Conservation of Hemlock Species in the Eastern United States

INTRODUCTION

Figure 1: Carolina hemlocks at Mount Jefferson State Natural Area, North Carolina.

There are a number of factors that threaten the long-term stability of hemlock ecosystems in the eastern United States including exotic insects, severe drought, widespread wildfire, suburban development, and climate change.  Among these, the Hemlock Woolly Adelgid (HWA, Adelges tsugae) is of the most concern and threatens to eliminate both Eastern (Tsuga canadensis) and Carolina (T. caroliniana) hemlocks from their native range.  The adelgid is an exotic insect that was introduced from Japan to the eastern US sometime between 1920 and 1950.  It was initially considered simply an annoying ornamental pest easily controlled with pesticides, but lackadaisical management approaches allowed HWA to spread.  It is currently found in 17 eastern states from Maine south to Georgia where it infests approximately 50% of hemlock ecosystems.  HWA can kill trees in as little as four years and has caused widespread mortality of both hemlock species. 

In 2003, Camcore entered into a cooperative agreement with the USDA forest Service to conduct a 3-phase project on germplasm conservation for Eastern and Carolina hemlock.  This ex situ conservation effort includes seed banking at Camcore facilities (Raleigh, NC) and within the USDA’s National Plant Germplasm System (Fort Collins, CO), and the establishment of conservation reserves (seed orchards) in regions of the world suitable for growing hemlock but where HWA does not occur.  The overall goal of the project is to preserve hemlock gene pools in perpetuity until a time when effective HWA management strategies are in place and conserved seed resources can be utilized to repopulate depleted hemlock ecosystems.  Should adelgid control remain elusive, the seed banks and conservation reserves will serve as a genetic base for breeding HWA resistant stock for reforestation.  Phases 1 (Carolina hemlock) and 2 (Eastern hemlock) are focused on seed collections from hemlock populations distributed throughout the southeastern US and are ongoing.  Phase 3 will sample seeds from populations of Eastern hemlock in the northeastern and Midwestern regions of the country and is scheduled to begin in 2009.

PROGRESS ON SEED COLLECTIONS

Carolina Hemlock: Since 2003, Camcore has explored 22 Carolina hemlock populations distributed across the species’ range (Figure 2).  Due to its rarity and small geographic range, our conservation goal for this species is to sample 10 trees per population in as many populations as we can locate.  As of 2007 we have collected seed from 13 provenances yielding a total of 84 mother trees that are represented in the hemlock seed bank at NC State University.  Collections at three sites in North Carolina (Linville Falls, Carolina Hemlocks Campground, and Wildcat) provided the full complement of 10 mother trees sampled.  The Tallulah Gorge collectionon Georgia is also complete since this sample contains three of the four known trees at this site.  Despite yearly evaluations at 9 sites where we have made partial seed collections and 9 others where we have yet to collect from we have been unable to locate the cone bearing trees necessary to complete the sampling.  We surmise this could be due to a number of factors including, but not limited to, variation in cone production cycles, lack of adequate sunlight exposure, recent severe droughts in the southeastern United States, HWA infestations, or some combination of all of these factors.  We will continue annual evaluations of seed production at all sites and continue to work towards our goal of securing seed from all current and future Carolina hemlock sites identified. 

Figure 2: Carolina hemlock sites collected and explored from 2003 to 2008.

Eastern Hemlock: Since 2005, Camcore has explored 57 Eastern hemlock provenances across the southeastern US (Figure 3).  Seed collections were made in 18 of these yielding a total of 110 mother trees currently represented in the Camcore seed bank.  This is a little more than one-sixth our conservation goal of 600 mother trees (60 populations, 10 trees per population) for this species.  However, similar to our experience with Carolina hemlock, most Eastern hemlock populations have yielded small amounts of seed or no seed at all during collection efforts.  Again, we feel this could be due to a number of factors including within-population cone-cycle variation, lack of exposure to sunlight, severe drought, and adelgid infestation.  Recently, severe drought has loosened its grip across the southeastern US and site explorations during the summer of 2008 found that many populations of Eastern hemlock that have not yet suffered severe HWA infestation are producing decent cone crops following a wet spring.  We look forward to a successful seed collection season in the fall of 2008.    

Figure 3: Eastern hemlock sites collected and explored from 2005 to 2008

PROGRESS ON CONSERVATION RESERVE ESTABLISHMENT

Figure 4: Jaime Zapata from Bioforest-Arauco holds a healthy Carolina hemlock seedling in Chile.

FloraMap™: Using monthly average temperature, monthly diurnal temperature, and average monthly precipitation from natural hemlock populations, the FloraMap™ climatic model program predicted regions of the world where hemlock conservation banks can be planted with a high probability of survival (> 90%).  Based on these analyses, Camcore has targeted the Piedmont and coastal ranges of southern-central Chile, isolated regions of southern Brazil, and the Ozark Mountains in Arkansas for hemlock ex situ conservation plantings.  We have identified Camcore members in Chile and Brazil and cooperators in Arkansas who are willing to assist Camcore and the USDA Forest Service with our conservation efforts in the regions indicated by FloraMap™.

Carolina Hemlock: Camcore currently has Carolina hemlock seedlings growing at forest nurseries in Chile, Brazil, and at the University of Arkansas.  In Chile, Camcore cooperative member Bioforest-Arauco is coordinating the nursery production, field establishment, and subsequent management of the trees for seed production.  Initially, this planting will represent all Carolina hemlock populations (64 families total) collected in 2003 but will be expanded in the future to include all populations sampled.  Seedlings will be established on a plantation site at Predio Cullimpalihue as 3-0 stock in September 2008.

	In Brazil, Camcore members Klabin SA and Rigesa-MeadWestvaco are coordinating seedling production, establishment, and management.  At their Tres Barras nursery facility, Rigesa is growing seedlings for all Carolina hemlock populations collected as of 2006.  Rigesa will grow the seedlings up to 3-0 stock plants, at which time half of the seedlings will be given to Klabin.  Both companies will establish ex situ conservation banks on plantation sites in Santa Catarina State in 2010.
Figure 5: Mature Carolina hemlock cones are picked, dried, cleaned, and packaged for either placement in seed banks or shipped for ex situ establishment.
Dr. Brad Murphy in the Department of Horticulture at the University of Arkansas (Fayetteville) is growing Carolina hemlock seedlings for the Ozarks-based ex situ conservation plantings.  He has recently germinated seedlings for all populations collected through 2006 and should have 3-0 seedlings available for planting by early 2011.  These seedlings will be established and managed by the USDA Forest Service at seed orchard sites on the Ozark and Ouachita National Forests.

 

Eastern Hemlock: Rigesa-MeadWestvaco and Dr. Murphy have agreed to also coordinate ex situ conservation of Eastern hemlock in Brazil and Arkansas, respectively.  Rigesa received seed for all Eastern hemlock provenances and families collected in 2005 and 2006 with its Carolina hemlock seed shipment.  Seedlings have been germinated and should be ready for field establishment in 2010.  Dr. Murphy will receive Eastern hemlock seeds from all 2005, 2006, and 2007 collections in 2008.  As with Carolina hemlock, the USDA Forest Service will coordinate the establishment and management of Eastern hemlocks in Arkansas.  Camcore member CMPC Forestal Mininco has agreed to coordinate the ex situ conservation of Eastern hemlock in Chile.  They will receive their first seed shipments in 2008 and coordinate the nursery production of seedlings at their Centro Experimental Escuadrón quarantine facility. 

OTHER HEMLOCK INITIATIVES AT CAMCORE

In addition to our germplasm conservation work we are also involved in the following hemlock related projects:

1. Genetic diversity in natural populations and seed collections of Carolina hemlock using AFLP molecular markers. 2. Allozyme variation and evolutionary history of Eastern hemlock in the southeastern US. (2008 Camcore Publication on Eastern hemlock Genetic Diversity.) 3. Allozyme variation and evolutionary history of Eastern hemlock in the northeastern, Midwestern, and outlying portions of the species’ geographic range. 4. Genetic diversity in natural populations of Eastern hemlock across the species’ entire geographic range using microsatellite molecular markers.

Figure 6: Camcore Technical Director Juan Lopez stands in front of a nearly dead Eastern hemlock at Stone Mountain State Park, North Carolina.

5. Evaluation of optimal storage, pre-germination, and stratification treatments for hemlock seeds.     6. Analysis of soil conditions in natural stands of Eastern and Carolina hemlock. 7. Variation in susceptibility to infestation by the Hemlock Woolly Adelgid among populations of Carolina hemlock.  8. We also participate as a founding member of the Partnership for Saving Threatened Forests.

HEMLOCK CONSERVATION CONTACTS

If you would like more information about Camcore’s hemlock conservation program or would like to contribute to our effort please feel free to contact one of the following individuals:

Figure 7: Research Forester Andy Whittier and Project Leader Robert Jetton inspecting Eastern hemlock foliage.

Robert Jetton, Research Associate and Hemlock Conservation Project Leader

Phone: 919.515.6425
Email: robert_jetton@ncsu.edu

Andy Whittier, Hemlock Conservation
Research Forester

Phone: 919.513.4878
Email: wawhitti@ncsu.edu

Bill Dvorak, Director of Camcore
and Professor of Forestry &
Environmental Resources

Phone: 919.515.6424
Email: bill_dvorak@ncsu.edu

 

REFERENCES

The information presented above came from the following resources:

Camcore. 2005. Camcore 2006 Annual Report. NC State University, Raleigh, NC. 40 p.

Camcore. 2006. Camcore 2006 Annual Report. NC State University, Raleigh, NC. 34 p.

Camcore. 2007. Camcore 2006 Annual Report. NC State University, Raleigh, NC. 50 p.

Cheah, C., M.E. Montgomery, S. Salom, B.L. Parker, S. Costa, and M. Skinner. 2004. Biological control of hemlock woolly adelgid. USDA Forest Service. FHTET-2004-04. Morgantown, WV. 22 p.

Jetton, R.M., W.S. Dvorak, and W.A. Whittier. 2008. Ecological and genetic factors that define the natural distribution of Carolina hemlock in the southeastern United States and their role in ex situ conservation. Forest Ecology and Management 255: 3212-3221.

Jetton, R.M., W.A. Whittier, W.S. Dvorak, and K.M. Potter. 2008. Status of Ex situ Conservation Efforts for Eastern and Carolina Hemlock in the Southeastern United States. In: Proceedings of the Fourth Hemlock Woolly Adelgid Symposium. In Press.

McClure, M.S., S.M. Salom, and K.S. Shields. 2001. Hemlock woolly adelgid.USDA Forest Service. FHTET-2001-03. Morgantown, WV. 14 p.

Tighe, M.E., W.S. Dvorak, W.A. Whittier, J.L. Romero, and J.R. Rhea. 2005. The ex situ conservation of Carolina hemlock. pp. 180-190. In: B. Onken and R. Reardon (Eds.), Third Symposium on Hemlock Woolly Adelgid in the Eastern United States. USDA Forest Service. FHTET-2005-01. Morgantown, WV.

 

For addtional Information on HWA please visit the US Forest Service HWA Webpage