模拟氮沉降对杨树人工林土壤微生物群落碳源利用类型的影响

【目的】探究氮沉降对杨树人工林土壤微生物群落特征的影响。【方法】以江苏省东台地区沿海杨树人工林为对象,采用Biolog ECO微平板技术,设置4种氮添加水平:N0(0 kg/(hm²·a))、N1(50 kg/(hm²·a))、N2(100 kg/(hm²·a))、N3(150 kg/(hm²·a))模拟不同浓度氮沉降,经过2 a生长季(5—10月)处理,测定杨树林土壤微生物群落碳源利用变化情况。【结果】N2处理可以增强杨树人工林土壤微生物对碳源的代谢能力,氮添加浓度过高则会产生抑制作用; 土壤中微生物对胺类和酚类利用程度表现出较大差异,其中,酚类在高浓度氮处理(N3)时利用程度最高,胺类在低浓度氮(N1)条件下利用程度最高; 硝态氮和平均颜色变化率(AWCD)、Shannon多样性均具有显著正相关性(P<0.05),微生物代谢水平及其结构变化受到硝态氮影响较大。主成分分析表明,PC1和PC2可以表示施氮对微生物群落代谢多样性产生的差异,其中,PC1的方差贡献率最大,碳水化合物、酚类呈负相关(碳源相关系数分别为-0.869、-0.780),氨基酸、羧酸呈正相关(碳源相关系数分别为0.702、0.821),是起主要分异作用的碳源; PC2涵盖了聚合物和胺类两种碳源大类,其中聚合物呈负相关(相关系数为-0.688),胺类呈正相关(相关系数为0.802)。【结论】氮添加会导致杨树人工林土壤微生物群落对碳源利用类型改变,土壤中硝态氮含量与微生物生长代谢及功能多样性呈显著正相关; 六大类碳源中碳水化合物、羧酸是影响土壤微生物群落功能多样性的主要碳源。 关键词:氮沉降; 土壤微生物; 碳源代谢; 群落功能多样性; 杨树人工林

Effects of nitrogen deposition on soil microbial community C-source metabolism of poplar plantation

【Objective】Study the effects of elevated nitrogen deposition on soil microbial community structure in a poplar plantation.【Method】 The field experiment was designed at Dongtai Forestry Farm in Jiangsu Province, a coastal area of eastern China in June 2015, and we used Biolog ECO method and conducted nitrogen addition at four levels: N0(0 kg/(hm²·a)), N1(50 kg/(hm²·a)), N2(100 kg/(hm²·a)), and N3(150 kg/(hm²·a)). 【Result】The soil microbial C-source metabolic capacity was improved under N2 treatment, but was inhibited under higher levels of nitrogen deposition. Utilization of phenols and amines were the highest in N3 and N1, respectively. Average well color development(AWCD)and the Shannon diversity index were both significantly and positively correlated with nitrate nitrogen content(P<0.05), indicating that the C-source metabolism and community structure were influenced significantly by nitrate nitrogen content. The PC1 and PC2 in a principal component analysis(PCA)accounted for 50.04% and 25.02%, respectively, of the variation in microbial community metabolic diversity caused by nitrogen deposition. The PC1 was correlated with carbohydrates(-0.869), phenols(-0.780), amino acids(0.702)and carboxylic acids(0.821). The PC2 was correlated with polymers(-0.688)and amines(0.802).【Conclusion】After two years of nitrogen addition during May-October each year, the nitrogen amendment significantly changed the types of carbon utilized by the microbial community. There were significantly positive correlations between the contents of soil nitrate nitrogen and bacterial carbon metabolism levels as well as the diversity indices. The results of PCA indicated that the dominant carbon sources were carbohydrates and carboxylic acid.