Landscape mosaic is a heterogeneous area, composed of different communities or a cluster of different ecosystems. Ecosystems are quite similar in function and origin in landscape. A component of spatial distribution related to dispersion is the concept of grain (Pielow, 1974).
Grain relates to relationship of landscape patch size to animals mobility. A habitat or landscape patch is coarse-grained for a given animal species, if its vagility, i.e., ability to move freely about is low relative to size of habitat patches.
A habitat is fine-grained for a species, if that organism has high vagility relative to size of habitat patches. For example a wide ranging predator, a red-tailed hawk (Buteo jamaicensis) experience a mosaic of agro ecosystems patches (woodlots) as a fine grained habitat. Species such as a white-footed mouse (Peromyscus leucopus) experience a more coarsegrained agricultural landscape by spending most of its time in single patch (woodlot).
Image Source: mozaico.net
ADVERTISEMENTS:
‘Landscape corridors are landscape elements that provide a means of enabling animal’s dispersal, reducing soil and wind erosion, allowing transfer of genetic information between patches, aiding in integrated pest management, and providing habitat for non game species. Corridors have negative, as well as positive effects. For example, transmission of contagious diseases, spread of disturbance such as fire, and increased exposure of animals to predation (Simberloff and Cox, 1987) may be the corridors effect.
Corridors are classified into several types. Remnant corridors occur, when most of original vegetation is removed from an area, but a strip of native vegetation is left uncut. Such corridors include uncut vegetation along streams, steep land, railroad tracks or property borders. Remnant patches and corridors provide “outdoor teaching and learning laboratories” for comparing ecological processes in young and mature systems (Barrett and Bohlen, 1991).
ADVERTISEMENTS:
Remnant corridors increase species diversity improve nutrient cycling, protect natural capital and provide habitat for K- selected edge species including many game species. A linear disturbance through landscape matrix produces a disturbance corridor that disrupts natural, more homogeneous landscape, and provides habitat for native plant and animal “opportunistic” species adapted to disturbance or for species commonly found during early stages of secondary succession.
Power line corridors cut through a forest landscape is an example of a disturbance corridor. Forest interior species seldom use such corridors to nest or reproduce. Forest edge wildlife species may flourish in such corridors.
Disturbance corridors may act as barriers to movement of some species; while they provide routes of dispersal of species, such as white-footed mouse (Peromyscus leucopus) and eastern chipmunk (Tamias striatuse) (vide Henderson et al., 1985).
Disturbance corridors act as filters for some species but not for others. This filter effect can be minimized by providing gaps or nodes of matrix vegetation in corridor, allowing certain species to cross while restricts others. Planted corridors are strips of vegetation planted by humans for a variety of economic and ecological reasons.
ADVERTISEMENTS:
For example, thousands of miles of planted tree corridors were established in treeless Great Plains as part of Shelterbelt Project during 1930s, to reduce wind erosion and to provide wood and wildlife habitat (Shelterbelt Project, 1934). Planted corridors also provide excellent habitat for insectivorous birds, predaceous insect, and function as dispersal routes for small mammals.
Resource corridors are narrow strips of natural vegetation that extend for long distances across landscape, such as a gallery forest along a stream. Lawrence et al., (1984) described how vegetated stream corridors benefits agricultural landscape by intercepting nutrient and sediment runoff from croplands, that otherwise would end up in streams, contributing to cultural eutrophication.
These strips improve water quality, reduce fluctuations in stream levels and help to conserve natural biotic diversity within agricultural landscape mosaic. A regenerated corridor results from re-growth of a strip of vegetation in a landscape matrix. Hedgerows that develop along fences due to natural processes of secondary succession is an excellent example of a regenerated corridor.
Birds are common inhabitants and aid the development and plant species composition of these corridors by providing a mechanism of seed dispersal. Insect pests cause economic damage by feeding on crops adjacent to corridors.
Forman and Baudry (1984) found that regenerated corridors were often source of natural enemies that colonize adjacent crops and aid biotic pest control. Forest edge bird species, and birds that forage in croplands, often nest in wooded regenerated corridors also help to regulate insect species in agricultural corps.
Red fox (Vulpes wipes), white tailed deer (Odocoileus virginianus), and wood chucks (Marmota monax) frequently use regenerated corridors. Small mammals suffer local extinction in relatively isolated patches of habitat, such as, forest woodlots but use regenerated corridors to reestablish their populations and metapopulation (Sanderson and Harris, 2000).