Seasonal Dynamics of Soil Respiration and Its Autotrophic and Heterotrophic Components in Subtropical Camphor Forests

On a global scale, soil respiration (R-s), representing the CO2 flux between the soil surface and the atmosphere, ranks as the second-largest terrestrial carbon (C) flux. Understanding the dynamics between R-s and its autotrophic (R-a) and heterotrophic (R-h) components is necessary for accurately evaluating and predicting global C balance and net ecosystem production under environmental change. In this study, we conducted a two-year root exclusion experiment in subtropical China's Camphor (Cinnamomum camphora (L.) Presl.) forests to assess seasonal changes in R-a and R-h and their relative contributions to R-s. Additionally, we examined the influence of environmental factors on the dynamics of R-a, R-h, and R-s. Our results showed that seasonal mean R-s values were 2.88 mu mol m(-2) s(-1), with mean R-a and R-h of 1.21 and 1.67 mu mol m(-2) s(-1), respectively, in the studied forests. On an annual basis, the annual values of mean R-s in the studied forests were 405 +/- 219 g C m(-2) year(-1), with R-h and R-a accounting for 240 +/- 120 and 164 +/- 102 g C m(-2) year(-1), respectively. The seasonal mean ratio of R-h to R-s (R-h/R-s) was 58%, varying from 45 to 81%. Seasonal changes in R-s and R-h were strongly correlated with soil temperature but not soil water content. Both R-h and R-s increased exponentially with the average soil temperature measured in the topsoil layer (about 5 cm), with Q(10) values of 2.02 and 1.73 for R-h and R-s, respectively. Our results suggest that the composition and activity of soil microbes and fauna play a primary role in releasing carbon flux from soil to the atmosphere in the studied forest ecosystems.