Restoring American chestnut and associated products

to the Northern Forest Principal Investigator: Gary J. Hawley

Affiliation/Institution: UVM-RSENR Email: ghawley@uvm.edu

Mailing address: 81 Carrigan Drive, Burlington, VT Co-Principal Investigators: Paul G. Schaberg

Affiliations/Institutions: USDA-FS-NRS Emails: pschaberg@fs.fed.us

Collaborators and Affiliations: The American Chestnut Foundation (TACF) Completion date: July 31, 2012

• American chestnut nuts and shoots are barely cold tolerant enough to survive winter temperature lows within the Northern Forest.

• Despite this vulnerability, significant variations in winter injury associated with tree genetics and silvicultural management suggest that scientific guidance can be used to increase hardiness and growth in the Northern Forest.

Funding support for this project was provided by the Northeastern States Research Cooperative (NSRC), a partnership of Northern Forest states (New Hampshire, Vermont,

Maine, and New York), in coordination with the USDA Forest Service. http://www.nsrcforest.org

Project Summary • Rationale: American chestnut was once an ecologically and economically important

component of the eastern US hardwood forest until it was functionally wiped out as an overstory tree by chestnut blight (caused by an exotic fungal pathogen). The American Chestnut Foundation (TACF) is working with the US Forest Service and other partners to breed chestnut trees that are resistant to chestnut blight and can be used to restore the species across its entire range – including the cold Northern Forest. This research was conducted to determine if genetic selection and silvicultural management could be used to improve American chestnut growth and cold tolerance at the species’ northern range limit.

• Methods: We evaluated two methods for bolstering the cold tolerance of American chestnut trees through: 1) the identification of seed sources exhibiting greater cold hardiness, and 2) studying the influence of overstory silvicultural treatments on the growth and winter injury of chestnut seedlings. We established an American chestnut progeny planting in a replicated design under three levels of silvicultural treatments (open, partial, and closed canopy overstories) on the Green Mountain National Forest. Seed sources included lines from throughout the species’ range, including the Northern Forest.

• Major findings: Both genetics and silvicultural treatment influenced American chestnut growth and winter shoot injury. In general, sources from warm and moderate climates grew the most but experienced the most winter injury. Chestnuts in open canopy treatments also grew the most but experienced the most winter injury. Overall there was a tradeoff between growth and protection from the cold. Separate cold tolerance tests of nuts suggested that they may provide a reliable indicator of shoot cold tolerance.

• Implications for the region: There are certain genetic sources (e.g., from cold temperature zones) and silvicultural treatments (e.g., some canopy closure) that seem to result in limited winter shoot injury in American chestnut. Refinement of genetic and silvicultural approaches to improve American chestnut growth and survival in the north could help restore the species to the Northern Forest – a region critical to species range extension predicted to occur as climates change.

Background and Justification • American chestnut was once a prized forest products species

throughout the eastern US. It was fast growing, very large, produced high-quality wood and abundant nut masts.

• American chestnut was functionally eliminated as an overstory tree following the introduction and spread of chestnut blight.

• The American Chestnut Foundation is leading a breeding program to develop a chestnut tree that is resistant to chestnut blight and can be used to restore the species across its range.

• Despite considerable progress toward species restoration in the heart of the species’ range, little is known about specific barriers to restoration in the north.

• Indeed, preliminary evidence suggests that limited nut and shoot cold tolerance could complicate northern restoration.

American chestnut (Castanea dentata) A major component of eastern forests Fast growth, large, extremely rot resistant High-value timber species Nuts valuable to wildlife/livestock/people Tannins used in tanning leather

Photos provided by The American Chestnut Foundation (TACF)

Historic Range – extended into the Northern Forest

Map provided by TACF

Chestnut Blight (Cryphonectria parasitica)

Blight first identified in New York in 1904 Girdling cankers cause mortality in 2-10 years Spread quickly, functionally wiped out

chestnut as overstory tree by 1950s

Photos provided by TACF

Restoration Attempts

Cultural methods - fungicide, tree surgery, forest gap barriers

Hypovirulence Breeding

Pure American chestnut Hybrid/backcross

Photo provided by TACF

Breeding chart provided by TACF

Restoration in the Northeast Breeding material

currently from southern and central states (often from low elevation, warm locations)

Uncertain if resulting

stock has adequate cold tolerance for colder sites?

Map provided by TACF

Restoration in the Northeast

Shoots have marginal cold tolerance

Vulnerable to field freezing injury in winter

Terminal shoots on leader

and side branches

Photo by Kendra Gurney TACF

Restoration in the Northeast

Loss of apical dominance releases dormant lateral buds

Saplings take on shrubby

habit

Experimental evidence (Gurney et al. 2011) and observed in TACF plantings from PA north

Bolster Cold Tolerance? Genetic Selection Influence of Chinese chestnut on backcross stock?

Chinese chestnut may be less cold-tolerant than American chestnut?

Variation among American chestnut sources? Pattern to variation – e.g., regional?

Silvicultural selection Differential light exposure could alter growth and

sugar buildups that act as cellular antifreeze agents

Open-grown stock greater exposure to cold?

Overall goal Assess growth and winter injury of American and Chinese

chestnut, and red oak (a native competitor) saplings under 3 silvicultural treatments (open, partial- and closed canopies) on the Green Mountain National Forest

Photos by Paula Murakami USDA-FS-NRS

Methods - overview • American chestnut, Chinese chestnut and red oak

seedlings were grown in a greenhouse and then outplanted into 3 replicates of 3 silvicultural treatments (open, partial and closed canopies) on the GMNF.

• Heights and diameters were measured at the end of greenhouse growth and again at the end of the 1st growing season.

• Shoot winter injury (visible assessments of stem death and discoloration) was assessed in the spring after the 1st winter of field growth.

• Analyses of variance were used to test for significant differences in height and diameter growth associated with species, source within species, silvicultural treatment, etc.

• The cold tolerance of American chestnut nuts was also evaluated to assess whether these measures may provide an expedited method of evaluating shoot vulnerability to freezing damage.

GMNF Study: growth and winter injury

Three species: American chestnut, Chinese chestnut, red oak

Thirteen pure American sources, two Chinese sources and two red oak sources

Three silvicultural treatments – closed canopy, partially closed and open canopy

Three treatment replicates

About 880 saplings planted overall

13 Overall

5 North 4 Central 4 South

American chestnut sources and regions

Map provided by TACF

Used temperature data to estimate typical low temps Temperature from nearest weather station Mean winter minimums (Dec – Feb) Adjusted for elevation – adiabatic lapse rate 6.5°C/1000m

3 Temperature groups: Warm (°C) -1.0 to -5.0 °C Moderate (°C) between -5.0 and -9.0 °C Cold (°C) colder than -9.0 °C

Temperature Zone ?

13 American Chestnut Sources Code County, State Latitude Longitude Elevation (m) Region Temperature Zone

NC1 Jackson County, NC 35° 22' 21" N 82° 47' 29" W 1387 South Warm

VA1 Smyth County, VA 36° 49' 40" N 81° 25' 49" W 1036 South Moderate

VA2 Smyth County, VA 36° 51' 55" N 81° 26' 10" W 1041 South Moderate

KY1 Metcalfe County, KY 37° 00' 16" N 85° 37' 34" W 269 South Warm

MD1 Montgomery County, MD 38° 57' 53" N 77° 05' 33" W 100 Central Warm

PA1 Franklin County, PA 39° 59' 38" N 77° 23' 55" W 600 Central Moderate

NJ1 Monmouth County, NJ 40° 36' 20" N 73° 07' 10" W 20 Central Warm

PA2 Mercer County, PA 41° 20' 58" N 80° 04' 58" W 384 Central Moderate

NY1 Westchester County, NY 41° 19' 41" N 73° 41' 10" W 94 North Moderate

NY2 Wyoming County, NY 42° 37' 44" N 78° 03' 17" W 417 North Moderate

ME2 Knox County, ME 44° 10' 55" N 69° 08' 09" W 68 North Cold

VT1 Chittenden County, VT 44° 31' 39" N 73° 12' 11" W 57 North Cold

ME1 Piscataquis County, ME 45° 09' 35" N 69° 04' 58" W 101 North Cold

Results - overview • Species differences: Chinese chestnut had the greatest growth

(greenhouse and field), but also experienced the most winter shoot injury.

• American chestnut: sources from the warm and moderate temperature zones had the greatest growth, but also experienced the most winter shoot injury.

• Silvicultural treatment: the open canopy provided more light, but also less protection from winter temperature lows.

• Consequently, seedlings in the open treatment grew more, but also experienced greater winter shoot dieback.

• Across species, American chestnut sources, and silvicultural treatments there appeared to be a tradeoff between growth and protection from winter injury.

• Separate tests suggest that nut cold tolerance measurements may be used to estimate shoot hardiness levels.

Greenhouse Results

Photo by Tom Saielli TACF

Means with different upper case letters for height and lower case letters for diameter are significantly different based on Tukey HSD tests (P <0.0001).

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Means with different upper case letters for temperature zone and lower case letters for source within temperature zone are significantly different based on Tukey HSD tests (P <0.0001).

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Field component

Site prep:

Trimming understory and grasses

Placing competition matting around each seedling

Vole shelters and deer cages

Photo by Paula Murakami USDA-FS-NRS

Silvicultural Treatments - Verification Canopy analysis – hemispherical photography Temperature variations – i-buttons air temps

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Canopy openness of silvicultural treatment in 3 replications

Means with different upper case letters are significantly different based on Tukey HSD (P < 0.001), replication means with different lower case letters are significantly different based on Tukey HSD results within the treatment x replication interaction (P < 0.001).

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Mean minimum temperature (± SE) of coldest December day by silvicultural treatment

Means with different letters are significantly different based on Tukey HSD tests (P < 0.005).

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Height (cm) Diameter (mm) Dieback (cm) Species mean ± SE MC* mean ± SE MC* mean ± SE MC* Chinese chestnut 4.22 0.58 A 1.72 0.16 A 10.21 0.75 A American chestnut 2.39 0.21 B 1.06 0.06 B 3.90 0.27 B Red oak 0.74 0.85 B 0.5 0.24 B 2.78 1.12 B

Difference in mean (± SE) height, diameter and total shoot dieback among species

for seedlings grown at Green Mountain National Forest

*MC multiple comparisons for specified variables, means with different letters are significantly different based on Tukey HSD tests (P < 0.001).

Field Results - Species

Field results – American chestnut growth

Means with different upper case letters for temperature zone and lower case letters for source within temperature zone are significantly different based on Tukey HSD tests (P < 0.001).

aa a

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Field results – American chestnut winter injury

Means with different upper case letters for temperature zone and lower case letters for source within temperature zone are significantly different based on Tukey HSD tests (P < 0.05).

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Silvicultural Height (cm) Diameter (mm) Dieback (cm) treatment mean ± SE MC* mean ± SE MC* mean ± SE MC*

Open canopy 21.46 1.8 A 2.35 0.12 A 9.18 0.73 A Partial canopy 3.88 0.61 B 0.73 0.05 B 2.62 0.32 B Closed canopy 4.18 0.6 B 0.31 0.04 C 3.03 0.38 B

Difference in mean (± SE) height, diameter and total shoot dieback among

silvicultural treatments for seedlings grown at Green Mountain National Forest

*MC multiple comparisons for specified variables, means with different letters are significantly different based on Tukey HSD tests (P < 0.001).

Field Results – Silvicultural treatment

Tying it all together – what matters?

Species Temperature zone Source within temperature zone Silvicultural treatment Tradeoff between growth and winter injury - can it be

bridged? (e.g., sources with decent growth and cold tolerance?)

Will this tradeoff diminish or become manageable?

Silvicultural treatments – may be influenced by size of “open area” – is there a “sweet spot”?

Species – likely a juvenile issue for growth but not cold tolerance

Temperature zone – general patterns, but with interesting exceptions?

Map provided by TACF

Tradeoffs between growth and winter injury

Silvicultural treatments

Species Temperature zone How consistent?

Map provided by TACF

Nut Cold Tolerance Nuts may not be cold-tolerant enough to survive

cold winters if not buried (Schaberg et al. 2009; Saielli et al. 2011)

Is there a correlation between nut cold tolerance and shoot cold tolerance?

Nut cold tolerance versus winter shoot dieback

Results of linear regression of mean nut cold tolerance and shoot dieback from the twelve American chestnut sources. Shoot dieback averaged over all silvicultural treatments.

Implications for the Northern Forest • American chestnut nuts and shoots are vulnerable to injury from

winter temperature lows.

• Although vulnerable to winter injury, both genetic selection and silvicultural treatment can reduce the risk of low temperature damage.

• On a broad scale, woody growth and low temperature protection appear to be inversely related – suggesting that there is a general adaptive tradeoff between these traits.

• However, some sources had both good growth and low winter shoot injury, suggesting that further testing could identify sources better adapted for optimal competition in the north.

• Chinese chestnut is needed to provide blight resistance in backcrossed stock. However, crossing with Chinese chestnut may reduce progeny cold tolerance across the generations if not identified and selected against.

Future directions • New research will test if patterns of winter injury and growth

noted in first year saplings hold true as plants mature.

• As saplings grow, woody shoots will be harvested in laboratory assessments of 1) cold tolerance, and 2) non-structural carbon concentrations (used for growth and to enhance cold hardiness).

• We will assess differences in spring leaf phenology among the genetic sources and silvicultural treatments to see if these influence the vulnerability of trees to spring frost injury.

• We will add the final product of TACF’s breeding program (the B3F3 Restoration Chestnut) to the GMNF plantation to test its performance in the north.

List of products • Peer-reviewed articles

- Schaberg, P.G.; Gurney, K. M.; Janes, B.R.; Halman, J.M.; Hawley, G.J. 2009. Is nut cold

tolerance a limitation to the restoration of American chestnut in the northeastern United

States? Ecological Restoration. 27:266-268.

- Gurney, K.M., Schaberg, P.G.; Hawley, G.J.; Shane, J.B. 2011. Inadequate cold tolerance as a

possible limitation to American chestnut restoration in the Northeastern United States.

Restoration Ecology. 19:55-63.

- Saielli, T.M.; Schaberg, P.G.; Hawley, G.J.; Halman, J.M.; Gurney, K.M. 2012. Nut cold

hardiness as a factor influencing the restoration of American chestnut in the northeastern

United States. Canadian Journal of Forest Research, 42:849-857.

- Schaberg, P.G.; Saielli, T.M.; Hawley, G.J.; Halman, J.M.; Gurney, K.M. 2013. Growth and

shoot winter injury of American chestnut seedlings grown in common garden at the species’ northern range limit. In: Miller et al. eds. Gen. Tech. Rep. NRS-P-117. USDA Forest Service,

Northern Research Station Pp 72-79.

- Saielli, T.M.; Schaberg, P.G.; Hawley, G.J.; Halman, J.M.; Gurney, K.M. In review. Genetics and silvicultural treatment influence the growth and shoot winter injury of American and Chinese chestnut seedlings grown in Vermont, USA. Submitted to Forest Science.

Products continued • MS Thesis – Saielli, T.M. 2011. Cold as a possible limitation for the restoration of

American chestnut. Burlington, VT: University of Vermont. 108p. M.S. Thesis.

Portions of this thesis were published in the Canadian Journal of Forest Research.

• Non-peer-reviewed article

- Gurney, K.M.; Schaberg, P.G. 2010. Life in the cold – another challenge to American chestnut restoration? Journal of the American Chestnut Foundation, 24(3): 12-14.

Products continued • Presentations at meetings (14 total)

- Gurney, K. M., P.G. Schaberg, G.J. Hawley. 2009. Limited cold tolerance could complicate

the restoration of American chestnut to the northeastern United States. (Poster) In

Proceedings of the Ecological Society of America’s 94th Annual Meeting, Albuquerque,

NM, August 6, p165.

- Gurney, K. M., P.G. Schaberg, G.J. Hawley 2009. Cold tolerance as a possible limitation to

American chestnut restoration in the northeastern United States. In Proceedings of the

International Society of Aboriculture’s 85th Annual Conference and Tradeshow,

Providence, RI, July 26. DVD/Educational Sessions/Poster Presenters/Kendra

Gurney/Poster5.

- Gurney, K.M., P.G. Schaberg, G.J. Hawley. 2010. Limited cold tolerance could hinder the

restoration of American chestnut to cold climates. Poster and short oral presentation by

Gurney at the Winter Meeting of the New England Chapter of the Society of American

Foresters, Nashua, NH, March 10.

- Saielli, T., P.G. Schaberg, G.J. Hawley, K.M. Gurney. 2010. Preliminary Research to

Restore American Chestnut to the Northern Hardwood Forest. NE-1033 Multistate

American Chestnut Project Annual Meeting, Chattahoochee Ranch, North Carolina,

October 1.

Products continued • Presentations at meetings

- Schaberg, P.G., T.M. Saielli, G.J. Hawley, J.M. Halman, and K.M. Gurney. 2011. Nut cold

hardiness as a factor influencing the restoration of American chestnut in the northeastern

United States. ESA Annual Meeting, Austin, Texas, August 11. p.126.

- Saielli, T.M., P.G. Schaberg, G.J. Hawley, J.M. Halman, and K.M. Gurney. 2011. Genetics

and silvicultural treatment influence the growth and winter shoot dieback of American

and Chinese chestnut seedlings grown in Vermont, USA. ESA Annual Meeting, Austin,

Texas, August 11. p.137. (Abstract)

- Saielli, T., P.G. Schaberg, G.J. Hawley, J.M. Halman, K.M. Gurney. 2011. Cold as a

possible limitation for the restoration of American chestnut. The 4th Annual Disease and

Insect Resistance in Forest Trees Conference, Valley River Inn, Eugene, OR. (Oral

presentation and poster).

- Saielli, T.M.; Schaberg, P.G.; Hawley, G.J.; Halman, J.M.; Gurney, K.M. 2011. Could

freezing injury threaten American chestnut restoration in the north? Proceedings of the

Annual Meeting of the Vermont Monitoring Cooperative, Burlington, VT, October 31,

p23 (Abstract).

- Saielli, T.M.; Schaberg, P.G.; Hawley, G.J.; Halman, J.M.; Gurney, K.M. 2011. Does

freezing injury threaten American chestnut restoration in the Northern New England?

Northern New England Forests Symposium, The University of Vermont, Burlington, VT.

December 16, 2011. p. 23 (Abstract).

Products continued • Presentations at meetings

- Schaberg, P.G.; Saielli, T.M.; Hawley G.J.; Halman, J.M.; Gurney, K.M. 2012. Winter injury

of American chestnut seedlings grown in a common garden at the species’ northern range

limit. Proceedings of the 18th Central Hardwood Forest Conference, West Virginia

University, Morgantown, WV. March 27, 2012. p. 30 (Abstract).

- Schaberg, P.G. 2012. Update on the American chestnut progeny test at the Green Mountain

National Forest in Leicester, Vermont. The American Chestnut Foundation 2012 New

England Chapters Meeting, Beaver Brook Association, Hollis, NH, September 15, 2012.

- Schaberg, P.G.; Saielli, T.M.; Gurney, K.M.; Hawley G.J.; Halman, J.M.; Murakami, P.F.

2012. Exploring the fit between genes and the environment relative to American chestnut

restoration. Oral presentation at the 2012 American Chestnut Summit, Asheville, NC.

October 20, 2012.

- Schaberg, P.G.; Murakami, P.F.; Gurney, K.M.; Saielli, T.M.; Hawley G.J.; Halman, J.M.;

Fitzsimmons, S.F. 2012. Exploring how genetics and silvicultural management influence

the performance of American chestnut in the north. Poster presentation at the 2012

American Chestnut Summit, Asheville, NC. October 20, 2012.

- Schaberg, P.G.; Saielli, T.M.; Hawley G.J.; Halman, J.M.; Gurney, K.M. 2012. Growth versus

protection from the cold: a tradeoff for American chestnut grown at the species’ northern

range limit? Eastern CANUSA Forest Science Conference, The University of New

Hampshire, Durham, NH, November 3, 2012.

Acknowledgements

This research was conducted with the help and cooperation of volunteers and staff with The American Chestnut Foundation, the US Forest Service Northern Research Station, the Green Mountain National Forest, the Student Conservation Association, and the University of Vermont.

Acknowledgements

This research was supported by in part by funds provided by the Northeastern States Research Cooperative, the USDA CSREES McIntire-Stennis Forest Research Program and the Forest Service, U.S. Department of Agriculture.