Enzyme Activities and Microbial Communities in Subtropical Forest Soil Aggregates to Ammonium and Nitrate-Nitrogen Additions |
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Authors: | WEI Yan WANG Zhongqiang ZHANG Xinyu YANG Hao LIU Xiyu LIU Wenjing |
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Institution: | 1. Northeast Normal University, College of Geographic Science, Changchun 130024, China; 2. Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China; 3. College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100190, China |
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Abstract: | A laboratory incubation experiment was established to examine the impacts of nitrate and ammonium nitrogen additions on soil microbial attributes of a subtropical Pinus elliottii forest ecosystem in southern China. Soils were subjected to three different treatments: the control with no nitrogen addition (CK), the ammonium nitrogen addition (NH4+-N), and the nitrate nitrogen addition (NO3--N). Samples from bulk and two different size fractions (macroaggregate (>250 μm) and microaggregate (53-250 μm)) were analyzed for soil properties, enzyme activities and microbial communities on day 7 and 15 of the incubation. Our study demonstrated that NH4+-N had a greater influence on soil microbial activities than NO3--N. NH4+-N additions resulted in significant increases in β-1,4-glucosidase (βG) and β-1,4-N-acetyl glucosaminidase (NAG) enzyme activities in bulk, macroaggregate and microaggregate soils after 7 and 15 days incubation. NO3--N additions only significantly increased in βG and NAG enzyme activities in bulk, macroaggregate soils after 7 and 15 days incubation, but not in microaggregate. All NH4+-N and NO3--N additions resulted in significant increases in gram-positive bacterial PLFAs in microaggregates. Only a significant correlation between soil nutrient contents and enzyme activities in macroaggregates was founded, which suggests that the soil aggregation structure played an important role in the determining enzyme activities. |
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Keywords: | ammonium nitrogen enzyme activity phosphor-lipid fatty acid (PLFA) soil aggregate nitrate nitrogen |
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