通过室内培养实验,研究铵态氮和硝态氮添加对我国南方亚热带湿地松森林生态系统土壤微生物特性的影响.采用的氮添加处理为:对照(CK)、铵态氮(NH4+-N)和硝态氮(NO3–-N).经7天和15天培养,分别分析两种不同粒径(大团聚体(>250μm)和微团聚体(53–250μm))样品的土壤特性、酶活性及微生物群落.结果表明,NH4+-N比NO3–-N更显著影响土壤微生物活性.添加NH4+-N培养7天和15天,土壤大团聚体和微团聚体的β-1,4-葡萄糖苷酶(βG)和β-1,4-N-乙酰葡糖胺糖苷酶(NAG)的活性显著增加,而添加NO3–-N仅使大团聚体中的 β-1,4-葡萄糖苷酶(βG)和 β-1,4-N-乙酰葡糖胺糖苷酶(NAG)的活性显著增加.NH4+-N和NO3–-N添加导致土壤微团聚体革兰氏阳性细菌的磷脂脂肪酸含量显著增加.然而,仅在大团聚体中,土壤养分含量与酶活性呈显著相关.本文结果表明土壤团聚体结构对土壤酶活性具有重要影响.%A laboratory incubation experiment was established to examine the impacts of nitrate and ammonium nitrogen additions on soil microbial attributes of a subtropical Pinus eliotti forest ecosystem in southern China. Soils were subjected to three different treatments: the control with no nitrogen addition (CK), the ammonium nitro-gen addition (NH4+-N), and the nitrate nitrogen addition (NO3?-N). Samples from bulk and two different size fractions (macroaggregate (>250μm) and microaggregate (53–250μm)) 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 inβ-1,4-glucos-idase (βG) andβ-1,4-N-acetyl glucosaminidase (NAG) enzyme activities in bulk, macroaggregate and microag-gregate soils after 7 and 15 days incubation. NO3?-N additions only significantly increased inβG and NAG enzyme activities in bulk, macroaggregate soils after 7 and 15 days incubation, but not in microaggregate. Al NH4+-N and NO3?-N additions resulted in significant increases in gram-positive bacterial PLFAs in microaggregates. Only a sig-nificant 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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