Relation between Soil Fungi and Seed Plants in Three Successional Forest Communities in Oklahoma

The soil fungi from three areas representing successional stages in bottomland forest vegetation in central Oklahoma were compared throughout the year at two-month intervals. The numbers of accompanying bacteria and actinomycetes were also determined. Importance percentages based on relative density and relative frequency were calculated for both green plants and fungi. The pioneer area had a high density of arboreal seedlings and no trees, the transitional area had a low density of trees, and the climax areas had a high density of trees. Each area had a different type of herbaceous vegetation. There was some overlapping in the occurrence of both arboreal and herbaceous species. The soil moisture, organic carbon, water-holding capacity, and total number of micro-organisms were low in the pioneer stage of succession, intermediate in the transitional stage, and high in the climax stage. The number of fungal species was low in the pioneer area and slightly higher in the transitional area than in the climax. Apparently the maximum number of fungal species attained during succession is reached before the climax stage. The total count of micro-organisms was high in spring. The minima for fungi occurred in summer and for bacteria and actinomycetes in late fall or winter. The correlation between the number of micro-organisms and the oxygen uptake was poor. The number of species of fungi restricted to any given area was low. Although many of the fungal species were ubiquitous in occurrence, they appeared in considerably different frequencies in different areas indicating definite community relationships. This overlapping in the occurrence of fungal species in different plant communities simulates that of the green plants. In other words, a continuum exists, rather than completely discrete communities.