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Brief Review

Brief Review. Game species (Leopold 1933) Biophysics in wind tunnels & fields (50s-70s) Vegetation responses (50s – present) Wildlife population (30s – present) Microclimate (late 80s – present) Ecosystem processes: very rare.

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Brief Review

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  1. Brief Review • Game species (Leopold 1933) • Biophysics in wind tunnels & fields (50s-70s) • Vegetation responses (50s – present) • Wildlife population (30s – present) • Microclimate (late 80s – present) • Ecosystem processes: very rare • Productivity of tropical forests declined by about 36% as a result of edge creation (Laurance et al. 1997, Science)

  2. Forman (1995): Membranes Theory “The cellular membrane is an intriguing and useful model to understand landscape boundaries (edges)… “ “The inner and outer surfaces (of the membrane) differ markedly”. “… The landscape boundary exhibits these functions and more.”

  3. Frontiers in Edge Study Euskirchen et al. (2001) • Edge effects of two sides are not sympatric; • The maximum edge effect does not always occur at 0 m.

  4. Edge Vs Interior Species

  5. Frontiers in Edge Study • Within the area-of-edge influence (AEI), most areas are under multiple edge effects!

  6. Distribution of area-of-edge influences (AEI) around older clearcut, showing a complex AEI composition.

  7. Composition of AEI around 4 patch types in the CNF

  8. Interior Area of Edge Influence (AEI) (84%) 800 m So what? Assuming the depth of edge influence is 240 m, a 50 ha (125 acre) forested patch surrounded by open area contains very little interior environment. Indeed, 84% of the forest is AEI.

  9. Fragmentation of Continental U.S. Forests(43.5% of forest land is within 90 m of forest edge) Ohio Delaware River Basin Riitters and others, 2002, from Birdsey and colleagues

  10. Forest Fragmentation of the Delaware River Basin • Derived from National Land Cover Data, 1992 • Northern half of river basin appears to be mostly interior forest • Southern half of river basin appears to be mostly forest patches Delaware Water Gap NRA Birdsey and colleagues

  11. Climate Change and the Carbon Cycle:Biomass and Productivity of Areas with Fragmented vs. Interior Forests Predominance of interior forest Predominance of fragmented forest Birdsey and colleagues

  12. Biomass for Areas of Fragmented vs. Interior Forests Birdsey and colleagues

  13. NPP for Areas of Fragmented vs. Interior Forests Birdsey and colleagues

  14. Frontiers in Edge Study Continue to develop empirical database on edge structure and composition.

  15. Determining depth-of-edge influence continue to pose a major challenge. Chen et al. (2002) proposed the 1st method. Other Critical Values Program for Assessing Edge Influences can be found at Harper & MacDonald (2002), Bulletin of ESA.

  16. (a) DEI (m) (b) MEI Primary processes Tree mortality/damage Primary responses Primary strucutre Canopy trees Canopy cover Snags & CWD Secondary processes Recruitment Growth rate Canopy foliage Understory foliage Fruit aboundance Seedling mortality Secondary responses Secondary strucuture Understory tree density Herb cover Shrub cover Secondary composition Species composition Exotic species Edge species Interior species Species diversity 0 100 200 300 400 500 0 0.2 0.4 0.6 0.8 1

  17. Our knowledge on net carbon exchange of agricultural landscapes is very limited. http://www.unl.edu/nac/windbreaks.html

  18. Harris & Sanderson (2000): Edge Theory “Generalist species are more likely to be found along edges or ecotones that are avoided by specialist species”

  19. Species abundance across a jack pine edge in N. WI. Distance from the Edge (m)

  20. Physical, biological, and ecological processes across edges. One example is to mechanically model turbulence as function of forest structure ISO-POTENTIAL CONTOURS x y Tree m

  21. Direct and indirect of edge influences on ecological pattern and processes. What properties are really affected?

  22. (a) • Direct effects of edge creation: • Physical damage • Exchange of energy, matter, species 1° process responses: Productivity, evapotranspiration, nutrient cycling, decomposition, dispersal Abiotic and biotic gradients Magnitude of edge influence Distance of edge influence 1° structural responses: Canopy cover, tree density, biomass, downed wood (b) 2° process responses: Recruitment, growth, mortality, reproduction • Edge development: • ‘sealing’ • ‘softening’ • ‘expansion’ 2° structural responses: Sapling density, understory cover MEI DEI MEI DEI MEI • 2° compositional responses: • Change in understory composition DEI

  23. Research Need: Quantify the ecological responses to multiple edges, especially in highly fragmented landscapes.

  24. Biotic & Abiotic Independents Biotic & Abiotic Dependents

  25. Hansen et al. (in review). Biomass Accumulation Hypothesis “The Biomass Accumulation Hypothesis asserts that edge effects have the highest magnitude of influence in ecosystems that accumulate high levels of biomass.”

  26. Research Need: Design sound experiments to test various hypotheses to form a united theory on edge effects. Questions?

  27. Hypothesized effects of edges on NEP within the AEI. Edge orientation and edge age will be the two most important factors determining the changes in NEP and/or WUE within the AEIs.

  28. Management Philosophies Leopold-Thomas-Harris/Yanher-Noss-… Create as much edge as possible because wildlife is a product of the places where two habitats meet. This has been the management principle for both public & private land owners until mid-90s. -- Aldo Leopold (1933) The essential requirements of wildlife- food, cover, and water- will be maintained so as to provide optimum ‘edge effect’ and interspersion of habitat components in important wildlife areas. -- BLM Manual 1603 (1973)

  29. The law of dispersion and interspersion work together to show the forest manager how to increase wildlife populations associated with edge. -- Thomas et al. (1979) But increasing emphasis on plant and nongame wildlife conservation during the last two decades has revealed many characteristics of edges and ecotones are now considered undesirable. -- Larry Harris (1988) We must not conclude that creation of more edge in landscapes will always have a positive effect on wildlife … -- Richard H. Yahner (1988)

  30. John Rademacher Methods: Study Site YO YR & MR

  31. Methods:Variables measured Forest structureComposition • DWD Seedling composition • Overstory tree density Function • Seedling density Litterc • Basal area AGTc • Canopy openness DWDc • LAI DWDc • LMA Fine rootc Coarse rootc

  32. YR MR YO MO Results: Forest Structure ~ DWDa and DWDv DWDa and DWDv for the four edge sides (YR,MR, YO and MO). ▲replicate 1, Δ replicate 2, and ● replicate 3 YR MR YO MO

  33. YR MR YO MO Results: Forest function ( carbon pools) ~ AGTc AGTc(MG ha-1) for the four edge sides (YR,MR,YO and MO). Symbols represent the three replicates per edge side; ▲replicate 1, Δ replicate 2, and ● replicate 3

  34. Conclusion • This study indicates young edge sides have a DEI of 5 m and mature edge sides have a DEI of 22 m for both forest structure and carbon pools. • A 22 m DEI is comparable previous forest structure studies in mixed hardwood forests (Harper and McDonald 200x; Malack 199x).

  35. YR MR YO MO Results: LAI & LMA LAI and LMA for the four edge sides (YR,MR, YO and MO). ▲replicate 1, Δ replicate 2, and ● replicate 3

  36. Results:canopy structure (opennessfull & opennesshalf ) Opennessfull & opennesshalf (%) for the four edge sides (YR,MR, YO & MO). ▲replicate 1, Δ replicate 2, and ● replicate 3 YR MR YO MO

  37. Results: Forest function ( carbon pools) ~ Litterc Litterc (MG ha-1) for the four edge sides (YR,MR, YO and MO). Symbols represent the three replicates per edge side; ▲replicate 1, Δ replicate 2, and ● replicate 3

  38. Results: Forest function ( carbon pools) ~ DWDc and Snagc DWDc and Snagc (MG ha-1) for the four edge sides (YR,MR,YO and MO). Symbols represent the three replicates per edge side; ▲replicate 1, Δ replicate 2, and ● replicate 3 YR MR YO MO

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