Berney, M., G.Bird, and R.R. Harwood
Presented at the Campus Symposium (2001-04-19 )
Nematode community structure analysis at the LTER reflects both ecosystem disturbance and seasonal responses. Four LTER treatments were selected for this study: (1) sites that were rototilled in 1999, (2) sites that were allowed to enter “old field succession” after the removal of woody plant species, (3) sites that were not tilled but annually mowed and (4) selected old field sites that were not disturbed in approximately 30 years. Three sampling dates were used, March 15, June 20 and October 3, 2000. All samples were taken from designated one meter square sampling sites, subjected to Baerman funnel nematode extraction procedures (50 cubic centimeters of soil per funnel), and the total number of nematodes were counted, and 100 individuals were selected at random and identified to genus. The genera were classified as plant parasites, plant associates, bacterial feeders, fungal feeders, algal feeders, omnivores or predators. Comparisons were made based upon the number of individuals in each feeding group. Two ratios were developed to help assess the differences among the treatments, and within each treatment over time. The first ratio illustrated the relationship between non plant parasitic nematodes and plant parasites [non-plant parasites/plant parasites (NPP/PP)]. In general, there appears to be a positive correlation between disturbance and plant parasitic nematode numbers. Plots that had more disturbances had more plant parasitic nematodes, and lower NPP/PP ratios. In all three disturbed sites, the ratios were higher in March, lower in June, and increased again in October. For example, in the annually mowed plot, the ratio was 19.5 in March, 15.6 in June and back to 19.0 in October, 2000. The old field site did not exhibit this behavior (25.1 in March, 32.0 in June, and 85.2 in October, 2000). The second ratio assessed the relationship between bacterial feeders and fungal feeders (BB/FF). These two groups made up the majority of the non-plant parasitic nematodes. The BB/FF ratios were highest in the old field plots and exhibited the same seasonal fluctuation as in the disturbed plots (27.0 in March, 15.7 in June, and 22.0 in October, 2000, for annually mowed plot). The BB/FF ratios also exhibited a slight seasonal fluctuation in the old field plot (44.6 in March, 38.0 in June, and 108.0 in October, 2000).
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