Ecological Restoration (BIO 409)Dr. McEwan

Invasion Ecology

Regional Invasive Species Pool

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Colonization

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# 2

Proliferation Proliferation

# 3habitat space

Regional Invasive Species Pool

Dis

pe

rsal

Colonization

# 1{

# 2

Proliferation Proliferation

# 3habitat space

The invasion process involves three general phases…

Colonization

Prol

ifera

tion

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Pha

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Nascent Foci

Invasion & Other Processes:- Invasion causes ecosystem alteration- but it can also be a consequence of other (alteration) processes.

Invasional Meltdown

Invasion and Resource Supply:- Invasion has been conceptually linked to the idea of excess available resources. Where do these resources come from? Either some of the native species that normally absorb resources are lost from the system, or resources are being added to the system artificially raising the resource level above that which would naturally be there, or both.

The Ecological History of American The Ecological History of American Chestnut (Chestnut (Castanea dentataCastanea dentata))

Davis, M. 1969. Ecology 50:409-422

Castanea dentata, initial invasion (?)

Paillet, F. L. 2002

Castanea dentata, initial invasion (?)

Delcourt et al. 1998

Castanea dentata, initial invasion (?)

By 1900: chestnut was found throughout most of the Eastern Deciduous Forest.

Russell (1987)

C. dentata, maximum extent

( ~ 200 million acres)

Chestnut distribution at the county level (early 1900s)

Transeau (1935)

C. dentata, extent

C. dentata, abundance/dominance

Chestnut reached enormous size(13 feet DBH..heights of 120 ft. [Brewer 1995])

…and formed pure stands(> 80 % Basal Area in some stands)

Chestnut grew extremely fast…even in a forested setting.

C. dentata, extent

McEwan and McCarthy (unpublished)

C. dentata, ecological importance

Soil effects?

Coarse Woody Debris Paillet 2002

Boetcher and Kalisz (1990)

The most decay resistant wood of any eastern tree (Brewer 1995).

C. dentata, ecological (and practical) utility

Heavy and reliable seed crop (Brewer 1995)

The Chestnut Blight

In 1904, it was noticed that chestnuts in New York city were

exhibiting a strange canker

This canker was caused by the fungal pathogen Endothia parasitica…

Changed to: Cryphonectria parasitica.

The Chestnut Blight

Photos from: http://botit.botany.wisc.edu/toms_fungi/may98.html

Biology of C. parasitica

- Asian in origin

- Member of the Ascomycota

Reproduces sexually and asexually…both routes produce wind/rain splash dispersed spores (conidia and ascospores, respectively)

The Chestnut Blight

Photos from: The Canadian Chestnut Council: http://www.uoguelph.ca/~chestnut

Disease Progression-- Trees are infected via fissures in the bark (or lenticels).-- Cankers form.-- Cankers girdle tree…tree dies (rapidly).-- 100% mortality in (practically) every stand.

The disease migrated along the Appalachian Mountains very quickly (25 miles/ year).

The Chestnut Blight

By 1960, chestnut blight had spread throughout the native range of C. dentata.

The Chestnut Blight

This migration route is not unique…

The Chestnut Blight

- Contrary to popular belief, Cryphonectria parasitica, is NOT host specific.

-- Impacts many species in the Family (Fagaceae).

-- Does not (generally) cause mortality.

-- In eastern forests, C. parasitica, is particularly common on scarlet oak (Quercus coccinea: look for orange pustules) .

-- Provides a ready source of inoculum.

The Chestnut Blight

Chestnut remains important as an understory sprout.

From Paillet (2002)

The Chestnut Blight

Castanea dentata was rendered functionally extinct as a canopy tree throughout its native range..in a matter of decades.

In 1951, a “strain” of C. parasitica was discovered that was less damaging.

Chestnut Restoration: Hypovirulence

Dubbed “Hypovirulence”, this aided in chestnut restoration in Italy

Caused by a viral disease (or suite of diseases) of the Cryphonectria fungus!!

After initial promise, has failed to have stand-level impacts in N.A.

Anagnostakis, S. L. (1982)

The American Chestnut Foundation has developed a program to breed blight resistant American chestnuts.

Chestnut Restoration: Breeding Program

American chestnut crossed with Asian chestnuts (Castanea mollissima or C. crenata).

Hybrid then back-crossed with American

Trees that are 94% American now available.

American Chestnut Foundation: http://www.acf.org/

Near 100% Americans available by 2006

Regeneration niche ?

- shade tolerance

- silvicultural considerations

Chestnut Restoration: challenges

Fire ecology ?

- Thin bark

- Coincidence with charcoal

The chestnut blight left us with an information vacuum…

how to proceed?

Photo by Corie McCament, Ohio University

John Pickering, University of Georgia, Athens.Delcourt et al. 1998.

Chestnut Restoration: challenges

Rieske et al. 2003

Future challenges: Lymantria dispar

Chestnut Restoration: challenges

Rhoades et al. 2003

Future challenges: Phytothora cinnamomi

Brosi (2001) found 60% chestnut mortality within 4 months of planting.

Russell (1987) and others indicate that Phytopthora was a problem prior to the arrival of Cryphonectria.

J. Watkins, U. of Nebraska

Summary

?

The loss of American chestnut, although in itself is an interesting ecological story. It is perhaps most interesting as a cautionary tale- or maybe even predictive- of an invasive species onslaught in eastern forests.

Restoration in forests of eastern North America (all of North America for that matter) may ultimately be an exercise in reintroducing decimated species. For example:

Fungi-Dogwood anthracnose-Dutch Elm Disease-Butternut Canker-White pine blister rust

Insects-Hemlock adelgid-Emerald Ash Borer-Gypsy Moth (generalist)