fundamentals of restoration ecology. ecological succession: the key to restoration succession is the...

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

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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

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Historical Range of Variability

Figure from Aplet and Keeton (1999)

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HRV

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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