The Princeton Guide to Ecology

Landscapes consist of a mosaic of distinct vegetation types and their intervening boundaries with distinctcharacteristics. Boundaries can exist along abrupt environmental gradients or along gradual changes that are reinforced by feedback mechanisms between plants and soil properties. Boundaries can be defined based on the abundance, spatial distribution, and connectivity of the underlying patches. There are three major types of boundary dynamics that differ in the direction and rate of movement of the boundary in response to climatic fluctuations: stationary, directional, and shifting. Future conditions in climate and the disturbance regime, including land use, may fundamentally alter the type of boundary as well as its location and composition through time.

boundary (ecotone). Transition area where spatial changes in vegetation structure or ecosystem process rates are more rapid than in the adjoining plant communities

corridor. Edge that promotes movement or allows unimpeded movement of organisms between local populations

directional transition. Location of a boundary between two areas that moves unidirectionally through time

edge. Well-defined area between patch types; often a barrier, constraint, or limit to the movement of animals and plants

patch. Discrete, bounded area of any spatial scale that differs from its surroundings in its biotic and abiotic structure and composition

shifting transition. Boundary location that shifts back and forth with no net change over time

state. Defined by either the dominant species or composition of species, and associated process rates

stationary transition. Boundaries that are stable with little movement through time

Landscapes consist of a mosaic of distinct vegetation types and intervening boundaries (or ecotones) with different characteristics from the adjacent communities. An ecotone is a transition zone in time and space. Ecotones along spatial gradients in edaphic and climatic factors (e.g., elevation, soil texture, precipitation) have a long history in ecological studies. Gradual environmental gradients underlying vegetation transitions also exist, often related to positive feedbacks between plants and their environment. Ecotones are increasingly recognized as important elements of dynamic landscapes because of their effects on the movement of animals and materials, rates of nutrient cycling, and levels of biodiversity. Because dramatic shifts in location of vegetation types can occur at ecotones, these can also be important for management and as indicators of climate change.

Ecotones along spatial gradients, such as the treeline along an elevation gradient, have long been recognized by ecologists as important elements of landscapes. The term zone of tension between two plant community types dates to Clements (1904). Focused research on a broader definition of ecotones began in earnest in the late 1980s and early 1990s. Theoretical models were developed that laid the foundation for future research that considered ecotones as transitional areas between

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