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Abstract Soil‐surface CO 2 efflux and its spatial and temporal variations were examined in an 8‐y‐old ponderosa pine plantation in the Sierra Nevada Mountains in California from June 1998 to August 1999. Continuous measurements of soil CO 2 efflux, soil temperatures and moisture were conducted on two 20 × 20 m sampling plots. Microbial biomass, fine root biomass, and the physical and chemical properties of the soil were also measured at each of the 18 sampling locations on the plots. It was found that the mean soil CO 2 efflux in the plantation was 4.43 µmol m −2 s −1 in the growing season and 3.12 µmol m −2 s −1 in the nongrowing season. These values are in the upper part of the range of published soil‐surface CO 2 efflux data. The annual maximum and minimum CO 2 efflux were 5.87 and 1.67 µmol m −2 s −1 , respectively, with the maximum occurring between the end of May and early June and the minimum in December. The diurnal fluctuation of CO 2 efflux was relatively small (14%. Understanding the spatial and temporal variations is essential to accurately assessment of carbon budget at whole ecosystem and landscape scales. Thus, this study bears important implications for the study of large‐scale ecosystem dynamics, particularly in response to climatic variations and management regimes.
Xu et al. (Wed,) studied this question.