氮磷添加对亚热带常绿阔叶林土壤微生物群落特征的影响

Effects of nitrogen and phosphorus addition on soil microbial community characteristics in a subtropical evergreen broadleaved forest

为了探讨氮磷添加对土壤微生物特点的影响,选择安徽省池州仙寓山常绿阔叶老龄林,设定了4个水平的氮磷添加试验,即对照(CK,0 kg N/hm^2)、低氮(LN,50 kg N/hm^2)、高氮(HN,100 kg N/hm^2)、高氮+磷(HN+P,100 kg N/hm^2+50 kg P/hm^2)。利用氯仿熏蒸法和Biolog微平板技术,分析不同水平氮磷添加对不同土层(0-10 cm、10-20 cm和20-30 cm)土壤微生物生物量C(MBC)、N(MBN)和微生物群落功能多样性的影响。结果表明:MBC、MBN随土层加深而降低,且差异性极显著,MBC与MBC/MBN比在氮磷添加后均表现出显著性差异;土壤微生物群落的代谢活性随土层加深而降低,HN与LN处理的土壤微生物活性最高;Mc Intosh、Shannon和Simpson多样性指数在不同土层和不同N、P添加水平上都存在差异,表层土壤微生物多样性指数差异性较为显著。土壤微生物对羧酸类、氨基酸类和碳水类碳源利用率最高;主成分分析显示不同土层的土壤微生物碳源利用上有明显的变化,表层土壤微生物碳源利用在不同N、P添加水平上有明显的空间变异性,其他土层分布较为集中,空间差异性主要表现在对碳水类与羧酸类碳源的利用上。土层与氮、磷添加剂量对土壤微生物生物量C、N及功能多样性都有显著影响,其中高氮处理对表层土壤微生物影响最大。

To reveal the effects of nitrogen and phosphorus addition on soil microbial characteristics, an old-growth evergreen broadleaved forest in the Xianyu Mountains in Chizhou of the Anhui Province was selected. Four treatments of nitrogen and phosphorus addition were designed, including a control （CK, 0 kg N/hm2）, low nitrogen （LN, 50 kg N/hm2）, high nitrogen （HN, 100 kg N/hm2）, and high nitrogen ＋ phosphorus （HN ＋ P, 100 kg N/hm2 ＋ 50 kg P/hm2） treatments. Microbial biomass carbon （MBC）, biomass nitrogen （MBN）, and microbial community functional diversity for different soil layers （0-10 cm, 10-20 cm, and 20-30 cm） were analyzed using the methods of chloroform-fumigation and the Biolog system. The results showed that MBC and MBN decreased with soil depth, with significant differences among soil layers （P 〉 0.05）. The MBC and MBC/MBN ratio changed significantly after N and P addition. The metabolic activity of the soil microbial community also declined with soil depth. Soil microbial activities were highest in the HN and LN treatments. McIntosh, Shannon, and Simpson diversity indices differed in different soil layers and at different dosages of N and P. Microbial diversity indices for the 0-10 cm soil layer were significantly different among treatments. Carbon source utilization by soil microbes was highest for carboxylic acids, amino acids, and carbohydrates. The results of principal component analysis showed that carbon source utilization was different among the soil layers. There was significant spatial variability in carbon source utilization in the upper 0-10 cm of soil under different N and P treatments, whereas it was relatively stable in other soil layers （10-30 cm）. This spatial heterogeneity was mainly manifested in carbon source utilization of carbohydrates and carboxylic acid. In general, the soil layer and N and P treatments had significant impacts on MBC, MBN, and soil microbial functional diversity, with greatest impacts occurring on the surface soil with high N treatment.