Responses Of Arbuscular Mycorrhizal (AM) On Grazing Intensity In The Arid Grassland Of The Loess Plateau And Its Seasonal Dynamic

Arbuscular mycorrhizal fungi(AMF)are ubiquitous symbionts in both man-made and natural ecosystems.It has been demonstrated that AMF could enhance plant growth,and-transfer nutrient resources within a species or between species. AMF species also mediate plant competition and play an important role in the functions and performance of plants in terrestrial ecosystems.AMF and herbivores (vertebrate and invertebrate)both consume photosynthate from the host plants for their life activity as the sole carbon source,thus,there must be some interactions between each other.However,the mechanisms of interactions between AMF and herbivore are not well known.This study was designed to investigate the responses of AMF to grazing(herbivores)and their temporal and spatial dynamic.Two species of perennial dominant plants Stipa bungeana and Artemisia capillaries were chosen as materials in the arid grassland of Loess Plateau.The main conclusions were drawn below:1)The root systems of S bungeana and A capillaries both could form arbuscular mycorrhizal symbiont with AMF in the arid grassland ecosystem.The AMF colonization rates were both low,while the AMF spore densities in the rhizosphere soils were both high.2)The different herbivores levels didn't have significantly influence on the rates of AMF colonization of S bungeana and A capillarie(P＞0.05),but it had significantly inflence on AMF spore densities in the rhizosphere soils of S bungeana and A capillaries.The AM spore densities declined with the increasing of the herbivores levels(P＜0.05).3)Both AM colonization rates and the spore density levels had significantly influence with the temporal variety(P＜0.05).In the different stages of germination, the growth,flowering,and fruiting,physiology and growth of the host plant determined the AMF colonization rates and the spore densities.Results showed that S bungeana and A capillaries exhibited the highest colonization rates at the phase of turning green and flowering stage when they need more nutrients and moisture from soils.4)The spores in rhizosphere soils of S bungeana and A capillaries both abundantly existed at 0-30cm depth region or some special word else in the and grassland ecosystem of Loess Plateau.While soil depth increased;AMF spore densities decreased significantly(P＜0.05).And there have no significant difference of the spore densities in horizontal soils with different distance from plant roots (P＞0.05).5)The colonization rates and spore densities in natural grassland were higher than that of Vicia faba and Fagopyrum mill in man-made farm ecosystem(P＜0.05).