Abstract
In a period of 36 months, the partitioning of rainfall was studied in plantations of 30-year-old Eucalyptus urophylla and Pinus elliottii cultivated in flat drainage lysimeters. Gross precipitation was measured with one rain gauge installed in an open area located near the plantations; throughfall was determined by the arithmetic mean of five rain gauges located under the canopy of each species; stemflow was obtained with polyurethane foam collars connected to plastic containers installed on four trees of each species. The mean proportions of throughfall, stemflow and interception in relation to gross rainfall for eucalyptus were 89.0%, 5.4% and 5.6%, respectively, and for pine, they were 79.8%, 1.0 % and 19.2%, respectively. The interannual variation in the percentages of interception for the two species had an amplitude of approximately 6%. There was marked variation in the proportion of stemflow depending on the season for eucalyptus, averaging 8.7% between April and September and 4.6% from October to March. There was a large number of events with negative interception for eucalyptus. One of the likely causes of the negative interception was capture of fog water by the canopy. Linear regressions estimated that rainfall amounts were responsible for approximately 99% and 70% of the variation in throughfall and stemflow, respectively, in the two plantations.
Highlights
The area of trees planted for industrial purposes in Brazil totaled 7.8 million hectares in 2015
Studies after this review found values of throughfall, stemflow and interception at 84.0%, 1% and 15.0%, respectively, for P. caribaea; 85.2%, 1.0% and 13.8%, respectively, for E. cloeziana (TONELLO et al, 2014); 81%, 5% and 14%, respectively, for E. urograndis (TREVISAN et al, 2012); and 78.1%, 11.1% and 14.6%, respectively, for E. grandis (SARI et al, 2016)
The analyses of the results of rainfall partitioning during the 36-month collection period allow us to conclude the following: ● The mean throughfall, stemflow and interception in relation to gross precipitation were 89.0%, 5.4% and
Summary
The area of trees planted for industrial purposes in Brazil totaled 7.8 million hectares in 2015. One of the main influences of the forest in the hydrological cycle occurs immediately upon the interaction of rainfall with the canopy of trees, when the water is partitioned into three flows: interception, throughfall and stemflow. This process determines the amount of water that is evaporated while still in the canopy and how much water effectively reaches the forest floor. Partitioning of rainfall is influenced by factors related to vegetation, such as tree height, canopy opening and storage capacity, forest density, branch angle, the uniformity or lack of uniformity in crown height, leaf shape and inclination, leaf area index, species composition, the nature and thickness of the bark
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