丛枝菌根真菌对中性紫色土土壤团聚体特征的影响

Impacts of arbuscular mycorrhizal fungi on soil aggregation dynamics of neutral purple soil

利用分根装置研究了接种丛枝菌根真菌对中性紫色土土壤团聚体数量、大小和稳定性的影响,分析了土壤团聚体数量、分布和分形维数,并运用通径分析对不同影响因子进行了分析。结果表明:接种G.intraradices和G.m osseae的菌根室土壤有机质和总球囊霉素相关土壤蛋白含量有增加的趋势;湿筛条件下菌根室土壤的平均重量直径(MWD)和几何平均直径(GMD)均显著高于根室土壤,而且降低了土壤分形维数,显示了丛枝菌根真菌提升土壤结构特征的作用。通径分析的结果表明,在影响MWD的众多因子中,菌丝密度对MWD有最大的直接作用。两种菌种对土壤结构均有不同程度的改良作用,反映了丛枝菌根真菌功能的多样性。

Soil structure plays important roles in soil ecosystem functioning as it controls fluxes of water,gases and nutrients.Aggregate stability is used as an indictor of soil structure.Current approaches to investigate the formation and stabilization of aggregates in soils have been influenced considerably by the hierarchical model of the aggregation process in which primary particles and clay microstructure are bound into microaggregates（20-250 μm）,and larger macroaggregates（250 μm up to several millimeters diameter） are formed by the binding together of microaggregates and smaller macroaggregates.Many physical,chemical and biological factors（and their interactions） contribute to soil aggregation,yet among the biological aspects,mycorrhizas are recognized as being of special importance.Arbuscular mycorrhizal（AM） fungi form mutualistic symbiosis with more than 80% of the higher plant species.The contribution of AM to soil structure varied at different hierarchical levels： plant community,individual root,and the soil mycelium.In our studies to investigate the impacts of AM fungi on soil aggregation dynamics in the neutral purple soil,split root device was used and the soil were passed through sieves and then amounts of different size of aggregate were measured to obtain fractal features of soils.Path analysis was also used to evaluate the indirect or direct influencing factors.The results showed that inoculation with both G.intraradices and G.mosseae tends to increase the organic matter content and total glomalin related soil protein content in mycorrhizal soil.Mean weight diameter（MWD） and geometric mean diameter（GMD） with wet-sieving methods in mycorrhizal compartment were significantly higher than that of root compartment which resulted in the lower fractal features of mycorrhizal soil.All these results account for the important role of AM fungi in improving soil structure.Path analysis showed that hyphal density had the most important direct effect.The different ability of AM fungus to improve soil structure revealed the function diversity of AM fungi.More AM fungal species and soil types will be considered in our following studies.