Self-Organizing Processes in Landscape Pattern and Resilience: A Review

Donald L Deangelis

doi:10.5402/2012/274510

Abstract

Environmental conditions influence the way different types of vegetation are distributed on various scales from the landscape to the globe. However, vegetation does not simply respond passively but may influence its environment in ways that shape those distributions. On the landscape scale, feedbacks from vegetation can lead to patterns that are not easily interpreted as merely reflecting external abiotic conditions. For example, sharp ecotones exist between two vegetation types, even if the basic abiotic gradient is slight, somewhere along the gradient. These are observed in transitions between numerous pairs of ecosystem types, such as tree/grassland, tree/mire, tree tundra, and halophytic plants/glycophytic plants. More complex spatial vegetation patterns may also exist, such as alternating stripes or irregular patterns of either two types of vegetation or vegetation and bare soil. One purpose of this paper is to emphasize that these two types of patterns, sharp ecotones between vegetation types and large-scale landscape patterns of vegetation, both have a common basis in the concept of bistability, in which alternative stable states can occur on an area of land. Another purpose is to note that an understanding of the basis of these patterns may ultimately help in management decisions.

Highlights

A fundamental goal of ecology is to understand the processes underlying the patterns found in nature [1]
Other landscape features that have attracted much attention are regular or irregular spatial vegetation patterns that are often observed on areas that are virtually homogeneous in external abiotic properties; that is, abiotic properties not created by feedback of the vegetation
Alternative stable states from positive feedbacks are hypothesized to be the basis for the existence of “tree islands” that dot the landscapes of freshwater marshes such as the Everglades [52, 98], Okefenokee Swamp, the Pantanal wetland in Brazil [99], the Okavango delta, Botswana [100], the wetlands of northern Belize [101], and boreal bogs [102,103,104]

Summary

Introduction

A fundamental goal of ecology is to understand the processes underlying the patterns found in nature [1]. If the underlying environment is homogeneous except for an elevation gradient, and water or nutrients are limiting, it is possible for a regular landscape patterns of alternating stripes of either two vegetation types or one vegetation type and bare soil to emerge perpendicular to the downhill flow of water and nutrients to emerge [9] These landscape patterns can occur on a flat landscape, as long as there are mechanisms to redistribute the resources, through water movement, toward vegetation patches that are large enough to monopolize resources, producing long-distance negative effects on resource levels away from the patches [10, 11]. One question is whether such shifts in ecosystems will occur gradually, at the same pace as climate changes, or whether it will occur episodically, with large-scale changes occurring

Formation of Sharp Ecotones

Resilience of Ecotones to Disturbances

Landscape Vegetation Patterns in Terrestrial Ecosystems

Conclusion and Future Directions