Landscape Ecology Chapter 21 1 1 Outline Introduction

Landscape Ecology Chapter 21 1 1

Outline • • Introduction Landscape Structure Landscape Processes v Habitat Patches and Corridors v Landscape Position Origins of Landscape Structure and Change v Climate v Organisms 2 2

Introduction • Landscape Ecology: Study of landscape structure and processes. v Landscape: Heterogeneous area composed of several ecosystems. v Landscape Elements: Visually distinctive patches in an ecosystem. 3 3

Landscape Structure • Landscape structure includes the size, shape, composition, number, and position of different ecosystems within a landscape v Quantified patch shape by ratio of patch perimeter to perimeter of a circle with an area equal to that of the patch. v v v S = Patch shape § Increasing value indicates less circular shape P = Patch perimeter A = Patch area 4 4

Landscape Structure 5 5

Fractal Geometry of Landscapes • Perimeter estimates of a complex shape depend on size of measuring device. v Smaller features may only show up with smaller measuring devices. 6 6

Fractal Geometry of Landscapes 7 7

Two components of spatial scale 8 8

Quantifying landscape pattern 9 9

Two principal methods for representing spatial data 10 10

Caveats for landscape pattern analysis • Classification scheme 11 11

Caveats for landscape pattern analysis • Grain size (resolution) 12 12

Caveats for landscape pattern analysis • Spatial extent 13 13

Caveats for landscape pattern analysis • • Appropriate landscape metrics - most metrics are correlated - what constitutes a significant change References - Riitters, K. H. et al. 1995. A factor analysis of landscape pattern and structure metrics. Landscape ecology 10: 23 -39. - J. A. G. Jaeger. 2000. Landscape division, splitting index, and effective mesh size: new measures of landscape fragmentation. Landscape ecology 15: 115130. 14 14

Landscape metrics • • • Metrics of landscape composition Measures of spatial configuration – contagion & patch-based metrics Software for spatial pattern analysis - FRAGSTAT http: //www. umass. edu/landeco/research/fragstats. html - Patch Analyst http: //flash. lakeheadu. ca/~rrempel/patch/ 15 15

Research tools for landscape ecology • GPS - Overview http: //www. colorado. edu/geography/gcraft/notes/gps_f. html • • GIS - ESRI http: //www. esri. com/ Remote sensing & photogrammetry - SPOT http: //www. spotimage. fr/html/_167_. php - Li. DAR http: //www. aeromap. com/lidar - Leica Geosystems http: //www. gis. leicageosystems. com/default. aspx - VLS http: //www. featureanalyst. com/index. htm 16 16

Landscape Processes • Landscape structure influences processes such as the flow of energy, materials, and species between the ecosystem within a landscape. 17 17

• Landscape Structure and Dispersal of Small Mammals Ecologists have proposed landscape structure can influence movement of organisms between potentially suitable habitats. v Metapopulations: Populations of many species occur in spatially isolated patches, with significant exchange of individuals. § Rate of movement of individuals between subpopulations can affect species persistence in a landscape. 18 18

• Landscape Structure and Dispersal of Small Mammals Diffendorfer et. al. studied how patch size affects movement of three small mammal species. v Predicted animals would move farther in more fragmented landscapes. § Must move farther to obtain resources. v Predicted animals would stay longer in more isolated patches. 19 19

Landscape Structure and Dispersal of Small Mammals 20 20

Habitat Patch Size and Isolation and Density of Butterfly Populations • Hanski et. al. found butterfly density significantly affected by size and isolation of habitat patches. v Population size within patch increased with patch area. v Population density decreased as patch area increased. v Isolated patches had lower butterfly densities. § Population partially maintained by immigration. 21 21

Habitat Patch Size and Isolation and Density of Butterfly Populations 22 22

Habitat Corridors and Movement of Organisms • Connecting habitat fragments with corridors of a similar habitat has long been an approach to mitigating the effects of habitat fragmentation. v Haddad and Baum found corridors influenced the movement of butterflies associated with early successional habitats. 23 23

Landscape Position and Lake Chemistry • • Webster explored how lake position in a landscape affected chemical responses to drought. Lake position in landscape determined portion of water received as groundwater. v Upper lakes dropped more than lower lakes. § Concentration of dissolved ions increased most at upper and lower ends. 24 24

Landscape Position and Lake Chemistry 25 25

Origins of Landscape Structure and Change • Geological processes such as volcanism, sedimentation, and erosion are a primary source of landscape structure. 26 26

Soil and Vegetation Mosaics In Sonoran Desert • Mc. Auliffe showed bajadas in Sonoran Desert are complex mosaic of distinctive landforms. v Found wide range of soil types and plant distributions that correspond closely to soil age and structure. § Soil structure influences perennial plant distributions. Ø Plant distributions map clearly onto soils of different ages. 27 27

Soil and Vegetation Mosaics In Sonoran Desert 28 28

Climate and Landscape Structure • Mc. Auliffe: Soil mosaics consisted of patches of material deposited during floods originating in nearby mountains. v Materials eroded from mountain slopes and deposited as alluvium on surrounding bajadas. § Alluvial deposits gradually changed; dependent upon climate. Ø Different soils and plant types. 29 29

Organisms and Landscape Structure • Many studies have focused on conversion of forest to agricultural landscapes. v Eastern NA, many abandoned farms have reverted to forest, thus forest cover has increased. § Similar patterns in parts of Europe. 30 30

Organisms and Landscape Structure • Hulshoff found forest and heathland coverage changed over time as well as number and average area of patches. v Cadiz Township - agricultural economy converted area from forest to farmland. § Economy collapsed in response to introduction of synthetic fertilizers and inexpensive imported wool. 31 31

Organisms and Landscape Structure 32 32

Organisms and Landscape Structure • • • African elephants knock down tress. v Change woodland to grassland. Kangaroo Rats dig burrow systems that modify soil structure and plant distributions. Beavers cut trees, build dams and flood surrounding landscape. v At one time, beavers modified nearly all temperate stream valleys in Northern Hemisphere. 33 33

Organisms and Landscape Structure • Johnston and Naiman documented substantial effects of beavers on landscape structure. v Over 63 yrs, area created by beavers increased from 200 ha to 2, 661 ha. v Changed boreal forest landscape to complex mosaic. 34 34

Organisms and Landscape Structure • Beaver activity between 1927 -1988 increased quantity of most major ions and nutrients in impounded areas. Three possible explanations: v Impounded areas may trap materials. v Rising waters captured nutrients formally held in vegetation. v Habitats created by beavers may promote nutrient retention by altering biogeochemical processes. 35 35

• Fire and Structure of a Mediterranean Landscape Minnich used satellite photos to reconstruct fire history of S. CA and N. Baja (1971 -80). v Landscape consisted of patchwork of old and new burns. v Similar climates with deviated fire histories: § Fire suppression in S. CA allowed more biomass accumulation and resultant large fires. Ø Small burns more frequent in N. Baja. – Other factors 36 36

Review • • Introduction Landscape Structure Landscape Processes v Habitat Patches and Corridors v Landscape Position Origins of Landscape Structure and Change v Climate v Organisms 37 37

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