ABSTRACT
Gange (1993) showed that earthworm feeding activity is concentrated on dead and dying root material, and as a result the worms ingest large amounts of arbuscular mycorrhizal spores. By depositing spores that are still viable in their casts, earthworms provide local sources of inoculum for establishing plant species. The number of spores per cast increases as vegetation succession proceeds (Fig. 4.9). The effect of this process is to enhance the colonization of recruits into the plant community as succession proceeds by providing available spores in patches of enriched nutrient status (worm casts), in which the opportunities for seedling establishment are increased. Doube et al. (1994a,b; 1995) have shown that earthworms of the genus Aporrectodea are important in assisting plant roots to be colonized by bacteria (especially species of Pseudomonas) that are antagonistic to root pathogenic fungi. They have shown that earthworms can be effective
vectors for these biocontrol bacteria against the take-all fungus, Gaumannomyces graminis (Fig. 4.10).
