Revegetation of earthen mounds along a topographic‐productivity gradient in a northern mixed prairie

The influence of productivity gradients on plant succession, richness, and community composition is the focus of much interest. Earthen mounds and other soil disturbances are a conspicuous feature of many temperate and semi‐temperate grasslands. The revegetation of artificial earthen mounds located at different positions along a topographic‐productivity gradient was studied in a North American northern mixedgrass prairie over a five year period. Relative stem density increased the most on mounds in low prairie (81% of off‐mound density in 1992), followed by mounds in middle (64%) and high prairie (38%). Species richness was significantly different between prairie types by the fifth year of the experiment, but there was not a strong correlation between species richness and stem density within prairie‐types. Composition on mounds reflected species composition in the surrounding off‐mound areas and only three species were sampled regularly in all three prairie types. Results of this experiment suggest that models and experiments attempting to relate productivity to species richness and composition should include a spatial component.