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7/27/2019 Lecture 9 Landscape Ecology
http://slidepdf.com/reader/full/lecture-9-landscape-ecology 1/21hallenges, Threats & Opportunities
Principles of
Landscape Ecology
Learning OutcomesLearning Outcomes
n Learn terminology associated withlandscape ecology principles—patches,
buffers, fragmentation, corridors, edges,
and matrixes
n Understand how landscapecharacteristics and patterns influence
the distribution and survivability of
species
n Be able to apply principles to project
design and land use planning
Source for Landscape EcologyPrinciples to Follow:
Source for Landscape EcologyPrinciples to Follow:
Dramstad, W.E., Olson, J.D., and R.T.
Forman. 1996. Landscape Ecology
Principles in Landscape Architecture and Land-Use Planning . Washington,
DC: Harvard University and IslandPress.
7/27/2019 Lecture 9 Landscape Ecology
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Landscape EcologyLandscape EcologyLandscapes are living systems with
3 broad characteristics: structure,function, and change
landscape structure —spatial pattern orarrangement of landscape elements
landscape function —movement and flowsof animals, plants, water, wind,materials and energy
landscape change —dynamics of spatialpattern and function over time
Landscape ElementsLandscape Elementsn Patches —differentiated by size,
number, and location; e.g., large or
small, round or elongated, few or numerous, dispersed or clustered
n Corridors —attributes are narrow or
wide, straight or curvy, continuous or
disconnected .
n Matrix —attributes are single or subdivided, variegated or homogenous,
continuous or perforated
High
Low
R a t e o f i m m i g r a t i o n
o r e x t i n c t i o n
Equilibrium number
Immigration and extinction rates
Number of species on island
(a)
© 2004 Brooks/Cole – Thomson Learning
Theory of
island
biogeography
(a.k.a. species
equilibrium
model)– number
of species is
determined by
balance
between species
immigration
rate and
species
extinction rate
High
Low
R a t e o f i m m i g r a t i o n
o r e x t i n c t i o n
Small island
Effect of island size
Number of species on island
(b)
Large island
© 2004 Brooks/Cole – Thomson Learning
With time,
larger
islands have
larger
equilibrium
number of
species thansmaller
islands
7/27/2019 Lecture 9 Landscape Ecology
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PatchesPatches
Edge Habitat and SpeciesEdge Habitat and SpeciesDividing a large patch into two smaller ones
creates additional edge habitat leading to greater
number of edge species
Interior Habitat and SpeciesInterior Habitat and SpeciesDividing large patch into two smaller ones
removes interior habitat reducing population
sizes and number of interior species
A larger patch has larger population size for a
given species than smaller patch, making it less
likely that the species will go locally extinct
Local Extinction ProbabilityLocal Extinction Probability
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ExtinctionExtinctionProbability of species becoming locally extinct is
greater if a patch is small or of low habitat quality
A large patch is likely to have more habitats
present and therefore contain a greater number
of species
Habitat DiversityHabitat Diversity
Barrier to DisturbanceBarrier to DisturbanceDividing large patch into two smaller ones
creates barrier to spread of some disturbances
Large Patch BenefitsLarge Patch BenefitsLarge patches of natural vegetation (e.g., forest) protect aquifers and
interconnected stream networks, sustain viable populations of interior species, provide core habitat and escape cover for large-home-range
vertebrates and permit near natural disturbance regimes
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Small Patch BenefitsSmall Patch BenefitsSmall patches provide different and supplemental ecological benefits.
When they interrupt extensive matrix, act as stepping stones for
species movement. They also contain uncommon species where large
patches are absent or are unsuitable for a species..
Habitat LossHabitat LossRemoving a patch causes habitat loss, reducing
population size of a species dependent on that
habitat type leading to fewer species
Metapopulation DynamicsMetapopulation DynamicsRemoval of patch reduces size of metapopulation (interacting
subdivided population) increasing the probability of local, withi n-
patch extinctions, slowing down recolonization, and reducing
stability of metapopulation
Number of Large PatchesNumber of Large PatchesWhere one large patch contains almost all the species for that patch
type, two large patches may be considered minimum for mainta ining
species richness. Where one patch contains a limited portion ofthe
species pool, up to four or five large patches are probably required.
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Grouped Patches as HabitatGrouped Patches as HabitatSome generalist species can survive in a number
of nearby smaller patches, although individually
inadequate, are together suitable.
ExtinctionExtinctionProbability of species going locally extinct is greater in
isolated patch. Isolation is a function of both distance and
characteristics of the matrix habitat.
RecolonizationRecolonization A patch located close to other patches or the “mainland” will have
higher chance of being re-colonized within a time interval than more
isolated patch.
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Patch Selection for ConservationPatch Selection for ConservationSelection of patches for conservation should be based on 1)
contribution to overall system (relation to other links or patches) and 2)
unusual or distinctive characteristics (rare, threatened, or endemic
species).
Edges and BoundariesEdges and Boundaries
edge or boundary—outer portion of patch where
environment differs from interior of patch
--whether a boundary or edge iscurvilinear or straight influences the flow of
nutrients, water, energy, and species along or
across it.
--boundaries may be ‘political’ or ‘administrative’ (artificial)
--human development influences
interaction between human-made and natural
habitats
Edge Structural DiversityEdge Structural DiversityVegetative edges with high structural diversity, vertically,
or horizontally, are richer in edge animal species.
Edge WidthEdge WidthEdge width differs around a patch with wider edges on on sides
facing predominant wind direction and solar exposure.
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Florida
Administrative and natural
ecological boundary interaction
Administrative and natural
ecological boundary interactionWhen administrative boundary of protected area doesn’t coincide
with ecological boundary, the area between boundaries often
becomes distinctive and may act as buffer, reducing influence oninterior of protected area.
Edge as FilterEdge as FilterPatch edges normally act as filters that dampen the
influence of the surroundings on the patch interior.
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Edge AbruptnessEdge AbruptnessIncreased edge abruptness increases movement along
an edge whereas less edge abruptness favors movement
along an edge.
Example of Edge AbruptnessExample of Edge Abruptness
Natural and Human EdgesNatural and Human EdgesMost natural edges are curvilinear and complex, whereas
humans tend to make straight, simple, and hard edges.
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Straight and Curvilinear BoundariesStraight and Curvilinear Boundaries A straight boundary tends to have more species
movement along it while a more complex boundary is
likely to have movement across it.
Hard and Soft BoundariesHard and Soft Boundaries A curvilinear “tiny-patch” boundary may provide
ecological benefits such as less soil erosion and greater
wildlife usage.
Edge Curvilinearity and WidthEdge Curvilinearity and WidthCurvilinearity and edge width determine the total amount
of edge habitat within a landscape.
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Coves and LobesCoves and LobesCoves and lobes along an edge provide greater habitat
diversity than a straight edge encouraging higher species
diversity.
Edge and Interior SpeciesEdge and Interior SpeciesMore convoluted patches have a higher proportion of
edge habitat, slightly increasing the number of edge
species, but sharply decreasing interior species.
Interaction with SurroundingsInteraction with SurroundingsThe more convoluted the shape of a patch, the more
interaction (both positive or negative) between the patch
and the surrounding matrix.
Ecologically ‘Optimum’ Patch ShapeEcologically ‘Optimum’ Patch Shape An ecologically optimum patch provides several ecological benefits
an is generally “spaceship shaped” with rounded core plus curvilinear
boundaries and fingers for species dispersal.
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Shape and OrientationShape and Orientation A patch oriented with its long axis parallel to the dispersal
route will have lower probability of being recolonized.
Loss and Isolation of HabitatLoss and Isolation of Habitat
fragmentation—breaking up larger, intact habitatinto smaller dispersed patches
dissection—splitting an intact habitat into two
patches separated by a corridor
perforation—creating holes within essentially
intact habitat
shrinkage—decrease in size of one or morehabitats
attrition—disappearance of one or more habitat
patches
Corridors and ConnectivityCorridors and Connectivity
Continued habitat loss and isolation requireslandscape connectivity
--wildlife movement corridors and stepping
stones
--corridors may function as barriers or filters to
species movement
--stream or river systems are especiallysignificant corridors in landscapes
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Controls on Corridor FunctionsControls on Corridor FunctionsWidth and connectivity control the 5 major functions of
corridors: habitat, conduit, filter, source, and sink.
Corridor Gap EffectivenssCorridor Gap EffectivenssEffect of corridor gap depends on length of gap relative toscale of species movement and contrast between corridor
and gap.
Structural vs. Floristic SimilarityStructural vs. Floristic SimilaritySimilarity in vegetation structure and floristics(plant species)
between corridors and patches is preferable but similarity in structure
alone may be adequate for interior species movement.
Stepping Stone ConnectivityStepping Stone Connectivity A row of stepping stones or patches is intermediatebetween a corridor and no corridor in providing for interior
species movement.
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Distance Between Stepping StonesDistance Between Stepping StonesFor highly visual species, the effective distance for
movement between stepping stones is the ability to see
each successive stepping stone.
Stepping Stone LossStepping Stone LossLoss of one small patch functioning as stepping stone for movement inhibits movement and increases patch
isolation.
Cluster of Stepping StonesCluster of Stepping StonesThe optimal spatial arrangement of a cluster of stepping stones
between large patches provides alternate or redundant routes whi le
maintaining linear orientation between large patches.
Roads and “trough” CorridorsRoads and “trough” CorridorsRoad, railroad, powerline, and trail corridors tend to be connected,
relatively straight, and subject to regular human disturbance. Act as:
1) barriers that subdivide populations of species into metapopultions;
2) conduits for disturbance tolerant species; 3) sources of erosion,
sedimentation, exotic species and human effects on matrix.
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Wind Erosion and ControlWind Erosion and ControlModest winds reduce soil fertility by removing and blowing fineparticles long distances. Wind erosion control reduces field size in
the preponderant wind direction and maintains vegetation, furrows, or
soil clods in spots susceptible to vortices.
Stream Corridor and Dissolved SubstancesStream Corridor and Dissolved SubstancesDissolved substances (nitrogen, phosphorus, toxins) entering
vegetated stream corridor are controlled from entering the channel
and reducing water quality by friction, root absorption, clay, and soil
organic matter. Wide corridors of dense natural vegetation are most
effective.
Corridor Width for Main StreamCorridor Width for Main StreamTo maintain natural processes, maintain interior upland habitat on
both sides wide enough to control dissolved substance inputs fromthe matrix; also provides conduit for upland interior species and
habitat for floodplain species displaced by flooding or lateral channel
migration.
Corridor Width for a RiverCorridor Width for a RiverTo maintain natural processes, maintain upland habitat on both sides as a
conduit for upland interior species displaces by lateral channel migration. A
“ladder pattern” of large patches crossing the floodplain provides a hydrologic
sponge, traps sediment, provides organic soil matter for aquatic food chain,
logs for fish, and habitats for rare floodplain species.
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Connectivity of a Stream CorridorConnectivity of a Stream CorridorWidth and length of vegetated stream corridors interact to deter mine
stream processes. A continuous stream corridor, without major g aps,
is essential to maintain cool water temperature and high oxygen
content required by certain fish species.
Landscape MosaicsLandscape Mosaicsecological health of landscape measured by
connectivity of natural systems.
mosaics reflect the pattern and scale of
landscapes.
corridors interconnect to form networks.
Networks exhibit connectivity, circuitry, and
mesh size.
Spatial scale is perspective from which landscape
is analyzed--ranges from fine scale (zoomed
in) to broad scale (zoomed out)
Network Connectivity and CircuitryNetwork Connectivity and CircuitryConnectivity (degree to which all nodes are connected) combined
with circuitry (degree to which alternate routes are present) indicates
how simple or complex a network is and provides index of
effectiveness of linkages for species movement.
Loops and AlternativesLoops and Alternatives Alternate loops or routes in a network reduce negative effects of
gaps, disturbances, predators, and hunters within corridors.
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Corridor Density and Mesh SizeCorridor Density and Mesh Size As mesh size of a network decreases, probability of
survival drops sharply for species that avoid or is inhibited
by corridors.
Intersection EffectIntersection Effect At intersection of natural vegetation corridors, commonly
a few interior species are present and species richness is
higher than elsewhere in network.
Species in a Small Connected PatchSpecies in a Small Connected Patch A small patch or node connected to a network of corridors
is likely to have more species and lower rate of local
extinction than equal sized isolated patch.
Dispersal and Small Connected PatchDispersal and Small Connected PatchSmall patches or nodes along a network provide effective
habitat for individuals to pause and/or breed, resulting in
higher survival rate for dispersing individuals.
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Loss of Total vs. Interior HabitatLoss of Total vs. Interior HabitatFragmentation decreases total amount of a habitat type,
but proportionally causes much greater loss of interior
habitat.
Fractal PatchesFractal PatchesFractal configuration is natural reaction to transition, with
isolated patches reacting similarly to disturbance as a
group.
Suburbanization, Exotics, and Protected AreasSuburbanization, Exotics, and Protected AreasIn landscapes undergoing urbanization and consequent invasion of
exotic species, a nature reserve may be protected against damageby
invaders using a buffer zone with strict controls on wildlife species.
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Grain Size of MosaicsGrain Size of Mosaics A coarse-grained landscape containing fine-grained areas
is optimum to provide for large patch ecological benefits.
Animal Perception of Scale and Fragmentation Animal Perception of Scale and Fragmentation A fine ly-fragmented habitat is normally perceived as continuous
habitat by wide ranging species whereas coarsely fragmented habi tat
is discontinuous to all species except the most wide-ranging animals.
Specialists and GeneralistsSpecialists and GeneralistsSpecialist species are more likely to be negatively affected by fine-
scale fragmenation than are generalist species of similar size.
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Mosaic Patterns for Multihabitat SpeciesMosaic Patterns for Multihabitat SpeciesMultihabitat species are favored by 1) “convergency points” where
three or more habitats converge, 2) “adjacencies” where different
combinations of habitats adjoin, and 3) habitat “interspersion” where
habitats are scattered rather than aggregated.
Applications Vary by Scale Applications Vary by Scalen Macro or regional scale
--regional wildlife conservation park or
forest reserve
--forest plan
--new suburban development project
n Meso or landscape scale
--new roads or powerline corridors
n Micro or site scale
--smaller logging concession
Human reactions to visual changein the environment depends on
where change occurs …
Human reactions to visual changein the environment depends on
where change occurs …
n Immediate foreground: up to 100m away
People see fine details (leaf, broken limbs)
n Foreground: 100-800m away
General shape and scale most importantn Middle ground: 800-6400m away
Patterns and topography dominate
n Background: more than 6400m away
Blocks of color is main perception
Assessing visual quality Assessing visual quality
n What types of trees grow in area?
n Age, maturity and density?
n What shape, colors and tecture do trees and
vegetation create?
n Are there water features that draw
attention?
n How do rock outcrops and landformscontribute to the landscape character?
n Do environmental elements change with the
seasons? Special species blooms when ---
e.g. raffelesia?
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Scenic Management StrategiesScenic Management Strategies
n Buffer zones along roads “viewshed”
n Do not harvest at top of ridges
n Natural appearing clearings with edges
and curves [could be fire or naturaldisturbance]
n Put signs up explaining reforestation of
clearcuts
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