Effect of Burning on Soil Nutrient Status and Abundance of VA-mycorrhizal Fungi in a Savannah Type Grassland Ecosystem in South India.

The influence of fire on the frequency of occurrence and species richness of VAM fungi in a tropical grassland in southern India was examined for a period of one year from July 1991 to June 1992. Burning in tropical grassland increased the VAM spore density in soils. Glomus mosseae and G. geosporum were the most frequently occurring species in the study site. There was no considerable variation in species richness of VAM fungi between burned and unburned control plots. Burning was found to increase the soil P content, however, subsequent watering was shown to deplete the soil P status suggesting the uptake of P by plants after watering treatment. This was further supported by a gradual increase in the P content of plants over a period of one year in burned and watered plots. However, there exhibited no considerable variation in the VAM infection intensity in major crops of the plots viz., Cymbopogon caesius, Heteropogon contartus, Rhynchosia cana and Azadirachta indica. The influence of various ecological factors and climatic conditions on the dynamics of VAM fungal populations after fire is discussed.