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The initial response of several forage species to prescribed burning in southeastern British Columbia Thomson, S. M. (Sandra Mary)


This study was initiated in 1985 to assess the response of seven key forage and browse species to prescribed burning for wildlife habitat and range improvement in the East Kootenay region of British Columbia. The species studied were Agropyron spicatum (bluebunch wheatgrass), Amelanchier alnifolia (saskatoon), Ceanothus velutinus (snowbrush), Festuca scabrella (rough fescue), Purshia tridentata (bitterbrush), Stipa occidentalis (stiff needlegrass), and Symphoricarpos albus (common snowberry). The primary objective of the study was to determine how these species respond to burning in terms of percent cover and current annual growth. There were two approaches to this study. First, experimentally burned plots were established on two sites. Spring and fall burning were carried out on one site and fall burning on a second site. Second, five previously operationally burned areas were compared with immediately adjacent unburned areas to assess differences in the percent cover of all the species and in the sprouting response of bitterbrush. Three of the sites were sampled in the first postburn growing season, one site was sampled in the second postburn growing season, and one site was sampled in the fourth postburn growing season. The total preburn fuel load on these sites ranged from 1.2 to 2.0 kg/m². Total fuel consumption varied from 53 to 91% on the experimentally burned plots. The variability of each fuel load component was high. In the first growing season following fall and spring burning, and the second growing season following fall burning, there were no significant differences in the percent cover of all species except bitterbrush and stiff needlegrass between burned and unburned plots. There was significantly less bitterbrush following both spring and fall burning. By the second growing season, bitterbrush had recovered slightly following fall burning. There was significantly more (33%) percent cover of stiff needlegrass on the fall burned plots both in the first and second growing season following burning. The only species for which there was a significant difference in the current annual growth on fall burned plots compared with control plots, were bitterbrush and saskatoon. There was 71% less current annual growth of bitterbrush the first growing season following fall burning. Saskatoon had 48% less current annual growth on the fall burned plots compared with the control plots. The results for percent cover were similar on the operationally burned areas. At all but the four-year-old operationally burned site, there was significantly less percent cover of bitterbrush on the burned plots compared with unburned plots. The percent decrease varied from 76 to 90%. At a two-year-old operationally burned site, there was 58% less snowberry on burned plots compared with unburned plots. At the same site there was less rough fescue (94%) but this represented only a 2% decrease in the percent cover. There was 58% more percent cover of stiff needlegrass on one of the one-year-old operationally burned sites. On these sites the postfire survival adaptation of all these species was by resprouting from either buds at the surface or the base of the plant, or from underground rhizomes. Some graminoid species seeded in from off-site seed sources. This study shows that where bitterbrush is the focus of enhancement, prescribed burning may have initial detrimental effects regardless of the timing of burning. The effects appear to be more variable and less dramatic for the other species studied. The implications of the response of these forage species to current prescribed burning practices are discussed and recommendations on future research are made.

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