Transcript Fundamentals 2008

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
Primary Succession
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.
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
Secondary Succession
Figure adapted from Franklin and Spies (1991).
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.
Timber volume
blown down by the
1938 hurricane per
each township
Legend
Estimated volume of timber
blown down
Over 10,000 board feet
1,000 to 10,000 board feet
Sources: Figure from Boose et al (1994);
Data compiled by the Northeastern Timber
Salvage Administration (1943)
< 1,000 board feet
Not affected or no report
Hurricanes in New England
1635 (8/25)
Great Colonial Hurricane*
1879 (8/18-19) Cape Cod Hurricane of '79
1893 (8/24)
1638 (8/3)
1675 (9/7)
Second Great Colonial Hurricane
1893 (8/29)
passed well-inland
1683 (8/23)
Hurricane and Flood of 1683
1896 (10/12-13) offshore hurricane
1713 (8/30)
1916 (7/21)
excessive rain+all
1727 (9/27)
1924 (8/26)
Off-shore Hurricane of '24
1743 (11/2)
Ben Franklin's Eclipse Hurricane
1933 (9/17-18) 13.27 inches rain at Provincetown
1749 (10/19)
1936 (9/18-19) 7.79 inches rain at Provincetown
1761 (10/23-24) Winthrop's Hurricane
1938 (9/21)
1770 (10/20)
1944 (9/14-15) Great Atlantic Hurricane*
Stile's Hurricane
Great New England Hurricane*
1778 (8/12-13) The French Storm
1950 (9/11-12) Hurricane Dog
1788 (8/19)
Western New England Hurricane
1954 (8/31)
Carol*
1815 (9/23)
The Great September Gale*
1954 (9/11)
Edna*
1821 (9/3)
Redfield's Hurricane (arrived at low tide)
1954 (9/11)
Hazel
1841 (10/3)
The October Gale
1955 (8/17-19) Diane -- extreme floods
1856 (8/21)
Charter Oak Storm
1960 (9/12)
Donna
1869 (9/8)
September Gale of '69
1985 (9/27)
Gloria
1991 (8/19)
Bob
1878 (10/23-24)
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
Proportion
of events
Low Intensity
High Intensity
High Intensity
Proportion
of events
Low Intensity
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 postdisturbance 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?
Ecosystem Structure and Function
Time
Ecosystem Structure and Function
Disturbance
Disturbance
Time
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.
Historical Range of Variability
Proportion of Landscape in Old-growth
1
HRV
0.5
0
1400
1500
1600
1700
1800
1900
Year
Figure from Aplet and Keeton (1999)
Proportion of Landscape
in Old-growth
Scale: Small
Watershed
1
Hurricane
HRV
0.5
0
Scale: Drainage
Basin
Proportion of Landscape
in Old-Growth
0
100
200
300
400
500
Years
1
Hurricanes
HRV
0.5
0
0
100
200
300
400
500
Scale: Region
Proportion of Landscape
in Old-Growth
Years
1
HRV
0.5
0
0
100
200
300
Years
400
500
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
Management
European Buckthorn
Japanese Knotweed
Japanese
Honeysuckle
Tartatian
Honeysuckle
Using fire to control exotics…
Kudzu Case Study
• 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 infestation
1. Mechanical and hand
removal
3. Prescribed burning then
herbicide application
4. Native grasses planted
Completed restoration