UTTAR PRADESH JOURNAL OF ZOOLOGY

The present study examined the vertical distribution, population ecology, and soil–cast nutrient characteristics associated with earthworms in the Tropical Dry Evergreen Forest of Kolli Hill, Eastern Ghats, Tamil Nadu, India. Monthly field sampling was conducted from June 2009 to May 2011 in Karavallikombai Reserved Forest near Solaikkadu. Twenty quadrats were sampled to assess earthworm occurrence, population size, biomass, density, and abundance in relation to selected abiotic factors. Three earthworm species, Drawida gracilis, Drawida bullata, and Hoplochaetella stuarti, were recorded. These species were categorised as epigeic forms and were mainly associated with the upper soil layers and litter microhabitat. During the study period, 801 individuals of D. gracilis, 794 individuals of D. bullata, and 990 individuals of H. stuarti were enumerated. Populations of all three species were generally lower in the first year than in the second year, corresponding with lower annual rainfall in 2009–2010 than in 2010–2011. Seasonal rainfall and associated soil moisture appeared to influence earthworm population size, biomass, density, and abundance. Soil and vermicast hill samples were analysed across pre-monsoon, monsoon, post-monsoon, and summer seasons. Nutrient values were generally higher in cast hills than in the surrounding soil. Significant positive relationships were observed between earthworm population and biomass and between earthworm parameters and selected environmental variables, particularly rainfall, soil moisture, and ambient humidity. The findings indicate that seasonal moisture availability and organic-rich forest soil conditions play important roles in regulating earthworm population ecology in the study area.