Effects of soil and climatic variables on earthworm community structure at altitude in the Himalayan forest ecosystem

Assessing biodiversity in forest ecosystem is essential for conserving and managing of fragile mountain ecosystems. This study was carried out to assess the earthworm community structure along the elevation gradient from 350 to 2200 m above sea levels in six forest types in the Western Himalayas, India. Furthermore, the influence of soil physicochemical characteristics and climatic conditions on earthworm community structure was investigated. Species composition varied significantly along the elevation gradients, with high density of Lumbricidae (Aporrectodea caliginosa, A. rosea, Octolasion tyrtaeum) at high and middle elevations, and Octochaetidae (Eutyphoeus waltoni, Octochaetona beatrix) at low elevations. The exotic species dominated the earthworm communities in all the forest sites between middle and high elevations. Native species were observed in degraded forest sites or in those sites where exotic species were either absent or having low population. Out of the 11 identified species, three were found in both Acacia forest patch (NAF) and mixed forest (NMF). Four species were recorded in the mixed forest (CMF), five species in the Cedrus forest (CCF), and six species in both the mixed forest (SMF) and pine forest (SPF). Multivariate analysis revealed a maximum similarity of 91% between the forest sites of low elevations and of 81% between the sites of high elevations. Soil and climatic factors, viz., rainfall, soil moisture, temperature, and organic carbon, were the key environmental factors driving the earthworm community structure in forest ecosystems. We also determined that high reproduction rates in non-native species Octolasion tyrtaeum, Aporrectodea rosea and A. caliginosa facilitated them to survive and colonize new areas in temperate like climatic conditions.