PS 14-130
Effects of nitrogen additions on soil extracellular enzyme activity: A meta-analysis

Monday, August 10, 2015
Exhibit Hall, Baltimore Convention Center
Jianwei Li, Department of Agriculture and Environmental Sciences, Tennessee State University, Nashville, TN
Siyang Jian, Agriculture and Environmental Sciences, Tennessee State University, Nashville, TN
Dafeng Hui, Department of Biological Sciences, Tennessee State University, Nashville, TN
Yiqi Luo, Microbiology and Plant Biology, University of Oklahoma, Norman, OK

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. Ten enzymes are studied in the meta analysis including 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 N 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 also further explored under different environmental, edaphical and physiological conditions.


In this meta-analysis, we synthesized responses of ten soil extracellular enzymes to N additions in more than 35 published field and laboratory studies. Our preliminary results showed that on average, the activity of BG increased by 10.1% and POX decreased consistently by 10.8% in response to N addition, and the elevated directional trends were consistent across different studies. On average, the activity of LAP increased by 3.4% and the activity of urease, AG, BX, CBH, NAG, PER and AP activities decreased by 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 potentially help clarify the overall effect of N addition on EEA and elucidate the influences of environmental, edaphical and physiological situations in altering N effect on EEA. The information obtained in this study can be useful to simulate responses of nutrient release and cycling to N enrichment in enzyme-driven SOM decomposition models.