Earthworm population dynamics in traditional slash and burn cultivation in Mizoram, Northeast India

Aim: This paper describes the influence of traditional slash and burn (shifting) cultivation on earthworm population structure and species diversity. Methodology: The study was conducted in a tropical hilly terrain natural forest in northeast India. The first year was taken as pre–cultivation phase. During second-year traditional slash and burn cultivation was carried out with rice (Oryza sativa) as the main crop, where local weeding practice using had hoe was done thrice. The land was left fallow in the third year. Earthworms were sampled from five random quadrats at monthly interval by digging and hand sorting method. Results: Nine species of earthworms belonging to three families were identified, out of which three epigeic species (P. excavatus, P. macintoshi and A. alexandri) were not recorded during the cultivation phase. There was a significant (p<.05) reduction in earthworm density during the cultivation phase. M. houletti was the most dominant species in terms of density, while D. nepalensis was the most versatile in seasonal distribution. Shannon Index of diversity was lowest in the cultivation phase (H ̅=0.84, 1-D=0.46) as compared to pre-cultivation (H ̅=1.67, 1-D=0.76) and post-cultivation (H ̅=1.67, 1-D=0.77).Interpretation: The reason for negative effect of traditional slash and burn cultivation on earthworm population density and diversity could be due to multiple weeding practices resulting in the disturbance of surface soil that directly or indirectly affects earthworms.Key words: Earthworms, Epigeic species, Mizoram, Slash and burn cultivation, Soil, Weeding