Picture a tranquil landscape with undulating topography, idyllic streams, scenic glades, and verdant vegetation. Left to its own devices, this landscape would eventually become dominated by late successional communities that would slowly shift in composition and structure in response to climate fluctuations over long time periods. This scene often forms the foundation and reference for most land management across the globe. However, this peaceful panorama rarely happens in nature because gradual successional change rarely drives landscape dynamics. Abrupt change is usually the rule with vegetation development suddenly truncated by a set of ecological processes more dynamic than succession – disturbance. A wide variety of insect, disease, animal, fire, weather, and even human disturbances, can interact with current and antecedent vegetation and climate to perturb the landscape and create a shifting mosaic of diverse seral vegetation communities and stand structures that in turn, affect those very disturbances that created them. This complex interaction of vegetation, climate, and disturbance results in unique landscape behaviors that create a wide range of landscape patterns which ensures high levels of biodiversity. The impacts of disturbances on landscape pattern, structure, and function drive most ecosystem processes and ultimately set the bounds of management for most landscapes of the world. In this article, disturbance regimes are discussed in terms of how they affect landscape dynamics and how historical disturbance regimes can form the range and variation of possible landscape conditions that can be used as a reference for managing today’s landscapes.

In this article, disturbance regimes can be generally described by 11 characteristics (Table 1; synthesized from Simard, 1996; Agee, 1993, 1998; Skinner and Chang, 1996). The disturbance agent is the entity that causes the disturbance, such as wind, fire, and beetles. Sometimes disturbance agents have a source that triggers the agent. Lightning can be a source for wildland fire and heavy snow loads may be the source for avalanches. The disturbance agent occurs at a particular frequency that is often described over a period of time depending on scale and objective. Point-level measures, such as disturbance return interval and occurrence probability, describe the number of disturbance events experienced over time at one point on the landscape (Skinner and Chang, 1996; Baker and Ehle, 2001). Spatial measures of disturbance rotation and disturbance cycle estimate the number of years it takes to disturb an area the size of the landscape (Johnson and Gutsell, 1994; Van Wagner, 1978; Reed et al., 1998). The frequency distribution of disturbance sizes on a landscape or region, for example, will depend primarily on the size and number of the largest events and landscape complexity (Yarie, 1981; Strauss et al., 1989; McKenzie et al., 2011).