The Status of Bur Oak (Quercus macrocarpa) in New Brunswick

D.A. McPhee, J. Loo
Atlantic Forestry Centre - Canadian Forest Service

Introduction

The history of human intervention and its effect on the present-day forests of New Brunswick started approximately 11,000 years ago with the Mi'kmaq and Maliseet entering the maritime region from the south and southwest. European settlements were established in 1604, and the resulting timber harvest grew steadily but slowly until 1805. At this time Great Britain offered massive protection to colonial timber on the British market. Explosive population growth followed this development C from 20,000 to 150,000 people in just 40 years. As a result, much of the prime land along the St. John River valley where bur oak once grew was cleared for farming or heavily logged for timber.

Bur oak in NB

Bur oak is a member of the white oak group. Its contiguous native range extends from south-central Quebec and west to central Manitoba, then funnels down into Texas, with isolated populations located in the New England states and in the province of NB. The bur oak in NB are separated from the fringe of the species's present continuous range by approximately 750 km, and are approximately 220 km from the next nearest population. Recently published species range maps imply that it is found along the lower St. John River valley, stretching from Perth Andover to the city of Saint. John, and along Grand Lake and its flood plains. The forests of this region are influenced by the warm climate, and peppered with species of southern affinities that are not common to the rest of NB.

Assessing Present Status

Lack of recent observations of the species in some areas indicates a possible reduction in the range of bur oak in NB. This is cause for concern, as these populations may be important sources of genetic material, giving the species an adaptive advantage through long-term climate changes and species range shifts. In view of this, an intensive survey of bur oak was conducted. The objective was to accurately illustrate the current species range and the number and location of bur oak stands that remain in NB, to determine if a conservation effort is warranted for the species

Survey methods

In 1996-97, a survey was conducted throughout the St. John River valley and Grand Lake Basin

Ecoregion in three stages. The first consisted of an intensive literature review. In the second stage, evidence of recent occurrences, either documented or anecdotal, was collected. The final stage consisted of a thorough ground search throughout the potential species range. All stands were documented, as well as isolated individuals. Stands were described in terms of age, associated species, and presence and condition of bur oak regeneration.

Results

Excluding individual trees or isolated clumps of small numbers of trees, there are eight stands of bur oak in NB. Of these, only one stand has more than 500 trees. Where stands do occur, most are small and threatened by development. Bur oak still exists around Grand Lake and in one location on Belleisle Bay. In addition, it can still be found in the Jemseg and Cambridge Narrows area. A few trees can be found in Keswick Ridge, and there are a few other isolated examples. All of the NB populations occur on flood plains or riverbanks.

Discussion

The survey for bur oak throughout the St. John River valley and Grand Lake Region indicates that the current species range has been reduced to a combined area of less than 5 km2, of which only 0.024 km2 is protected. With no historical environmental, insect or disease cause for decline, human intervention is the primary suspect for the decline of bur oak in NB. The history of the St. John River valley includes over 200 years of intense agriculture and logging along the river, lakeshores, and flood plain. With the exception of the most poorly drained areas, much of the region has been cleared at one time or another. Dam construction for hydroelectricity at both Mactaquac (1968) and Beechwood (1957) have permanently flooded sections of the St. John Rivers= natural flood plain. Human demands on suitable habitat for bur oak and other flood plain species continues. Of the eight identified stands that currently support bur oak, and their associated communities, three are currently threatened due to development. Due to the human-based pressures for waterfront cottages and with the aid of landfill, road construction and drainage, these once remote and inaccessible sites are now in demand as prime real estate. There is cause for concern regarding the future of bur oak in the province, given that the reduction in the stands is ongoing.