Effects Of Grazing Management And Intensity On Diversity Of Arbuscular Mycorrhzal Fungi In Stipa Breviflora Desert Steppe

As an important component of grassland ecosystem, arbuscular mycorrhizal fungi (AMF) promote the growth and nutrient-uptaking of plant through arbuscular mycorrhiza (AM). In this way, it can strengthen plant resistance and influence plant diversity and community productivity. However in Inner Mongolia, inappropriate grazing methods and anthropogenic interference cause serious soil degradation to the desert grassland. In this paper different grazing managements (rest grazing, rotational grazing, banning grazing and continuous grazing) and different degrees of grazing intensity (light grazing, moderate grazing and heavy grazing) in Inner Mongolian Stipa breviflora desert steppe were analyzed to find out their influence on plants and soil factors of the steppe, especially the effects on AMF diversity. It also attempts to evaluate the effects of the present grazing managements and grazing intensity to grassland ecosystem from the perspectives of AMF diversity change and relationship between AMF and plants, as well as soil factors. This paper aims to provide scientific materials to grassland production methods and sustainable development and utilization of resources. Results were concluded as follows:1. The influence of rest grazing (resting grazing for40,50,60days respectively in spring), banning grazing and continuous grazing management on AMF, plants and soil factors was analyzed. The result shows that stopping grazing for a period of time in spring improves AMF diversity and infection capacity and increases plant biomass and soil microorganisms and soil nutrient. AMF diversity, spore density, soil phosphatase activity, physical and chemical properties of soil and soil microbial quantity become well from rest grazing, banning grazing to continuous grazing. And the differences are significantly (P<0.05). AMF spore density, diversity, colonization rates, plant biomass, organic matters, total N of soil physical and chemical properties, phosphatase activity and microbial quantity in60days rest grazing areas are all higher than in continuous grazing areas. AMF spore density and microbial quantity are significantly higher in the60days rest grazing area than in banning grazing areas and plant biomass is also higher than banning grazing areas in August and September (P<0.05). The result of60days rest grazing in spring is the best among all rest grazing managements. Its AMF spore density, colonization rates, content of organic matters, total N, phosphatase activity and soil microbial quantity are all significantly higher than40or50days rest grazing (p<0.05). Under rest grazing management, AMF diversity and soil factors such as soil N content, phosphatase activity and bacterial quantity shows positive interactions.2. The influences of rotational grazing, banning grazing and continuous grazing managements on AMF, plant and soil were analyzed. The result shows that rotational grazing is beneficial to improve AMF diversity, plant biomass, soil nutrient and soil microbial quantity. AMF spore density and species richness are higher in rotational grazing areas than in continuous grazing ones. And plant biomass, soil physical and chemical properties and soil microbial quantity are higher in rotational grazing>banning grazing> continuous grazing and the differences are significantly. AMF spore density, species richness, soil phosphatase activity and soil microbial quantity in rotational grazing areas are significantly higher than banning grazing or continuous grazing areas and plant amount and soil physical and chemical properties are significantly higher than continuous grazing areas. AMF colonization rate is the highest in continuous grazing area, maybe because continuous grazing interference the ability of AMFo colonization. In rotational grazing areas, AMF diversity shows positive relationships with soil microbial amount, N content, phosphatase activity and soil factors.3. By comparing the influence of light, moderate and heavy stocking rates and banning grazing on AMF diversity, plant and soil factors, it is concluded that light grazing can improve AMF diversity, colonization rate, plant biomass, soil microbial quantity and the maintaining of soil nutrients. AMF diversity, colonization rate, soil physical and chemical properties and soil microbial amount are higher in light grazing>moderate grazing>banning grazing>heavy grazing areas and the difference is significant between light grazing and other grazing areas. Plant biomass shows higher in light and banning grazing than moderate and heavy grazing areas and the difference is significantly. AMF spore density, colonization rate, organic matters, soil physical and chemical properties and soil microbial quantity are all significantly higher than banning grazing and heavy grazing areas and AMF species richness and plant biomass are significantly higher than moderate and heavy grazing areas (p<0.05). Light grazing intensity is the best for growth of grass and maintaining of soil nutrients among the three kinds of grazing intensity. Because AMF diversity and some soil physical and chemical properties are the highest under light grazing, this grazing way not only improves AMF diversity, but also increases contents of some soil factors. Light grazing is good for plant growth, and which is more, plant biomass in this area is even higher than non-grazing area during plant growing seasons. AMF diversity, soil physical and chemical properties and microbial in non-grazing areas are lower than light grazing areas, so we can see that the result of light grazing method is better than the latter one. As far as the influence on AMF diversity and soil factors is concerned, moderate grazing is better than heavy grazing. AMF diversity, plant biomass, soil physical and chemical properties and microbial amount are all lower in heavy grazing areas. So heavy grazing has an adverse effect on grassland ecosystem. Under different grazing conditions, AMF spore density shows positive relationship with plant biomass, soil phosphorous content, soil moisture and fungal quantity. AMF species richness has significant positive relationship with plant biomass and nitrogen content.