Responses Of Arbuscular Mycorrhizae On Three Grazing Factors In The Grassland On Loess Plateau

Arbuscular mycorrhize(AM)is an important symbiont between plant roots and AM fungi in natural grassland.In ecosystem,the important ecological function of the natural grassland is to support the grazing animals.Recently,the relationship between AM fungi,host plants and the grazing animals has been paid more attention in ecology research,especially the relationship between AM fungi and host plants,and the relationship between grazing animals and host plants.However,the inter-relationships among AM fungi,host plants and grazing animals have not been discovered yet.On the basis of this,this study focused on the influence of AM fungi on the inter-relationship between host plants and grazing animals.We carried out three experiments to investigate the responses of AM fungi to the three grazing factors,defoliation,trampling,urine patchs,and the different densities of these garzing factors.Otherwise,the influence of the three grazing factors on the inter-relationship between AM fungi and the population of Leymus secalinus.The results were listed below:1)The root systems of L.secalinus could form arbuscular mycorrhizal symbionts with AM fungi in the grassland ecosystem.The AM colonization rates could enhanced the growth of host plant.2)In the grassland ecosystem,defoliation have significant influenced on the AM fungi colonization rates(P<0.05).As the intensity of the defoliation increased,the rates of AM colonization increased.Biomass and population traits of L.secalinus were decreased by AM fungi in the experiment of the various intensities of defoliation.AM fungi increased plant regrowth following defoliation,and the lower level of colonization rates showed overcompensation.The results of AM fungi indicated a response to benomyl after tissue removal by herbivores or fungal growth response to increased plant C allocation to roots after defoliation.3)Trampling have significant influenced on the AM fungi colonization rates(P<0.05).As the intensity of the defoliation increased,the rates of AM colonization were improved.Biomass of L.secalinus was decreased by AM fungi in the experiment of the various intensity of trampling,indicating a decrease of growth,but there was no signifant difference between the benomyl treatments and CK for coverage and the population density.In the control treatments,trampling negtively influenced the traits population of L.secalinus,showed antiherbivore defenses.AM fungi can influence the response to increased plant C allocation to roots after trampling.4)The patch of urine have significant influenced on the AM fungi colonization rates(P<0.05).There was signifant increased in biomass and population triats of L.secalinus by AM fungi in the experiment of the various density of urine,indicating a increase of growth.The different level of AM fungi colonization rates can change the response to plant C allocation to roots after treating urine.5)AM colonization rates had significantly influence with the temporal variety(P<0.05).In the different stages of the growth,flowering,and fruiting,physiology and growth of the host plant determined the AM fungi colonization rates.Results showed that L.secalinus exhibited the highest colonization rates at the phase of reproductive when they need more nutrients and moisture from soils.Three mechanisms were provided to explain the inter-relationship among AM fungi,host plant and grazing animals.First,AM fungi could regulate the compensatory growth of host plants on different grazing pressure.Second,the response of morphological plasticity of the host plant varied with AM fungi or without AM fungi.Third,the plant community structure and plant diversity could be changed with AM fungi.Thus,AM fungi could regulate the plant and the grazing behavior in grassland.This study could be used for the reclamation and conservation in the over-grazing grassland and it will benefits for the grassland management and grassland healthy.