Study On Ecological Function Of Arbuscular Mycorrhizal Fungi On Soil Nutrient Leaching Loss On Songnen Grassland

Nutrient loss from ecosystems is among the top enviromental threats to ecosystems worldwide,leading to reduced plant productivity and environmental pollution.Arbuscular mycorrhizal fungi?AM fungi?form below ground symbiotic associations with the majority of land plants which provides mineral nutrients to the plant in exchange for carbohydrates.Numerous studies domonstrated that AM fungi can reduce soil nitrogen leaching loss in agroecosystems and grassland ecosystems.However,the mechanism and process of how do AM fungi affect nitrogen loss in leaching event is less well understood.We conducted field experiments in situ control and pot experiment in songnen grassland ecosystem of western Jilin Province to explore the function of AM fungi on leching loss of inorganic nitrogen and organic carbon in community with different nutrient availability.Resutls of this study will provide a theoretical basis and technical support for improving plant productivity and maintaining soil nutrient avilability,thereafter helping to maintain the sustainable development of ecosystem.Main results and conclusions were obtained as follows:?1?AM fungi reduced leaching loss of soil inorganic nitrogen?ammonium and nitrate?in grassland ecosystem,and it was affected by community background characteristics?such as soil nutrient availability level?and fertilization.AM fungi reduced ammonium?NH₄⁺?leaching loss in community with low nutrient availability by 16%-26%;while AM fungi decreased nitrate?NO₃^-?leaching loss by increasing soil nitrate levels in community with high nutrient availability.?2?Nitrogen addition influenced the pathway of AM fungi.AM fungi increased plant nitrogen content under nitrogen addition,while reduced the leaching loss of ammonium in community with low nutrient availability.Nitrogen reduced the ability of AM fungi to prevent nitrate leaching loss in both communities.AM fungi reduced leaching loss of soil organic carbon,especially under nitrogen addition condition.?3?Effects of AM fungi on inorganic nitrogen and orgnic carbon leaching loss were influenced by environmental factors.In community with low nutrient availability,vegetation characteristics?such as plant nitrogen,phosphorus content,grasses biomass and total aboveground biomass?had effects on the interception of inorganic nitrogen and organic carbon leaching by AM fungi,while soil factors was more important on the leaching loss of inorganic nitrogen and organic carbon when AM fungi is less abundant or absent.In contrast,soil factors?such as soil pH,conductivity,water content,bulk density?was a major factor in leaching loss of inorganic nitrogen and organic carbon in community with high nutrient availability.?4?In the pot experiment we found AM fungi reduced leaching loss of soil inorganic nitrogen,and it was affected by soil nutrient availability levels,fertilization and plant functional group.The effects on reducing nitrate leaching were greater when grasses predominate in low nutrient levels compared to community with high nutrient availability.In addition,nitrogen addition significantly increased the risk of nitrate loss and reduced the ability of AM fungi to prevent nitrate leaching loss in both communities.?5?In the pot experiment we also found AM fungi had no significant effect on leaching loss of soil organic carbon,however,nitrogen significantly enhanced the leaching loss of soil organic carbon.In summary,AM fungi do have the ability of reducing inorganic nitrogen and organic carbon leaching loss in Songnen grassland ecosystems.However,nutrient leaching loss in Songnen grassland ecosystems is a very complex process,which is not only related to symbiotic relationship between plants and AM fungi but also is affected by soil nutrient availability and plant community characteristics.