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| Effects of Simulated Nitrogen Deposition on Enzymatic Activities and Inorganic Nitrogen Contents in Soil During Freeze - Thaw Cycles |
| Received:November 16, 2014 |
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| KeyWord:grassland;nitrogen deposition;freeze-thaw cycle;soil enzyme;soil inorganic nitrogen;clipping |
| Author Name | Affiliation | E-mail | | YU Ji-tong | Key lab of Ground Resources and Environment, Ministry of Education, College of Environment and Resources, Jilin University, Changchun 130012, China | | | TAO Jia-hui | Key lab of Ground Resources and Environment, Ministry of Education, College of Environment and Resources, Jilin University, Changchun 130012, China | | | MA Xiao-fan | Key lab of Ground Resources and Environment, Ministry of Education, College of Environment and Resources, Jilin University, Changchun 130012, China | | | LI Lin-hui | Key lab of Ground Resources and Environment, Ministry of Education, College of Environment and Resources, Jilin University, Changchun 130012, China | | | WANG Guan-zhu | Key lab of Ground Resources and Environment, Ministry of Education, College of Environment and Resources, Jilin University, Changchun 130012, China | | | GUO Ping | Key lab of Ground Resources and Environment, Ministry of Education, College of Environment and Resources, Jilin University, Changchun 130012, China | guoping@jlu.edu.cn |
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| Abstract: |
| Atmospheric nitrogen deposition and freeze-thaw cycles impact soil nitrogen transformation. In this study, a field simulation experiment was conducted to investigate the effects of nitrogen deposition on enzymatic activities and inorganic nitrogen contents in soil during freeze-thaw cycles in Songnen grassland of Northeastern China. Nitrogen deposition exerted some impacts on soil urease and protease activities. The activities of both enzymes increased with nitrogen rates, but decreased at higher nitrogen, which may relate to N saturation. Urease and protease activities were significantly higher in the sampling time 2(T2)(freeze-thaw cycles during winter/ spring seasons) than in the sampling time 1(T1)(freeze-thaw cycles during fall/ winter seasons), due to more freeze-thaw cycles occurred in T2 resulted from higher temperature. The contents of soil ammonium nitrogen increased with nitrogen deposition, and was significantly higher in T2 than in T1. With nitrogen addition, nitrate nitrogen contents in soil increased in T1, while it increased initially but decreased then in T2. Soil nitrate nitrogen contents were significantly higher in T1 than in T2, which might be due to nitrate leaching by water from the melting process in the early spring. Compared with non-clipping, clipping significantly reduced soil nitrate nitrogen contents in T1, but increased soil urease activity and soil ammonium nitrogen contents in T2. The changes in soil surface temperature and grass residues caused by clipping may also influence soil enzyme activities and inorganic nitrogen contents. |
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