restricted access IV.2 Landscape Pattern and Biodiversity
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IV.2 Landscape Pattern and Biodiversity Joern Fischer, David B. Lindenmayer, and Richard J. Hobbs OUTLINE 1. Introduction 2. Conceptual landscape models 3. Key components of landscape pattern 4. Landscape pattern and biodiversity: Concluding remarks The amount and spatial arrangement of different types of land cover are major drivers of terrestrial biodiversity. Conceptual landscape models provide the terminology needed to analyze the effects of landscape pattern on biodiversity . Conceptual landscape models vary in their degree of complexity and realism. In increasing order of complexity , conceptual landscape models include the island model, the patch–corridor–matrix model, the variegated landscape model, the hierarchical patch dynamics model, and species-specific gradient models. Less complex models are easier to communicate than complex models, but they may oversimplify the relationship between landscape pattern and biodiversity (especially in highly heterogeneous landscapes). Key components of landscape pattern that have an important effect on biodiversity include patches of native vegetation, the nature of land use outside these patches, the connectedness of patches and ecological processes (connectivity), and the variability in land cover types (heterogeneity). Landscapes with (1) large areas of native vegetation, (2) areas outside patches that are similar in structure to native vegetation, and (3) high landscape heterogeneity are likely to support a high level of biodiversity. GLOSSARY biodiversity. The diversity of genes, species, communities , and ecosystems, including their interactions conceptual landscape model. A theoretical framework that provides the terminology needed to communicate and analyze how organisms are distributed through space connectivity. The connectedness of habitat, land cover, or ecological processes from one location to another or throughout an entire landscape landscape. A human-defined area, typically ranging in size from about 1 km2 to about 1000 km2 landscape heterogeneity. The variability in land cover types within a given landscape landscape pattern. The combination of land cover types and their spatial arrangement in a landscape matrix. The dominant and most extensive patch type in a landscape, which exerts a major influence on ecosystem processes patch. A relatively homogeneous area within a landscape that differs markedly from its surroundings 1. INTRODUCTION Life is not distributed uniformly across the surface of the planet. In terrestrial systems, several biophysical variables such as nutrient availability, radiation, and water availability are fundamental influences on where different organisms occur (see chapter IV.1). In addition , in a given area, the types of land cover present and where they occur have a major influence on how biodiversity is distributed through space. This chapter summarizes several conceptual models that are commonly used to help us think about landscapes. These conceptual models facilitate an understanding of the relationship between key components of ‘‘landscape pattern’’ and biodiversity. 2. CONCEPTUAL LANDSCAPE MODELS The effect of landscape pattern on biodiversity can be analyzed and communicated in many different ways. Implicitly or explicitly, ecologists and nonecologists alike rely on conceptual models that summarize the most important features in a given landscape. Do we need to know where there are trees? Or what the density of buildings is? Or where the warmest areas are that are suitable basking sites for a particular reptile species? Different features of landscapes will be most important for different purposes, and therefore, different conceptual models of landscapes may be required. A conceptual landscape model can be defined as a theoretical framework that provides the terminology needed to communicate and analyze how organisms are distributed through space. Typically, a conceptual landscape model also can be used to draw a picture of the most important features in a given landscape, that is, to visualize landscape pattern. There are many different conceptual landscape models, and different people may perceive the same landscape in quite different ways. However, some general conceptual models and descriptions of landscapes and landscape pattern are broadly agreed on and are used by many ecologists. These conceptual models simplify the complexity of landscape patterns. This simplification is useful because it enables meaningful communication, provides a common terminology, and focuses people’s attention on particular features within a landscape. A potential disadvantage of any particular simplification is that important aspects of complexity may be overlooked. In this regard, conceptual landscape models are no different from many other models that face a trade-off between useful simplicity and undesirable oversimplification. Five conceptual landscape models are outlined in the remainder of this section: (1) the island model, (2) the patch–corridor–matrix model, (3) the hierarchical patch dynamics model, (4) the variegated landscape model, and (5) a suite of...


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