by Marie-Claude Boileau | 30 January 2019
Published in Forest Ecology and Management 405 (Supplement C): 360-366. https://doi.org/10.1016/j.foreco.2017.09.024
High abundance of large herbivore has major impacts on the composition, structure, and functioning of forest ecosystems, which can result in regeneration failures. Reduction of large herbivore density, however, does not warrant the successful establishment of tree species sensitive to browsing. In such contexts, planting in combination with silvicultural treatments can be used to restore forest cover over large areas. Using an experimental plantation on Anticosti Island (Quebec, Canada), we investigated how white-tailed deer (Odocoileus virginianus) browsing affects the performance of planted balsam fir (Abies balsamea L. Mill.) seedlings following site preparation and mechanical release. After seven growing seasons, seedling height, leader length and ground-level diameter were 30% bigger in fenced plots compared to unfenced ones as a result of cumulative browsing. Seedling survival was low (62%) and unaffected by either silvicultural treatments or deer after the onset of the mechanical release treatment. Site preparation and mechanical release did not improve morphological parameters and did not increase browsing occurrence on fir, likely because they had little influence on surrounding plants that compete for resources and may hide seedlings from deer 7years after planting. Selective browsing on neighbouring plants also acted as a release treatment for balsam fir seedlings, allowing them to reach full sunlight at a lower height (125–146 cm), compared to fir seedlings in deer exclosures (161–184 cm). We propose that managers aim at target deer densities that promote browsing positive effects. In such context, prescription for site preparation and mechanical release should be based on other considerations than promoting seedling growth, such as facilitating practical reforestation work.
by Audrey Verreault | 30 January 2019
Published in Tree Planters’ Notes 57(2): 53-61
A 7-day study of foliar fertilization was carried out after fall budset of containerized 2+0 black spruce (Picea mariana [Mill.] B.S.P.) to assess if one application of urea (U), alone or with surfactant (US), can lead to a rapid increase of foliar nitrogen (N) concentration. Two washing treatments of seedling shoots (W: 15 sec washing [control], WS: W + 5 min soaking) were also performed to evaluate their efficiency to remove urea residues from the needle surface before foliar N concentration analysis. At day 0 (2 hours after application), fertilized seedlings already had significantly greater foliar N concentration than unfertilized seedlings (NF) and after 7 days, it had increased 7 and 12 percent for U and US seedlings, respectively. The addition of a surfactant did not significantly improve N status. Foliar N concentration of fertilized seedlings was not significantly affected by washing treatments. These results indicate that foliar urea fertilization after budset is an effective tool for rapidly increasing foliar N concentration without affecting seedling shoot height.
by Marie-Claude Boileau | 30 January 2019
Published in Forest Science 61(5): 966-972. https://doi.org/10.5849/forsci.14-205
In Canada, Norway spruce (Picea abies [L.] Karst.) is an exotic species mainly used as a fast-growing tree in intensive silviculture. However, this species is sensitive to attacks by white pine weevil (Pissodes strobi Peck [Coleoptera: Curculionidae]) (WPW), a pest that girdles and kills leader shoots, targeting open-growing individuals with fully sunlit terminals. We hypothesized that there is a compromise when releasing planted Norway spruce between growth interference by competing vegetation and avoiding creation of favorable conditions for attacks and growth reduction by WPW. We evaluated the effects of stock type, scarification, and vegetation management on WPW incidence and early Norway spruce growth in southeastern Québec (Canada). Our study confirmed that after 11 growing seasons, the growth of Norway spruce seedlings was driven by the presence of competing species, a factor that can be managed through vegetation control. Although released seedlings were at a higher risk of WPW attack, the trees were ultimately taller than those growing in control conditions. Although significant in some treatment combinations, stock type effects were limited and marginal compared with vegetation effects. Scarification did not improve seedling establishment on this site characterized by a thin humus layer.
by Svetlana Savin | 30 January 2019
Published in Forests 6: 344-359. https://doi.org/10.3390/f6020344
Northern white-cedar (Thuja occidentalis L.) is an important commercial species with a high wildlife value, both as a food source and habitat for many bird and mammal species. Concerns have been expressed about its decreasing abundance across its range, and especially in mixedwood stands, where it has to compete with several other species and can suffer from heavy browsing. In this study, we quantified the development of natural northern white-cedar seedlings and saplings under various partial cutting regimes, with and without white-tailed deer (Odocoileus virgianus Zimmerman) browsing, in three selected sites in Quebec (Canada) and in Maine (USA). Our data show that northern white-cedar regeneration was present in all studied stands, but that only a few stems were taller than 30 cm on the two sites with high densities of deer. In the absence of heavy browsing, stems reached a height of 30 cm in 11 years, and 130 cm in 28 years. Height growth of northern white-cedar regeneration increased with canopy light transmittance, while ground-level diameter increment increased after partial cutting. This suggests that partial cutting can be used in mixedwood stands to release natural northern white-cedar regeneration, but also that the recruitment of northern white-cedar seedlings to larger size classes constitutes a major challenge in stands subject to heavy deer browsing.
by Claire Morin | 30 January 2019
Published in Environmental Review 23: 66-77. https://dx.doi.org/10.1139/er-2014-0048
Liming, the application of carbonate materials (e.g., CaCO3, CaMg(CO3)2) to soils and surface waters, has been used extensively in Europe, and to a lesser extent in Canada and the United States, to mitigate the effects of acid deposition on forest and aquatic ecosystems. This literature review was conducted to assess the effects of liming on ecologically and economically important sugar maple dominated ecosystems of northeastern North America, where it is increasingly used to treat sugar maple dieback. Potential direct and indirect effects were considered to determine whether the use of liming to revitalize these forests could negatively affect other ecological parameters, including those in adjacent aquatic habitats. Based on current scientific literature, it is not anticipated that liming at rates of 1–3 t ha−1 would have major detrimental effects on these ecosystems. However, liming could have negative effects on northern hardwood forests with regard to earthworm invasions. The choice of liming as a mitigation tool should be made not only after weighing the potentially negative effects against the benefits of restoring sugar maple dominated stands in poorly buffered soils, but also after considering ecological components that could be lost or never recovered if an acidified forest ecosystem is not limed.
