Different effects of litter and root inputs on soil enzyme activities in terrestrial ecosystems

Abstract

Soil extracellular enzymes are involved in the decomposition of plant litter and soil organic matter, and their activities are of critical significance to soil carbon and nutrient turnover in terrestrial ecosystems. However, the coupling of litter and root inputs and soil enzyme activities across terrestrial ecosystems still remains not fully understood. In this study, we compiled 788 paired observations to evaluate changes in soil β-1,4-glucosidase (BG), β-d-cellobiosidase (CBH), phenol oxidase (PHO), β-1,4-N-acetyl-glucosaminidase (NAG), and acidic phosphatase (AP) activities after the removal of litter, living roots, and both litter and living roots in different ecosystems (forests, grasslands, croplands and tundra). Soil BG, NAG, and AP activities were decreased by 22.5 %, 16.6 % and 28.7 %, respectively, after removing both litter and living roots, but these effects varied in different ecosystems. Removing both litter and living roots decreased soil BG and CBH activities in forests and BG activity in croplands but increased soil CBH activity in croplands. Soil NAG activity was decreased by 15.1 % in forests but increased by 6.1 % in croplands after both litter and living roots were removed, while soil AP activity was decreased significantly across all of the studied ecosystems after both litter and living root removal. However, litter addition greatly increased soil BG, CBH, NAG and AP activities, suggesting that soil enzyme activities involved in carbon, nitrogen and phosphorus cycling were strongly controlled by plant carbon input, with an additive effect of litter and root inputs observed for C-degrading enzymes. Our synthesis also found that these enzymatic responses to plant carbon input were strongly controlled by edaphic and not climatic factors across terrestrial ecosystems. These results suggested that soil enzyme activities increased after litter addition to accelerate the decomposition of litter input but decreased after litter removal. Removing both litter and root inputs had a similar but additive effect on soil enzyme activities across sites. Although these responses varied greatly among ecosystems and litter types, edaphic factors predominantly controlled enzymatic responses over terrestrial ecosystems. Our results highlighted the importance of plant inputs in enzymatically involved carbon and nutrient cycles in terrestrial ecosystems.