Abundance and Diversity of AM Fungi across a Gradient of Land Use Intensity and Their Seasonal Variations in Niligiri Biosphere of the Western Ghats, India

The impact of land use intensity on the abundance and diversity of arbuscular mycorrhizal fungi (AMF) was investigated at six land use types viz., natural forest, grassland, acacia plantations, cardamom plantations, coffee plantations and paddy fields in the Niligiri Biosphere of the Western Ghats in South India. There was no significant difference in AMF root colonization in different land use types during pre-monsoon but there was a significant difference in AMF root infection ratings between different land use types during post-monsoon season, where it was higher in natural forests and grasslands. The AMF spore density and infective propagules were significantly higher in grasslands and acacia plantations compared to all other land use types during both seasons. Except for paddy fields, the spore density and number of infective propagules were higher in post-monsoon season compared to pre-monsoon season in other land use types. The numbers of AMF species identified were 56 during pre-monsoon and 67 species during post-monsoon season suggesting seasonal variations in diversity. During both seasons Glomus fasciculatum was recorded in maximum number of sampling points across the landscape followed by G. geosporum during pre-monsoon and G. mosseae during post-monsoon season. The species diversity was highest in natural forests and grasslands as compared to other land use types in both seasons. The species richness index for AMF was highest in natural forests and least in paddy fields during both study periods. The sand content, bulk density, total N, organic C, alkaline and acid phosphatases positively correlated with AMF activity while clay, silt, K, total P and available P were negatively correlated.