PS 9-88
Effects of nitrogen additions on soil extracellular enzyme activity: A meta-analysis
Anthropogenic nitrogen (N) deposition could affect the rate of forest litter decomposition and soil organic matter (SOM) storage by regulating extracellular enzyme activity (EEA). Effects of long-term N additions on microbial enzyme activities have been a research focus over decades, but few studies have synthesized the extant datasets to elucidate the mechanistic controls of N impact on EEA. The 10 enzymes studied in the meta analysis, include labile carbon (C) acquired enzymes α-1,4-Gulcosidase (AG), β-1,4-Glucosidase (BG), β-D-Cellobiosidase (CBH) and β-1,4-Xylosidase (BX), N acquired enzymes β-1,4-N-Acetyl-glucosaminidase (NAG), Leucine aminopeptidase (LAP) and Urease, phosphorus (P) acquired enzymes Acid phosphatase (AP), refractory C acquisition enzymes Phenol Oxidase (POX) and Peroxidase (PER). We hypothesized that adding nitrogen would significantly depress EEA associated with microbial N and recalcitrant C acquisitions, and increase EEA associated with labile C acquisitions across a wide range of environmental, edaphical and physiological conditions. The varying responses of each EEA to N additions were further explored under different environmental, edaphical and physiological conditions.
Results/Conclusions
In this meta-analysis, we synthesized responses of 10 soil extracellular enzymes to N additions in more than 35 published field and laboratory studies. Our preliminary results showed that, only the activity of BG increased consistently in response to N addition by an average of 10.1%, while the activity of POX decreased consistently by 10.8%. The activity of LAP increased at enriched N by 3.4%. Urease, AG, BX, CBH, NAG, PER and AP activities decreased by an average of 9.2%, 5.7%, 3.2%, 2.5% 1.8%, 1.5% and 0.7% respectively. Further analysis showed that the response of EEA to N addition varied significantly across different soil types. Our study can help 1. Clarify the overall effect of N addition on EEA; 2. Elucidate the influences of environmental, edaphical and physiological situations in altering N effect on EEA; 3. The database and information obtained in this study can be useful in enzyme-driven SOM decomposition models to simulate responses of nutrient release and cycling to N fertilization or deposition.