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Landscape Ecology Landscape Ecology I. A Landscape Perspective A. Integrating Communities and Ecosystems forest field Landscape Ecology I. A Landscape Perspective A. Integrating Communities and Ecosystems How Do: Habitat types Patch sizes Patch Arrangement Connectivity Affect: Species Distributions Community Parameters Ecosystem Processes forest field Landscape Ecology I. A Landscape Perspective A. Integrating Communities and Ecosystems B. Landscape Elements 1. Landscape: A landscape is any bounded area. It can be small (1m2) or large… up to a biome. However, for it to be an interesting level of organization to study, it must be heterogeneous… (the focus is on interactions between patches, so there must be > 1) B. Landscape Elements 1. Landscape: 2. Matrix: the element with the greatest area and connectivity. The primary ‘cover type’ in the landscape - the ‘background’ in which patches and corridors exist. Exerts the greatest degree of control over landscape dynamics, as a consequence of the ‘permeability’ of the matrix. Forest as Patch in Grassland Matrix Forest as Matrix B. Landscape Elements 1. Landscape: 2. Matrix: 3. Patch: a ‘bounded area’ (that can be defined by coordinates and ‘mapped’) embedded in the matrix. Important characteristics are size, shape, origin (disturbance? Remnant?), number location; functions are habitat type, migratory stepping stones, and source/sink relationships. B. Landscape Elements 1. Landscape: 2. Matrix: 3. Patch: 4. Corridor: These are narrow ‘patches’ that differ from neighboring patches, matrix, or corridors. Corridors both divide and connect patches. Characteristics are width, length, and perhaps volume; they have an origin and may contain an internal entity (stream) that adds complexity. They function as habitat, conduit, barrier/filter, source/sink. Landscape Ecology I. A Landscape Perspective A. Integrating Communities and Ecosystems B. Landscape Elements C. Scale “For it to be an interesting level of organization to study, [a landscape] must be heterogeneous… (the focus is on interactions between patches, so there must be > 1) Landscape Ecology I. A Landscape Perspective A. Integrating Communities and Ecosystems B. Landscape Elements C. Scale “For it to be an interesting level of organization to study, [a landscape] must be heterogeneous… (the focus is on interactions between patches, so there must be > 1)” Independent Variables How Do: Habitat types Patch sizes Patch Arrangement Connectivity Must be multiple levels of an independent variable to assess the effect of that variation on a dependent variable. Dependent Variables Affect: Species Distributions Community Parameters Ecosystem Processes C. Scale “viewer defined” –the scientist C. Scale “viewer defined” –the scientist “user defined” – the organism C. Scale “grain” Coarse: purple Fine: Heterogeneous C. Scale Coarse Grained = “field” C. Scale Fine Grained ‘patches’ C. Scale 1. Species responses vary at different scales, so scalar analysis can reveal the scale of importance At which scale does amount of wetland habitat correlate best with local abundance? II. Insights from Landscape Ecology A. Patch Size Matters 1. Species-area Effects: Smaller patches, fewer species II. Insights from Landscape Ecology A. Patch Size Matters 1. Species-area Effects: Smaller patches, fewer species 2. Loss of Predators and Keystone Effects: Animals at the top of a trophic pyramid, which are already at low density, are more sensitive to patch size reduction. These are predators. When predators are lost, competition in lower levels increases. II. Insights from Landscape Ecology A. Patch Size Matters 1. Species-area Effects: Smaller patches, fewer species 2. Loss of Predators and Keystone Effects: Animals at the top of a trophic pyramid, which are already at low density, are more sensitive to patch size reduction. These are predators. When predators are lost, competition in lower levels increases. 3. Increase in particular populations and their pathogens: The animals that remain reach higher densities (not necessarily larger populations on the smaller island, but higher density. At higher densities, transmission rates of pathogens increase. Lyme Disease: - fragmentation reduces patch size - abundance of predators like fox declined - white-footed mice (host of Borrela burgdorferi bacterium) increase. - increase host density, increase infection rate of ticks. West Nile Virus Low Diversity: High Relative Abundance of Hosts High Diversity: Low Relative Abundance of Hosts Swaddle and Carlos, 2008. PLoS one 3:e2488 II. Insights from Landscape Ecology A. Patch Size Matters B. Connectance Matters Increased connectivity among patches allows for the ‘rescue effect’ and increased species colonization and persistence on patches. II. Insights from Landscape Ecology A. Patch Size Matters B. Connectance Matters Underpasses in everglades restores animal movement and reduces mortality from cars. II. Insights from Landscape Ecology A. Patch Size Matters B. Connectance Matters II. Insights from Landscape Ecology A. Patch Size Matters B. Connectance Matters II. Insights from Landscape Ecology A. Patch Size Matters B. Connectance Matters II. Insights from Landscape Ecology A. Patch Size Matters B. Connectance Matters Mesoamerican Biological Corridor II. Insights from Landscape Ecology A. Patch Size Matters B. Connectance Matters San Juan – La Selva Biological Corridor II. Insights from Landscape Ecology A. Patch Size Matters B. Connectance Matters II. Insights from Landscape Ecology A. Patch Size Matters B. Connectance Matters II. Insights from Landscape Ecology A. Patch Size Matters B. Connectance Matters C. Scale Matters 1. different species respond at different scales II. Insights from Landscape Ecology A. Patch Size Matters B. Connectance Matters C. Scale Matters 2. Measuring Diversity at a Landscape Scale α – alpha diversity: this is the diversity within a habitat unit, or the mean diversity among units of the same habitat type. β-beta diversity: typically, this refers to the ‘diversity’, or difference, among communities using different habitat types. (α = 6 for forest, α = 6 for field). We can calculate the Beta diversity as:(S1 – c) + (S2 – c), γ-gamma diversity: This is the total diversity across the entire landscape, regardless of habitat. So, if the forest and field have no species in common, then gamma diversity = 12. If the forest and field share 2 species, then gamma = 10 (6 in the forest, and four additional NEW species in the field).