by Marie-Claude Boileau | 30 January 2019
Published in Annals of Forest Science 74: 53. https://doi.org/10.1007/s13595-017-0646-x
Pilodyn and acoustic velocity measurements on standing trees, used for predicting density and stiffness, can be good genetic selection tools for black spruce. Genetic parameters and selection efficiency were conserved in two breeding zones with contrasted bioclimatic conditions. Given the recent progress made in the black spruce genetic improvement program, the integration of juvenile wood mechanical properties as selection criteria is increasingly relevant. This study aims to estimate the genetic parameters of in situ wood density and modulus of elasticity (MoE) measurements and to verify the efficiency of various measuring methods used for large-scale selection of black spruce based on wood quality. Height, diameter, wood density, and some indirect measures of density (penetration and drilling resistance) and MoE (acoustical velocity and Pilodyn) were estimated on 2400 24-year-old trees of 120 open-pollinated families in progeny trials located in the continuous boreal or mixed forest subzones. Heritability of growth, density, and indirect density measurements varied from low to moderate and was moderate for acoustical velocity in both vegetation subzones. Expected genetic gains for wood properties based on in situ methods were higher for MoE proxy estimation combining Pilodyn and acoustic velocity. Acoustic velocity is a good predictor of MoE. It is virtually unaffected by the environment and can be used on a large scale in the same manner as the Pilodyn for density. Using a proxy estimation that combines both methods helps optimize genetic gain for MoE.
by Claire Morin | 30 January 2019
Published in The Forestry Chronicle 92(2): 221-231. https://doi.org/10.5558/tfc2016-041
Scarification contributes to creating planting microsites for reforestation by mixing organic matter (OM) with the upper layers of mineral soil. However, on some boreal sites characterized by a thick humus layer and dominated by ericaceous shrubs, competition seems to limit the benefits of scarification. A potential solution would be to remove OM completely through scalping. The objective of our study was to compare the short-term effects of scarification and scalping on the growth of Picea mariana and Pinus banksiana on such sites. After three growing seasons, we explored the relationships between seedling growth, groups of competing vegetation species, planting depth and distance to the nearest OM accumulation. The two treatments had similar effects on these variables. Growth on plots subjected to scalping was independent from the distance to OM. Planting depth had a nil or positive effect on seedling growth. Pinus seedlings largely outgrew Picea seedlings. However, the lack of short-term difference between scarification and scalping must be interpreted with caution, given the potential mid- and long-term effects of OM exportation on soil fertility, erosion and seedling nutrition.
by Marie-Claude Boileau | 30 January 2019
Published in Forest Ecology and Management 358: 261-271. https://doi.org/10.1016/j.foreco.2015.09.020
We used long-term data collected from 22 study sites in northern hardwood stands comprised of sugar maple (Acer saccharum Marsh.), yellow birch (Betula alleghaniensis Britt.), and American beech (Fagus grandifolia Ehrh.) to establish relationships between sapling abundance and tree ingrowth. After 10 years, postharvest sapling density in the 6 cm diameter class (5.1–7.0 cm) showed linear relationships with ingrowth. Proportion of variation explained (r2) varied from 36% to 83% depending upon tree species and silvicultural treatment (partial cutting vs. uncut control). After 20 years, linear relationships were also established (r2 = 24–65%) between ingrowth and sapling density in the 2 cm diameter class (1.1–3.0 cm). From a wide pool of variables related to stand species composition, climate, physiography, and soil nutrients, postharvest sapling density was most strongly correlated to merchantable tree density (r = 0.43–0.75). Sugar maple sapling density was also positively correlated with base saturation and calcium saturation of the B horizon (r = 0.56 and 0.58). Over a 30-year period, the increase in American beech sapling basal area was substantial compared to mitigated increases found in sugar maple and yellow birch depending upon treatment. Our results provide useful information on integration of sapling data into forest management.
by Marie-Claude Boileau | 30 January 2019
Published in PLOS ONE 10(8): e0136674. https://doi.org/10.1371/journal.pone.0136674
Silvicultural restoration measures have been implemented in the northern hardwoods forests of southern Quebec, Canada, but their financial applicability is often hampered by the depleted state of the resource. To help identify sites most suited for the production of high quality timber, where the potential return on silvicultural investments should be the highest, this study assessed the impact of stand and site characteristics on timber quality in sugar maple (Acer saccharum Marsh.) and yellow birch (Betula alleghaniensis Britt.). For this purpose, lumber value recovery (LVR), an estimate of the summed value of boards contained in a unit volume of round wood, was used as an indicator of timber quality. Predictions of LVR were made for yellow birch and sugar maple trees contained in a network of more than 22000 temporary sample plots across the Province. Next, stand-level variables were selected and models to predict LVR were built using the boosted regression trees method. Finally, the occurrence of spatial clusters was verified by a hotspot analysis. Results showed that in both species LVR was positively correlated with the stand age and structural diversity index, and negatively correlated with the number of merchantable stems. Yellow birch had higher LVR in areas with shallower soils, whereas sugar maple had higher LVR in regions with deeper soils. The hotspot analysis indicated that clusters of high and low LVR exist across the province for both species. Although it remains uncertain to what extent the variability of LVR may result from variations in past management practices or in inherent site quality, we argue that efforts to produce high quality timber should be prioritized in sites where LVR is predicted to be the highest.
by Audrey Verreault | 30 January 2019
Published in Journal of Sustainable Forestry 34(3): 169-198. https://doi.org/10.1080/10549811.2014.980895
Tree improvement programs aim to develop families that are well-adapted to future growing conditions. To gain insight into the stability of the family genetic response to climate change, white spruce ( Picea glauca) seedlings from 60 full-sib families were subjected to a combination of two temperature regimes and two levels of CO2 over two growing seasons. There was positive effect of warmer temperatures and higher CO2 on some growth variables but no significant family × treatment interactions. Instantaneous water use efficiency was the only physiological trait that was affected positively by the CO2 treatment, showing a 51% increase that was consistent across families.
