Arbuscular mycorrhiza and rhizosphere soil enzymatic activities as modulated by grazing intensity and plant species identity in a semi-arid grassland

Understanding the symbiosis of arbuscular mycorrhizal fungi (AMF) with plants in relation to soil nutrients and enzyme activities under different grazing intensities can be an important guide for the management and protection of semi-arid grasslands. The aim of the present study was to evaluate how the interaction of grazing intensity and plants shapes the composition of AMF communities and enzyme activities in a semi-arid grassland ecosystem in Iran. Sampling focused three dominant plant species (i.e., Salsola laricina, Artemisia siberia, and Stipa hohenackeriana) at sites with different grazing intensities. Soil chemical properties, enzyme activities, root colonization by AMF and AMF communities in the roots were evaluated. Potassium and nitrogen, as well as alkaline phosphatase and urease enzymatic activities were significantly increased at the heavily grazed site, whereas root colonization by AMF was reduced by the high grazing intensity. In addition, AM fungal root colonization is dependent on the host plant species and easier to measure as a sensitive indicator of sustainable grazing. Neither plant species nor grazing intensity affected AM fungal diversity in roots, which could be due to the overall low phylogenetic diversity of AMF in the grassland and the lack of significant differences in soil humidity, pH and organic carbon between the sites. However, plant species and soil properties were the two factors explaining variation in AMF community composition, while grazing had no significant effect. Therefore, AMF communities in root of the semi-arid grassland plants responded largely to plant type rather than to grazing intensity.