Assessing fine-scale heterogeneity and its influence on large herbivore foraging behavior

I used a combination of ground-based vegetation sampling and low-altitude aerial photography to describe plant composition and spatial structure in an oak savanna. I compared measures of heterogeneity and spatial structure to understand how the plant community in 4 pastures responded to past burning and grazing treatments. Plant communities in MC, B87 and B94 were comprised of fine-grain mixtures of relatively uncommon species. As expected, HC contained the lowest species diversity. Species diversity was surprisingly similar between MC, B87 and B94 pastures despite differences in management regime. Comparisons between pastures suggest that moderation of grazing pressure from historical levels and the use of fire have resulted in elevated plant species diversity. Comparisons between MC, HC and the 2 burned pastures suggest that the management of grazing alone may be adequate to rehabilitate degraded oak savanna.; In addition, I developed a blimp-camera system for obtaining low-altitude aerial photographs. Photographs were classified and used to compare the composition and fine-scale spatial structure between pastures. Despite several technical challenges and problems identifying individual plant species, classified images provided detailed spatial representations of vegetative and non-vegetative components and provided a basis for evaluating structural differences between 4 pastures. Image resolution had little influence on estimates of composition but greatly influenced the description of structural elements. At the 0.5 m scale, low-altitude photography provided a more detailed representation of heterogeneity than could be derived remotely using other available sources of imagery.; Finally, I assessed the influence resource heterogeneity on short-term spatial and behavioral responses of white-tailed deer (Odocoileus virginianus) and Angora goats in experimental enclosures. I tested competing hypotheses explaining animal spatial responses to fine-scale patterns of acceptable forage species. Deer and goats selected different diets and responded differently to the distribution of plant species in enclosures. Both herbivores spent more time feeding in areas where they achieved high intake. However, the availability of total plant biomass, and even the distribution of diet species were inadequate to predicted animal spatial responses. Traditional approaches of rangeland assessment are unlikely to provide meaningful predictions of the actual foraging opportunities experienced by different herbivores.