La régénération du thuya après coupes partielles en peuplements mixtes
|Advisor:||Ruel, Jean-Claude; Lussier, Jean-Martin; Kenefic, Laura|
|Abstract:||Factors affecting the regeneration of northern white-cedar (Thuja occidentalis L.) after partial cuts in mixedwood stands on mesic sites were studied using three distinct approaches. Firstly, single-tree selection cutting (25% of basal area removed), shelterwood seed-cutting (50% of basal area removed), and group selection cutting (gaps of 1.5H × 1.5H; 625 m2) were monitored over three years in the Outaouais Region (Quebec, Canada) to measure the abundance, establishment, and short-term growth of a new regeneration cohort. Secondly, a retrospective study was conducted in partial cuts in the Outaouais Region, Papineau-Labelle wildlife reserve (Quebec, Canada), and at the Penobscot Experimental Forest (PEF, Maine, United States) to compare diameter and height growth of white-cedar seedlings, layers, and small saplings in regions with different densities of white-tailed deer (Odocoileus virginianus Zimmerman). Thirdly, the abundance and recruitment of seedlings, and turning rates and mortality of white-cedar saplings, were studied in stands managed by repeated partial cutting over a 40-year period at the PEF. These three approaches demonstrated that small white-cedar seedlings (< 15 cm high) are present under many intensities of partial cuts, but the best combination of conditions to establish seedlings are: proximity of seed trees, partial opening of the canopy (single-tree selection cutting), exposed mineral soil, and low competition level. Height growth appears to be primarily a function of the region and light availability, and diameter growth increases following partial cutting. With a high density of deer, recruitment of seedlings over 30 cm high and to sapling stage is low, limiting density of saplings. In light of these results, it is preferable to pre-establish white-cedar regeneration by partial cutting of low intensity, or to work with naturally pre-established regeneration. After seedlings are established, a wider canopy opening can release seedlings and saplings and increase height and diameter growth. It may be necessary to control browsing pressure according to deer population densities.|
|Document Type:||Thèse de doctorat|
|Open Access Date:||16 April 2018|
|Collection:||Thèses et mémoires|
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