Woody vegetation responses to fire versus clear-cutting logging: A comparative survey in the central Canadian boreal forest

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Abstract
The woody vegetation of 131 clear-cut, postlogged boreal forest stands in central Canada, previously dominated by Picea mariana (Mill.) BSP., is compared with 250 natural postfire stands from the same region. Each dataset represents a stand chronosequence on a range of substrate types. Correspondence analysis (CA) based ordination methods is used for structural and compositional comparison in order to address the question of the extent to which woody vegetation recovery and succession are similar between the two disturbance types. In addition, canonical CA is used as a general linear model strategy to examine unique and covariant influences on forest composition. The postlogged stand dataset had a much lower representation of conifer-dominated stands than the postfire dataset and a far greater proportion of stands dominated by poplars. Detrended and canonical CA on all 381 stands indicated a primary influence on stand composition due to site factors, but disturbance type and intensity, i.e. wildfire versus horse or mechanical hauling in postlogged stands, showed the strongest correlation of any single variable. Analyses of each dataset, separately, indicated similar predictability of vegetation composition from associated stand environmental and age data but regressions were weak (R2 ~ 22%). Whereas skidding type and stand age were the most important correlates with the postlogged data, soil variables were the most prominent correlates with the postfire woody vegetation. In addition to Abies balsamea (L.) Mill. dominated woodland deriving from postfire succession, such forests also arose on a widespread basis in horse skidded, postlogged stands through the persistence of advanced growth seedlings. Mechanically skidded, postlogged stands show a wholesale conversion from conifer dominance, mostly Picea mariana, to dominance by Populus. It is concluded that both the qualitative nature and the intensity of boreal forest disturbance lead to different woody vegetation recovery patterns.