Mudança do uso da terra e efeitos ecohidrológicos em área de caatinga e pastagem no semiárido pernambucano

Abstract

Arid and semi-arid lands are regions with a lasting period of water scarcity. The Brazilian semi-arid region has an area of approximately one million square kilometers with about 27 million people mainly occupying the northeastern region of the country. The changes in these systems of water deficit, mainly due to the exploitation and environmental degradation, in contributing to the process of desertification, for the invasion of exotic species, of the appearance of extreme weather events (intense and prolonged drought rain), for mortality of trees in a large scale, as well as to increase the intensity of these phenomena occur. Thus, studies investigating the effects of land use change are of fundamental importance for understanding the ecohydrology in arid and semi-arid environments. Thus the present work aimed to verify the influence of an area of Caatinga and pasture in the water balance components; ii) quantify the water slide intercepted by the canopy of vegetation Caatinga and iii) apply an interception model to evaluate the maximum canopy water storage capacity of the Caatinga in the dry and wet seasons. Measurements of the water balance components were carried from August 2014 to July 2015 in both areas. During the twelve months of study total rainfall in the two areas was below the climatological normal. Caatinga the greatest variations in solar radiation will occur from October 2014 to March 2015. The average air temperature indicates that there is greater heat absorption in the pasture area which resulted in higher air heating 1.9ºC in the Caatinga. The water storage (Az) in the Caatinga soil showed a variation (ΔAz) between -10.34 and 11.78 mm, reaching a total value of -8.57 mm throughout the evaluation period. The variation (ΔAZ) in water storage in Caatinga and pasture area is ranged between -20.74 and 22.65 mm, with a total value of 3.24 mm, respectively. The internal precipitation Caatinga corresponded to 80.15% of the external rainfall and the interception losses accounted for 19.85%. The rain hits the soil surface, 6.23 and 10.08% were lost by drainage (-QZ), 0.37 and 5.77% were lost by runoff (ES) and total evapotranspiration (ETr) was of 496.31 and 434.43 mm yr-1 for Caatinga and pasture, respectively. The maximum water storage capacity (Smax) of Caatinga canopy increased by 50% in the rainy season compared to the dry season. Based on data from this study, it can be inferred that the replacement of native vegetation by grazing affects considerably the variation of water balance components, indicating a close relationship between climate variables, in addition to confirming the predictions about the climate impacts of this action.