Windthrow following four harvest treatments in an Engelmann spruce - subalpine fir forest in southern interior British Columbia, Canada

Abstract

We used transect surveys at a large-scale experimental site at Sicamous Creek, B.C., to measure the effects of five treatments on windthrow: 10-ha clearcuts, arrays of 1-ha patch cuts, arrays of 0.1-ha patch cuts, individual-tree selection cuts, and uncut controls. We also examined edge effects and conditions predisposing trees to windthrow. Windthrow of subalpine fir (Abies lasiocarpa (Hook.) Nutt.) in the 2.7 years following harvesting increased from 0.6% of basal area per year in uncut forest to 0.8-1.8% per year in harvested treatments, with highest rates in individual tree selection units and lowest rates in 0.1-ha patch-cut arrays. Engelmann spruce (Picea engelmannii Parry ex Engelm.) showed similar patterns of windthrow but lower rates (0.2-0.7% of basal area per year in harvested treatments). Windthrow was concentrated near north and east edges of 1-ha and 10-ha openings but was dispersed throughout the more uniform treatments. Windthrown trees did not differ from random trees in diameter but had lower height/diameter ratios, probably reflecting the greater windthrow observed in subxeric sites on complex, elevated topography. The rates and distribution of windthrow in different harvest treatments have implications for ecological processes, salvage, long-term windthrow potential, and mitigation possibilities.

Partial harvesting in the Canadian boreal: Success will depend on stand dynamic responses

“…Most information concerning mortality following partial harvests pertains to the U.S. Pacific Northwest and British Columbia (BC). Coates (1997) found a 1.1% increase in windthrow mortality two years after harvest at the Date Creek Silvicultural site in interior BC, while rates were elevated by a mere 0.2% to 1.2% in a subalpine forest 2.7 years after harvest (Huggard et al 1999). Similarly, there was no significant increase in mortality found after high-retention historical and recent partial cutting in southwestern Alaska (Deal et al 2002).…”

Wind-firmness in Pinus pinaster A�t. stands in Southwest France: influence of stand density, fertilisation and breeding in two experimental stands damaged during the 1999 storm

“…These four components are subject to modification under the influence of silvicultural practices. The management and spatial structure of the stand determine dimensional features and tree morphology [1,10,11,40,45,48], wind permeability [21,26,41,51] and mechanical properties of the wood influenced by exposition to wind [20,53,54]. Wind-firmness of individual trees also depends on external or internal defects due to insects or fungi [47].…”

Wind and snow damage nine years following four harvest treatments in a subalpine fir – Engelmann spruce forest at Sicamous Creek in southern interior British Columbia, Canada

“…The analysis of the 1999 and 2003 surveys followed the same procedure used for 1997 data reported in Huggard et al (1999). We summarize basal area/ha for both uprooted and snapped stems for live and dead subalpine fir and live Engelmann spruce.…”

“…Results after the first 2.7 years were reported by Huggard et al (1999) who showed that harvesting at the site led to a significant increase in wind or wind-related damage. Among the harvesting types, the individual tree selection treatment suffered more damage than the 0.1-ha group selection treatment.…”

“…While Laiho (1987) reported that damage following single-tree cutting was greatest immediately following the completion of cutting, operational reports from coastal British Columbia suggest that damage on the edge of large openings continues for many years (Mitchell 1995(Mitchell , 1998. We were also concerned that initial damage at Sicamous Creek was low because the recorded wind speeds were low during the initial monitoring period, with mean speeds of 2 m/s and short duration gusts to 15 m/s (Huggard et al 1999, Spittlehouse et al 2004), compared to mean speeds of 2.7 to 6.9 m/s, and gusts of 37 to 50 m/s, in the Pacific Northwest and the west coast of Scotland (Quine et al 1999). We thought that higher wind speed events might occur in the future, which also might lead to changes in damage patterns.…”