Microbial diversity of the earthworm burrow wall

Abstract

Earthworms known as ?ecological engineers? are increasingly being recognized as key indicators of sustainable soil health and fertility. There are more than 3,000 different earthworm species which are placed into one of the three groups? epigeic,endogeic and anecic. With the earthworm ?sphere? constantly changing in space and time, its importance as a ?hot spot? of microbial activity in the soil, has been widely accepted. The role of earthworms as keystone animal group regulating activities of soil microorganisms, plant growth and interactions within soil communities has been extensively investigated. These factors are exclusively due to their burrowing activity. One of the most significant effects of earthworms on soils is the stimulations of microbial activity that occurs in their burrows. The nature of burrows formed in the soil is usually species specific and the micro environment associated with the walls of earthworm burrow may be substantially different from soil only a few millimeters away. It is also known that earthworms largely influence the soil microbial community with regards to their composition and function. The aim of the present study was to investigate the microbial community structure and function within the burrows and in soil close to burrow wallsunder laboratory conditions. The burrow walls of the two species of earthworms commonly found in Bangalore, India- Pontoscolexcorethrurus and Lampitomauritii,were considered to analyze whether these different earthworm species have their own role to play in influencing the microbial community. An enhanced microbial activity was expected in the burrow linings at different depths and time intervals. Hence this study included analysis at two different depths of 0-15 cm and 15- 30 cms and at two time intervals of 30 and 45 days.