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An ecological and land use study of Burns bog, Delta, British Columbia Biggs, Wayne Griffin

Abstract

Burns bog is a large sphagnum peat bog occupying approximately 4,000 ha of the Fraser River delta in south-western British Columbia. The area has been extensively disturbed by peat extraction, landfilling and other land-uses. Much of the bog remains in a natural or semi-natural state. As such it represents one of the largest single tracts of underdeveloped land in the Corporation of Delta. Land development and growth in the municipality has been rapid in the past ten years. Because the Burns bog area was not well known and the pressures for development of the area were mounting, this study was initiated in January 1975. Available existing environmental and land-use information pertaining to the Burns bog area was reviewed and collated. Basic vegetation and wildlife inventories were carried out in the area, and a cover map of extant vegetation was prepared. Several aspects of peatland ecology were investigated. These included the determination of the rate of spagnum peat accumulation, an estimate of the energy (caloric content) of the peat stored with Burns bog, and net primary productivity. The bog was found to be floristically interesting and to be quite unlike most of the remaining underdeveloped areas of the Fraser River lowland. Because of its large size, waterlogged character, and location between the Fraser River, Boundary Bay and the foreshore areas of Roberts and Sturgeon banks, Burns bog is believed to be an important natural refuge for many species of birds. The area is an important loafing area for waterfowl, particularly mallard, pintail, and teal, and is a nesting area for a number of raptorial , passerine and other birds. Perhaps one of the more important birds of Burns bog is the greater sandhill crane, which nests in the bog in small numbers. Burns bog supports a number of mammal species. In addition to a variety of "common" small mammals, the area supports a small number of black bear, and Columbian black-tailed deer which are believed to be isolated populations. The land-use patterns of lands surrounding the bog area are believed to be of key importance to bird and mammal life in the area. For example many species of birds (ducks, raptors and sandhill cranes) and mammals (Columbian black-tailed deer and eastern cottontail rabbit) feed at the interface between the forested sections of the bog and the neighbouring agricultural lands. The agricultural character of these peripheral lands appears to influence use of the bog by various wildlife species. The peat samples analysed were found to be high in nitrogen and minerals, although these nutrients were not believed to be available for plant utilization. The volume of peat in the bog was crudely estimated to be 108.8 hm3 . The dry weight of this material was estimated to be 3,949,440 metric tons, and the caloric content of this material was found to be approximately 20,023.76 G. cal. This figure is believed to be the approximate amount of energy stored as peat in the bog. The sphagnum peat accumulation rate and net primary productivity appeared to be considerably higher at hummock sites as compared to wet depressional areas. The average rate of accumulation of ten samples (six hummock and four -wet depression sites) was found to be .43 cm/yr, while the average net primary productivity was 128.8 g/m2 /yr. The vegetation and wildlife of the bog are largely determined by the land-use practices surrounding and within the bog. For example, "improving" the drainage of the area for the agricultural reclamation of the peatland, or for other purposes will probably result in the rapid decomposition and subsidence of the drained peat. The increased availability of nutrients, and drier conditions will consequently alter the vegetation and wildlife species distribution in the bog.

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