应用PLFA法分析氮沉降对缙云山马尾松林土壤微生物群落结构的影响

氮沉降虽可提升林地生产力却会给环境造成压力,而土壤微生物对环境变化敏感.通过野外模拟试验,探讨不同氮沉降量对马尾松土壤微生物群落的影响,探索该区域马尾松土壤微生物群落与土壤温湿度、氮沉降浓度的关系,为深入研究氮沉降对马尾松林土壤生态系统的影响提供参考.2014年5月~2015年6月在缙云山马尾松林设置3个氮添加水平和一个无氮添加的对照处理:低氮N20,20 g·(m~2·a)~(-1)]、中氮N40,40 g·(m~2·a)~(-1)]、高氮N60,60 g·(m~2·a)~(-1)]和对照N0,0g·(m~2·a)~(-1)],采用磷脂脂肪酸(PLFA)标记法和ACE(automated soil CO_2 exchange station,UK)自动土壤呼吸监测系统分别对土壤微生物群落结构、土壤温度和土壤湿度进行分析测定.结果表明:1季节变化对土壤细菌、真菌、放线菌及总PLFA量有显著影响(P0.05),各类型均在春季最高,冬季最低.在不同季节,土壤微生物量对氮沉降的响应趋势不同,总体而言,春季和秋季氮沉降抑制了土壤微生物量,夏季和冬季氮沉降促进了土壤微生物量.2氮沉降对土壤微生物群落结构有显著影响(P0.05),在春季和夏季,低、中氮沉降使土壤微生物丰富度指数和多样性降低,使均匀度指数升高;在秋季和冬季,低氮和中氮则使丰富度指数、多样性指数及均匀度指数升高.高氮沉降使4个季节土壤微生物丰富度指数、多样性指数和均匀度指数降低.3相关性分析表明,氮沉降浓度与细菌呈极显著负相关(P0.01),与总PLFA呈显著负相关(P0.05);土壤温度与放线菌呈极显著负相关;土壤湿度与细菌和总PLFA呈极显著正相关.综上所述,缙云山马尾松林土壤微生物群落结构主要受土壤湿度和氮沉降的影响,受土壤温度影响较小.

Effect of Nitrogen Deposition on Soil Microbial Community Structure Determined with the PLFA Method Under the Masson Pine Forest from Mt. Jinyun, Chongqing

Nitrogen deposition increases the productivity of forest-land, yet may cause environmental damage, while soil microorganisms are sensitive to the ecological environment. The objective of this study was to investigate the effects of nitrogen deposition on soil microbial communities and the relationship among soil microbial communities, soil temperature, soil moisture and the concentration of nitrogen deposition in the Masson pine forest. The results might provide a reference for further study on the effects of nitrogen deposition on forest ecosystem of Masson pine. From May 2014 to June 2015, three nitrogen application treatments and the control treatment were set up:low nitrogen N₂₀,20 g·(m²·a)^-1], moderate nitrogen N₄₀, 40 g·(m²·a)^-1], high nitrogen N₆₀, 60 g·(m²·a)^-1] and control treatment N₀, 0 g·(m²·a)^-1] in the Masson pine forest. Soil microbial community structure, soil temperature and soil moisture were measured by phosphorus lipid fatty acids (PLFAs) and automated soil CO₂ exchange station. The results showed that:1 Seasonal variation had a remarkable effect on soil bacteria, fungi, actinomycetes and the total PLFA(P<0.05), all kinds of soil microorganisms had the highest amounts in spring and the lowest in winter. In different seasons, the response of different soil microorganisms to nitrogen deposition was different. Generally, nitrogen deposition decreased soil microorganisms in spring and autumn, while in summer and winter, nitrogen deposition had a positive effect on soil microorganisms. 2 Nitrogen deposition had a significant effect on soil microbial community structure(P<0.05). In spring and summer, low nitrogen and moderate nitrogen decreased the soil microbial richness index and diversity index, yet increased the evenness index. In the autumn and winter, low nitrogen and moderate nitrogen promoted the soil microbial richness index, diversity index and evenness index. In all four seasons, nitrogen deposition reduced the soil microbial richness index, diversity index and evenness index. 3 Correlation analysis showed that the concentration of nitrogen deposition had a very significant negative correlation with soil bacteria (P<0.01), and a significant negative correlation with total PLFA (P<0.05). Soil temperature had a significant negative correlation with soil actinomycetes. Soil moisture had a significant positive correlation with bacteria and total PLFA. In conclusion, soil microorganisms of Masson pine forest were mainly influenced by soil moisture and less affected by soil temperature in Jinyun Mountain. Nitrogen deposition had a significant effect on microbial community structure and diversity.