Transcript New Paradigms - School of Environmental and Forest Sciences

New Paradigms
• Stable, Simple, Predictable, Equilibrium systems are out
• Heterogeneity, Transitions, Patches, Landscapes,
Disturbance, Nonequilibrium systems are in
– Ecological systems are heterogeneous
– There are many sorts of patches that are arranged into mosaics
and landscapes
• Disturbance, remnant, regenerated, environmental resource,
planted/constructed patches
– Boundaries are variously sharp and fuzzy, graded and discrete
– Patches, mosaics, and landscapes change temporally and
spatially in response to disturbances
– We must pay attention to the spatial matrix of ecological
processes, understand fluxes of materials and organisms in
nature, study the dynamic role of ecotones and edges, know
the dynamics of entire landscapes and their parts
Equilibrium to Nonequilibrium
• Views of communities as integrated superorganisms
(Clements 1916) replaced by views of community as
group of individuals (Gleason 1917, Whittaker 1965)
• Views of competition as dominant structuring force
replaced by more pluralistic view (density dependent
and density independent of many types)
• View of uniform responses leading to predictable
equilibrium replaced by stochastic, variable,
individualistic responses disturbed at various spatial
and temporal scales leading to mixture of equilibrium
and nonequilibrium conditions
– Local unpredictability is globally the most predictive aspect
of the system (Levin and Paine 1974)
Connections
•
Abiotic Inputs
Population is the fundamental unit of
conservation ecology, but higher and lower
levels have important links to populations
Ecosystem Function
Ecosystem Services
Predators,
Prey,
Keystones,
Competitors,
Symbionts
Community Composition
Extinction or Persistence
Population Viability
Genetic Variation
Breeding Opportunities
Survival, Reproduction,
and Dispersal
Individual Fitness
(modified by age, experience, status)
Nutrients
and
Energy
Different Responses to
Disturbance (Vogl 1974, White and Harrod 1997)
• General categories of response
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–
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–
–
Increasers—present before, increase after
Decreasers—present before, decrease after
Invaders—not present before, present after
Retreaters—present before, not present after
Neutrals—unresponsive to disturbance
Integrators—use multiple patches with variable
disturbance history in mosaic (Lynx)
• Disturbance type specific
• Assumes species are available at larger scale
Patchiness and Conservation (Wiens 1997)
• Elements of a landscape mosaic vary in quality
determined by many cost-benefit functions that are
dynamic rather than fixed
• Boundary effects are important
• Matrix affects the boundary (edge) effects
• Connectivity among patches (or lack of it) is
important
• All these features of a landscape are defined by
the structure of the landscape mosaic and by the
responses of organisms to that structure
Landscapes as Cost-benefit Contours
(Wiens 1997)
Valleys
where
risks and
stresses
are great
Peaks with good access to resources
Our Basic
Approach
Interpolating Predator
Use of Study Area
Mapping
Predators
Relating Annual
Productivity or Nest
Success to
Predator Use
A Landscape of Risk to Nesting
View1
Birds in Mora
Campground
Mora _cam pground.shp
Contours _Ker nel(84)M or a_pr edators.txt
10
20
30
40
50
60
70
80
90
95
Allc am pgrounds_line .shp
N
W
0.5
0
0.5
E
1 Miles
S
Change in Productivity from Areas
Used Most to Least by Predators
30
Pacific Slope Flycatcher
20
F (7,112) = 4.53, P < 0.001
10
Relative Nesting Success
In Predator Use Area
(Success Inside - Outside
Predator Use Area)
0
-10
-20
-30
-40
13
7
60
50
7
22
25
30
20 <11
48
11
27
>81
70
40
Relative Use of Area by Predators
Contiguous
Young
Forest
Interface
Between
Contiguous
Old growth
And young
forest
Days to predation for eggs
(the darker the color the lower the predation)
Lowest Predation where
landscape is not patchy, edges
are between young forest and old
growth, and forest patches are
predominantly of a single type
Days to predation =
8.04 – 8.16 landscape patch density at 5km +
1.10 landscape contrast weighted edge density
at 2km
– 10.31 Shannon-Weaver evenness index at
2km
(R2 = 0.27)
Landscape
Correlating
Predators and Prey
at 3 Scales
Within Patch
Forest patch
Occurrence
of Corvids
0 -2 / count
1 – 1.5 / count
0.25 – 1.5 / count
0.6
0.4
Landscape (1km2)
Forest Patch
Within Forest Patch
American Crow
0.2
0.0
-0.2
n =64 62
55
-0.4
-0.6
Species May
Vary in Their
Exposure to
Nest
Predators
Pearson Correlation Coefficient (r)
0.6
0.4
Steller's Jay
0.2
0.0
-0.2
-0.4
n =64 39
55
-0.6
0.6
0.4
Sciurids
0.2
0.0
-0.2
-0.4
n =64 89
55
-0.6
0.6
0.4
Corvids and Sciurids
0.2
0.0
-0.2
-0.4
n =64 135
55 Bewick's
Wren
Dark-eyed
Junco
Song
Sparrow
Swainson's
Thrush
Winter
Wren
-0.6
American
Robin
Blackthroated
Gray Warbler
Pacific
Slope
Flycatcher
Spotted
Towhee
Wilson's
Warbler
Importance of Patchiness to Managers
• Patches are real, pervasive, and increasing
• Leads to important generalities
– Don’t homogenize landscapes—do not do the same thing everywhere
(Bunnell 1999)
– The matrix matters—management of a patch requires management and
planning of surrounding patches (entire landscape; Pickett and Rogers
1997)
– Larger landscapes are more resilient (persistent native species and
communities in the face of local fluctuation)—variety of patch types
allows all needs of integrators to be met, provides diversity of conditions,
and large area is unlikely to be disturbed in entirely allowing for refuges
as needed. (White and Harrod 1997)
• Requires cooperation and partnerships with many landowners
• Forces use of adaptive management
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Assess expected changes in system
Relate changes to management goals
Adjust as needed
Leads to greater interaction between managers and researchers
More Insights for Management
(Wiens 1997)
• The amount and arrangement of habitat can be
important. Knowing which is more important
requires an understanding of dispersal.
– Inadequate knowledge about dispersal (or invasion) can
lead to the inverse of the “field of dreams”
phenomenon: build a reserve and no one (or the wrong
one) will come
• Modeling suggests that size and spacing of habitat
fragments (reserves) may be less important than
their persistence over time
References
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Bunnell, F. L. 1999. What habitat is an island? Pages 1-31 in J. A. Rochelle, L. A. Lehmann,
and J. Wisniewski, Eds. Forest fragmentation: wildlife and management implications. Brill,
Leiden.
Pickett, S.T.A. and M. L. Cadenasso 1995. Landscape ecology:spatial heterogeneity in
ecological systems. Science 269:331-334.
Kotliar, N. B. and J. A. Wiens. 1990. Multiple scales of patchiness and patch structure—a
hierarchical framework for the study of heterogeneity. Oikos 59:253-260.
Vogl, R. J. 1974. Effects of fire on grasslands. Pages 139-194 in T.T. Kozlowski and C. E.
Ahlgren, eds. Fire and ecosystems. Academic Press. New York.
Whittaker, R.H. 1965. Dominance and diversity in land plant communities. Science 147:250260.
Gleason, H. A. 1917. The structure and development of the plant association. Bull. Torrey
Botanical Club 43:463-481.
Clements, F. E. 1916. Plant succession: an analysis of the development of vegetation.
Publication Number 242. Carnegie Institute, Washington, DC.
Levin, S.A. and R. T. Paine. 1974. Disturbance, patch formation, and community structure.
Proc. National Acad. Sci, USA 71:2744-2747.