Divergent responses of carbon-degrading enzyme activities to litter alterations: Implications for soil respiration

Global change affects terrestrial litter inputs with cascading effects on soil respiration (SR). Cellulase and ligninase are dominant carbon-degrading enzymes, targeting the decomposition of readily decomposable and structurally complex carbon pools, respectively. Nevertheless, how litter alterations influence cellulase and ligninase activities and the implications for SR remain unclear. We conducted a meta-analysis to show that litter addition increased cellulase activity by 25.2%, whereas litter removal decreased it by 25.9%. Neither litter addition nor removal influenced ligninase activity. The changes in cellulase activity correlated positively with changes in SR, but not for ligninase activity. The effects of litter addition and removal on cellulase activity decreased with treatment duration. These results indicate that litter alterations affect SR primarily by controlling the microbial decomposition of readily decomposable rather than structurally complex carbon pools. Altogether, we suggest that the total and long-term effects of litter alterations on SR might be smaller than previously thought.