Foliar Responses of Understorey Abies lasiocarpa to Different Degrees of Release Cutting in a Betula papyrifera and Conifer Mixed Species Stand
Abstract:Foliar responses of subalpine fir [Abies lasiocarpa (Hook.) Nutt.] to thinning were studied in a 35-yr-old mixed stand of paper birch (Betula papyrifera Marsh.) and conifers. The stand regenerated naturally after a wildfire with a canopy dominated by paper birch (average height 9.8 m) and an understorey dominated by subalpine fir (average height 1.6 m). The stand was thinned to four densities of birch: 0, 600 and 1200 stems ha-1 and control (unthinned at 2300-6400 stems ha-1) in the autumn of 1995. The understorey conifers, mainly subalpine fir, were thinned to 1200 stems ha-1. The study used a completely randomized split-plot design. Three sample trees were systematically selected from each treatment replicate and each tree stratum (upper, intermediate and lower understorey). One-year-old and older age class needles were collected from one south-facing branch within the fifth whorl from the tree top. Thinning of paper birch significantly (p <0.001) increased leaf area and dry weight per 100 needles for intermediate and short trees except in the 0 birch treatment. Understorey subalpine fir trees in 600 stems ha1 birch (T3) had the largest leaf area and leaf dry weight per 100 1-yr-old needles. Specific leaf area (SLA) decreased from unthinned (T1) to 0 birch (T4). Lower understorey trees had the largest SLA. One-year-old needles had significantly higher N, P and K concentrations in all the thinning treatments. These responses are consistent with the shade tolerance of subalpine fir. The results suggest that when managing a paper birch-conifers mixed-wood forest it may be of benefit to understorey conifers to leave a birch canopy as a nursing crop.
Document Type: Research Article
Affiliations: 1: Red Rock Research Station, Ministry of Forests, 18435 Forest Nursery Road, Prince George, BC, Canada V2N 5Y7 2: BC Ministry of Forests, Research Branch, P.O. Box 9519, Station Provincial Government, Victoria, BC, Canada V8W 9C2 3: BC Ministry of Forests, Prince George Forest Region, 1011 4th Ave., Prince George, BC, Canada V2L 3H9
Publication date: 2000-12-01