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Succession after Slashburning in an Engelmann Spruce-Subalpine Fir Subzone Variant: West Twin Site

Author(s) or contact(s): E.H. Hamilton and L.D. Peterson
Source: Research Branch
Subject: Vegetation Management
Series: Technical Report
Other details:  Published 2006. Hardcopy is available.
 

Abstract

This study was undertaken to determine the successional development after a slashburn of known severity on an Engelmann Spruce-Subalpine Fir (ESSF) biogeoclimatic zone site. Herbaceous and shrubby vegetation composition, cover, and height were monitored along with the growth of planted spruce seedlings for 11 years in 30 permanent sample plots. Fire effects were determined using depth-of-burn pins to measure forest floor consumption and fuel assessment triangles to measure fuel loading and consumption following a microplot approach. Fire weather conditions were determined using standard methods outlined in the Canadian Forest Fire Weather Index System.

The fire on this site was quite severe and consumed 52% of the organic layer. The consumption of such a high percentage of the forest floor favoured establishment of invasive species. Regrowth of some native forest species was quite slow. This may be attributable to the severity of the conditions on the site after burning (e.g., poorer in nutrients, more extreme temperature fluctuations). Planted conifer establishment was quite successful and growth fairly rapid; this may have restricted the growth of understorey species.

Eleven years after burning, the site was dominated by small spruce trees, aspen, Vaccinium membranaceum, Menziesia ferruginea, Epilobium angustifolium, Cornus canadensis, Calamagrostis canadensis, and Polytrichum sp. Burning increased the number of native species on the site by stimulating the germination of buried seeds of shade-intolerant plants. Fire favoured species such as Vaccinium membranaceum over other shrubs such as Menziesia ferruginea. Most of the native vascular plants on this site were sufficiently adapted to survive burning so that at least some individuals survived and resprouted. Species of open forests such as Cornus canadensis, which are well adapted to open, dry environments with high levels of sunlight, proliferated in the open cutblock, whereas Gymnocarpium dryopteris, a shade-adapted fern, declined in cover. For many years, Epilobium angustifolium was the dominant herb. Fire also led to the loss of some shallowly rooted species such as Lycopodium annotinum and establishment by new species, including Salix and Populus, which are important for wildlife. Most of the forest mosses did not survive burning and had not re-established by year 11.

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Updated May 11, 2007