0416-B1
Judy A. Loo, Tannis[1] L. Beardmore, J. Dale Simpson and Donnie McPhee
In 1997, the Gene Conservation Working Group came together in New Brunswick, Canada to begin developing gene conservation strategies for forest tree and shrub species of concern. The process that emerged over a period of time is presented as a model that could be applied in any jurisdiction. The working group consists of industrial, private woodlot, academic and provincial and federal government representatives, each with a vested interest in sustainable management of forest ecosystems.
The model that was developed and followed by the working group has several steps. First, a set of criteria was agreed upon. Each native tree and shrub species was tested using these criteria to determine whether gene conservation measures were required. Second, a rating system was applied to define the level of attention needed for each of the species meeting one or more of the criteria. Third, a project was undertaken to find and review all sources of relevant information about each of the identified species and a research programme was initiated to address knowledge gaps. Fourth, a field guide was developed to involve volunteers and to assist them in identifying each of the targeted species. The field guide is being distributed to people most likely to encounter the species, such as foresters, biologists and naturalists. Gene conservation strategies have been developed for several tree species: butternut (Juglans cinnerea), bur oak (Quercus macrocarpa), white elm (Ulmus americana), and beech (Fagus grandifolia) and members of the Gene Conservation Working Group are responsible for implementing these strategies within their respective realms of activity.
The province of New Brunswick (NB), on the east coast of Canada, is forested over approximately 85% of its land base. New Brunswick falls within the Acadian Forest Region, characterized by tolerant mixedwood, in a transition zone where hardwood forests to the south meet the predominantly softwood northern forests. Almost all tree species native to NB have naturally high levels of genetic variability. Less is known about the genetic variability of shrub species. All native tree species must interbreed with trees that are not closely related to produce healthy offspring. If the gene pool becomes too small, the species may become locally endangered.
Forest species and ecosystems in NB have been confronted by various threats during the past three centuries. Human activities continue to change the forest environment at an accelerating rate, probably more rapidly than species are able to adapt. Conservation of genetic variability is increasingly important as environmental uncertainty increases, principally as a result of the greenhouse effect and exotic species invasions.
Forests in NB have a 300-year history of exploitation for timber and pulp. Areas of the province having rich soil were converted to agriculture; some of these areas have since reverted to forest, but usually not to the original species. Forest harvest practices have changed over the years from pure exploitation to a planned sustained-yield approach, but even so the forests of NB have changed substantially. Certain species were favored for harvest at particular times and, as a result of harvest and other factors, some species have almost disappeared from NB forests.
A gene conservation strategy is an action plan that seeks to ensure that genetic variability is preserved and that naturally high genetic variability is retained. It is not an effort to keep all the genes or all the genetic variants in a species or a population. A gene conservation strategy for a commercial species is usually designed to ensure that the genetic variability is maintained at a level that allows for continued selection for a particular trait, and to ensure that the potential to breed for a new trait if necessary, is maintained. The primary goal of a gene conservation strategy for a species having a more ecological than commercial importance is to ensure that the evolutionary potential of the species is retained. In other words, a gene conservation strategy will seek to maintain sufficient genetic variability to allow adaptation to new environmental conditions.
The objective of the work reported here was to identify species of trees and shrubs in NB that require conservation measures to maintain their genetic viability and to develop gene conservation strategies that are likely to be adopted by forest managers.
In 1997, a group of forest practitioners and researchers in NB was brought together to begin working on gene conservation. An effort was made to include not only the most knowledgeable people for identifying species of concern, but also people who would ultimately be responsible for implementing the strategies. Toward that end, naturalists from the New Brunswick Museum of Nature, scientists from the University of New Brunswick, specialists from the provincial and federal government natural resource departments, and representatives from woodlot owner associations and the forest industry were invited to participate in a series of meetings to develop gene conservation strategies. The group became known as the New Brunswick Gene Conservation Working Group (NBGCWG).
The process of developing and initiating gene conservation strategies included several steps: identifying which species require attention, assigning priorities to those species, compiling all available information about the present status of species of concern, identifying and initiating required research, publishing a field guide for volunteers, and, finally, writing strategies for species for which sufficient information is available.
Identifying species and assigning priorities
The species identified are not only those that may be threatened with local extinction or extirpation but also include those that have experienced the loss of a significant number of populations, or that are believed to have dramatically declined in NB over the past 300 years.
Eight criteria, listed below, were used to judge whether a species requires conservation attention.
1 - Is the species naturally rare in the area?
2 - Is there no or an uncertain viable seed source?
3 - Is there a serious threat from disease or insect pest or from changes in environmental quality?
4 - Is the range or frequency of the species substantially decreasing?
5 - Is the preferred habitat of the species in high demand for other uses?
6 - Do certain harvesting practices prevent the regeneration of the species?
7 - Is there high demand for the species for a special purpose?
8 - Is there a threat of loss of the species due to hybridization and introgression?
An expert opinion process was used to assign criteria. All tree and shrub species native to the province were listed and the NBGCWG discussed, during the course of several open meetings, whether any of the criteria applied to the each species. In some cases, a criterion assigned to a species was considered provisional until specific information could be obtained. When all species were evaluated for conservation criteria, priorities were assigned using the same expert opinion process.
The priority rating system was as follows, to identify the type of action required for each species:
0 - species does not need attention
1 - information is inadequate to judge
2 - species requires attention at the level of forestry practices
3 - species requires a gene conservation strategy
Compiling available information and identifying gaps
A project was initiated to compile all available information about the status of species having rating categories of 1 or 3. Sources of information were broad, including data held by provincial and federal departments, the New Brunswick Nature Trust, the Atlantic Canada Conservation Data Centre, and herbaria. All known locations from all sources were plotted for each indicated species, providing estimates of relative frequency in the province. Documented evidence of threats to each of the species was compiled, as well as descriptions of habitat requirements, ecology, and history. Criteria and rating assignments were reviewed after evaluating the compiled information and knowledge gaps were identified. Research projects were initiated for several species to determine regeneration potential, condition of populations with respect to dieback, procedures for seed storage, and genetic diversity of natural populations to assist in development of strategies.
The primary focus in provincial and federal government surveys and sample plots is on commercially important species. Data collected by herbaria and from ecologically significant areas include all species of interest, but provide an incomplete coverage of the province. Thus, knowledge is incomplete for several species, even after evaluating all the compiled data. Researchers at the Canadian Forest Service who are interested in developing gene conservation strategies have limited time and resources to conduct surveys, so a project was initiated to develop an identification guide for those species for which current knowledge is insufficient, and to distribute it to people who spend time in the forest. Target recipients of the guide include technicians working for woodlot owner associations, provincial government and industry, regional nature clubs, and any other interested individuals. Addressed forms are included in the guide with encouragement to report information about any occurrences of the indicated species.
Four tree species (butternut (Juglans cinerea), bur oak (Quercus macrocarpa), white elm (Ulmus Americana), and American beech (Fagus grandifolia)) were identified as requiring specific gene conservation strategies. The first two species have declined both in numbers and area of distribution since the arrival of European settlers and recently butternut has declined as a result of a fatal, apparently, introduced disease. Elm and beech are still relatively common, but most are diseased, infected by fungal organisms that were inadvertently introduced from Europe many decades ago. For species threatened by disease, gene conservation measures focus on maintaining as much diversity as possible within the portion of the gene pool that exhibits resistance to the disease.
Butternut
Butternut is native and common in the upper Saint John River and upper SW Miramichi River Valleys (Hinds 1986) and occasional to common on alluvial soils in the Saint John River Valley near Fredericton.
The most serious threat to butternut is the butternut canker caused by the fungus Sirococcus clavigignenti juglandacearum (Renlund 1971). Butternut canker infects all sizes and age classes of trees on all sites and can occur through buds, leaf scars, and various wounds (Ostry 1995). To date, there is no control for the canker. In Canada, the first report of the canker was in Quebec in 1990 (Innes and Rainville 1996), then in Ontario in 1991 (Davis et al. 1992), and in NB in 1997 (Harrison et al. 1998). Overall, butternut mortality as a result of the canker exceeds 77% in American forests (Ostry et al. 1994), but in Canada, mortality has been estimated in Ontario to be 80% (Fleguel 1996).
Strategy: Knowledge at this time is insufficient to develop a full strategy. The following steps must first be taken:
survey NB populations and assess presence of the canker and its contribution to mortality of NB butternut trees,
develop an education program for identification of butternut trees, the canker, and putatively resistant trees, and
control the movement of seed (canker spores can be present in seed).
Bur oak
Bur oak is also found in the St. John River Valley, primarily around the Grand Lake complex in central NB. It occurs on flood plains, usually very close to the water’s edge. Its range and frequency has decreased substantially and its preferred habitat remains in high demand for other uses. Only eight small stands (40 to 500 trees) remain in the province, in addition to the occasional isolated tree (McPhee 2001). One small population is currently protected and another is under negotiation. All other populations are threatened by cottage development or harvesting.
Strategy: All populations are on private land, so the gene conservation strategy focuses on private landowners as follows:
continue education efforts that include distributing a field guide to help landowners and naturalist groups recognize and conserve bur oak,
ensure landowners know about conservation options and encourage them to choose a conservation option,
collect seed for restoration planting and encourage local nurseries, town landscapers, and others to use it, and
monitor the status of remaining populations.
White elm
White elm trees are found throughout NB, primarily adjacent to rivers and water courses, where soils are rich and moist. They are generally not found in the uplands regions of the province. The species is threatened by Dutch elm disease (DED) throughout the province. Dutch elm disease is caused by a fungus, Ceratocystis ulmi (Buism.) C. Moreau, which is introduced into a tree by the native elm bark beetle (Hylurgopinus rufipes (Eichh.)). The disease was first reported in New Brunswick in 1957. No efficient, effective control other than sanitation has been found. The occurrence of large, healthy older elms in the wild indicates the possibility that some sort of mechanism exists in these trees to either prevent or tolerate infections.
Strategy: Due to the nature of the insect/disease interaction, the gene conservation strategy focuses on ex situ measures, as follows:
survey the province where elm occurs to locate putatively resistant live, healthy, uninfected trees greater than 65 cm,
collect cuttings in the winter and graft onto white elm rootstock,
test grafted material for resistance and deploy into a combination gene bank and seed orchard to produce seed, and
provide seed to private horticultural nurseries, where seedlings will be marketed to the public.
American beech
American beech is widely distributed throughout the province, except for a small area in the extreme northeast of the province. The species occurs wherever tolerant hardwood conditions are found.
The main threat to American beech is beech bark disease, which was introduced more than 100 years ago through Halifax (Shigo 1972). Cryptococcus fagisuga is a scale insect that renders the tree susceptible to a beech bark fungus, Nectria coccinea var. faginata (Houston et al. 1979). Most of the beech in the southern two-thirds of the province is diseased. Many tolerant hardwood stands with a beech component contain some disease-free individuals, but there is no policy regarding conservation of these individuals. Stands with a substantial beech component are commonly clearcut and converted to other species because of the low value of diseased wood. Disease-free trees are harvested along with the diseased ones.
Strategy: A combination of in situ and ex situ methods are required for beech as follows:
apply best management practices in forestry operations, including removal of diseased trees but leaving putatively resistant ones,
assess putatively resistant trees for genetic resistance, determine resistance mechanism and gene action,
develop vegetative propagation techniques for disease-resistant beech, and
establish a grafted seed orchard of resistant trees.
The process initiated by NBGCWG with its goal to develop and implement gene conservation strategies for forest tree and shrub species of concern, can be used as a model for other jurisdictions. The conservation strategies are a first step, providing focus to current and future conservation requirements. Implementation of strategies requires concerted effort of numerous groups, consisting of industrial, private woodlot, academic, and provincial and federal government representatives. It is assumed that that the list of species requiring conservation efforts will change over time, with various species removed or added to the list. The success of this group depends on the active participation of all members with a vested interest in sustainable management of forest ecosystems.
Davis, C.N., D.T. Myren and E.J. Czerwinski, 1992. First report of butternut canker in Ontario. Plant Dis. 76: 972
Fleguel, V.R., 1996. A literature review of butternut and the butternut canker. Eastern Ontario Model Forest Information Report 20
Harrison, K.J., J.E. Hurley and M.E. Ostry, 1998. First report of butternut canker caused by Sirococcus clavigignenti-juglandacearum in New Brunswick, Canada. Plant Dis. 82: 1282
Hinds, R.H., 1986. Flora of New Brunswick. Primrose Press, New Brunswick 460 p. + maps and illust.
Houston, D.R., E.J. Parker and D. Lonsdale, 1979. Beech bark disease: patterns of spread and development of the initiating agent Cryptococcus fagisuga. Can. J. For. Res. 9: 336-344
Innes, L. and A. Rainville, 1996. Distribution and detection of Sirococcus clavigignenti-juglandacearum in Quebec. Phytoprotection 77: 75-78
McPhee, D.A., 2001. Status Description for Bur Oak, Quercus macrocarpa, in the Province of New Brunswick., MSc For. Thesis, University of New Brunswick
Ostry, M.E., M.E. Mielke and D.D. Skilling, 1994. Butternut strategies for managing a threatened tree. USDA Forest Service General Technical Report NC-165 7 p
Ostry, M.E., 1995. Conservation of Butternut in the Eastern Forests. In: Proceedings Forest Gene Conservation Principles to Practice¾Workshop. Ottawa, ON
Renlund, D.W., 1971. Forest pest conditions in Wisconsin. Wisconsin Dept. Natl. Res. Ann. Rep. 1-53
Shigo, A.L., 1972. The beech bark disease today in the northeastern United States. J. For. 70(5): 286-289
The authors wish to thank Dr. Nadine Ives, Mr. Peter Salonius and Mr. Ed Hurley, and Mr. Ken Harrision for their comments and review of the butternut strategy, and Mrs. C. Simpson for her review of this paper. Also Dr. Michael Dumas, a research scientist at Natural Resources Canada, Canadian Forest Service, GLFC; Mr. Ken Harrison, Biologist with Natural Resources Canada, Canadian Forest Service - Atlantic Forestry Centre; and Mr. Henry Kock, Interpretive Horticulturist at the Arboretum, University of Guelph, ON provided assistance with the American elm strategy.
| [1] Natural Resources Canada,
Canadian Forest Service - Atlantic Forestry Centre, P.O. Box 4000, Fredericton,
New Brunswick, E3B 5P7 Canada. Tel: 506-452-3500; Email: [email protected] |