Fundamentals of Restoration Ecology
Jan 24, 2016
Fundamentals of Restoration Ecology
Ecological Succession: The key To Restoration
• Succession is the process of change in ecosystem structure and composition over time.
• Succession drives ecosystem response to restoration efforts.
• Restoration, then, is the attempt to initiate and/or direct successional processes.
Linear model of Primary Succession
H.C. Cowles’ successional stages at the southern end of Lake Michigan
Figure from Keeton, W.T. (1980)
Models of Succession
• Relay floristics or “facilitation model”– Facilitative replacement of species– Sequential, directional, somewhat predictable
• Initial floristics or “tolerance model”– All or most species present at early successional stage– Change in relative abundance over time
• Intermediary models– Some aspects of facilitation and fluctuations in relative
abundance due to competition and environmental modification as a community develops
Sere 1 (colonization): Initially by specialist stress-tolerant species able to cope with rudimentary soils and extreme moisture/nutrient availability, e.g. mosses, lichens.
Sere 2 (development): Soils improve, organic content increases, productivity increases. Environment less stressful, but still vulnerable to disturbance. Stress-tolerant species replaced by more competitive and productive sere 2 species, which tolerate some disturbance, e.g. grasses and weeds.
Sere 3 (mature): soil now developed, soil conditions more stable, nutrient and water system is not stressful. Competitive species predominate(many still short life cycle), e.g. grasses, bushes and shrubs. Productive system with more complex trophic structure and cycling.
Sere 4 (climax): relatively stable vegetation community (???), productivity is high and ecosystem structure complex. Often dominated by competitors, which are long-lived species (e.g. trees). Little evidence of initial conditions or stress/disturbance tolerant species (but occur locally: river banks, gaps left by tree-fall). Stable climax may not exist.
Primary Succession
Grimes (1979) life history strategies for plants
• Competitive– reduce allocation towards vegetative growth and reproduction. This is not necessary in an environment
where there is little interspecific competition. Instead they invest in features that ensure the endurance of mature individuals, i.e. special adaptations in growth form and structure (below ground biomass).
• Stress-tolerant– maximize the capture of resources in productive but relatively undisturbed habitats. Bracken fern (Pteridium
aquilinium) is a classic competitor. It has large reserves of energy stored in underground organs that can be mobilized rapidly in the growing season to produce large vegetative canopies.
• Ruderal– are usually herbs having a short life-span and high seed production. They are found in highly disturbed, but
potentially productive environments (e.g trampled but arable ground). Initially, competition is reduced in disturbed environments. Ruderals invest in regenerative phases (e.g. seeds, vegetative propagules or runners, protective growth forms/structures). Many such species are considered to be weeds. Rapid growth and development means that they mature and set seed quickly, which ensures population persistence through subsequent disturbances.
Important for the selection of plants in restoration efforts
Figure adapted from Franklin and Spies (1991).
Secondary Succession
Succession difficult to predict
• Multiple determinants of early succession
• Multiple pathways of succession are possible
Multiple Pathways of Succession:
f (Timing, Type, and Intensity of Disturbances + Masting and Seed Availability)
From Hemstrom and Logan (1986), in Spies (1997)
Altered Successional Pathways Resulting from a Complex History of Land-use
Figure from Foster (1992)
Why is an understanding of natural disturbance regimes so important for restoration?
• Potential for disturbances to impair restoration success
• Potential for disturbances to facilitate restoration success
• Desired future condition must be dynamic
• Mimic the role of biological legacies in post-disturbance ecosystem recovery
Natural Disturbance Regimes
• Type
• Intensity
• Frequency
• Spatial extent and pattern
• Specificity
• Synergisms
Types of Natural Disturbances
Ice Storms
Insect and Pathogens Outbreaks
Floods
Fine-scale Windthrow
Large-scale Windthrow: Hurricanes, Tornadoes, etc.
Legend
Estimated volume of timber blown down
Over 10,000 board feet
1,000 to 10,000 board feet
< 1,000 board feet
Not affected or no report
Timber volume blown down by the 1938 hurricane per each township
Sources: Figure from Boose et al (1994); Data compiled by the Northeastern Timber Salvage Administration (1943)
1635 (8/25) Great Colonial Hurricane*
1638 (8/3)
1675 (9/7) Second Great Colonial Hurricane
1683 (8/23) Hurricane and Flood of 1683
1713 (8/30)
1727 (9/27)
1743 (11/2) Ben Franklin's Eclipse Hurricane
1749 (10/19)
1761 (10/23-24) Winthrop's Hurricane
1770 (10/20) Stile's Hurricane
1778 (8/12-13) The French Storm
1788 (8/19) Western New England Hurricane
1815 (9/23) The Great September Gale*
1821 (9/3) Redfield's Hurricane (arrived at low tide)
1841 (10/3) The October Gale
1856 (8/21) Charter Oak Storm
1869 (9/8) September Gale of '69
1878 (10/23-24)
1879 (8/18-19) Cape Cod Hurricane of '79
1893 (8/24)
1893 (8/29) passed well-inland
1896 (10/12-13) offshore hurricane
1916 (7/21) excessive rain+all
1924 (8/26) Off-shore Hurricane of '24
1933 (9/17-18) 13.27 inches rain at Provincetown
1936 (9/18-19) 7.79 inches rain at Provincetown
1938 (9/21) Great New England Hurricane*
1944 (9/14-15) Great Atlantic Hurricane*
1950 (9/11-12) Hurricane Dog
1954 (8/31) Carol*
1954 (9/11) Edna*
1954 (9/11) Hazel
1955 (8/17-19) Diane -- extreme floods
1960 (9/12) Donna
1985 (9/27) Gloria
1991 (8/19) Bob
Hurricanes in New England
Predicted Topographic Susceptibility to Windthrow
Figure from Boose et al. (1994)
Fire
Forest fires happens in New England too!
Intensity of Natural Disturbances
Low Intensity
Low Intensity High Intensity
Proportion of events
Low Intensity High Intensity
Proportion of events
High Intensity
Frequency
• High frequency regimes typically have low average intensity
• Low frequency regimes typically have high average intensity
Think of purposeful disturbance as a tool for restoration
High-intensity disturbance = large opening or big area + high mortality sets back succession
Low-intensity disturbance = small gap or area + low mortality accelerates succession
Spatial extent and specificity of disturbances influence ecosystem pattern
Mosaic of Patches: Fine-Scale, Dynamic
Mosaic of Patches: High Contrast, Dynamic
Mosaic of Patches: High Contrast, Stable
Mosaic of Patches: Coarse-scale, Dynamic
Mosaic of Patches: Anthropogenic disturbances
Synergism
What are biological legacies?
• Whole organisms• Reproductive structures: seeds, spores, stumps,
rhizomes• Organically derived structures: snags, logs, SOM,
soil aggregates• Patterns: organic and inorganic
– Microbial distribution– Soil chemistry and inhibition– Community patterns: e.g. gaps and antigaps
Implications of biological legacies for restoration
Restoration at Mount St. Helens: Passive and Active Approaches Aided by Biological Legacies
Biological Legacies of the 1938 Hurricane in MA
Biological legacies: organic matter carryover
•“Lifeboats” organisms above and below-ground
Organic matter helps ameliorate post-disturbance stress:
•soil moisture retention
•microclimate: shade, windspeed, etc.
•soil stabilization
•nutrient cycling
Linkages between terrestrial and aquatic ecosystems:
• Bank stabilization
•organic matter inputs
Biological legacies can persist on a site for a long-time; ecological functions change as the structure ages (e.g. decays)
How do ecosystems respond to disturbance?
Disturbance Disturbance
Eco
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Time TimeE
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unct
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Desired Future Condition
• Given that ecosystems are dynamics, what should the desired future condition be?
Early Successional?
Mid Successional?
Late-Successional?
Reference Condition
• What should we use as reference condition?– Historic condition – which one?
– Reference site: e.g. an extant, ecologically similar but un-degraded site. But which site? What part of it?
– Predicted future condition in light of global climate change. Should we take this into consideration?
• The key is to understand the range of variability. Restore to something within this range.
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1400 1500 1600 1700 1800 1900
Year
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HRV
Historical Range of Variability
Figure from Aplet and Keeton (1999)
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HRV
HRV
HRV
Scale: Small Watershed
Scale: Drainage Basin
Scale: Region
Hurricane
Hurricanes
Source: Aplet and Keeton (1999)
Restoration of Native Vegetation: Exotic Organism Control
1. Understand biology (i.e. life history) of the exotic organism
2. Identify critical life history stage
What life history traits make organisms successful invasives?
3. Determine possible control practices/techniques
What intensity of treatment is acceptable?
4. Map your site compartmentalize based on exotic species occurrence, density, threat, etc.
5. Develop removal program and schedule
Invasive Species Invasive Species ManagementManagement
European Buckthorn
Japanese Knotweed
Tartatian Honeysuckle
Japanese Honeysuckle
Using fire to control exotics…
• Kudzu (Pueraria lobata) is a perennial vine in the legume family
• Imported from Japan in 1876 to landscape a garden at the Japanese Pavilion at the Philadelphia Centennial Exposition.
• In the early 1900's, this vine was discovered to be excellent forage for cows, pigs, and goats in the South in acidic soils and during droughty seasons. It was also promoted as cover for erosion control in gullies.
• The distribution of kudzu in the United States today extends from Connecticut to Missouri and Oklahoma, south to Texas and Florida. Before 1970, kudzu was planted along Missouri highways to control erosion and some farmers experimented with kudzu for livestock fodder.
Kudzu Case Study
Kudzu infestation
1. Mechanical and hand removal
3. Prescribed burning then herbicide application
4. Native grasses planted
Completed restoration