Knowledge of stand dynamics (Chapter 4) and landscape structure (Chapter 5) are combined in this chapter to examine in detail the relationship between disturbance and landscape characteristics. The topics progress from wind regimes to fire regimes to complex regimes with wind, fire and herbivory (this latter topic was introduced in Chapter 2). Detailed case studies of landscape characteristics and their sensitivity to changes in disturbance regime are considered in each case. Then two more important issues are introduced that can interact with fire, wind and herbivory to provide even more complexity to landscape structure: (1) disturbance size, and (2) interactions among trees themselves, or neighborhood effects. As we will see here and Chapter 8, trees superimpose a patch-forming mechanism of their own onto that created by disturbance dynamics.

Wind regimes and landscape structure

Windstorms have a great effect on structure and development of individual stands across the landscape in the Great Lakes Region. They pockmark the landscape with young stands in initiation and stem-exclusion phases of development. If wind is the dominant disturbance type in an ecosystem, the combination distribution of stand ages will result, because stands are not susceptible to massive blowdown until they reach the late stem-exclusion or demographic-transition phases, after which they will be hit at random by stand-leveling windstorms. Winds of less than standleveling force also create gaps in older stands, thereby determining the timing and size of new cohorts in multi-aged forests.