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Ecology 23.docx

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Western University
Biology 2483A
Mark Moscicki

Ecology-Lecture 23 Dec 3, 2013 Introduction  Ecology at a landscape level has been made possible by new tools that can view the environment in multiple dimensions and at many scales.  Aerial photography gave ecologists the first means to look at “the big picture.”  More recently, our access to space has vastly expanded our ability to acquire images of Earth through remote sensing. Remote sensing satellites provide images of Earth that expand our view of large-scale ecological patterns.  Geographic information systems (GIS) are used in landscape planning for conservation and urban development. Geographic Information Systems (GIS)  Computer-based systems that allow the storage, analysis, and display of spatial data (data pertaining to specific geographic areas).  The data used in GIS are derived from multiple sources, including aerial photography, satellite imagery, and ground based field studies (GPS and radio telemetry to document precise locations and track animal movements/migration patterns). Collected data includes rainfall, elevation, vegetation cover at specific locations, and land use. This data is referenced by spatial coordinates to geographic locations and displayed as multi layered maps.  Layers of mapped GIS data can be put together to show patterns and answer specific questions.  Multilayered maps can be used to address questions posed by the Gap Analysis Program (GAP) in the USGS. The goal of GAP is to identify species of concern that are not adequately represented on existing conservation lands (prevent biodiversity decline). Identifying species of concern that reside in unprotected areas will enable ecologists to make decisions about which lands should be protected in order to prevent future losses of biodiversity.  GAP analysis is a two step process. First, you must input information about vegetative cover, and other environmental conditions required/preferred by the species of interest. This information will be used to predict its geographic distribution. Next, the predicted distribution is compared with another GIS layer that shows the locations of conserved lands.  We can do a GAP analysis for lark bunting. The lark bunting depends on Prairie habitats for breeding, but much of this habitat has been destroyed by humans. As a result, populations of lark bunting are declining. Data for environmental conditions and vegetation preferred by lark buntings are mapped to predict its distribution. Locations of conservation lands are mapped in another layer. By comparing the two layers, it is clear that only a small portion of the bird’s potential range is in protected areas.  Data analysis and GIS continually improve with better computers and statistical methods. Landscape Ecology  Landscape ecology examines spatial patterns and their relationship to ecological processes and changes.  Landscape ecology emphasizes the causes and consequences of spatial variation across a range of scales.  Landscape ecologists look at the spatial arrangement of landscape elements across Earth’s surface. Landscape elements include forest patches, soil types, lakes, etc.  Spatial patterns of landscape elements can influence what species live in an area, and the dynamics of ecological processes (disturbance/dispersal). Landscapes  Landscape: An area in which at least one element is spatially heterogeneous (varies from one place to another) Landscapes often include multiple ecosystems.  Landscapes may be heterogeneous with regards to composition (what different types of landscape elements are present?) or in the way their elements are arranged (small patches occurring regularly or large clusters?)  Ecologists refer to the pattern of heterogeneous elements that make up a landscape as a mosaic.  The images below indicate landscape heterogeneity. Landscapes can be heterogeneous in many different kinds of elements, which may be arranged independently of one another. The image to the left shows a map of 6 different soil types within the same area. The map to the right shows 7 different landscape elements within the same area.  Multiple ecosystems make up a landscape. The ecosystems that make up a landscape are dynamic and interacting. Interactions include the flow of water, energy, nutrients, or pollutants between ecosystems. There is also biotic flow as animals, seeds, pollen, etc., move between them.  For biotic flow to occur, patches of the same habitat must be connected to one another, or the surrounding habitat (matrix) must be a type through which dispersal is possible.  The image below indicates movements across a landscape. Movements between landscapes may occur frequently (thick arrow) or rarely (thin arrow). Exchange between similar habitats is frequent if a corridor connects them (A). Exchange between a habitat and the surrounding environment (matrix) is rare (B).  The heterogeneity we see in landscapes can be described in terms of composition and structure.  Landscape composition: The kinds of elements or patches and how much of each kind is present.  Landscape structure: Physical configuration of the landscape elements (habitat fragmentation).  Landscape structure is characterized by: Size of patches, whether patches are aggregated or dispersed, complexity of patch shape (simple/complex), and degree of fragmentation.  Example: In Yellowstone National Park, researchers designated 5 different age classes of lodgepole pine forest (5 landscape elements), thus indicating landscape composition. The five elements were mapped to show structural complexity. Looking at the below map, we can see that some parts of the landscape contain continuous blocks of old forest, while other parts are highly fragmented (small patches with a variety of different age classes)  The image below shows that only remnants of older forest remain in areas that have been fragmented by recent fires. However, large stands of old forest remain in the unburned regions. This information can be used to compare fire caused fragmentation within the park to fragmentation caused by clear cutting in areas outside of the park.  Consideration of scale is very important in landscape ecology.  A landscape may be heterogeneous at a scale important to a tiger beetle, but homogeneous to a warbler or a moose. The scale chosen for a study determines the outcomes.  Scale: the spatial or temporal dimension of an object or process, characterized by grain and extent.  Grain: size of the smallest homogeneous unit of study (e.g., a pixel in a digital image); it determines the resolution at which we view the landscape (more pixels=higher resolution, but more data to store and analyze). The selection of grain will affect the quantity of data that must be manipulated and analyzed. A large-grained approach may be appropriate for regional to continental scales (resolution drops but there are fewer pixels to store and analyze than if you were to use a small grained approach for a large area).  Extent: boundary of the area or time period encompassed by the study. How the extent is defined can change the composition of the landscape being described. There may be natural or human created boundaries that determine the extent of a study, or they may be defined by the researcher.  Panel 4 shows little late successional whitebark pine (dark blue), while panel 6 contains a considerable area of it.  Landscape ecologists must also consider how processes scale up or down.  Example: A researcher studying carbon exchange at the landscape level needs to know how leaf-based measurements of CO exch2nge scale up to the whole plant, the ecosystem, and to the mosaic of ecosystems that make up the landscape. Landscape Patterns Affect Ecological Processes  Landscape structure plays an important role in ecological dynamics. It can affect whether and how animals move, therefore influencing rates of pollination, dispersal, or consumption.  Henry et al. (2007) studied the movements of a fruit eating bat in a tropical forest that had been fragmented by the construction of a reservoir. They found that more isolated forest fragments were less likely to be visited by bats, even if they contained abundant food resources. In other words, patch connectivity determined bat density. Thus, they determined that landscape structure affected bat foraging behavior. Furthermore, because frugivorous bats disperse plant seeds, it is also likely that landscape structure also affected dispersal of the plants the bats fed on.  Landscape structure influences biogeochemical cycling. Ecologists have identified biogeochemical "hotspots" where chemical reaction rates are higher than in the surrounding landscape. Many of these hotspots are found at interfaces between terrestrial and aquatic ecosystems. However, it was noted that other factors must play a role.  Example: Inputs of sulfur, calcium, and nitrogen from atmospheric deposition were higher at forest edges than in forest interiors. Denser canopies and greater physical complexity at forest edges resulted in greater interception of airborne particles.  Fragmented forests surrounding urban areas may be strongly influenced by atmospheric inputs of pollutants and nutrients.  Landscape patches vary in terms of habitat quality and resource availability. This variation can affect the population densities of species inhabiting each patch, the time animals spend foraging in a patch, and the movement of organisms between patches.  Patch boundaries, connections between patches, and the matrix between patches can also affect population dynamics.  Example: Bog fritillary butterflies would cross readily from patch to patch when suitable patches were close together.Where there was a wider distance of matrix to cross, the butterflies were more hesitant to leave a patch (Schtickzelle and Baguette 2003).  The shape and orientation of landscape patches can be important in physically intercepting organisms.  Gutzwiller and Anderson (1992) found that northward-migrating, cavity-nesting birds were more likely to nest in forest patches in Wyoming grasslands that were oriented along an east–west axis (oriented perpendicular to dispersal path of migratory organisms). The habitat patches serve as a net, intercepting birds as they migrate north.  Habitat loss and fragmentation has con
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