Exam 4 Part 5/5

Definition of landscape ecology

Landscape is a heterogeneous area consisting of distinct patches  (landscape  elements) orgnaized into a mosaic-like pattern

A mosaic is the patchwork of different types of land covers/elements (e.g., forests, bogs, meadows, lakes, streams, etc.)

Examples of a landscape

Landscape Ecology 

• The study of the causes and consequences of landscape-level (ie., intermediate- to large-scale) ecological patterns

  • The causes behind the formation of patches and boundaries, and 

  • The ecological consequences of these spatial patterns on the landscape

• Is concerned with spatial patterns in the landscape and how they develop, with an emphasis on the role of disturbances

• Is a relatively new branch of ecology

• Goal: Predict the responses of different organism to changes in landscape

Landscape Ecology is the science and art of studying and influencing the relationships between spatial pattern and ecological processes across hierarchical levels of biological organization and different scales in space and time. - Wu and Hobbs, 2007

Importance of scale

Landscape ecologists often grapple with issues associated with spatial scale

Two important aspects of spatial scale: grain and extent

Grain refers to the spatial resolution of a study or data set; e.g., are the data or samples obtained at a resolution of 1m², 100 m² or 1 km²?

Extent refers to the size of the study area being considered; e.g., is the landscape small or large?

• “Are you focusing on the whole of arizona, or tucson, or just the UA campus” - Professor Daijiang

• There is NO FIXED scale, for grain or extent, unambiguously identifies landscape ecology (a landscape ecological approach can also be applied to a very small area with fine resolution)

• Low grain high extent, example, a satellite circles the earth in 8 days, a takes images of the earth, take 1 km and analyze that space over time.

• Imagine you divide the earth by one 1 km or 100 km, that would be about 30,000-40,000 pixels in that space, you could be measuring the climate or temperature, measuring a week at a time, over time this data keeps recycling through the system and adding on to the data building large data pools in the google earth search engine 

Landscape struct: the physical configuration of lansca[e elements, e.g., patch size shapes, patch connectivity / isolation, etc.

PAtches in the landscape

• Patches: relatively homogenous community types that differ from their surroundings in structure (e.g., size, shape) and in species composition

• Patches results from factors: geology, topography, soils, and climate, human activity

• The area, shape, and orientation of the landscape patches influence:

  • Habitat suitability

  • Wind flow

  • Dispersal of seeds

  • Movement of animals

• E.g., lodgepole pine stand age classes (stand ages since last major fire-disturbance) in Yellowstone National park

Patches have edges

• Some patches are stables and permanent (inherent edges) while others are subject to successional changes over time (induced edges)

• The height, width, and porosity or borders influence the gradients of wind flow, moisture, temperature, and solar radiation between adjoining patches

1. Narrow border, tractor did it maybe

   1. Straight, sharp, abrupt

2. Wide border

   1. Ecotone

3. Convoluted border

   1. No particular shape

Can have farm land on one side and forest on the other, when you get in the woods it's much cooler than the farmland

Edge effects: negative (generally) effects a habitat edge on interior conditions 

Edge effects (as you decline on the list the less amount of impact edge has on the condition in comparison to the rest).

1. Increased wind disturbance

2. Increased tree mortality

3. Invasion of disturbance-adapted beetles

4. Decreased soil moisture

5. Increased air temperature

6. Invasion of disturbance adapted plants

7. Increased phosphorus content of falling leaves

Some species can only inhabit the interior or core and some are especially attracted to the edge

Edge species ares restricted exclusively to the edge of the environment (e.g., indigo bunting) a pretty blue bird.

Edge species

• Gray catbird

• American Robin

Edge species: Their forest area is declining and the probability of occurrence declines as well.

Interior species: Their forest air is inclining and the probability of occurrence is inclining.

Area incentive species: Are relatively steady as they move around

The edge effect can also create problems: attract more predators: restrict dispersal, etc.

The graph shows the further in the forest the less likely the predation on bird eggs.

Two patches with the same area

• The shape of a habitat reserves matters! As patches become smaller, they come largely to the edge, losing the characteristics of the prior community, e.g., Brown-headed cowbird.

• Try to keep the interior intact to preserve the interior life, or it all becomes exterior.

Habitat loss and fragmentation

• 86% of heathland habitat lost (in England)

• Loss and fragmentation of the U.S. old-growth forest

Habitat Loss and fragmentation 

• The primary cause of loss of biological diversity

  • Loss of habitat 

  • Reduced population size

  • Loss of genetic variation

  • Increased edge

Design Principles for Protected Areas

1. Larger reserves are better than smaller ones.

2. One large reserve is better than a few small ones of the same total area

3. Several reserves close together are better than several reserves far apart

4. Reserves connected by  habitat corridors are better than uncontained reserves

5. Compact shapes are best for minimizing boundary length.

6. A reserve surrounded by a buffer zone is preferable to one without

The SLOSS Debate

• If only a limited amount of habitat can be protected in parks and reserves, which strategy is better: a Single Large reserve or Several Small reserves (SLOSS).

• Several small is better in this case

  • Ecological response

Connectivity and Corridors

• Examples: Highways with dirt bridges ahead so animals can cross without getting hit by cars.

  • Also keeps the vegetation alive through the forest that was cut as a ‘narrow border’ edge.

Corridors permit Movement

• Corridors facilitate movement among patches

  • Can encourage gene flow between subpopulations

  • Establish species in habitat that have experienced local extinction

The importance of corridors in fragmented landscapes 

• Corridors permit Movement: gene flow, reestablish species (rescue effect) etc.

• Corridors may provide habitat

Negative impacts of corridors

• Scouting posting predators 

• Disease spread

• Pathway for the invasion of exotic species

• If too narrow, can inhibit movement of social groups

Most organisms are organized into subpopulations and are linked by the movement of individuals between them. A group of interacting sub populations is called metapopulation.