American chestnut dominant forests to red maple dominant forests
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Summary
The eastern parts of the USA were once dominated by American chestnut tree forests (Castanea dentata), making up 40-85 % of canopy cover. However, an invasive alien fungus known as chestnut blight (Cryphonectria parasitica) was accidently introduced to New York in the early 1900s at a time of significantly increased global trade. American chestnut trees had no resistance to this Asian fungus and it spread rapidly across the eastern coast. By the 1930s it had reached the southern Application forests in Virginia and North Carolina and killed almost all chestnut trees in the area (Anagnostikas, 1982; Freinkel, 2007). It continued to spread further into South Carolina and Georgia. By the mid-1950s over 3.6 million hectares of chestnuts trees, almost the entire population, were dead or dying (Anagnostikas, 1987). Only about 1 % of chestnuts now remain, mainly as small coppiced shrubs.
The loss of chestnut trees in the USA had significant negative impacts on the supply of timber, tannins, fodder and food products, negatively impacting the livelihoods of foresters and local communities as well and native biodiversity and ecosystem functioning (Freinkel, 2007). It resulted in the loss of a key food and shelter sources for wild animals in the region and altered nutrient cycles (Smock and McGregor, 1988; Ellison et al. 2005). For up to 50 years many forests in the eastern US had large gaps.
Hickory filled in these gaps over time and became the dominant forest species (McCormick and Platt, 1980). Due to exclusion of fire in the mid to late 1900s, red maple outcompeted hickory and is now the dominate forest species in the Appellation area.
Historically a number of techniques have been used to try and manage chestnut blight invasion, but the majority have failed. This included spaying of fungicide that did not work, and the use of biological control that had limited success. More recently genetic modification and breeding techniques are being implemented to produce chestnut blight resistant strains of C. dentate (Milgroom and Cortesi, 2004; Jacobs, 2007). Replanting of resistant strains into native forests has begun recently.
Type of regime shift
- Invasive alien species
Ecosystem type
- Temperate & Boreal Forests
Land uses
- Urban
- Small-scale subsistence crop cultivation
- Large-scale commercial crop cultivation
- Intensive livestock production (eg feedlots, dairies)
- Extensive livestock production (natural rangelands)
- Timber production
- Conservation
- Tourism
Spatial scale of the case study
- Sub-continental/regional (e.g. southern Africa, Amazon basin)
Continent or Ocean
- North America
Region
- East coase of the USA
Countries
- United States
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Drivers
Key direct drivers
- Species introduction or removal
- Disease
Land use
- Urban
- Small-scale subsistence crop cultivation
- Large-scale commercial crop cultivation
- Intensive livestock production (eg feedlots)
- Extensive livestock production (rangelands)
- Timber production
- Conservation
- Tourism
- Land use impacts are primarily off-site (e.g. dead zones)
Impacts
Ecosystem type
- Temperate & boreal forests
Key Ecosystem Processes
- Primary production
- Nutrient cycling
Biodiversity
- Biodiversity
Provisioning services
- Livestock
- Wild animal and plant products
- Timber
- Woodfuel
- Fuel and fiber crops
Regulating services
- Climate regulation
- Water regulation
- Regulation of soil erosion
Cultural services
- Recreation
- Aesthetic values
- Knowledge and educational values
- Spiritual and religious
Human Well-being
- Food and nutrition
- Livelihoods and economic activity
- Cultural, aesthetic and recreational values
- Cultural identity
Key Attributes
Spatial scale of RS
- Sub-continental/regional
Time scale of RS
- Decades
Reversibility
- Irreversible (on 100 year time scale)
- Hysteretic
Evidence
- Models
- Contemporary observations
Confidence: Existence of RS
- Well established – Wide agreement in the literature that the RS exists
Confidence: Mechanism underlying RS
- Well established – Wide agreement on the underlying mechanism
Alternate regimes
American chestnut dominant forests
The original regime consisted of American chestnut dominant forests (40-85 % canopy cover) throughout the east coast of the USA. This was a keystone species in the area – particularly for its role as a food and shelter source for animals. It was also highly prized by humans for timber, tannin, food and fodder.
Hickory and red maple dominant forests
For up to 50 years in some cases there were large gaps within forests where American chestnuts had died. These gapes were later filled by hickory species which became the dominant tree cover. Later fire exclusion caused hickory to be replaced by red maple, which is now the dominant forest tree species in the Appellation area of the USA.
Drivers and causes of the regime shift
The main driver of the regime shift was the accidental introduction of an invasive alien fungus (chestnut blight). This was underpinned by an increase in global trade in the early 1900s.
How the regime shift worked
The accidental introduction of an alien fungus (chestnut blight) to New York was the primary driver of the shift. American chestnuts native to the US were not resistant to this Asian fungus, and it rapidly spread across the country killing almost all chestnut trees.
The hickory and red maple regime is maintained by the suppression of American chestnut biomass and seedbanks resulting from the severe reduction of adult chestnut trees due to the invasive chestnut blight fungus. Furthermore, exclusion of natural fires has aided red maple to become dominant over other tree species along the eastern parts of the USA, in particular in the Appellations.
Impacts on ecosystem services and human well-being
This regime shift had many negative impacts on ecosystem services. Negative effects on provisioning services include loss of timber, food, tannin production, and livestock fodder (Anagnostikas, 1987). The loss of chestnut trees has also resulted in altered water and soil nutrient cycling, and resulted in the loss of carbon sequestration potential (Ellison et al. 2005). The American chestnuts provided many cultural services, including aesthetic and spiritual values. The American chestnut had always been a tree that American citizens closely identified with (Anagnostikas, 1987; Freinkel, 2007).
These negative impacts of chestnut blight had substantial costs for local livelihoods and human well-being. This included the loss of livelihood strategies and income for people in the timber, tannin and nut production industry. Nuts were also commonly collected and traded (bartered) for other supplies especially by poorer households (Anagnostikas, 1987). It has also resulted in a negative change for cultural identity and loss of cultural practices, as chestnut trees were a popular ornamental, collecting of nuts was a cultural tradition for families, and the tree was symbolic for many Americans.
Management options
A number of actions were implemented to try and manage the impact of chestnut blight fungus. This included spraying of fungicide and quarantining and destroying infected trees. However, this did not work effectively. There was also attempted use of biological control for the chestnut blight fungus using a hypovirulence agent. This had mixed success, working well in some regions but not in others (Milgroom and Cortesi, 2004). Attempts are now being made to breed and genetically modify chestnut trees to produce chestnut blight resistant cultivars and hybrids for replanting and restoration of chestnut tree forests in the USA (Jacobs, 2007).
Key References
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Anagnostakis SL. 1982. Biological control of chestnut blight. Science, 466-471.
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Anagnostakis SL. 1987.Chestnut blight: The classical problem of an introduced pathogen. Mycologia 79, 23-37.
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Diskin M, Steiner KC, Herbard FV, Recovery of American chestnut characteristics following hybridization and backcross breeding to restore blight-ravaged Castanea dentate. Forest Ecology and Management 223, 439-447.
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Ellison AM et al. 2005. Loss of foundation species: consequences for the structure and dynamics of forested ecosystems. Frontiers in Ecology and the Environment 3, 479-486.
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Freinkel S. 2007. American chestnut: the life, death and rebirth of a perfect tree. University of California Press.
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Jacobs DF. 2007. Towards development of silvical strategies for forest restoration of American chestnut (Castanea dentata) using blight-resistant hybrids. Biological Conservation 137, 497-506.
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Loo JA. 2009. Ecological impacts of non-indigenous invasive fungi as forest pathogens. Biological Invasions 11, 81-96.
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McCormick JF, Platt RB. 1980. Recovery of an Appalachian forest following the chestnut blight or Caherine Keever – you were right! The American Midland Naturalist 104, 264-273.
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Milgroom MG, Cortesi P. 2004. Biological control of chestnut blight with hypovirulence: a critical analysis. Annual review of Phytopathology 42, 311-338.
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Paillet FL. 2002. Chestnut: history and ecology of a transformed species. Journal of Biogeography 29, 1517-1530
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Smock LA, MacGregor CM. 1988. Impact of the American chestnut blight on aquatic shredding macroinvertibrates, Journal of the North American Benthological Society 7, 212-221.
