Upland black spruce stand development 17 years after cleaning and precommercial thinning

Abstract

Density management is often used by silviculturists to guide stand composition and development. We examined the effects of cleaning (hardwood removal) and four levels of precommercial thinning (0, 20, 35 and 50% basal area removal) on stand development in a dense, 24-year-old upland black spruce (Picea mariana [Mill.] BSP) plantation near Beardmore, Ontario. Immediately before treatment, stand densities and basal areas for all species and for black spruce averaged 7375 and 6415 stems ha -1 , and 27.9 and 20.5 m 2 ha -1 , respectively. Seventeen years after treatment, black spruce total stand volume (V T ) was higher in the cleaned, unthinned plots (243 m 3 ha -1 ) than in the untreated controls (171 m 3 ha -1 ) while total stand volume increment of all species combined was similar in these two treatments. Compared with cleaning alone, thinning cleaned plots from below increased quadratic mean diameters (D Q ) by up to 9% but decreased V T by up to 28%. At plantation age 41, increases in black spruce densities of 1000 stems ha -1 resulted in mean decreases of 0.6 cm in D Q and mean increases of 43 m 3 ha -1 in V T . Endemic black spruce stem mortality rates decreased with thinning intensity, with mortality concentrated in the smallest size classes. In some plots, mortality was increased by wind or snow damage, and by root rots. Height increment of dominant trees was unaffected by thinning. Projected yields at age 55 (the physical rotation age-the age at which maximum mean annual increment occurs) suggest the heaviest precommercial thinning could increase quadratic mean diameter from 16.1 to 17.7 cm, but decrease merchantable stand volume from 292 to 225 m 3 ha -1 . Results indicate that total black spruce fibre yields and product value on these sites will be maximized in denser stands. Cleaning appears to offer greater benefits for black spruce fibre production than precommercial thinning.Key words: black spruce, precommercial thinning, cleaning, density management, projected yields Tout juste avant le traitement, les densités du peuplement et les surfaces terrières pour toutes les espèces et pour l'épinette noire atteignaient respectivement en moyenne 7 375 et 6 415 tiges ha -1 et 27,9 et 20,5 m 2 ha -1 . Dix-sept ans après le traitement, le volume total du peuplement d'épinette noire (VT) était supérieur dans les parcelles dégagées et non éclaircies (243 m 3 ha -1 ) par rapport aux parcelles-témoins (171 m 3 ha -1 ) tandis que l'accroissement total en volume du peuplement, toutes espèces combinées, était semblable dans ces deux traitements. Par comparaison avec seulement le dégagement, les parcelles éclaircies par le bas et dégagées ont connu une augmentation des diamètres quadratiques moyens (DQ) atteignant jusqu'à 9 % mais une diminution du VT allant jusqu'à 28 %. Dans la plantation à l'âge de 41 ans, les accroissements des densités d'épinette noire de 1 000 tiges ha -1 ont entraîné des diminutions de 0,6 cm du DQ et des accroissements moyens du VT de 43 m 3 ha -1 . Les taux de mortalité endémique de...

Timing and intensity of precommercial thinning and their effects on the first commercial thinning in Scots pine stands

“…The response of diameter growth is greatest in stands with an intensive and early PCT, as reported earlier by Varmola (1996), Ruha and Varmola (1997), Varmola et al (1998), Varmola and Salminen 2004. Similar results on the growth response to precommercial thinning have also been reported in studies in Canada by Tong and Zhang (2005) for jack pine, by Johnstone (2005) for lodgepole pine, by Fleming et al (2005) for black spruce, and by Pothier (2002) for balsam fir.…”

“…In recent studies in Canada, precommercial thinning was reported to have positively affected merchantable stem volume production (Tong andZhang 2005, andJohnstone 2005). In contrast, Fleming et al (2005) found that cleaning improved black spruce growth, but precommercial thinning resulted in only a slight increase in mean tree size but a larger reduction in merchantable stand volume. Pothier (2002) also found that precommercial thinning did not increase the merchantable wood volume at maturity but, on the other hand, he found that thinning improved the yield composed of large diameter trees (≥15.1 cm), while obviously the effect of the treatments on wood volume depends on the minimum usable diameter in question.…”

Effect of soil preparation method on economic result of Norway spruce regeneration chain

“…However, delaying a young stand management operation increases an impending consumption of working time (Kaila et al 2006) and decreases diameter growth of crop trees (Pothier 2002, Fleming et al 2005, Pitt and Lanteigne 2008 and is in generally reasonable only if it enables to avoid some of later management operations. Anyhow, similar procedure could also be performed in spot-mounded site by delaying early cleaning.…”

“…Disadvantage caused by competition depends on the distance and height difference between the crop tree and the disturbing tree (Andersson 1993, Laaksonen 2008). Therefore, a properly timed pre-commercial thinning accelerates or at least sustains growth of crop trees (Folkesson and Bärring 1982, Pothier 2002, Fleming et al 2005, Huuskonen and Hynynen 2006, Pitt and Lanteigne 2008.…”

Precommercial thinning of overtopping aspen to release coniferous regeneration in a boreal mixedwood stand

“…B.S.P.) were weak or even negligible in some experiments (e.g., McClain et al 1994, Fleming et al 2005, but good growth responses have been obtained on productive sites (Karsh et al 1994, Newton andWeetman 1994). Experiments conducted in the eastern United States and Canada also have reported significant DBH growth increases to PCT for northern hardwoods including paper birch (Betula papyrifera Marsh.)…”