by Audrey Verreault | 30 January 2019
Published in Forest Science 60(1): 57-62
The boreal zone of northeastern North America is characterized by mixedwood forests dominated by balsam fir (Abies balsamea (L.) Mill.) in the south and by coniferous forests dominated by black spruce (Picea mariana (Mill) B.S.P.) in the north. Site index values of balsam fir and black spruce were compared in 364 sites spread across the boreal zone of northwestern Quebec to determine if the northward dominance shift from balsam fir to black spruce could be explained by a difference in height growth. Site index of both species decreased along a south–north gradient, although the trend was only significant for balsam fir on clay deposits. Site index values shifted from being significantly higher for balsam fir in the boreal mixedwood forest, to being slightly (but not significantly) higher for black spruce in the coniferous forest. Mean annual temperature had a significant positive effect on site index for both species, and precipitation of the growing season had a significant negative effect only for balsam fir. The competitive advantage of black spruce over balsam fir in coniferous forests is due to a greater tolerance to cooler temperatures and water-logged soils.
by Audrey Verreault | 30 January 2019
Published in Journal of Biodiversity and Environmental Sciences 6(2): 297-305
Tunisia has made considerable efforts to solve major environmental problems. Reforestation of vast marginal spaces with appropriate species, such as poplar, is one of the economic and environmental challenges (I-488). The fast-growingof this rupicolous species has a high specific versatility in its use. However, its need for water will limit their use in reforestation in areas where water resources are scarce. To cope with this situation, the use of unconventional water resources, including wastewater treatment, is a promising way to increase domestic production of wood. Thus, the treated wastewater is valued as a source of unquestionable water, but also as a source of nutrients. These plants were raised under non-binding for four months and divided into two lots irrigated daily to field capacity with (i) potable water (control : T) and (ii) with treated waste water (TWW). Biomass production, gas exchange and some mineral ions were measured during the experiment, in summer. Our results indicate that irrigation with treated wastewater has submitted a substantially marked effect resulting in an increase of gas exchange. Furthermore, after 60 days, the accumulation of certain metal ions (Cd, Pb and Ni) has resulted in a major malfunction on gas exchange.
by equipewp | 30 January 2019
Published in Tree Seed Working Group – News Bulletin. 60(December): 3-7.
by Marie-Claude Boileau | 30 January 2019
Published in BioMed Central Genomics 15: 1048. https://doi.org/10.1186/1471-2164-15-1048
Genomic selection (GS) may improve selection response over conventional pedigree-based selection if markers capture more detailed information than pedigrees in recently domesticated tree species and/or make it more cost effective. Genomic prediction accuracies using 1748 trees and 6932 SNPs representative of as many distinct gene loci were determined for growth and wood traits in white spruce, within and between environments and breeding groups (BG), each with an effective size of Ne ≈ 20. Marker subsets were also tested.
by Claire Morin | 30 January 2019
Published in Forest Ecology and Management 345: 29-38. https://dx.doi.org/10.1016/j.foreco.2015.02.024
Quantifying soil organic carbon (SOC) stocks in forests and identifying the factors that control their size is crucial to predict how they will be affected by climate and land-use changes. Here, we assessed variations in SOC stocks in the forest floor (FF) and the mineral soil of 21 temperate and boreal forest sites in Québec, and analyzed their relationships with 13 biophysical variables. Across the studied area soil C stocks ranged from 9.2 kg m-2 to 27.8 kg m-2 with on average 78% of this C located in the mineral horizons. Carbon stocks in the FF increased with Mean Annual Precipitation (MAP) and the Percentage of Conifers (Pc), and decreased with Mean Annual Air Temperature (MAAT). Total and mineral soil carbon stocks increased with MAP but were poorly correlated with the other variables mainly because of the high variability in C concentration in B-horizons and mineral soil thickness. When the latter was restricted to 50 cm, the explanatory power of the statistical model for total soil C stock shifted from 34% to 49%, illustrating the impact of soil sampling thickness on C stocks estimates and on the ability to predict them. Regression analyses showed that SOC stocks were mainly controlled by MAP. The depth at which 50% of the mineral soil C stock is reached (D50) was used as an index for the distribution of SOC across the soil profile. The D50 values ranged from ~2 cm to ~40 cm and increased with altitude and Pc, and conversely decreased with the percentage of hardwoods and MAAT. In light of the recent findings on the origin of C stabilization in soils, these results suggest that these impacts on SOC distribution might also affect the stability of the SOC pool. They also emphasize the importance of sampling depth choice according to site characteristics and the importance of the vegetation not only on FF C stocks but also on C distribution across the soil profile.
