Fire history and secondary vegetation succession in the forest-tundra near Churchill, Manitoba
Monson, Kimberly M. M.
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Concerns about increasing CO2, in the global atmosphere and how this may affect climatic patterns and ultimately the structure, composition and distribution of the northern boreal forest prompted an examination of secondary succession in a segment of forest-tundra south of Churchill, Manitoba. Fire is the main disturbance in the boreal forest and climate change is expected to have an impact on the frequency of fire and the area burned in these forests. By reconstructing the fire history of these forests, we can evaluate the potential effects a change in fire activity will have upon this landscape. In addition to our lack of knowledge on fire in the forest-tundra of Manitoba, little is also known about the response of the vegetation and forest stand dynamics following fire. The fire history of the Churchill, Manitoba forest-tundra was reconstructed following the determination of the time-since-last-fire (TSLF) dates from 119 locations using dendroecological methods. The dates were used to create a TSLF map. A bootstrapping procedure was used prior to the fire frequency analysis. The point data used for the bootstrap analysis was coded by forest type (black spruce, white spruce and eastern larch). Area data from the TSLF map and frequency data from the bootstrap analysis were converted into 25-year age classes and used to produce reverse cumulative area/frequency distributions to assess possible changes in the fire-cycle. The fire-cycle for homogenous fire periods was calculated using 1) natural fire rotation (area data) and 2) fire frequency analysis fitted to an negative exponential model (area and frequency data). All forest groupings showed a change in the fire-cycle in the AD 1700's to a longer fire-cycle. Using the natural fire rotation (NFR) the fire-cycle has changed from 345 years to 558 years at AD 1725...