Precipitation and landscape related effects on soil moisture in semi-arid rangelands of Patagonia

CORONATO, F.R.; BERTILLER, M.B.

JOURNAL OF ARID ENVIRONMENTS

ACADEMIC PRESS LTD-ELSEVIER SCIENCE LTD

Año: 1996 vol. 34 p. 1 - 9

0140-1963

The dynamics of soil water was evaluated in different landscapes during four growing seasons in a semi-arid grassland of Patagonia. At intervals of 60?90 days, the (gravimetric) soil moisture content was determined at four depths in uplands and north-eastern slopes of grazed and ungrazed areas. Climatic data (precipitation and maximum and minimum temperature) were recorded daily. Maximum and minimum soil temperature per sampling interval was also registered. Soil moisture was strongly influenced by the recharge through precipitation. Most precipitation occurred during autumn and winter and the highest soil moisture values were measured at the end of the winter (September) after snowmelt. The occurrence of wet and dry years was observed during the study period and, as occurs in other semi-arid ecosystems, it may be attributed to the amount of rain delivered in events exceeding 10 mm. Soil moisture varied spatially with the topographic site while maintaining a similar seasonal pattern. North-eastern slopes were drier than uplands. These differences may be traced back to the protection of these slopes from the strong westerly winds prevailing in the area that results in a more favourable thermic balance as compared with uplands. No grazing related effects on soil moisture were observed in this study. This fact may probably be explained by a variety of factors involved in the partition of soil water between transpiration and evaporation. These results show north-eastern slopes to be sensitive places for land degradation which eventually may have a restricted restoration potential imposed not only by physical changes in the upper soil but also by limited soil water availability.