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 Forest Ecology and Management 357: 195-205. https://doi.org/10.1016/j.foreco.2015.08.003
We experimented three selection cutting patterns using different sizes of canopy opening, including single-tree (SIN, <100 m2 in area), hybrid single-tree and small groups of trees (HGR, 100–300 m2), hybrid single-tree and one larger gap (HGA, 700 m2), and an uncut control (CON) to regenerate tree species with a range of shade tolerance in a yellow birch (Betula alleghaniensis Britt.)–conifer stand, in Quebec, Canada. In this paper, we are presenting the 10-year effects on regeneration dynamics, seedbed coverage and light availability. During the six summers of monitoring, incoming solar radiation increased with canopy opening at a rate of 1.5, 3.9, 4.9 and 8.9 MJ/m2/day in microsites distinctive of the CON, SIN, HGR and HGA, respectively. Yellow birch established well in the three cutting patterns (including the matrix and openings), which contained 5–6 times more seedlings >5 cm in height than the control (2400/ha) after 10 years (all p < 0.001). Raspberry (Rubus idaeus L.) coverage was also higher in the three cuts (9–15% at year 10) than in the CON (<1%, p < 0.001). Pin cherry (Prunus pensylvanica L. f.) rapidly emerged independently from the cutting pattern (6000–7000 stems/ha, year 2), but had almost disappeared by year 10 (100–300 stems/ha). The 100–300 m2 groups and 700 m2 gap were favourable niches for yellow birch development. The gap, where light blade scarification was carried out in areas without conifer advance growth, was by far the worst niche for both red spruce and balsam fir (Abies balsamea [L.] Mill.). Therefore, the hybrid method that removed small groups of trees revealed the best option to maintain yellow birch and conifer species in the study site.
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 Forest Ecology and Management 375: 172-181. https://doi.org/10.1016/j.foreco.2016.05.037
Fire is considered the major disturbance in boreal forests. Nonetheless, in several areas logging has become the primary driver of forest dynamics. In many areas of the boreal forest, stands may undergo paludification (i.e. the accumulation of thick, poorly decomposed organic layers over the mineral soil) in the prolonged absence of fire, which reduces forest productivity. Whereas high-severity fires (HSF) may restore forest productivity by burning the soil organic layer (SOL), low-severity fires (LSF) mainly burn the soil surface and do not significantly reduce SOL thickness. In the Clay Belt region of eastern Canada, an area prone to paludification, forest stands have historically been harvested by clearcutting (CC), but concerns about the protection of soils and tree regeneration lead to the replacement of CC by careful logging (CL). Whereas CC disturbs the SOL and is thought to favor tree growth, CL has little impact on the SOL. Furthermore, it has been suggested that prescribed burning after clearcut (CCPB) could also be used to control paludification. Using a retrospective approach, this study sought to understand how CC, CL, and CCPB compare to LSF and HSF with respect to soil properties, SOL thickness, vegetation ground cover, tree nutrition, and stand height in paludified black spruce stands of the Clay Belt region. HSF led to significantly taller trees than CL and LSF, but did not differ from CC and CCPB. Foliar N was significantly higher in HSF and CCPB sites relative to CL and LSF, with an intermediate value in CC sites. Ground cover of Rhododendron groenlandicum was significantly lower in HSF and CC sites relative to LSF, with intermediate values in CL and CCPB sites. Sphagnum spp. ground cover was significantly lower in HSF and CCPB sites relative to CL, with intermediate values in CC and LSF sites. High-severity fire sites had a significantly thinner SOL than the four other disturbances. Finally, regression tree analysis showed that SOL thickness represented the best predictor of tree height, whereas segmented regression showed that tree height was negatively correlated to SOL thickness and revealed a cut-off point circa 23 cm, which suggests that tree growth is impeded beyond this threshold. These results support the idea that management strategies intending to regenerate paludified forests should primarily aim at reducing organic layer thickness, either through mechanical disturbance or combustion.
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.
