Quantifying organizational change after fire in lodgepole pine forest understorey

Abstract

Temporal changes in community organization were examined in a 300+ year chronosequence of understorey vegetation data from lodgepole pine forests recovering from fire in central British Columbia. Changes between six age-classes of forest were quantified as shifts in the orientation of equal frequency ellipses depicting the main correlation structure of the vegetation in multivariate space. Different developmental trajectories were obtained for sites differing in soil moisture status. Mesic sites displayed sharp changes in community organization within the first 100 years following fire but only gradual changes thereafter. In contrast, xeric sites exhibited sharp organizational changes at the beginning and again toward the end of the chronosequence. The unanticipated behaviour of dry sites is interpreted as reflecting a lower degree of integration of such communities resulting from their particular species composition and susceptibility to biotic disturbance. Analyses of separate life-form strata indicated continuing organizational changes in shrubs, forbs–grasses, and lichens, but relative stability in bryophytes after 100 years. The movement through time of mesic sites towards increasing persistence is predicted from an interpretation of ecological succession as a process of self-organization, directed by principles of nonequilibrium thermodynamics. Keywords: postfire succession, Pinus contorta forest understorey, plant community organization, equal frequency ellipses, principal components analysis, self-organization, nonequilibrium thermodynamics.

7th North Armerican Caribou Conference, 19-21 August 1996, Thunder Bay, Ontario, Canada.

“…comm.). Xeric growing sites support abundant terrestrial lichens for hundreds of years (Brulisauer et al, 1996) (Cichowski & Banner, 1993).…”

Towards an understanding of the management of pine-lichen woodlands in the Omineca region of British Columbia.

“…The extent, or duration, of changes in lichen successional trajectories after forest harvesting is additionally dependant on regional climate and other environmental factors (Brulisauer et al 1996, Lesica et al 1991. Regional variation in the climate has been proposed as one of the primary factors influencing the development of lichen communities (Johnson 1981, Momeau & Payette 1988.…”

“…Most previous research has focussed on identifying the temporal changes on sites influenced by wildfire (Brulisauer et al 1996, Carroll & Bliss 1982, Coxson et al 1999, Johnson 1981, Maikawa & Kershaw 1976, Momeau & Payette 1988. Generalisations have been made regarding the mechanisms resulting in succession.…”

“…The niche that lichens dominate is very susceptible to change and has been the subject of many successional studies (Brulisauer et al 1996, Carroll & Bliss 1982, Coxson et al 1999, Johnson 1981, Maikawa & Kershaw 1976, Momeau & Payette 1988, Oksanen 1986, Payette et al 2000. Across Canada, this niche is often characterised by forest stands that are influeneed by a continental climate and are dominated by pine (Pinus Contorta Dougl.…”

“…The shift between a lichen-dominated mid-seral stage and a moss-dominated late-seral stage is often associated with stand characteristics at a site (Brulisauer et al 1996, Johnson 1981, Lesica et al 1991, Maikawa & Kershaw 1976. Among factors that have been postulated as important in this respect are increased levels of shading and resultant changes in moisture availability that result from reduced incident solar radiation at the forest floor surface (Johnson 1981, Lesica et al 1991.…”