Succession and Disturbance in Sandhills Vegetation: Constructing Models for Managing Biological Diversity

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Abstract
The Centennial Sandhills of southwest Montana support a mosaic of shrub‐dominated vegetation in various stages of succession. The persistence of rare plants and plant communities depends on the presence of both early and late seral vegetation. Disturbances by fire, grazing, and burrowing are important processes opposing plant succession and influencing vegetation dynamics. We sampled vegetation in wind erosion (blowout), deposition, and stabilized sites on upper and lower slopes. Canonical correspondence analysis was employed to describe vegetation changes that occur during succession as soil organic matter and plant canopy cover increase and bare soil decreases. We used information on the effects of fire, ungulate grazing, and pocket gopher ( Thomomys talpoides) burrowing, and our empirically derived successional sequence, to develop a model of sandhills vegetation dynamics operating at local and regional scales. The model suggests that fire followed by intense ungulate grazing may be the only way to restore early seral vegetation to areas of low topographic relief. In areas of high topographic relief, restoring presettlement fire frequency should be adequate to maintain pocket gopher habitat and thus a high proportion of early seral vegetation. These hypotheses should be tested through a process of adaptive management aimed at sustaining a mosaic of early and late seral vegetation capable of supporting the full spectrum of native species.