Water balance and hydrochemistry of precipitation components in forested ecosystems in the arid zone of Rajasthan, India

Abstract

The water balance and hydrochemistry of precipitation components in Acacia tortilis and Chlorophospermum mopane forests in the arid zone of Rajasthan, India, were studied for four years (1993–1996). Rainfall and throughfall were measured for each rainfall event during the monsoon season (June-September) using an automatic raingauge and 96 graduated containers, respectively. Stemflow was measured around twelve trees in each forest type varying in diameter at breast height (dbh) from 28–96 cm in A. tortilis and 17–38 cm in C. mopane. Rainfall, throughfall and stemflow samples were collected for each rain event for chemical analysis. Weighted mean bulk precipitation was 423 mm. Interception was 21.77 and 12.72% in A. tortilis and C. mopane forests, respectively. In A. tortilis net precipitation was partitioned into throughfall (77.5%) and stemflow (0.73%), whereas, in C. mopane net precipitation was 87.61% of which, throughfall was 86.3% and stemflow was 1.31%. In only 3.8% of the rainfall periods recorded during this study, net precipitation was higher than bulk precipitation, suggesting direct input by horizontal precipitation is not an important water source for forest cover in this region. Nutrient inputs in bulk precipitation varied from 3.63 kg ha−1 year−1 of organic carbon to 37.63 kg ha−1 year−1 of chloride. In general, there was significantly greater deposition of total nutrients per unit area under large trees. Nutrient enrichment in throughfall relative to incident precipitation was higher for potassium than for other elements in both the forests. Between 12 and 56% of the total nutrient input to the soil was accounted for by the precipitation. © 1999 Taylor & Francis Group, LLC.