EFFECTIVE PRECIPTATION, SOIL LOSS AND PLANT COVER SYSTEMS IN THE CAATINGA BIOME, BRAZIL

ABSTRACT The objective of this work was to evaluate the influence of anthropic activities on the effective precipitation (eP) and soil loss in watersheds under different land uses in a tropical dry forest region. The experimental area was located in the central part of the State of Ceará, Brazil. The land uses evaluated were: fallow Caatinga (FC), thinned Caatinga (TC) and deforested Caatinga followed by a burning procedure and pasture cultivation (DBP). The areas were monitored in the rainy season (January to May, 2010), when 57 natural rainfalls occurred, totaling 941 mm of precipitation. The eP and sediment productions were quantified by the sum of all occurrences during the study period, and the soil loss was represented by suspended and dragged sediments. The eP was 15.13 mm and sediment produced was 167.81 kg ha-1 in FC conditions. The eP values was smaller (11.28 mm) in the watershed with TC, which had soil loss sum of 42.04 kg ha-1. The largest annual eP was found in the DBP area, with 112.88 mm yr-1 of accumulated water depth, which also showed the greater annual soil loss (3114.97 kg ha-1). The greatest interference of plant cover in the two variables evaluated occurred in the first precipitation events, when the plants were not yet fully developed.

摘要
本研究旨在评估热带干旱森林区域内不同土地利用方式下流域的人类活动对有效降水量（effective precipitation, eP）与土壤侵蚀量的影响。试验区域位于巴西塞阿拉州（Ceará）中部。本次评估的土地利用类型包括：休耕卡廷加植被区（fallow Caatinga, FC）、疏伐卡廷加植被区（thinned Caatinga, TC），以及先清伐卡廷加植被、经焚烧后开展牧场种植的区域（deforested Caatinga followed by burning and pasture cultivation, DBP）。
监测时段为2010年雨季（1月至5月），期间共发生57次天然降雨，总降水量达941毫米。本研究通过汇总监测期内所有降雨事件的相关数据，量化了有效降水量与产沙量；其中土壤侵蚀量以悬移质与推移质泥沙量表征。休耕卡廷加植被区（FC）的有效降水量为15.13毫米，产沙量为167.81千克每公顷（kg ha⁻¹）。疏伐卡廷加植被区（TC）的有效降水量更低，为11.28毫米，对应的土壤侵蚀总量为42.04千克每公顷。经清林焚烧后开垦的牧场区（DBP）的年有效降水量最高，累积水深达112.88毫米每年（mm yr⁻¹），同时其年土壤侵蚀量也最高，为3114.97千克每公顷。植被覆盖对本次评估的两项指标的最大影响出现在首批降雨事件中，彼时植被尚未完全发育。