by Claire Morin | 30 January 2019
Published in Canadian Journal of Forest Research 45: 541-552. https://doi.org/10.1139/cjfr-2014-0124
The capacity of a forest stand to produce timber is related to the interactions that exist between its regeneration capacity, physical site characteristics (climate, surficial deposit, drainage), and disturbances. Minimally, to be sustainably managed, a forest needs to be sufficiently productive and able to regenerate after a disturbance so that its productive capacity is maintained or enhanced. To this effect, we evaluated timber productivity over a large area (175 000 km2) covering the latitudinal extent of closed-canopy black spruce (Picea mariana (Mill.) B.S.P) forest. Site index and relative density index were used to identify stands that cannot reach a minimum volume of trees of minimum size over one rotation. A nonparametric method was used to estimate their values for all stands within the study area. This imputation used either physical site attributes alone to assess potential productivity independent of stand history or physical and vegetation site attributes to assess current productivity. The proportion of productive stands was then estimated at the scale of landscapes ranging from 39 to 2491 km2. Physical site factors alone explain 84% of the variability in the percentage of potentially productive stands (78% for currently productive stands); their combination resulted in an abrupt transition in productivity over the study area. However, burn rate alone also explains 63% of variation in the proportion of currently productive stands and 41% of the relative difference between percentages of potentially or currently productive stands. These results have implications for strategic forest management planning at land classification stage, as timber production area is assumed to remain stable through time, whereas it is apparently related to the disturbance rate.
by Marie-Claude Boileau | 30 January 2019
Published in ISCHP 2015: 5th International Scientific Conference on Hardwood Processing. 15-17 septembre 2015. Québec, QC. 107-114
The establishment of precise relationships between the characteristics of standing trees and log grade volumes would improve forest management decisions in hardwood stands. In this study, a two-part conditional model (to account for the excess of zero responses within certain log grades) was used as a framework to establish this relationship for some important species in hardwood and mixed stands. Models were developed for sugar maple (Acer saccharum Marsh.), yellow birch (Betula alleghaniensis Britt.), paper birch (Betula papyrifera Marsh.) and American beech (Fagus grandifolia Ehrh.). In the model assessment process, we also tested whether the tree grade classification based on stem quality evaluation could be simplified without losing too much information about log product assortment. Higher variations among species were observed in the predictions of log grade occurrences, while the estimations of conditional volume followed similar and increasing trends with tree size. The Akaike information criteria (AIC) showed that the specifically designed tree grade classification best predicted both log grade occurrence and log grade volume for sugar maple and yellow birch, but not for paper birch and American beech. For these two species, grouping the highest quality classes of the tree grade classification system was found to be the best predictor of log grade occurrence and volume. This result can probably be explained by insufficient sampling, especially for large trees of higher grades. Our results support previous findings that tree grade classification would improve the prediction of log product assortments in northern hardwood stands.
by Claire Morin | 30 January 2019
Published in Reforesta 1: 261-280. https://doi.org/10.21750/REFOR.1.13.13
Plantations offer a high potential to respond to the increasing pressure on forests to deliver social, economic, and environmental services. Exotic tree species have a long history of use in plantation forestry, mostly because of their improved productivity compared with that of native species. Because of their impacts on land management and the environment, questions arise regarding the compatibility of exotic tree plantations with sustainable forest management (SFM), the overarching paradigm driving forest legislations in Canada. Our objectives were thus to i) briefly review the historical and current use of exotic tree species in Canada, ii) identify the social, economic and environmental issues related to the use of exotic tree species in Canadian forestry, based on sustainable forest management criteria, and iii) identify perspectives related to the use of exotic tree species in the sustainable management of Canadian forests. Results show that six out of ten Canadian provinces do not have specific legislations to control the use of exotic tree species for reforestation within their borders. The use of exotic tree species is mainly controlled through third-party certification agencies. Exotic tree species represent a small proportion of the planted seedlings in Canada and Norway spruce is the most common one. The use of exotic tree species is compatible with sustainable forest management criteria used in Canada, but forest managers must take into account several issues related to their use and maintain a social license to be entitled to plant them. Issues are highly dependent upon scale. The zoning of management intensity could provide environmental, economic and social benefits, but costs/benefits analyses should be carried out. The concept of naturalness could also be useful to integrate plantations of exotic species in jurisdiction where SFM strategies are based on ecosystem management principles. Monitoring of hybridization and invasiveness of exotic species must be included in landscape analyses to forestall loss of resilience leading to compromised structural and functional ecosystem states. The use of exotics species is recognized as a tool to sequester carbon and facilitate adaptation of forests to global changes, but it is necessary to carefully identified contexts where assisted migration is justified and disentangle planned novel ecosystems coherent with global changes generated by assisted migration from those emerging from invasive species forming undesired states.
by Marie-Claude Boileau | 30 January 2019
Published in Canadian Journal of Forest Research 46: 783-793. https//:doi.org/10.1139/cjfr-2015-0484
Some regenerating stands of the boreal forest exhibit low juvenile growth after major disturbances, which compromises sustainable forest management objectives. In black spruce – feather moss stands of eastern Canada subject to paludification, careful logging methods could decrease stand productivity with time by preventing a beneficial reduction in organic soil thickness. The aim of this project was to confirm decreases in juvenile growth between stands originating from careful logging and the former stands originating from old fires on the same sites. Stem analyses showed that stands originating from CPRS had significantly better juvenile height growth than the former stands but significantly lower growth than stands originating from recent fire in the study region. If organic matter thickness apparently played a role in the growth differences observed between fire and harvesting, it was not the only factor determining stand productivity. According to our results, cohort status, climatic regime, and quality of the residual organic matter are other factors that seem to drive productivity. Our results show that postharvest management approaches (e.g., site preparation) should be used to increase yields after harvest for the sites to express their full growth potential.
by André Boily | 30 January 2019
Published in For. Ecol. Manage. 427: 446-455. https://doi.org/10.1016/j.foreco.2017.12.026
Generally, the effects of climate change on tree growth focus on changes in one dimension of a tree. However, diameter increment along the main stem reacts differently to climatic variables, which in turn influences tree form. These differences can thus have important implications on stem volume, which could induce biases in future forest biomass estimation. A stem taper model including climatic variables was fitted to stem analysis data of five different species (Abies balsamea, Betula papyrifera, Picea glauca, Picea mariana, Populus tremuloides) distributed along a gradient from the temperate to the boreal forest of Eastern Canada. The effects of shifts in stem form on tree volume between different climatic scenarios were then estimated and related to different functional traits. Changes in stem form with climatic variables were observed for four of the five species, with up to 5% differences in stem volume between different climatic situations. Changes in stem volume were found to decrease with increasing waterlogging and shade tolerance. The most important differences in stem volume can induce changes of 3–4% in the biomass of a single tree. Not taking into account shifts in stem form could have implications in forest biomass estimations.
