by Svetlana Savin | 30 January 2019
Published in Journal of Forestry 112(3): 276-286. http://dx.doi.org/10.5849/jof.13-035
We evaluated silvicultural scenarios for the rehabilitation of impoverished northern hardwood stands in Québec (Canada). The experiment comprises five treatments: a control, a hybrid single-tree and group selection (SC), two continuous cover irregular shelterwoods (CCIS) with respective residual basal areas (BAs) of 16 m2.ha-1 and 14 m2.ha-1, and an extended irregular shelterwood (EIS) with a residual BA of 14 m2.ha-1. American beech (Fagus grandifolia Ehrh) advance regeneration was removed with brush saws and the soil was mechanically scarified in all cutting treatments. Postcut values showed significant improvements of acceptable growing stock and a significant reduction of American beech; both effects were proportional to the intensity of removal. Simulated outcomes of the four scenarios were compared over a 120-year period. Results show that the EIS scenario should require a longer period to restore the desired uneven-aged stand structure; also, its harvests removed less BA of large-diameter trees than the SC scenario.
by Svetlana Savin | 30 January 2019
Published in Landscape Ecology 29: 905-918. https://doi.org/10.1007/s10980-014-0026-y
Forest productivity is driven by a suite of direct climatic and non-climatic factors that are transient or permanent. The kind of productivity driver and the nature of their effects vary by species, and scale dependencies potentially complicate these relationships. This study explored productivity-driver relations in eastern Boreal Canada and determined spatial effects in productivity control when expressed with stand dominant height at a reference age (site index). Data from 4,217 temporary sample plots obtained from boreal mixedwood and conifer bioclimatic domains, and with varied species composition, were used in this study. A single-level global model that assumes equal sensitivities across spatial scales was calibrated and compared with three alternative models reflecting different hypotheses on possible spatial heterogeneities. Alternative models were calibrated by plot-level soil deposit types (microscale), landscape dominant deposit (mesoscale) and bioclimatic domains (macroscale). A marked difference between the global and alternative models was observed, suggesting that a single global model does not sufficiently reflect existing heterogeneity in productivity-driver relationships. A combination of macro- and microscale models provided the best explanation of site index. Results further showed that site index is mainly driven by species composition (complementarity effects of aspen and jack pine compositions) and stand diameter structural diversity effects. It is concluded that successional changes, more than direct climatic effects, drive productivity.
by Svetlana Savin | 30 January 2019
Published in Forest Ecology and Management 302: 154-162
Black spruce and Jack pine are the tree species most often planted in the boreal forest of the province of Québec. Higher radial growth is expected from these stands in comparison with naturally regenerated forests. The fast growth response of these tree species in plantation has been associated with stem displacement and compression wood formation. This study aims to examine these parameters and to relate them with dendrometric variables. Analysis were conducted in 10 black spruce and 10 Jack pine plantations over 20 years old. Stem horizontal displacement was evaluated at stand level within plots of at least 50 stems. A sub-dataset of five dominant trees per plantation was then sampled in order to quantify the occurrences of compression wood. Stem horizontal displacement was mostly sparse for black spruce. In agreement with this observation, compression wood ratio (0.6% of total tree volume) can be considered low for this species. For Jack pine, the measurements of compression wood (5.0% of total tree volume) were higher than black spruce. Compression wood ratio was negatively correlated to stem height and positively to maximum stem horizontal displacement and tree crown cover ratio. We think that the capacity of Jack pine to grow faster, in given conditions, than black spruce is the main reason for the higher occurrence of sinuosity and compression wood in Jack pine plantations.
by equipewp | 30 January 2019
Published in Tree Seed Working Group – News Bulletin 58(December): 7-11.
by equipewp | 30 January 2019
Published in Tree Seed Working Group – News Bulletin 59(July): 4-5.
