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由于人类生产活动,增长了大气中含氮化合物含量增长速度,沉降场所不断向陆地和水生生态系统转移,因而影响了生态系统的氮循环。本实验选取三明庄国有林场马尾松树种的凋落叶和土壤为研究对象,通过外源施氮方式进行室内模拟氮沉降,在凋落叶分解过程中,探讨氮沉降对土壤微生物生物量及土壤呼吸的影响。结果表明:(1)外源施氮会影响土壤呼吸。添加了马尾松凋落叶的样品各处理下的土壤呼吸速率和土壤累积碳排放量都高于空白样各处理。马尾松凋落叶分解前期,土壤呼吸速率较高、通过呼吸的碳累积快;分解后期土壤呼吸趋于稳定,通过呼吸的碳累积变慢。(2)外源施氮会影响土壤微生物生物量。经过232天的培养,土壤微生物生物量碳和MBC/MBN下降,而土壤微生物生物量氮含量增加。多因素方差分析表明,采样时间、凋落叶、氮水平(土壤微生物生物量氮除外)、采样时间和凋落叶、采样时间和氮水平、凋落叶和氮水平(土壤微生物生物量碳除外)、采样时间、凋落叶和氮水平三者的交互作用对土壤微生物生物量有显著性影响。土壤p H、有效氮、全氮和含水率与土壤微生物生物量碳和MBC/MBN呈显著的正相关,而与土壤微生物生物量氮具有显著的负相关。土壤铵态氮、硝态氮、有机质和土壤C/N与土壤微生物生物量碳和MBC/MBN呈显著的负相关,而与土壤微生物生物量氮具有显著的正相关。
As a result of human activities, the growth of nitrogen-containing compounds in the atmosphere has increased, and the settlement sites have been continuously moved to land and aquatic ecosystems, thus affecting the ecosystem nitrogen cycle. In this study, the litter and soil of Pinus massoniana from Sanmingzhuang National Forest Farm was selected as the research object. Nitrogen deposition was simulated indoor by means of exogenous nitrogen application. During the litter decomposition process, the effects of nitrogen deposition on soil microbial biomass and soil respiration influences. The results showed that: (1) Exogenous nitrogen application would affect soil respiration. The soil respiration rate and soil cumulative carbon emissions of the samples with the added Pinus massoniana litters were higher than those of the blank samples. In the early stage of decomposition of Pinus massoniana litter, the soil respiration rate was higher and the carbon accumulated through the respiration accumulated rapidly. The soil respiration stabilized in the late stage of decomposition, and the carbon accumulated through the respiration became slower. (2) Exogenous nitrogen application will affect soil microbial biomass. After 232 days of cultivation, soil microbial biomass carbon and MBC / MBN decreased while soil microbial biomass nitrogen increased. Multivariate analysis of variance showed that sampling time, litter, nitrogen level (excluding soil microbial biomass nitrogen), sampling time and litter, sampling time and nitrogen level, litter and nitrogen level (except soil microbial biomass carbon), sampling The interaction of time, leaf litter and nitrogen level had a significant effect on soil microbial biomass. Soil p H, available nitrogen, total nitrogen and water content had a significant positive correlation with soil microbial biomass carbon and MBC / MBN, but negatively correlated with soil microbial biomass nitrogen. Soil ammonium nitrogen, nitrate nitrogen, organic matter and soil C / N had a significant negative correlation with soil microbial biomass carbon and MBC / MBN, but had a significant positive correlation with soil microbial biomass nitrogen.