Modeling the hydroclimatic disturbance of soil landscapes in the southern Canadian plains: The problems of scale and place

The sensitivity of soil landscapes to climatic variability and hydroclimati c events can be expressed as a landscape change safety factor, the ratio of potential disturbance to resistance to change. The use of a geographic inf ormation system (GIS) enables the spatially-explicit modeling of landscape sensitivity, but also raises the risk of violating the characteristic scale s of disturbance and resistance, because the GIS technically simplifies the extrapolation of models, and associated concepts, to landscapes and scales not represented by the digital data base. Embedding landscape sensitivity into hierarchy theory, the formal analysis of the hierarchical structure of complex systems, provides a conceptual framework for the transfer of model s and variables among landscape scales. In the subhumid southern Canadian p lains, major hydroclimatic events (strong winds, intense rain, rapid snow m elt) cause much of the physical disturbance of soil landscapes and terrestr ial ecosystems. Prolonged dry or wet weather influences the resistance of s oil and vegetation to these events. The potential disturbance of soil lands capes therefore can be derived from the probabilities of extreme events and seasonal conditions, as recorded in instrumental and proxy climate records . This time series analysis can be linked to the modeling of landscape sens itivity by establishing the probabilities of hydroclimatic events and clima tic conditions which may exceed or lower the resistance of individual soil landscapes.