Landscape Ecology: Structure and Composition

• Landscape ecology studies the relationships between landscape structures, patterns, and processes.
• A landscape is a heterogeneous area composed of distinctive patches (landscape elements) arranged in a mosaic.
• Landscape ecology is highly interdisciplinary.

Landscape Structure

• Landscape structure includes the size, shape, composition, number, and position of patches (aka landscape elements).
• A patch is a relatively homogeneous area differing from its surroundings.
• Patches form the mosaic that is landscape structure.
• The matrix is the element in a landscape that is spatially the most continuous.
• Patch shape can be quantified where S = P/2√πA
• S = Patch shape.
• P = Patch perimeter.
• A = Patch area.
• An increasing value (above 1) indicates a less circular shape.
• Ecotones are physical and biological transitions between patches.
• Ecotones often support a mix of species.
• Edge effect is a term for the distinct ecological conditions and higher species richness in ecotones compared to either ecosystem.
• Species associated with ecotones are "edge" species, and “interior” species are not found in ecotones.
• Perimeter estimates of a complex shape depend on the size of the measuring device.
• Smaller features may only show up with smaller measuring devices.
• Milne measured the perimeter of Admiralty Island from two perspectives, by looking at animals of different sizes and space requirements.
• Bald eagle perimeter estimate = 760 km
• Barnacle perimeter estimate = 11,000 km

Landscape Processes

• Landscape structure influences processes such as the flow of energy, materials, and species between the ecosystems within a landscape.
• Landscape processes are responsible for many ecological phenomena
• These include dispersal of organisms, extinction of local populations, and flux of water between groundwater and lakes.
• Landscape structure influences the movement of organisms.
• The rate of movement of individuals between subpopulations making up a metapopulation affects the persistence of the species.
• Human activity often results in habitat fragmentation.
• Diffendorfer et al. studied the effect of patch size on the movement of 3 small mammal species.
• The study predicted animals would move farther in more fragmented landscapes to obtain resources.
• The study predicted animals would stay longer in more isolated patches.
• Study results supported the hypothesis that animal movement decreases with habitat fragmentation.
• Hanski et al. found butterfly density to be significantly affected by the size and isolation of habitat patches.
• Population size in a patch increased with patch area.
• Population density decreased as patch area increased.
• Isolated patches had lower butterfly densities
• Isolated populations were partially maintained by immigration.
• Connecting habitat fragments with corridors is used to mitigate the effects of fragmentation.
• Haddad and Baum studied the influence of corridors on butterflies associated with early successional habitats.
• Studies found corridors increased movement between patches and found higher densities in patches connected by corridors.
• Corridors also affect pollination and seed dispersal.

Origins of Landscape Structure and Change

• Geological processes such as volcanism, sedimentation, and erosion are primary sources of landscape structure.
• McAuliffe showed bajadas in the Sonoran Desert are a complex mosaic of distinctive landforms.
• McAuliffe found a wide range of soil types, ages, and structures
• Soil structure influences perennial plant distributions
• Plant distributions map clearly onto soils of different ages.
• Bajada soil mosaic is made of patches of material deposited in floods from nearby mountains.
• Material is eroded from mountain slopes and deposited as alluvium on bajadas.
• Alluvial deposits gradually changed dependent upon climate
• Water transports both clay particles and CaCO3
• Soil structure indicates water was highly episodic.
• Organisms that influence the structure of landscapes, ecosystems, or communities are ecosystem engineers.
• Humans are a dominant landscape modifier.
• Forests are converted to agricultural land.
• Cadiz Township forest cover dropped from 93.5% to 3.4% due to humans.
• In eastern North America, abandoned farms reverted to forest which increased forest cover and similar patterns were found in parts of Europe.
• Hulshoff found Dutch forest and heathland coverage changed over time, as well as the number and average area of patches.
• Cadiz Township was losing forest, while the Netherlands was gaining.
• A developing agricultural economy in Cadiz Township and a collapse of the sheep-raising economy in the Netherlands contributed to this phenomena.
• Beavers have modified nearly all temperate stream valleys in the northern hemisphere.
• Beaver activity changed the boreal forest landscape of the Kabetogama Peninsula to a complex mosaic of ecosystems.
• Beavers reduced the area of boreal forest, increased nutrient retention where ponds and meadows trap material, and increased rising waters and alterations in biogeochemical processes.
• Minnich used satellite photos to reconstruct the fire history of Southern California and Northern Baja between 1971-1980.
• Landscapes consisted of patchwork of old and new burns and similar climates with different fire histories.
• Fire suppression in Southern California allowed more biomass accumulation and resultant large fires, with small burns being more frequent in Northern Baja.

Explore landscape ecology, focusing on the structure and composition of landscapes. Learn about patches, matrix, and patch shapes. Understand ecotones, edge effects, and their influence on biodiversity and ecological processes.