Historical Vegetation, Fuel Loads, and Integrated Resource Information Systems for Bryce Canyon National Park

The composition and distribution of plant communities across a natural landscape is determined by a complex interaction of environment, interspecies relations and disturbance. Environmental factors associated with particular locations, such as precipitation. and temperature regimes, limit the species which can occur at a given site to those with a metabolism suited to the environmental conditions. These environmental factors, while variable across the landscape, are relatively constant at a fixed point in space. Consequently, environment acts as a relatively constant constraint on vegetation distribution and composition. Within the usually large set of species which can exist at a given point, interspecies competition further limits the species present at a given time. The ecological characteristics of the species are also rather fixed, and the interspecies relations lead to a fairly directional and predictable change with time, i.e. succession. Disturbance reduces or eliminates some species directly, and leads indirectly to changes in composition through changes in the competitive hierarchy. In contrast to environmental and interspecies effects, the occurrence and effects of disturbance are highly variable, and depend in a complex way on previous disturbance and the current and previous vegetation.