Forman, R; Godron, M (1981): Patches and structural components for a landscape ecology
Forman, R; Godron, M (1981): Patches and structural components for a landscape ecology
BioScience, Vol. 31, No. 10 (Nov., 1981), pp. 733-740
Published by: American Institute of Biological Sciences
Stable URL: http://www.jstor.org/stable/1308780
733
Landscape as ecological units with structure and function are composed primarily of patches in a matrix. Patches differ fundamentally in origin and dynamics while size, shape, and spatial configuration are also important Line corridors strip corridors, stream corridors, networks and habitations are major integrative structural characteristics of landscape.
In geographical literature, the landscape plays a central role, with most definitions focusing on the dynamic relationship between two characteristics- natural landforms or physiographic regions and human cultural groups (Grossman 1977, Mikesell 1968, Sauer 1963). In this article we ask whether the landscape is a recognizable and useful unit in ecology, with a distinctive structure and function that can be analyzed, as is done for organisms or ecosystems.
What are the structural components of a landscape and their characteristics? Are there interesting, indeed critical, ecological questions facing us that may be solved using a landscape approach?
(...)
A landscape is a kilometers-wide area where a cluster of interacting stands or ecosystems is repeated in similar form. The landscape is formed by two mechanisms operating together within its boundary-specific geomorphological processes and specific disturbances of the component stands.
(...)
We suggest that landscape' is a distinct, measurable unit with several interesting ecological characteristics. Within the landscape is a recognizable and repeated cluster of ecosystems and disturbance regimes. The boundary between landscapes (which differ in geomorphology and disturbance) is relatively distinct, particularly in vegetation structure. Ecologically, landscape structure is measured by the distribution of energy, mineral nutrients and species in relation
to the numbers, kinds, and configurations of the component ecosystems. Landscape dynamics is the flux of energy, mineral nutrients, and species among the component ecosystems, and consequent changes in those systems.
Nota al pie:
'Related concepts: A region is bounded by a complex of physiographice, conomic, social and cultural
characteristics (Dickinson1 970, Isard 1975).A stand (or a localized community) is the group of organisms at a specific locality, and is homogeneous enough to be considered a unit (Greig-Smith1 964, Daubenmire 1968). The ecosystem concept--organisms and their encompassinga biotice nvironment-may be applied at any level of spatial scale (Odum 1971). However, in practice one looks for relative homogeneity so as to characterize an ecosystem with a limited number of measurements (Woodwell and Whittaker 1968, Forman 1979a, Bormann and Likens 1980). Though one may apply the ecosystem concept to a heterogeneous region or landscape, in this article we limit its use to stands within a landscape.
734
(...) patches are communities or species assemblages surrounded by a matrix with a dissimilar community structure or composition. The matrix exhibits several characteristics itself, such
as the degree of heterogeneity and connectivity, but in this article we focus on patches and the other structural components, corridors, networks and habitations. We further limit the analysis to
patches at a single level of scale, the landscape, though most of the resulting patterns appear to apply to all levels of scale.
736
CORRIDORS
There are four types of corridors in landscapes: Line corridors, such as paths, roads, hedgerows, property boundaries, drainage ditches, and irrigation channels, are narrow and typically have only species characteristic of patch edges. Strip corridors are wider bands containing a patch interior environment in which interior species may migrate or live. Stream corridors, which border water
courses and vary in width according to the size of the stream, control water and mineral nutrient runoff, minimizing flooding, siltation, and soil fertility loss. Networks are formed by intersecting or
anastomosing corridors and therefore contain loops. Some overlap among the four basic types exists, such as edge species moving in all four, or a wide stream corridor also functioning as a strip corridor for movement of patch interior species.
738
CONCLUSION
The structure of a landscape is primarily a series of patches surrounded by a matrix. The origins of patches differ according to the disturbance regime in the patch, disturbance in the matrix, natural
distribution of environmental resources, species introductions by people, and time. These differences in patch origin determine the species dynamics and the stability and turnover of patches themselves.
Patch area, and secondarily isolation, have traditionally been considered the major variables i ndicating the species diversity of a patch. We hypothesize that species diversity in a landscape patch is a function of the following patch variables in order of overall importance: habitat diversity ?+ disturbance + area + age + matrix heterogeneity - isolation - boundary discreteness. Patch shape as a
modifier of area is important to species diversity and is mediated through the patch edge or edge effect. The numbers of patches of each patch origin, biotic patch type, size, and shape determine in part the landscape structure. However, the spatial configuration among the patches present may be just as important as the numbers. Corridors vary in width and function. Line corridors, particularly those resulting from human activities, are very narrow and used primarily for movement of edge species or people. Strip corridors, for effective movement of species characteristic of the interior of a patch, are wide enough to include an interior microenvironment as well as edge effect on
both sides. A special case is the stream corridor, which also controls water and nutrient flows across the landscape. Networks composed of intersecting corridors are prominent features of most landscapes. Networks provide an efficient migratory route as well as alter the flow of nutrients, water, and air across the landscape. The concept of repetitive patterns in the structure of landscapes opens up a host of ecological questions related to both structure and function, and provides a relatively simple framework for testing them. It also provides a land management tool for helping to determine
priorities in the land use. Finally, it emphasizes that no patch stands alone.
BioScience, Vol. 31, No. 10 (Nov., 1981), pp. 733-740
Published by: American Institute of Biological Sciences
Stable URL: http://www.jstor.org/stable/1308780
733
Landscape as ecological units with structure and function are composed primarily of patches in a matrix. Patches differ fundamentally in origin and dynamics while size, shape, and spatial configuration are also important Line corridors strip corridors, stream corridors, networks and habitations are major integrative structural characteristics of landscape.
In geographical literature, the landscape plays a central role, with most definitions focusing on the dynamic relationship between two characteristics- natural landforms or physiographic regions and human cultural groups (Grossman 1977, Mikesell 1968, Sauer 1963). In this article we ask whether the landscape is a recognizable and useful unit in ecology, with a distinctive structure and function that can be analyzed, as is done for organisms or ecosystems.
What are the structural components of a landscape and their characteristics? Are there interesting, indeed critical, ecological questions facing us that may be solved using a landscape approach?
(...)
A landscape is a kilometers-wide area where a cluster of interacting stands or ecosystems is repeated in similar form. The landscape is formed by two mechanisms operating together within its boundary-specific geomorphological processes and specific disturbances of the component stands.
(...)
We suggest that landscape' is a distinct, measurable unit with several interesting ecological characteristics. Within the landscape is a recognizable and repeated cluster of ecosystems and disturbance regimes. The boundary between landscapes (which differ in geomorphology and disturbance) is relatively distinct, particularly in vegetation structure. Ecologically, landscape structure is measured by the distribution of energy, mineral nutrients and species in relation
to the numbers, kinds, and configurations of the component ecosystems. Landscape dynamics is the flux of energy, mineral nutrients, and species among the component ecosystems, and consequent changes in those systems.
Nota al pie:
'Related concepts: A region is bounded by a complex of physiographice, conomic, social and cultural
characteristics (Dickinson1 970, Isard 1975).A stand (or a localized community) is the group of organisms at a specific locality, and is homogeneous enough to be considered a unit (Greig-Smith1 964, Daubenmire 1968). The ecosystem concept--organisms and their encompassinga biotice nvironment-may be applied at any level of spatial scale (Odum 1971). However, in practice one looks for relative homogeneity so as to characterize an ecosystem with a limited number of measurements (Woodwell and Whittaker 1968, Forman 1979a, Bormann and Likens 1980). Though one may apply the ecosystem concept to a heterogeneous region or landscape, in this article we limit its use to stands within a landscape.
734
(...) patches are communities or species assemblages surrounded by a matrix with a dissimilar community structure or composition. The matrix exhibits several characteristics itself, such
as the degree of heterogeneity and connectivity, but in this article we focus on patches and the other structural components, corridors, networks and habitations. We further limit the analysis to
patches at a single level of scale, the landscape, though most of the resulting patterns appear to apply to all levels of scale.
736
CORRIDORS
There are four types of corridors in landscapes: Line corridors, such as paths, roads, hedgerows, property boundaries, drainage ditches, and irrigation channels, are narrow and typically have only species characteristic of patch edges. Strip corridors are wider bands containing a patch interior environment in which interior species may migrate or live. Stream corridors, which border water
courses and vary in width according to the size of the stream, control water and mineral nutrient runoff, minimizing flooding, siltation, and soil fertility loss. Networks are formed by intersecting or
anastomosing corridors and therefore contain loops. Some overlap among the four basic types exists, such as edge species moving in all four, or a wide stream corridor also functioning as a strip corridor for movement of patch interior species.
738
CONCLUSION
The structure of a landscape is primarily a series of patches surrounded by a matrix. The origins of patches differ according to the disturbance regime in the patch, disturbance in the matrix, natural
distribution of environmental resources, species introductions by people, and time. These differences in patch origin determine the species dynamics and the stability and turnover of patches themselves.
Patch area, and secondarily isolation, have traditionally been considered the major variables i ndicating the species diversity of a patch. We hypothesize that species diversity in a landscape patch is a function of the following patch variables in order of overall importance: habitat diversity ?+ disturbance + area + age + matrix heterogeneity - isolation - boundary discreteness. Patch shape as a
modifier of area is important to species diversity and is mediated through the patch edge or edge effect. The numbers of patches of each patch origin, biotic patch type, size, and shape determine in part the landscape structure. However, the spatial configuration among the patches present may be just as important as the numbers. Corridors vary in width and function. Line corridors, particularly those resulting from human activities, are very narrow and used primarily for movement of edge species or people. Strip corridors, for effective movement of species characteristic of the interior of a patch, are wide enough to include an interior microenvironment as well as edge effect on
both sides. A special case is the stream corridor, which also controls water and nutrient flows across the landscape. Networks composed of intersecting corridors are prominent features of most landscapes. Networks provide an efficient migratory route as well as alter the flow of nutrients, water, and air across the landscape. The concept of repetitive patterns in the structure of landscapes opens up a host of ecological questions related to both structure and function, and provides a relatively simple framework for testing them. It also provides a land management tool for helping to determine
priorities in the land use. Finally, it emphasizes that no patch stands alone.
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