Forest Occurrence of Trichoderma Species: Emphasis on Potential Organochlorine (Xenobiotic) Degradation

Fungi of the genus Trichoderma are recognized as "keystone or controller" organisms in forest soils due to their involvement in decomposition and nutrient cycling and their regulation of associated mycoflora. Recent evidence has identified additional potential importance in the decomposition of xenobiotics. Both T. harzianum and T. viride have been shown capable of organochlorine degradation in vitro. During the 1990 growing season soil immersion tubes were employed to sample Trichoderma species growing in the forest floors of the Hubbard Brook Experimental Forest and of near-by Mount Moosilauke in New Hampshire. At Hubbard Brook, sample sites included a mature forest (100 years old) and a regenerating forest (5 years old). On Mount Moosilauke, sample sites included haplorthod and cryofolist soil types and low, medium, and high elevation. T. harzianum was isolated from both sites in relatively high amount. T. viride was also present at both sites but in relatively low amount. T. polysporum was consistently isolated at all elevations but in relatively low amount. The abundance of T. harzianum decreased with increasing elevation, while the abundance of T. viride increased with increasing elevation. The evidence presented is consistent with other studies stressing the high spatial variability of members of this genus. Causes of this variability are presumed to be numerous and involve abiotic and biotic forces. Persistence of organochlorine contaminants in northern forest soils may be influenced by the abundance of fungal degraders such as T. harzianum and viride.