information of spatial location and delimitation of the canopies of Araucaria, estimated the influence of the species in the process of forest interception. Loss of intercept of the Araucaria crown (in an isolated situation) is 3% of the gross precipitation, and the analytical model Revisto Gash is satisfactory to reproduce the loss of interception for the Mixed Ombrophilous Forest. The present work allows to conclude that the estimation of the interception in the Mixed Ombrophilous Forest can be obtained from images of remote sensors, adjusting the values from the coverage area of the Araucaria canopy. The estimation of this value is important for climatological studies and restoration of environmental services.