长期种植毛竹林土壤丛枝菌根真菌群落演变趋势

为揭示长期种植毛竹林土壤丛枝菌根(Arbuscular mycorrhizae,AM)真菌群落演变特征,通过磷脂脂肪酸(Phospholipid fatty acid,PLFA)和Illumina Miseq测序平台研究了AM真菌生物量及群落结构的演变趋势。结果表明,长期种植毛竹林土壤养分含量总体呈下降趋势,球囊霉素相关土壤蛋白(Glomalin-related soil protein,GRSP)含量及AM真菌生物量也显著降低(p0.05),其中易提取态球囊霉素相关土壤蛋白(Easily extractable glomalin-related soil protein,EE-GRSP)含量与有机质、碱解氮、速效钾显著正相关(p0.05),而AM真菌菌丝生物量(16:1ω5 PLFA)与碱解氮极显著正相关(p0.01)。长期种植毛竹林显著降低了土壤2~0.25 mm大团聚体比例(p0.05),且与AM真菌菌丝生物量极显著正相关(p0.01)。测序结果表明,毛竹林土壤AM真菌以球囊霉属(Glomus)为优势种群,其次为无梗囊霉属(Acaulospora),长期种植毛竹后土壤球囊霉属相对丰度显著增加而无梗囊霉属显著降低(p0.05)。非度量多维尺度转换排序(Non-metric multidimensional scaling,NMDS)分析显示,对照马尾松林与不同种植年限毛竹林土壤AM真菌群落显著区分(p=0.001),土壤含水量(p=0.005)、碱解氮(p=0.001)、有效磷(p=0.014)对AM真菌群落结构变异具有重要贡献。长期种植毛竹显著降低了AM真菌生物量、球囊霉素相关土壤蛋白含量以及2~0.25 mm大团聚体比例,并改变了AM真菌群落结构,不利于土壤碳固存和维持生态系统稳定。

Effects of Long-term Plantation of Phyllostachys edulis on Evolution of Arbuscular Mycorrihizal Fungus Community in Soil

[Objective]Arbuscular mycorrhizal(AM)fungi are ubiquitous in the terrestrial ecosystem and capable of forming mutualistic relationships with most high plants,increase soil carbon sequestration via both direct and indirect pathways,and then play a key role in building up carbon storage in the forest ecosystem. However,little has been reported in the literature about variation of the AM fungus community in the soil under long-term plantation of moso bamboo(Phyllostachys edulis). Hence,the primary concern of this study is to explore variation of soil AM fungus in biomass and community structure,and its key affecting factors in the soil under long-term planted moso bamboo forest. [Method]As the moso bamboo forests in this area were mostly converted from masson pine forests one by one in the past years,plots of moso bamboo stands different in plantation age(i.e. 5 a,9 a,15 a and 18 a,)for comparison with the plots of natural masson pine forest. Each plot(10×10 m)had three replicates and all the plots were laid out at least 10 m apart. Five sampling points were set randomly in each plot,and samples of topsoil(0~20 cm)were collected from the five sampling sites in each plot and thoroughly mixed up to make a single composite sample for each plot. The soil samples were analyzed for biomass and community structure of AM fungi using the phospholipid fatty acid(PLFA)method and the high-throughput sequencing based on the Illumina Miseq platform method, respectively. Glomalin-related soil protein(GRSP)was extracted with citrate solution and measured by spectrophotometer using boving serum albumin as standard. Soil water-stable aggregates were analyzed using the wet-sieving method. [Result]Results show that soil nutrients decreased in content with the moso bamboo plantation increasing in age. Moreover,the 18 year old plots were significantly lower than the 5 plots in both GRSP content and AM fungal biomass. Pearson correlation indicated that the content of easily extracted GRSP in the soil was positively related to organic C,available K,and available N(p<0.05),and AM fungal hyphal biomass(16:1ω5 PLFA)positively and significantly to available N(p<0.01). Fractionation of soil aggregates reveals that water-stable macroaggregates(2~0.25 mm in diameter)comprised the largest fraction of soil aggregates,varying in the range from 57.79% to 72.40% and long-term bamboo plantation reduced the fraction significantly. The percentage of macroaggregates was found positively and significantly related to the biomass of AM fungal hypha(p<0.01). Results of high-throughput sequencing indicate that Glomus dominated in the AM fungal community,followed by Acaulospora. In soils under long-term moso bamboo plantation soil Glomus increased in relative abundance while Acaulospora decreased significantly(p<0.05). Non-metric multidimensional scaling(NMDS)analysis demonstrates that the AM fungal communities in the soils under moso bamboo plantation varied sharply from those under masson pine plantation(p=0.001)and also significantly with age as was observed on the first axis of NMDS. When environmental variables were fitted onto NMDS ordination,AM fungal communities were found significantly related to soil moisture(p=0.005)and available N(p=0.001),but marginally to available P(p=0.014).[Conclusion]Long-term plantation of moso bamboo decreases AM fungal biomass,alters AM fungal community structure significantly and exhausts soil nutrients steadily. The changes in soil moisture,available P and available N contribute significantly to the variation of soil AM fungal communities. Long-term plantation of moso bamboo also decreases the content of GRSP,and the proportion of soil water-stable macroaggregates (0.25~2 mm)significantly,which poses a negative impact on soil carbon sequestration and hence stability of the ecosystem.