Landscape Ecology: Structure, Processes, and Change

Landscape Ecology

Introduction to Landscape Ecology

Landscape ecology is a sub-discipline of ecology that examines how spatial variation in the landscape (its structure) affects ecological processes (its function). Landscape ecologists study the structure, processes, and changes within landscapes, which are heterogeneous areas composed of several ecosystems. Visually distinctive patches within an ecosystem are referred to as landscape elements.

• Landscape: A region containing multiple interacting ecosystems.

• Landscape Elements: Distinctive patches such as forests, ponds, towns, or meadows.

• Landscape Structure: The arrangement and organization of these patches.

Example: A rural area with fields, forests, and streams forms a landscape with multiple elements.

Large Scale Ecology

Types of Large Scale Ecology

• Landscape Ecology: Focuses on spatial patterns and ecological processes at the landscape scale.

• Geographic Ecology: Studies large-scale patterns of plant and animal life that can be mapped, including biological diversity and species ranges.

• Global Ecology: Examines ecological phenomena and changes at a global scale, including the impact of humanity on Earth.

Landscape Structure

Components of Landscape Structure

Landscape structure refers to the size, shape, composition, number, and position of ecosystems within a landscape. The arrangement of patches forms a mosaic, which is the basis for landscape structure.

• Patch: A discrete area within a landscape, such as a woodlot or pond.

• Mosaic: The pattern formed by the arrangement of patches.

Example: A landscape with circular forest patches and irregularly shaped meadows.

Quantifying Landscape Structure

Landscape structure can be quantified by measuring patch area, shape, and distribution. These factors influence ecological processes and species interactions.

Landscape	Forest Cover (%)	Patch Shape
Monroe	Low	Less circular
Somerset	High	More circular
Hudson	Medium	Intermediate
Boston	Low	Less circular
Washington	High	More circular

Additional info: Patch shape affects perimeter-to-area ratio, influencing edge effects and species movement.

Landscape Processes

Influence of Structure on Processes

Landscape structure affects ecological processes such as the flow of energy, materials, and species between ecosystems. Key processes include dispersal, population density, extinction, and chemical composition.

• Dispersal of Organisms: Movement of species between patches.

• Local Population Density: Number of individuals per unit area within a patch.

• Extinction of Local Population: Loss of species from isolated patches.

• Lake Chemical Composition: Variation in water chemistry based on landscape position.

Landscape Structure and Dispersal

Small Mammals and Patch Size

Landscape structure can influence the movement of organisms between suitable habitats. Metapopulations are populations of species that occur in spatially isolated patches but exchange individuals through migration.

• Diffendorfer et al.: Studied how patch size affects movement of rats, voles, and mice.

• Animals move farther in fragmented landscapes to obtain resources.

• Animals stay longer in isolated patches.

Patch Size	Mean Dispersal Distance	Proportion Remaining
Small	Low	Low
Medium	Medium	Medium
Large	High	High

Additional info: Fragmentation increases movement distance; isolation increases time spent in patches.

Butterfly Populations and Habitat Patch Size/Isolation

Hanski et al. found that butterfly density is significantly affected by the size and isolation of habitat patches in southwestern Finland.

• Population size within a patch increases with patch area.

• Population density decreases as patch area increases.

• Isolated patches have lower butterfly densities, partially maintained by immigration.

Habitat Corridors

Connecting habitat fragments with corridors of similar habitat can mitigate the effects of fragmentation. Haddad and Baum found that corridors increase butterfly movement in early successional habitats.

Habitat Type	Butterfly Density
Connected patches	High
Isolated patches	Low

Landscape Position and Lake Chemistry

Effects of Lake Position

Webster explored how the position of a lake in a landscape affects its chemical response to drought. Lake position determines the proportion of water received as groundwater and the concentration of dissolved ions.

• Lakes at upper positions receive less groundwater, more precipitation.

• Lakes at lower positions receive more groundwater, higher ion concentrations.

Lake Position	Water Source	Ion Concentration
Upper	Precipitation	Low
Middle	Mixed	Medium
Lower	Groundwater	High

Origins of Landscape Structure and Change

Geological Processes and Climate

Landscapes are structured and change in response to geological processes (volcanism, sedimentation, erosion) and climate events (floods, droughts).

• Geological Processes: Create and modify landforms.

• Climate Variation: Alters landscape mosaic over time.

Organisms and Landscape Structure

Plants and animals can significantly influence landscape structure, sometimes acting as ecosystem engineers. Examples include nitrogen-fixing legumes and keystone species such as elephants and beavers.

• Beavers: Build dams, create ponds, alter hydrology, trap sediments, and increase wetland extent.

• Beaver activity can add new ecosystems to landscapes and increase patchiness.

• Johnston and Naiman: Documented beaver-induced changes in boreal forest landscapes over 63 years, increasing wetland area from 200 ha to 2,661 ha.

Human Activities and Disturbance

Human activities and disturbances such as fire also play a major role in shaping and changing landscape structure.

• Human Activities: Urbanization, agriculture, deforestation.

• Disturbance: Events like fire can reset or alter landscape mosaics.

Additional info: Landscape ecology integrates physical, biological, and human factors to understand ecosystem patterns and processes at large spatial scales.