296
G.A. Bradshaw et al.
timber harvesting and road construction are geometric in shape and
occupy large areas of the landscape for sustained periods of time simoultaneously (Ripple, Bradshaw, & Spies, 1991). To examine the effects of
such increased het erogenity and loss of connectivity in the landscape, we
employ a simple heuristic model. A binary state (i.e. , patch-matrix)
model was constructed to observe how landscape rate s and composition
changes as fine-scale spatial pattern varies under different landscape
conditions. Applications of the model and appro ach are discussed for
two cases-disturbance propagation (e.g., bark beetle infestation) and
seedling regeneration to which we refer for purposes of the present
discussion as " dissipative" and " restorative" processes, respectively. Both
seedling regeneration and bark beetle infestation are important agents
sculpting landscape dynamics in the PNW (Franklin, Cromack , Denison
et aI., 1988; Furniss & Carolin, 1980; Harmon, Ferrell, & Franklin,
Figure 14.12. An example of the generated landscapes used in the model: small
patch size.