凋落物对落叶松林雪盖下土壤真菌多样性的影响

为探究冬季雪盖下影响土壤微生物活性“碳亏缺”假说的全球一致性，在大兴安岭寒温带落叶松林采用人工堆雪的方法设置50 cm厚的有效雪被，并在雪被下布设不同质量的落叶松针叶作为凋落物，依据凋落物的质量分别设置自然对照组、凋落物去除组、凋落物加倍组和凋落物多倍组，用Illumina MiSeq高通量测序技术对土壤真菌ITS基因ITS1区进行测序，分析真菌群落组成结构和多样性，并结合土壤化学特征探究其相关性. 结果表明:雪盖下添加不同质量凋落物的土壤化学指标间存在显著性差异. 添加凋落物降低了土壤pH，增加了土壤有机碳(OC)、总氮(TN)、碱解氮(AN)、速效磷(AP)和速效钾(AK)含量. 其中凋落物多倍组中的OC、TN、AN、AP和AK含量均显著高于其他3组，但其pH却显著低于其他3组(P<0.05)；凋落物去除组的微生物生物量碳(MBC)含量显著高于其他3组，但其TN、AN、AP和AK含量均显著低于其他3组(P<0.05). 土壤真菌测序共获得1089个可操作分类单元(OTUs)，各组共有的OTUs数量为390个，特有OTUs的数量随凋落物量的增加呈递减趋势. 各组共检测到真菌11门42纲97目193科352属534种，其中伞菌纲(Agaricomycetes)的红菇属(Russula)为优势菌群. 各处理间Alpha多样性指数无显著性差异；Beta多样性和冗余分析结果表明，真菌被分为3组，其中优势菌群的相对丰度与OC、TN和AN含量均呈显著相关. 研究显示，凋落物的输入对寒温带落叶松林雪盖下土壤真菌的生物量和Alpha多样性没有显著改变，碳元素和氮元素可能是影响冬季土壤微生物活性的限制性因子. 

Effects of Litter Fall on Soil Fungal Diversity under Snow Cover in the Greater Xing'an Mountains

In order to explore the global consistency of ‘carbon deficiency’ hypothesis that soil microbial activities were affected by snow cover depth in winter, an effective artificial snow cover (50 cm) was set up in a larch forest that located in the cold temperate zone of the Greater Xing′an Mountains and different amount of larch litter was placed under the snow treatment for field simulation experiments, and according to the quality of litter, the natural control group, the litter removal group, the litter double group and the litter polyploid group were set up respectively. The ITS1 region of the soil fungi was sequenced using Illumina MiSeq high-throughput sequencing technology to analyze the composition and diversity of the fungal community, and to analyze the correlation with the chemical characteristics of the soil. The results showed there were significant differences in the soil chemical indicators of quality larch litter under snow cover. The litter addition decreased soil pH, but increased the contents of OC, TN, AP, and AK. The OC, TN, AP, and AK of litter double treatment were significantly higher than the other treatments, but the pH of litter double treatment was significantly lower than the other treatments (P<0.05). The MBC of litter removal treatment was significantly higher than the other treatments, but the TN, AN, AP and AK were significantly lower than the other treatments (P<0.05). A total of 1 089 operational taxonomic units (OTUs) were obtained through soil fungi sequencing, the numbers of common OTUs belonged for all treatment group were 390, and the number of unique OTUs showed a decreasing trend with the increase of litter quality. A total of 11 phyla, 42 classes, 97 orders, 193 families, 352 genera, and 534 species of fungi were detected, and the Russula belonged to Agaricomycetes was the dominant flora. Alpha diversity indices were not significantly different for the litter addition treatments. Beta diversity and RDA analysis showed that the soil fungal composition of different treatments could be divided into three groups, and the relative abundance of soil dominant flora was correlated significantly with soil OC, TN, and AN. The results showed that the input of litter did not significantly change the biomass and Alpha diversity of soil fungi under different snow cover in the larch forest located in a cold temperate zone, and the concentrations of soil carbon and nitrogen may be the limiting factors affecting soil microbial activities in winter.