21.2: Important Terms in Landscape Ecology
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Certainly, 'landscape' is a central concept in landscape ecology. It is, however, defined in quite different ways. For example: Carl Troll conceives of landscape not as a mental construct but as an objectively given 'organic entity', a harmonic individuum of space (Kirchhoff et al., 2013; Troll, 2007). Ernst Neef defines landscapes as sections within the uninterrupted earth-wide interconnection of geofactors which are defined as such on the basis of their uniformity in terms of a specific land use, and are thus defined in an anthropocentric and relativistic way (Neef, 1967; Haase, 1990). According to Richard Forman and Michel Godron, a landscape is a heterogeneous land area composed of a cluster of interacting ecosystems that is repeated in similar form throughout, whereby they list woods, meadows, marshes and villages as examples of a landscape's ecosystems, and state that a landscape is an area at least a few kilometers wide (1981). John A. Wiens defines 'landscape'—regardless of scale—as "the template on which spatial patterns influence ecological processes" (Wiens, 1999; Wiens, 2005). Some define 'landscape' as an area containing two or more ecosystems in close proximity (Sanderson & Harris, 2000).
Scale and heterogeneity (incorporating composition, structure, and function)
A main concept in landscape ecology is scale. Scale represents the real world as translated onto a map, relating distance on a map image and the corresponding distance on earth (Malczewski, 1999). Scale is also the spatial or temporal measure of an object or a process, or amount of spatial resolution (Turner & Gardner, 1991; Forman, 1995). Components of scale include composition, structure, and function, which are all important ecological concepts. Applied to landscape ecology, composition refers to the number of patch types (see below) represented on a landscape and their relative abundance. For example, the amount of forest or wetland, the length of forest edge, or the density of roads can be aspects of landscape composition. Structure is determined by the composition, the configuration, and the proportion of different patches across the landscape, while function refers to how each element in the landscape interacts based on its life cycle events (Turner & Gardner, 1991). Pattern is the term for the contents and internal order of a heterogeneous area of land (Forman & Godron, 1986).
A landscape with structure and pattern implies that it has spatial heterogeneity, or the uneven distribution of objects across the landscape (Forman, 1995). Heterogeneity is a key element of landscape ecology that separates this discipline from other branches of ecology.
Patch and mosaic
Patch, a term fundamental to landscape ecology, is defined as a relatively homogeneous area that differs from its surroundings (Forman, 1995). Patches are the basic unit of the landscape that change and fluctuate, a process called patch dynamics. Patches have a definite shape and spatial configuration, and can be described compositionally by internal variables such as number of trees, number of tree species, height of trees, or other similar measurements (Forman, 1995).
Matrix is the "background ecological system" of a landscape with a high degree of connectivity. Connectivity is the measure of how connected or spatially continuous a corridor, network, or matrix is (Forman, 1995). For example, a forested landscape (matrix) with fewer gaps in forest cover (open patches) will have higher connectivity. Corridors have important functions as strips of a particular type of landscape differing from adjacent land on both sides (Forman, 1995). A network is an interconnected system of corridors while mosaic describes the pattern of patches, corridors, and matrix that form a landscape in its entirety (Forman, 1995).
Figure \(\PageIndex{1}\): Basic terms to define landscape ecology (FISGRW 1998) from Understanding Landscape Structure Using Landscape Metrics (Ercan Gökyer) (DOI: 10.5772/55758).
Boundary and edge
Landscape patches have a boundary between them which can be defined or fuzzy (Sanderson & Harris, 2000). The zone composed of the edges of adjacent ecosystems is the boundary (Forman, 1995). Edge means the portion of an ecosystem near its perimeter, where influences of the adjacent patches can cause an environmental difference between the interior of the patch and its edge. This edge effect includes a distinctive species composition or abundance (Forman, 1995). For example, when a landscape is a mosaic of perceptibly different types, such as a forest adjacent to a grassland, the edge is the location where the two types adjoin. In a continuous landscape, such as a forest giving way to open woodland, the exact edge location is fuzzy and is sometimes determined by a local gradient exceeding a threshold, such as the point where the tree cover falls below thirty-five percent (Turner & Gardner, 1991).
Ecotones, ecoclines, and ecotopes
A type of boundary is the ecotone, or the transitional zone between two communities (Allaby, 1998). Ecotones can arise naturally, such as a lakeshore, or can be human-created, such as a cleared agricultural field from a forest (Allaby, 1998). The ecotonal community retains characteristics of each bordering community and often contains species not found in the adjacent communities. Classic examples of ecotones include fencerows, forest to marshlands transitions, forest to grassland transitions, or land-water interfaces such as riparian zones in forests. Characteristics of ecotones include vegetational sharpness, physiognomic change, occurrence of a spatial community mosaic, many exotic species, ecotonal species, spatial mass effect, and species richness higher or lower than either side of the ecotone (Walker et al., 2003).
An ecocline is another type of landscape boundary, but it is a gradual and continuous change in environmental conditions of an ecosystem or community. Ecoclines help explain the distribution and diversity of organisms within a landscape because certain organisms survive better under certain conditions, which change along the ecocline. They contain heterogeneous communities which are considered more environmentally stable than those of ecotones (Attrill & Rundle, 2002). An ecotope is a spatial term representing the smallest ecologically distinct unit in mapping and classification of landscapes (Forman, 1995). Relatively homogeneous, they are spatially explicit landscape units used to stratify landscapes into ecologically distinct features. They are useful for the measurement and mapping of landscape structure, function, and change over time, and to examine the effects of disturbance and fragmentation.
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Figure \(\PageIndex{2}\): An ecotone between grassland and woodland. "Ecotone" by Nicholas A. Tonelli is licensed under CC BY 2.0.
Disturbance and fragmentation
Disturbance is an event that significantly alters the pattern of variation in the structure or function of a system. Fragmentation is the breaking up of a habitat, ecosystem, or land-use type into smaller parcels (Forman, 1995). Disturbance is generally considered a natural process. Fragmentation causes land transformation, an important process in landscapes as development occurs.
An important consequence of repeated, random clearing (whether by natural disturbance or human activity) is that contiguous cover can break down into isolated patches. This happens when the area cleared exceeds a critical level, which means that landscapes exhibit two phases: connected and disconnected (Green et al., 2006).
Figure \(\PageIndex{3}\): Rapid deforestation in Cambodia resulted in habitat loss and fragmentation (credit: Global Forest Watch. World Resources Institute. Accessed on 1/5/2022. www.globalforestwatch.org).
Sources
Allaby, M. (1998). Oxford dictionary of ecology. Oxford University Press.
Attrill, M. J., & Rundle, S. D. (2002). Ecotone or ecocline: Ecological boundaries in estuaries. Estuarine, Coastal and Shelf Science, 55(6), 929–936. https://doi.org/10.1006/ecss.2002.1036
Forman, R. T. (1995). Land mosaics: The ecology of landscapes and regions. Cambridge University Press.
Forman, R. T., & Godron, M. (1981). Patches and structural components for a landscape ecology. BioScience, 31(10), 733–740. https://doi.org/10.2307/1308780
Forman, R. T., & Godron, M. (1986). Landscape ecology. John Wiley and Sons.
Green, D. G., Klomp, N. I., Rimmington, G. R., & Sadedin, S. (2006). Complexity in landscape ecology. Springer.
Haase, G. (1990). Approaches to, and methods of landscape diagnosis as a basis of landscape planning and landscape management. Ekológia, 9(1), 31–44.
Kirchhoff, T., Trepl, L., & Vicenzotti, V. (2013). What is landscape ecology? An analysis and evaluation of six different conceptions. Landscape Research, 38(1), 33–51. https://doi.org/10.1080/01426397.2011.640751
Malczewski, J. (1999). GIS and multicriteria decision analysis. John Wiley and Sons.
Neef, E. (1967). Die theoretischen Grundlagen der Landschaftslehre [The theoretical basics of landscape science]. Haack.
Sanderson, J., & Harris, L. D. (Eds.). (2000). Landscape ecology: A top-down approach. Lewis Publishers.
Troll, C. (2007). The geographic landscape and its investigation. In J. A. Wiens, M. R. Moss, M. G. Turner, & D. J. Mladenoff (Eds.), Foundation papers in landscape ecology (pp. 71–101). Columbia University Press. (Original work published 1950) https://doi.org/10.1007/978-3-662-38240-0_20
Turner, M. G., & Gardner, R. H. (Eds.). (1991). Quantitative methods in landscape ecology. Springer-Verlag.
Walker, S., Wilson, J. B., Steel, J. B., Rapson, G. L., Smith, B., King, W. M., & Cottam, Y. H. (2003). Properties of ecotones: Evidence from five ecotones objectively determined from a coastal vegetation gradient. Journal of Vegetation Science, 14(4), 579–590. https://doi.org/10.1111/j.1654-1103.2003.tb02185.x
Wiens, J. A. (1999). The science and practice of landscape ecology. In J. M. Klopatek & R. H. Gardner (Eds.), Landscape ecological analyses: Issues and applications (pp. 371–383). Springer.
Wiens, J. A. (2005). Toward a unified landscape ecology. In J. A. Wiens & M. R. Moss (Eds.), Issues and perspectives in landscape ecology (pp. 365–373). Cambridge University Press.
Contributors and Attributions
Modified by Andy Wilson (Gettysburg College) and Kyle Whittinghill (University of Vermont) from the following sources:
- Wikipedia, the free encyclopedia https://en.Wikipedia.org/wiki/Landscape_ecology