三江源区高寒草地不同生境土壤可培养纤维素分解真菌群落结构特征研究

Community structure characteristics of culturable cellulose-decomposing fungi in soils from different ecosystems in the Sanjiangyuan Regions

为了解三江源区不同生境土壤可培养纤维素分解真菌的群落结构特征,在黄河流域、长江流域、澜沧江流域共选取有代表性的12个样点,采集土层0～15cm,15～30cm 的土壤样品,采用稀释平板法在羧甲基纤维素钠平板培养基上进行可培养真菌的计数和分离,利用种群优势度、Shannon-Wiener多样性指数、均匀度、生态位宽度以及群落相似度等指标对不同生境土壤中可培养纤维素分解真菌群落结构特征进行了分析.结果表明,三江源区不同生境土壤可培养纤维素分解真菌的数量和类群差异明显,数量由大到小的顺序为：灌丛草地〉 嵩草草地〉 藏嵩草草地〉禾草草地;在4种生境土壤中共分离获得土壤可培养纤维素分解真菌17属,禾草草地土壤中群落的优势度指数、物种多样性指数、均匀度指数最高,除均匀度指数外,藏嵩草草地土壤中群落的优势度指数、物种多样性指数最低;物种生态位结果分析表明,毛霉属、镰孢菌属、被孢霉属、青霉属具有较宽的生态位,属于广适性物种;而亚隔孢壳属、梭孢壳属、腐质霉属等的生态位很窄,属于狭适性物种,只存在于某个生境中.禾草草地与藏嵩草草地土壤可培养纤维素分解真菌群落的相似性最低,灌丛草地和嵩草草地相似性最高.土壤纤维素分解真菌的群落结构及多样性与生境类型的特异性有着密切的关系.

In order to understand the community structure characteristics of culturable cellulose-decomposing fungi in soils from different ecosystem in the Sanjiangyuan Regions,the fungi in soil from four typical grassland types were isolated by dilution plate method using a sodium carboxymethyl cellulose plate medium.The population dominance index,Shannon- Wiener index,evenness,niche breadth and community similarity were employed to analyze the community structure of the isolated fungi.The results showed that the amount and species distribution of culturable cellulose-decomposing fungi varied strongly by ecosystem.Species number decreased in the following order:shrub grassland>alpine meadow>Kobresia tibetica grassland>grass pasture.In total 17 genera were isolated from the four grassland types.The population dominance index,species diversity index and evenness index of fungi from grass pasture were highest,whereas the population dominance and species diversity indices from alpine meadow were lowest.Analysis of community similarity between the different ecosystems showed that fungi in shrub grassland and Kobresiameadow soils had the highest similarity.The similarity coefficient for fungi in grass pasture and Kobresia tibetica grassland soils was the lowest.The results of niche breadth analysis indicated that the species of Mucor,Fusarium,Mortierellaand Penicilliumhad wider niche breadth and adaptability,while the species of Didymella,Thielaviaand Humicola had narrower niche breadth and adaptability.The study thus shows that the diversity and community structure of soil cellulose-decomposing fungi are closely related to ecosystem types.