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Published byRobert Maxwell Modified over 9 years ago
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Species-of-the-Week Wood Duck (Aix sponsa)
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Brink of Extinction By early 1900’s, culminative effects of: 1) wetland drainage (ag. expansion) 2) deforestation 3) overhunting
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Habitat Wooded swamps & river bottomlands Natural tree cavities for nesting (cypress, sycamore, silver maple, black ash) Home range changes with flooding events
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Food * In water <18”, feed on: - seeds of trees (e.g., acorns) - also field grains * Young = aquatic insects
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Reproduction Pairing in late Oct into spring (Mar-July nest) Clutch size = 6-10 eggs Behavior -Dump nests (up to 30+ eggs in 1 nest) = “egg dumping” behavior = intraspecific brood parasitism -may decrease hatch rates to 10%
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Factors Determining Patterns of Habitat Use
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Concept of Habitat Selection Wildlife perceiving correct configuration of habitat needed for survival – differences based on age/experience/chance? – Niche concept
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Concept of Habitat Selection Hutchison = n-dimensional hypervolume as explanation of the niche Fundamental vs. Realized Niche Species 1 Species 2
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Testing the Hutchinsonian Niche Concept of Habitat Selection James – work with birds in Arkansas…quantified habitat relationships How do birds select habitat? niche gestalt :
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Wildlife Habitat Ecology & Mgt Habitat from an evolutionary perspective Species distribution relative to habitat dist’n Climatic events Pleistocene Epoch & dist’n of modern species
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habitat interspersion – Leopold’s Law of Interspersion
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Habitat Fragmentation 1) gap formation 2) decrease patch size 3) increase isolation 4) increase edge 5) conversion of matrix
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Concepts Habitat = species-specific resources available (relative quality) Habitat Use = manner in which species use resources Habitat Selection = hierarchical decision process (innate & learned) of what habitats to use Habitat Preference = based on selection of habitat, which are used more than others (preferred vs. avoided)
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Concepts Habitat Availability = accessibility of resources Habitat Quality = positive relation with fitness (not just density) Critical Habitat = resources essential to the species….ESA designation….
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Scale Dependence of Habitat Selection 1 st Order 2 nd Order 3 rd Order 4 th Order Macrohabitat vs. Microhabitat 1 st order – innate? 2 nd order –decisions 3 rd &4 th order –decisions
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Guild Concept guild = group of species that exploit the same class of resources in similar way community guild = no taxonomic restrictions; guild members chosen based on investigator-defined resources assemblage guild = guild members based on taxonomic relations
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Models of Habitat Relationships Model (assess) habitat for wildlife species, e.g., USFWS Habitat Suitability Index (HSI) models -include top 3 environmental variables related to a species’ presence, distribution, & abundance HSI = (V 1 x V 2 x V 3 ) 1/3 = 0 to 1
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Yellow Warbler HSI for different forest conditions
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HSI models useful for representing possible major habitat factors true value as hypotheses Do not provide information on: -population size or trend -behavioral responses single-species approach
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Emergence of Landscape Ecology Equilibrium View Constant species composition Disturbance & succession = subordinate factors Ecosystems self-contained Internal dynamics shape trajectory No need to look outside boundaries to understand ecosystem dynamics Structure Function ? ? ? ?
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Emergence of Landscape Ecology Dynamic View Disturbance & ecosystem response = key factors Disturbance counter equilibrium Ecosystems NOT self- contained Multiple scales of processes, outside & inside Essential to examine spatial & temporal context Structure Function
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Scale What’s the big deal? Seminal pubs –Allen & Starr (1982) – Hierarchy: perspectives for ecological complexity –Delcourt et al. (1983) – Quaternary Science Review 1:153-175 –O’Neill et al. (1986) – A hierarchical concept of ecosystems
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Ecological Scaling: Scale & Pattern Acts in the “ecological theatre (Hutchinson 1965) are played out across various scales of space & time To understand these dramas, one must select the appropriate scale Temporal Scale Spatial Scale Fine Short Coarse Long Recruitment Treefalls Windthrow Secondary Succession Species Migrations Speciation Extinction Fire
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Ecological Scaling: Scale & Pattern Different patterns emerge, depending on the scale of investigation American Redstart Least Flycatcher American Redstart Least Flycatcher Local Scale (4 ha plots) Regional Scale (thousands of ha)
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Ecological Scaling: Components of Scale Grain: minimum resolution of the data –Cell size (raster data) –Min. polygon size (vector data) Extent: scope or domain of the data –Size of landscape or study area
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Ecological Scale Scale characterized by: –grain: smallest spatial resolution of data e.g., grid cell size, pixel size, quadrat size (resolution) Fine Coarse
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Ecological Scale Scale characterized by: –extent: size of overall study area (scope or domain of the data) Small Large
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Ecological Scaling: Components of Scale Minimum Patch Size: min. size considered > resolution of data (defined by grain)
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Ecological Scaling: Definitions Ecological scale & cartographic scale are exactly opposite –Ecological scale = size (extent) of landscape –Cartographic scale = ratio of map to real distance
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Scale in Ecology & Geography ecological vs. cartographic scale EcologyGeography Small (Fine) Fine resolution Small Extent Coarse resolution Large Extent Large (Broad) Coarse resolution Large extent Fine resolution Small extent
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Scale in Ecology & Geography ecological vs. cartographic scale –e.g., map scale 1:24,000 vs. 1:3,000 fine vs. coarse large vs. small extent
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1:24,000 1:200,000
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Ecological Scaling: Components of Scale Grain and extent are correlated Information content often correlated with grain Grain and extent set lower and upper limits of resolution in the data, respectively.
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Ecological Scaling: Components of Scale From an organism- centered perspective, grain and extent may be defined as the degree of acuity of a stationary organism with respect to short- and long-range perceptual ability
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Ecological Scaling: Components of Scale Grain = finest component of environment that can be differentiated up close Extent = range at which a relevant object can be distinguished from a fixed vantage point Fine Coarse Scale Extent Grain
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Ecological Scaling: Components of Scale From an anthropocentric perspective, grain and extent may be defined on the basis of management objectives Grain = finest unit of mgt (e.g., stand) Extent = total area under management (e.g., forest)
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Ecological Scaling: Components of Scale In practice, grain and extent often dictated by scale of available spatial data (e.g., imagery), logistics, or technical capabilities
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Ecological Scaling: Components of Scale Critical that grain and extent be defined for a study and represent ecological phenomenon or organism studied. Otherwise, patterns detected have little meaning and/or conclusions could be wrong
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Scale: Jargon scale vs. level of organization Space - Time Individual Population Community
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Ecological Scaling: Implications of Scale As one changes scale, statistical relationships may change: –Magnitude or sign of correlations –Importance of variables –Variance relationships
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Implications of Changes in Scale Processes and/or patterns may change Hierarchy theory = structural understanding of scale-dependent phenomena Example Abundance of forest insects sampled at different distance Intervals in leaf litter,
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Implications of Changes in Scale Insects sampled at 10-m intervals for 100 m
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Implications of Changes in Scale Insects sampled at 2000-m intervals for 20,000 m
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Identifying the “Right” Scale(s) No clear algorithm for defining Autocorrelation & Independence Life history correlates Dependent on objectives and organisms Multiscale analysis! e.g., Australian leadbeater’s possum
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Multiscale Analysis Species-specific perception of landscape features : scale-dependent –e.g., mesopredators in Indiana Modeling species distributions in fragmented landscapes
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Hierarchy Theory Lower levels provide mechanistic explanations Higher levels provide constraints
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Scale & Hierarchy Theory Hierarchical structure of systems = helps us explain phenomena –Why? : next lower level –So What? : next higher level minimum 3 hierarchical levels needed
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Constraints (significance) Level of Focus (level of interest) Components (explanation)
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