Partitioning soil respiration of subtropical forests with different successional stages in south China

The methods of root-excision and trenching were employed concurrently in the present study in order to partition total soil respiration (Rtotal) into root respiration (Rroot), rhizomicrobial respiration (Rrhizo) and root free soil microbial respiration (Rrfs). This study was conducted under the monsoon evergreen broad-leaf forest (BF), the pine forest (PF) and the pine and broad-leaf mixed forest (MF) in Dinghushan Biosphere Reserve, subtropical China from April 2001 to March 2002. The three forests represent different successional stages in this region. Our results showed that mean Rtotal were 477.9 ± 96.3, 429.5 ± 61.0 and 435.4 ± 95.1 mg CO2 m−2 h−1 in BF, PF and MF, respectively. Rtotal were significantly higher in rain season than those in dry season. However, no significant variations were found among three forests. Soil respiration rates were highly dependent on the combined effects of soil temperature and soil water content. Rroot was significantly higher in rain season than that in dry season, with the values of 113.8–166.0 mg CO2 m−2 h−1 in rain season and 48.6–97.1 mg CO2 m−2 h−1 in dry season. There were no significant differences for Rrfs and Rrhizo between rain and dry season. However, the contributions of each component to Rtotal in rain season differed from those in dry season. In rain season, Rroot-to-Rtotal, Rrfs-to-Rtotal and Rrhizo-to-Rtotal ratios were in the range of 26.1–35.4, 40.6–43.7, and 20.9–36.6%. In dry season, they were 18.1–22.1, 44.8–47.6 and 30.3–37.1%, respectively.