Analysis of Mycorrhizal Inoculum Potential of the Soil from the Ecological Gradient Constituting the Kalamazoo River Floodplain Forest Ecosystem
Riparian floodplains are dynamic and diverse ecosystems found between rivers and upland terrestrial habitats and are primarily influenced by a flood-pulse hydrology. We have proposed a model to describe the ecological gradient found in this system. This gradient ranges from low-lying areas containing moist and potentially anoxic soils, virtually no herbaceous vegetation, and low diversity of tree species to a higher area containing drier soil, abundant herbaceous vegetation, and increased diversity of tree species. One of the essential components of all forest ecosystems, including riparian forests, is nutrient cycling in which mycorrhizae typically participate significantly. Therefore, it is hypothesized that since mycorrhizal fungi are obligate aerobes, they would not be found in the moist, anoxic soils of the lower lying areas of the floodplain. Thus, mycorrhizae may contribute to the distribution of plant species within the riparian forest. To test this hypothesis, the mycorrhizal inoculum potential (MIP) (an indication of the soil's ability to provide in situ mycorrhizal inoculum) of soils from four areas of the Kalamazoo River floodplain was determined. In tum, the ecological gradient was characterized by analyzing the different floodplain microhabitats in terms of soil variables that would reveal relative degrees of anoxia in addition to the relative plant abundance, dominance, and diversity. Lower MIP was found in the lower lying, more moist, and less diverse areas but a mycorrhizal absence was not observed. Therefore, differences in plant species distribution are most likely not attributable to differences in mycorrhizal distribution but rather are due to other physiological adaptations to and tolerances of the flood-pulse hydrology of the ecosystem.With honors.