Canopy gap characteristics and tree replacement in the southeastern boreal forest

Kneeshaw, Daniel D. et Bergeron, Yves (1998). Canopy gap characteristics and tree replacement in the southeastern boreal forest. Ecology , 79 (3). pp. 783-794. doi:10.1890/0012-9658(1998)079[0783:cgcatr]2.0.co;2 Repéré dans Depositum à https://depositum.uqat.ca/id/eprint/1179

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Résumé

This study identifies patterns in the gap disturbance regime along a successional gradient in the southern boreal forest and uses this information to investigate canopy composition changes. Gaps were characterized in hardwood, mixed-forest, and conifer stands surrounding Lake Duparquet in northwestern Quebec. From 39 to 80 gaps were evaluated along transects established in each of these stands. The abundance of gap makers and gap fillers and total regeneration was evaluated by species, as well as the size of each gap encountered along the transects. The percentage of the forest in canopy gap was calculated directly from the proportion of the transect in gap and by using gap area and line-intercept techniques. Changes in composition were evaluated from gap-maker and gap-filler distributions and by using transition matrices based on species mortality and regeneration in canopy gaps. The percentage of the forest in canopy gap ranges from 7.1% in a 50-yr-old forest dominated primarily by aspen to 40.4% in a 234-yr-old fir-dominated forest. Gap events are due to individual or small-group tree mortality in the early successional forest but become species-specific events controlled by spruce budworm outbreaks in the later stages of succession. Due to the high latitude, direct light only reaches the forest floor in the very largest gaps of the conifer-dominated stands. However, these gaps form slowly as budworm-caused mortality occurs over a number of years, whereas in aspen-dominated stands gaps are formed quickly by the snapping of tree stems. Balsam fir is the most abundant gap-filling species; however, its abundance is negatively correlated to gap size in all stand types. Markovian transition matrices suggest that in the young aspen-dominated forests small gaps lead to species replacement by more shade-tolerant conifers but that in the oldest forests the larger gaps will result in maintenance of the intolerant species and an increase in the abundance of cedar.

Type de document:	Article
Mots-clés libres:	Balsam fir; Boreal forest disturbance regimes; Canopy composition; Canopy gaps; Canopy turnover times; Cedar; Gap characteristics along a successional gradient; Gap makers and gap fillers; Gap size distributions; Regeneration of trees and forest; Spruce budworm-caused gaps; Trembling aspen
Divisions:	Forêts
Date de dépôt:	14 mai 2020 14:24
Dernière modification:	14 mai 2020 14:24
URI:	https://depositum.uqat.ca/id/eprint/1179

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