Articles | Volume 12, issue 22
Reviews and syntheses
26 Nov 2015
Reviews and syntheses |  | 26 Nov 2015

Reviews and syntheses: Soil resources and climate jointly drive variations in microbial biomass carbon and nitrogen in China's forest ecosystems

Z. H. Zhou and C. K. Wang

Abstract. Microbial metabolism plays a key role in regulating the biogeochemical cycle of forest ecosystems, but the mechanisms driving microbial growth are not well understood. Here, we synthesized 689 measurements on soil microbial biomass carbon (Cmic) and nitrogen (Nmic) and related parameters from 207 independent studies published up to November 2014 across China's forest ecosystems. Our objectives were to (1) examine patterns in Cmic, Nmic, and microbial quotient (i.e., Cmic / Csoil and Nmic / Nsoil rates) by climate zones and management regimes for these forests; and (2) identify the factors driving the variability in the Cmic, Nmic, and microbial quotient. There was a large variability in Cmic (390.2 mg kg−1), Nmic (60.1 mg kg−1, Cmic : Nmic ratio (8.25), Cmic / Csoil rate (1.92 %), and Nmic / Nsoil rate (3.43 %) across China's forests. The natural forests had significantly greater Cmic (514.1 mg kg−1 vs. 281.8 mg kg−1) and Nmic (82.6 mg kg−1 vs. 39.0 mg kg−1) than the planted forests, but had less Cmic : Nmic ratio (7.3 vs. 9.2) and Cmic / Csoil rate (1.7 % vs. 2.1 %). Soil resources and climate together explained 24.4–40.7 % of these variations. The Cmic : Nmic ratio declined slightly with Csoil : Nsoil ratio, and changed with latitude, mean annual temperature and precipitation, suggesting a plasticity of microbial carbon-nitrogen stoichiometry. The Cmic / Csoil rate decreased with Csoil : Nsoil ratio, whereas the Nmic / Nsoil rate increased with Csoil : Nsoil ratio; the former was influenced more by soil resources than by climate, whereas the latter was influenced more by climate. These results suggest that soil microbial assimilation of carbon and nitrogen are jointly driven by soil resources and climate, but may be regulated by different mechanisms.

Short summary
Soil microbial biomass carbon (Cmic) and nitrogen (Nmic) and microbial quotient varied substantially across China’s forest ecosystems (CV 61–96%). Soil resources and climate together explained 24–41% of the variations. Cmic:Nmic ratio declined slightly with soil C:N ratio and changed with latitude and climate, suggesting a plastic homeostasis of microbial C-N stoichiometry. Divergent responses of microbial quotient of C and N to environment imply different mechanisms regulating Cmic and Nmic.
Final-revised paper