Landscape Ecology Notes

Introduction to Landscape Ecology

Landscape Definition

  • Landscape: A heterogeneous area composed of distinctive patches (landscape elements) arranged in a mosaic.

Landscape Ecology

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

How Are Landscapes Formed?

Abiotic Factors
  • Physical processes: wind, rain, flooding, geological activity (earthquakes, volcanoes, tornadoes).
  • Other abiotic characteristics: Temperature, latitude, humidity.
Biotic Factors
  • Living organisms change and create landforms (habitat modification).
  • Ecosystem engineers: Organisms that physically or chemically change their environment (e.g., beavers).

Origins of Landscape Structure and Change

  • Geological processes (volcanism, sedimentation, and erosion) are a primary source of landscape structure.
Landscape Position and Lake Chemistry
  • Webster et al. study: How lake position affects chemical responses to drought.
  • Lake position: Determined by the proportion of water received as groundwater.
  • Lakes receiving less groundwater dropped more in drought.
  • Concentration of dissolved ions increased most at upper and lower ends of the hydrologic flow system.
Soil and Vegetation Mosaics in Sonoran Desert
  • McAuliffe's research: Bajadas in the Sonoran Desert are complex mosaics of distinctive landforms.

Climate and Landscape Structure

  • Bajada soil mosaic: Patches of material deposited in floods from nearby mountains.
  • Alluvium: Material eroded from mountain slopes and deposited on bajadas.
  • Alluvial deposits change depending on climate.
  • Water transports clay particles and CaCO3CaCO_3 (calcium carbonate).
Soil and Vegetation Mosaics in Sonoran Desert (cont.)
  • Wide range of soil types, ages, and structures found.
  • Soil structure influences perennial plant distributions.
  • Plant distributions map clearly onto soils of different ages.

Fire and Structure of Mediterranean Landscape

  • Minnich's study: Reconstructed fire history of Southern California and Northern Baja (1971-1980) using satellite photos.
  • Landscape: Patchwork of old and new burns.
  • Similar climates, different fire histories.
  • Fire suppression in Southern California: More biomass accumulation, leading to large fires.
  • Small burns: More frequent in Northern Baja.

Fires in Mediterranean Landscapes

  • (Continuation of previous point)

Ecosystem Engineers

  • Organisms that physically or chemically change their environment.
    *Example: Beavers

Beavers and Landscape Structure

  • Beavers cut trees, build dams, and flood the surrounding landscape.
  • Results: Increased wetlands, altered hydrologic regime, added patchiness to tree community, reduced abundance of some tree species.

Beavers and Landscape Structure (cont.)

  • Beavers modified nearly all temperate stream valleys in the northern hemisphere.
  • Beaver activity changed boreal forest landscape to a complex mosaic of ecosystems.

Organisms and Landscape Structure

  • Humans are dominant landscape modifiers.
  • Example: Forest converted to agricultural land.
  • Cadiz Township forest cover dropped from 93.5% to 3.4%.

Anthropogenic Biogeochemistry

  • Humans change global biogeochemical landscapes.
  • Humans alter nutrient cycling on land and in water.

Animals and Landscape Structure

  • African elephants knock down trees, trample forests and grassland, create water holes, and disperse seeds in dung.

Animals and Landscape Structure (cont.)

  • Alligators maintain ponds in the Everglades, create trails, holes, nests.
  • Kangaroo rats dig burrow systems, modify soil structure and plant distribution.

Animals and Landscape Structure

  • Migrations and travel of animals impact landscape structure.
  • Materials transfer through animal activity.
Zoogeochemistry
  • Result: Animal activity (movement, excretion, feeding, birth, death) on chemistry (usually nutrient makeup) of their environment.

Landscape Structure

  • Landscape structure: Mainly size, shape, composition, number, and position of patches.
  • Patch: A relatively homogeneous area that differs from its surroundings.
  • Patches form a mosaic that is the landscape structure.
  • Background in mosaic is the matrix.
  • Patches can form from habitat fragmentation.

Habitat Fragmentation

  • Habitat fragmentation can occur naturally, but discussion mainly focuses on results of fragmentation.

Habitat Fragmentation

  • Patch sizes matter differently to different organisms.

Habitat Fragmentation: Patches

  • Herbivorous mammals vs. carnivorous mammals: Carnivorous mammals generally have larger home ranges and patch size needs.

Habitat Fragmentation

  • Boundaries: Zone composed of edges of adjacent ecosystems.
  • Boundaries can be abrupt (between lake and mountain basin) or diffuse (lake and marsh).

Corridors

Habitat Patch Size and Isolation and Density of Butterfly Populations
  • Hanski et al. study: Butterfly density significantly affected by size and isolation of habitat patches.
  • Population size in patch increased with patch area.
  • Population density decreased as patch area increased.
  • Isolated patches had lower butterfly densities.
  • Isolated populations partially maintained by immigration.

Habitat Fragmentation

Boundaries
  • Blend elements between different habitat patches.
  • Support species from adjacent patches as well as edge specialists.
Edge Effect
  • Increased biodiversity associated with boundaries.
  • Greater difference between two adjacent patches = greater edge effect.
  • Too many edges can result in too many edge specialists.

Habitat Fragmentation

Boundaries
  • Can also be risky habitats, attracting/concealing predators = higher predation rates.

Habitat Fragmentation

### Corridors

  • Connectivity channels between different patches.
  • Can be naturally occurring, but often created by humans.

Habitat Fragmentation

Corridors
  • Different organisms can move between patches differently.
  • Function as travel paths for individuals moving within their home range or traveling between habitats.
Habitat Corridors and Movement of Organisms
  • Haddad and Baum study: Corridors increased movements between patches.
  • Higher densities in patches connected by corridors.
  • Also affects pollination and seed dispersal.
  • Connect habitat fragments with corridors to mitigate effects of fragmentation.

Habitat Fragmentation

Corridors
  • Filter effect: Different corridor sizes (+ other characteristics) allow some organisms to cross but restrict others = changes in community composition within fragmented landscapes.

How is Landscape Structure Quantified?

  • Landscape structure can be quantified by describing various characteristics of patches within landscape.
Key Attributes
  1. Patch Number
  2. Patch Size
  3. Patch Shape
  4. Patch Position
  5. Patch Composition
Structure of Six Landscapes in Ohio
  • Bowen and Burgess analyzed 6 Ohio landscapes.
  • Forest cover, forest patch size, forest patch density, and forest patch shape varied.
  • Patch shape quantified as:
    • S=P2πAS = \frac{P}{2 \sqrt{\pi A}}
    • Increasing value (above 1) indicates less circular shape.
    • P = Patch perimeter.
    • A = Patch area.

Landscape Structure and Dispersal of Mammals

  • Landscape structure can influence the movement of organisms.
  • Rate of movement of individuals between subpopulations making up metapopulation can affect persistence of species.

Landscape Structure and Small Mammals

  • Results supported hypothesis that animal movements decrease with habitat fragmentation.
  • Proportion of individuals moving increased as patch size increased.

Applications: Landscape Approaches to Mitigating Urban Heat Islands

  • Heat waves: Weather-related phenomenon responsible for greatest loss of human life.
  • 2003 heat wave in Europe caused over 40,000 deaths.
  • Cause disproportionate deaths in urban centers.
  • Urban ecology is an important area of research.
  • Global population is shifting to urban centers.

Urban Heat Islands

  • Urban heat islands result from replacing trees and other vegetation with buildings, paved roads, and concrete walks.
  • Vegetation moderates surface and air temperatures.
  • Urban landscape structures increase surface and air temperatures.

Urban Heat Islands

  • (Continuation of previous point)

Mitigating Urban Heat Island Effect

  • (Open question for brainstorming ideas)