Abstract
Understanding the controls on soil carbon dynamics is crucial for modeling responses of ecosystem carbon balance to global change, yet few studies provide explicit knowledge on the direct and indirect effects of forest stands on soil carbon via microbial processes. We investigated tree species, soil, and site factors in relation to soil carbon density and mineralization in a temperate forest of central China. We found that soil microbial biomass and community structure, extracellular enzyme activities, and most of the site factors studied varied significantly across contrasting forest types, and that the associations between activities of soil extracellular enzymes and microbial community structure appeared to be weak and inconsistent across forest types, implicating complex mechanisms in the microbial regulation of soil carbon metabolism in relation to tree species. Overall, variations in soil carbon density and mineralization are predominantly accounted for by shared effects of tree species, soil, microclimate, and microbial traits rather than the individual effects of the four categories of factors. Our findings point to differential controls on soil carbon density and mineralization among contrasting forest types and highlight the challenge to incorporate microbial processes for constraining soil carbon dynamics in global carbon cycle models.
Highlights
Understanding the controls on soil carbon dynamics is crucial for modeling responses of ecosystem carbon balance to global change, yet few studies provide explicit knowledge on the direct and indirect effects of forest stands on soil carbon via microbial processes
Significant differences in soil carbon density were found among forest types in each of the three soil layers investigated (P < 0.05; d.f. = 3, 8); the values were mostly greatest in the Q. aliena plots and smallest in the Q. variabilis plots (Fig. 1a)
Significant differences in annual soil respiration occurred among forest types (P < 0.05; d.f. = 3, 8); the annual soil CO2 efflux was highest in the Q. glandulifera plots, followed by the Q. variabilis plots, and was similar between Q. aliena and P. armandii/Q. aliena plots (Fig. 2a)
Summary
Understanding the controls on soil carbon dynamics is crucial for modeling responses of ecosystem carbon balance to global change, yet few studies provide explicit knowledge on the direct and indirect effects of forest stands on soil carbon via microbial processes. Quantification of changes in soil carbon storage in space and time has proven to be a challenging issue in terrestrial ecosystem budgeting as well as in global carbon cycle research In this regard model simulations based on ecosystem processes provide a feasible and cost-effective tool for large scale mapping of soil carbon stocks and dynamics. Variations in litter chemistry and quality are widely recognized to explain species-dependent effects on soil carbon cycling[16,21]; whereas stand structure may affect forest floor microclimate, thereby influencing soil carbon dynamics via environmental impacts on soil microbial processes. Research to date has rarely linked the soil microbial community structure with functioning in explaining tree species mediated variations in soil carbon dynamics
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