Are variations in heterotrophic soil respiration related to changes in substrate availability and microbial biomass carbon in the subtropical forests?

摘要

Soil temperature and moisture are widely-recognized controlling factors on heterotrophic soil respiration (R_h), although they often explain only a portion of R_h variability. How other soil physicochemical and microbial properties may contribute to R_h variability has been less studied. We conducted field measurements on R_h half-monthly and associated soil properties monthly for two years in four subtropical forests of southern China to assess influences of carbon availability and microbial properties on R_h. R_h in coniferous forest was significantly lower than that in the other three broadleaf species-dominated forests and exhibited obvious seasonal variations in the four forests ( P h while moisture was not in these humid subtropical forests. The quantity and decomposability of dissolved organic carbon (DOC) were significantly important to R_h variations, but the effect of DOC content on R_h was confounded with temperature, as revealed by partial mantel test. Microbial biomass carbon (MBC) was significantly related to R_h variations across forests during the warm season ( P =?0.043). Our results suggest that DOC and MBC may be important when predicting R_h under some conditions, and highlight the complexity by mutual effects of them with environmental factors on R_h variations.