by Svetlana Savin | 30 January 2019
Published in Northern Journal of Applied Forestry 27(1): 5-12
The objective of this study was to assess the long-term dynamics of northern white-cedar (Thuja occidentalis L.) seedling and sapling growth and mortality on the Penobscot Experimental Forest in Maine. Data collected between 1965 and 2005 in four twice-replicated partial cutting treatments were analyzed. White-cedar seedlings established in all treatments despite relatively high white tailed-deer (Odocoileus virginianus Zimmerman) population densities. However, although it appears that regeneration cohorts of associated softwoods increased in size over time, the white-cedar cohort did not. Ingrowth of white-cedar from the seedling to sapling stage was lower than the combined rates of sapling mortality and recruitment to the pole stage; sapling density of this species in 2005 was >80% less than it was at the start of the measurement period. Sapling mortality was high, and recruitment to larger size classes was low, although mortality decreased and recruitment increased as sapling size increased. Browsing was prolific; 90% of white-cedar seedlings and small saplings showed signs of browse in 2005. Overall, white-cedar sapling growth was slow, with an estimated 100 years needed to grow from small sapling to merchantable size in the study stands. Efforts to release white-cedar saplings through precommercial treatment and control of browsing pressure are recommended.
by Claire Morin | 30 January 2019
Published in Canadian Journal of Forest Research 38: 92-100
Estimates of belowground biomass and mineralomass are fundamental to understanding carbon and element cycling in forest ecosystems. At two sites, we measured coarse root (diameter >2 mm) biomass by diameter class and their mineralomass for sugar maple (Acer saccharum Marsh.), black spruce (Picea mariana (Mill.) BSP), and jack pine (Pinus banksiana Lamb.) trees to relate them to stem diameter at breast height (DBH). All regressions describing coarse root biomass and nutrient content as a function of stem DBH were highly significant (r2 > 0.89, P < 0.001). Root mineral element (N, P, K, Ca, Mg, and S) concentrations varied with three species and root diameter class. Sugar maple roots had higher N, P, and S concentrations than the other two tree species. Black spruce had higher root Ca concentrations. Element concentrations increased consistently with the reduction of root diameter for the three studied species. We also found that the horizontal root extent of sugar maple was related to tree DBH. In conjunction with other studies, the relationship suggests that this tree species could tolerate a 10%-20% root loss but not losses >28%-34%; otherwise, sugar maple health and vigour would be compromised in the short term.
by André Boily | 30 January 2019
Published in Scientific Program and Abstracts – Soils in Colds Environment. Annual Meeting – Canadian Society of Soil Science – Association québécoise de spécialistes en sciences du sol. June 3-7, 2007. Duchesnay, Québec. p. 32.
by André Boily | 30 January 2019
Published in Simpson, J.D. (ed.). Comptes rendus du trentième congrès de L’Association canadienne pour l’amélioration des arbres – Les forêts du Canada : mise en valeur de la productivité, de la protection et de la conservation / Proceedings of the thirtieth meeting of the Canadian Tree Improvement Association – Canada’s Forests – Enhancing Productivity, Protection and Conservation. July 24-27, 2006. Charlottetown, Prince Edward Island. p. 32-34.
by Marie-Claude Boileau | 30 January 2019
Published in Silva Fennica 46(5): 667-682
We aimed at evaluating the interacting effects of silvicultural and nursery practices on planted black spruce (Picea mariana (Mill.) BSP) dimensions, growth, survival and nutrition, 8 years following planting on a carefully logged boreal stand heavily invaded by Kalmia angustifolia L. and Rhododendron groenlandicum (Oeder) Kron & Judd. We also evaluated functional traits related to light and nutrient acquisition and key environmental resource availability to interpret treatment impacts on spruce seedling leaf traits and growth. An experimental black spruce plantation, consisting in a randomized block split-split-split plot design with 13 replicates was established in northeastern Quebec (Canada). Scarification (single-pass, double-pass), fertilization at the time of planting (control; macronutrients only; macro + micronutrients), stock type (container-grown; bare-root), and initial foliar N concentration (4 increasing levels) treatments were applied, and measurements were performed 5 and 8 years following planting. Double-pass scarification significantly increased soil temperature and reduced the competition cover, compared to the single-pass treatment. As a result, double-pass scarification promoted seedling growth over the single-pass treatment, and influenced the expression of other treatment effects. However, the relative gains associated with the second scarification pass have to be balanced against the supplemental investment involved by the treatment before being recommended. Our results point to variable effects of fertilization at planting to stimulate seedling initial growth. In this ecosystem, it appears that the silvicultural gains of this treatment depend on the variable of interest. Bare-root seedlings grew faster than containerized seedlings in the most intense site preparation treatment, but the differences have limited silvicultural impacts.
