Heterotrophic respiration causes seasonal hysteresis in soil respiration in a warm-temperate forest

Abstract

To assess the effect of changes in organic litter stock on seasonal changes in heterotrophic respiration (R_H), soil respiration (R_S), and total ecosystem respiration (R_E), we measured seasonal changes in leaf litter respiration (R_LL) by the chamber method and estimated the seasonal change in total R_H using the RothC model in a warm-temperate mixed deciduous–evergreen forest in Japan. Both R_E and R_S had seasonal hysteresis and were higher in spring than at the same temperature during autumn. Under warm and humid conditions, the rate of decomposition of newly supplied leaf litter in one year was high (60% loss). Consequently, R_LL and R_H were higher in spring after leaf drop, when more fresh material was available, than in autumn. In this study, 42 and 88% of the difference in R_E and R_S between spring and autumn (soil temperature 16–18°C) could be accounted for by the difference in R_H, respectively, and 71% of the difference in R_H could be accounted for by the difference in R_LL. This study showed that seasonal changes in heterotrophic respiration (R_LL and R_H) could be a major factor in the seasonal hysteresis of R_E and R_S.

Keywords:

• Heterotrophic respiration
• Leaf litter respiration
• Organic matter
• RothC model
• Soil respiration

Acknowledgments

This study was partly supported by a Grant-in-Aid for Scientific Research (B) (20380182). We are grateful to the members of the Forest Resource Laboratory of Kobe University and the Forest Hydrology Laboratory of Kyoto University for their assistance.