ASSESSING NEMATODE COMMUNITIES IN AGROECOSYSTEMS OF VARYING HUMAN INTERVENTION

The effect of disturbance on soil nematode communities was studied in eight treatments varying in intensity of human intervention at the Kel logg Biological Station Long Term Ecological Research site, Hickory Co mers, MI. The agricultural treatments ranged from those manipulated wi th high chemical inputs and heavily impacted by human management to su ccessional treatments that had no chemicals and little human impact. A canonical discriminant analysis of the nematode data separated the tr eatments into four systems: high chemical input (the conventional till age and no tillage treatments, both corn/soybean rotations); organic ( the low input and zero input treatments, both wheat/corn/soybean rotat ions); perennial (poplar and alfalfa treatments); successional (abando ned after tillage and never tilled treatments). Nematode abundance was highest in the high input and organic systems and lowest in the popla r treatment. Overall, bacterial feeding, plant parasitic and fungal fe eding nematodes dominated the treatments. Species diversity was greate st in the successional treatments. The bacterial feeding trophic group and the modified Shannon index described differences at both the trea tment and system levels, while the Shannon index demonstrated diversit y at the system and annual and perennial crop level of analysis. Measu res that detected differences (P< 0.05) consistently across all treatm ents, systems, and annual vs. perennial crops were total abundance, th e predator trophic group, the maturity index (MI) and the plant parasi te index. The minimum analyses needed to detect disturbance reliably w ere a multivariate analysis and the MI. However, understanding and pre dicting the impact of the disturbance on the food web and ecosystem fu nctioning would be increased with results from diversity indices and n ematode functional groups.