Evaluating the Role of Resource Heterogeneity in Restoring Grasslands

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9603118 Knapp Attempts to restore ecosystems to a more or less "natural state" following agricultural use have usually fallen short of their goals. Although some attributes of natural ecosystems can be restored quickly, often times critical differences in the structure or function of natural and restored ecosystems persist for long periods. For example, native plant species richness and diversity in restored ecosystems is usually much lower than in comparable undisturbed ecosystems, and may take decades or longer to approach undisturbed ecosystem levels. This is particularly true for tallgrass prairie ecosystem. Although establishment of the dominant grasses in tallgrass prairie restoration efforts usually has been successful, it has been more difficult to restore the less common grasses and forbs that provide much of the species richness and diversity in these grasslands. Our research focuses on the role that heterogeneity of soil resources may play in grassland restoration efforts. Most grassland restoration efforts occur on former agricultural fields, where soil resources have been homogenized. In contrast, most natural communities are characterized by a high degree of spatial heterogeneity in resources, which is assumed to enhance plant species diversity. We contend that the problem of low plant species diversity that plagues most restoration effort is due to the slow conversion of an ecosystem from a state of relatively uniform resource availability to one with a more spatially heterogeneous pattern of resource availability. Our research will test the hypotheses that recovery of plant species richness, diversity and community heterogeneity will occur more rapidly during the restoration process if greater resource heterogeneity is impose on the system from the beginning.