Soil respiration under different forest species in the riparian buffer of the semi-arid region of northwest India

Soil temperature and soil moisture are the most important environmental factors controlling soil respiration (SR) in ecosystems. However, SR and associated edaphic factors have not been widely studied in semi-arid regions. In this study, SR was measured in a riparian zone and the effect of soil temperature and soil moisture on SR was examined under five forest species of the semi-arid region. The mean daily SR rate was 1.82, 2.08, 2.35, 2.27 and 2.07 g C m(-2) d(-1) in Jatropha curcas, Leucaena leucocephala, Acacia nilotica, Azadirachta indica and Prosopis juliflora sites respectively. It was found that SR was significantly and positively correlated with soil moisture. A univariate model of sub-surface soil moisture could explain 77% of temporal variation in soil CO2 efflux, irrespective of species and sites. The logarithmic model could best explain the relationship between SR and soil moisture at 10-20 cm of soil depth (P < 0.001). There were negative correlations between SR and soil temperature under majority of species. Overall, across all species, soil temperature poorly explained 26% variation in SR as independent variable. For SR rate-temperature relationship, a bell-shaped function gave the best fit in this ecosystem. Under all the species, SR increases with increase in soil temperature up to 33 degrees C (+/- 2); thereafter it decreases gradually under all species. There was strong evidence that deficit of soil moisture rather than soil temperature was the main regulating factor of SR under the semi-arid ecosystems.