The relationships of vegetation and bird communities with landforms and geomorphic processes on the Central Niagara Escarpment (Ontario).

摘要

This study has examined the relationships between geomorphic form and process, vegetation composition and dynamics, and avian populations for landscapes in the central Niagara Escarpment, Southern Ontario. This includes an area extending from Speyside Conservation area near Milton to Mono Cliffs Provincial Park north of Orangeville. Data was collected for geomorphic form and process parameters, vegetation species and structural parameters, and avian species. The physical parameters included a combination of landform characteristics including slope angle, aspect, and landscape position and geomorphic processes, such as creep and debris slides, measured as a level of disturbance. Human levels of disturbance were also measured for comparative purposes. Eleven vegetation structural parameters were measured, such as deciduous/coniferous ratio, stern density, snag density and canopy cover. This data was collected for 29 land units, divided between upland, slope and valley segments, at 11 sites along the Escarpment. Sampling for the avian populations took place during the breeding season between 1996–1999. Vegetation and bird associations were classified using cluster analysis (TWINSPAN). An ordination analysis (CANOCO) was also completed to determine the relationships between the biological components and biophysical form and process. The results of these analyses were combined with field observations to create a set of landscape units. These units were presented within a descriptive model to describe the relationships within the Escarpment landscape systems.; The results of this study found strong relationships between vegetation associations and landscape position. These patterns were related to disturbance and stress from natural and human processes. Avian populations were strongly related to the vegetation patterns of coniferous and deciduous cover, but there was not as strong a correspondence with landscape position and the levels of disturbance and stress. Natural disturbance created the greatest variation on species in the slope units, while human disturbance was a stronger control on upland sites. Stream gradient and the extent of floodplain were the main controls in the valley units. Overall, Escarpment landscape systems are dynamic and complex. They are composed of a strongly heterogeneic series of landscape units, which is evident in the diversity of forest and avian components. Management strategies need to recognize the role of natural and human processes in creating this heterogeneity and to develop policies that maintain the spatio-temporal pattern of the disturbance regimes.