Seasonal variability in soil-surface CO₂ efflux in selected young tree plantations in semi-arid eco-climate of Madurai.

摘要

The response of soil respiration (SR) to varying soil temperature and soil moisture was studied in three-year-old plantation sites of Dalbergia sissoo, Dalbergia latifolia, Albizia lebbeck, Hardwickia binata and Cassiasiamea during 2005-06. Significant seasonal differences in SR rates were observed in each site (P?0.001). The highest rates of soil CO₂ efflux were generally found during the rainy season and the lowest during summer in all the study sites. Highest SR rates were found in D. sissoo, 9.89.0.78 .mol m-2 s-1 in November and December, followed by H. binata, 9.68.0.45 .mol m-2 s-1 in September and October 2005, A. lebbeck,8.84.0.43 . m-2 s-1 between November 2005 and January 2006, D. latifolia, 7.6.0.12 . m-2 s-1 in November and December 2005 and C. siamea, 7.3 .mol m-2 s-1 in December 2005.There was a positive and significant (P?0.001) relationship between SR rates and soil moisture in all the sites (r2above 0.60), except C. siamea (r2=0.30). A poor relationship was observed between SR andsoil temperature in all the sites (r2 below 0.2). Examination of the seasonal pattern of SR rates suggests that much of the variability could be attributed to variations in soil moisture. There was a strong indication suggesting that the soil-water deficits served to reduce SR rates during summer and after subsequent rain events. Overall sensitivity of SR rate to soil moisture seems to be good for this semi-arid ecosystem.