PS 9-88
Effects of nitrogen additions on soil extracellular enzyme activity: A meta-analysis

Monday, August 10, 2015
Exhibit Hall, Baltimore Convention Center
Siyang Jian, Department of Agricultural and Environmental Science, Tennessee State University, Nashville, TN
Jianwei Li, Department of Agriculture and Environmental Sciences, Tennessee State University, Nashville, TN

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.


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.