Comparison of Soil CO2 Efflux from a Secondary Forest and Tea Plantations in Taiwan

Soil CO2 efflux, soil temperatures, and soil water content of 2 stands in a secondary forest, with differing canopy openness, and 2 tea plantations, one actively cropped and the other abandoned for 2 yr, in Taiwan were measured monthly from June 2004 to July 2005. The first objective of this study was to quantify and compare soil CO2 efflux of the 4 stands. The second objective was to examine the relationship of environmental conditions, specially soil temperature and soil water contents, with soil CO2 efflux of the forest and tea plantations. Seasonal patterns were found in soil CO2 efflux and soil temperature but not in soil water content. The magnitude of the soil CO2 efflux varied from 1 to 3.5 μmol m^(-2)s^(-1) and from 0.5 to 5.0 μmol m^(-2)s^(-1) in the secondary forest and tea plantations, respectively. Within stands, seasonal changes in soil respiration were most highly correlated with soil temperature. The highest Q10 value, the factor by which the respiration rate differs for a temperature interval of 10℃, of 2.92 occurred in the actively cropped tea stand, the lowest of 1.83 was calculated for the open forest stand, and intermediate values of 1.94 and 1.98 were found in the dense forest stand and abandoned tea stand, respectively. The results indicate that among the 4 stands, the soil CO2 efflux of the actively cropped tea stand was most sensitive to changes in soil temperature.