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Chapter 21 - Lecture

Chapter 21: Landscape Ecology

Overview

  • Landscape ecology: Study of relationships between landscape structures, patterns, and processes.

  • Landscape: Heterogeneous area comprised of distinctive patches (landscape elements) arranged in a mosaic.

  • Highly interdisciplinary field.

21.1 Landscape Structure

  • Landscape Structure: Defined by the size, shape, composition, number, and position of patches (landscape elements).

    • Patches: Relatively homogeneous areas differing from surroundings, forming the mosaic that represents landscape structure.

    • Matrix: Background in the mosaic that is spatially the most continuous element.

Structure of Landscapes

  • Analysis of six Ohio landscapes indicates:

    • Variation in forest cover, patch size, density, and shape.

    • Patch Shape Measurement:

      • Formula: P/S = πA^2 (P: Patch perimeter, S: Patch shape, A: Patch area).

Ecotones and Edge Effects

  • Edges of patches are not clearly defined.

  • Ecotones: Physical and biological transitions between patches, often supporting a mix of species.

  • Edge Effect: Distinct ecological conditions and higher species richness in ecotones compared to their adjacent ecosystems.

    • Edge Species: Species associated with edges; Interior Species: Not found in ecotones.

The Fractal Geometry of Landscapes

  • Measurement of landscape perimeter varies with the size of the measuring device.

  • Example: Measurements from different species perspectives (e.g., Bald eagle vs. Barnacle) reveal vast differences in perimeter measurements (e.g., 760 km for eagles vs. 11,000 km for barnacles).

21.2 Landscape Processes

  • Landscape Processes: Influence movement and interaction of energy, materials, and species within ecosystems.

    • Key processes include:

      • Dispersal of organisms.

      • Extinction of local populations.

      • Water flux between groundwater and lakes.

Landscape Structure and Organism Movement

  • Movement of organisms influenced by landscape structure:

    • Impacts metapopulation persistence.

    • Habitat fragmentation due to human activity affects movement rates.

Small Mammals and Patch Size

  • Diffendorfer et al. study on three small mammal species indicated:

    • Predicted longer movement in fragmented landscapes to access resources.

    • Results supported that animal movements decrease with habitat fragmentation.

Butterfly Populations and Patch Dynamics

  • Hanski et al. study results:

    • Butterfly population size in patches increases with area size.

    • Density decreases as patch area increases; isolated patches support lower densities.

    • Isolation affects population dynamics and maintenance through immigration.

Habitat Corridors

  • Connecting habitat fragments with corridors mitigates fragmentation effects.

    • Study findings indicate:

      • Increased movement between patches with corridors.

      • Higher densities in connected patches, positively influencing pollination and seed dispersal.

21.3 Origins of Landscape Structure and Change

  • Geological Processes: Major sources of landscape structure (e.g., volcanism, sedimentation, erosion).

Soil and Vegetation Mosaics

  • Sonoran Desert Research: Complex mosaics of landforms due to diverse soil types, ages, and structures affecting plant distributions.

Influence of Climate on Landscape Structure

  • Bajada soil mosaic represents material deposited from mountain floods; altered by climate effects on erosion and sediment.

Organisms as Ecosystem Engineers

  • Organisms that modify landscapes are termed ecosystem engineers; humans being the most significant.

    • Example of drastic changes by agricultural expansion in Cadiz Township (forest coverage declining).

Changes in Landscape Structure Over Time

  • Hulshoff’s study: Observed changes in forest and heathland coverage and patch characteristics in the Netherlands versus Cadiz Township.

Beavers as Landscape Modifiers

  • Beavers significantly alter temperate stream valleys, affecting boreal forest landscapes through increased nutrient retention and biogeochemical process changes.

Fire's Role in Landscape Ecology

  • Minnich's research utilized satellite imagery to reconstruct fire histories in California and Baja California, highlighting how fire suppression leads to biomass accumulation and larger fires in Southern California compared to the frequent smaller burns in northern Baja.

Review

  • Key Concepts:

    • Landscape Structure, Processes, and their Origins.

    • Impact of biological and geological processes on landscape dynamics.