JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org. ABSTRACTA comparison of a natural, undisturbed ecosystem, a mid-elevation sage community, with a severely disturbed old roadbed through this community revealed that more than 99% of the plant cover in the natural community was mycorrhizal (vesicular-arbuscular), whereas less than 1% of the plant cover in the disturbed area (roadbed) was mycorrhizal. Examples of nonmycorrhizal plants as primary successional species in severely disturbed habitats are discussed. The importance of maintaining or re-establishing the mycorrhizal fungal component in reclamation programs designed to produce stable ecosystems is emphasized.

A comparison of a natural, undisturbed ecosystem, a mid‐elevation sage community, with a severely disturbed old roadbed through this community revealed that more than 99% of the plant cover in the natural community was mycorrhizal (vesicular‐arbuscular), whereas less than 1% of the plant cover in the disturbed area (roadbed) was mycorrhizal. Examples of nonmycorrhizal plants as primary successional species in severely disturbed habitats are discussed. The importance of maintaining or re‐establishing the mycorrhizal fungal component in reclamation programs designed to produce stable ecosystems is emphasized.

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org. ABSTRACTPopulations of the endomycorrhizal fungus Glomus fasciculatus were significantly reduced following land disturbance in western Colorado soil. A bioassay was developed to measure changes in the endomycorrhizal population. In the bioassay, inoculum levels were measured by comparing the percentage infection in corn (Zea mays) root systems thirty days after planting in undisturbed or disturbed soils. The percentage infection was 2% in the disturbed soil compared to 77% in the adjacent undisturbed soil. Glomus fasciculatus was identified as the endophyte in both soils. Considering the importance and function of endomycorrhizal fungi to their plant hosts the reduction of active inoculum in the disturbed soil may be an important ecological factor in subsequent succession. 1

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Large intact soil cores of nearly pure stands of Pascopyrum smithii (western wheatgrass, C3) and Bouteloua gracilis (blue grama, Ca) were extracted from the Central Plains Experimental Range in northeastern Colorado, USA and transferred to controlled environment chambers. Cores were exposed to a variety of water, temperature and CO2 regimes for a total of four annual growth cycles. Root subsamples were harvested after the completion of the second and fourth growth cycles at a time corresponding to late winter, and were examined microscopically for the presence of mycorrhizae. After two growth cycles in the growth chambers, 54% of the root length was colonized in P. smithii, compared to 35% in blue grama. Field control plants had significantly lower colonization. Elevation of CO2 increased mycorrhizal colonization in B. gracilis by 46% but had no effect in P. smithii. Temperatures 4°C higher than normal decreased colonization in P smithii by 15%. Increased annual precipitation decreased colonization in both species. Simulated climate change conditions of elevated CO2, elevated temperature and lowered precipitation decreased colonization in P. smithii but had less effect on B. gracilis. After four growth cycles in P. smithii, trends of treatments remained similar, but overall colonization rate decreased.