by Claire Morin | 30 January 2019
Published in Microbial biotechnology 9(3): 316-329. https://doi.org/10.1111/1751-7915.12348
The impact of mechanical site preparation (MSP) on soil biogeochemical structure in young larch plantations was investigated. Soil samples were collected in replicated plots comprising simple trenching, double trenching, mounding and inverting site preparation. Unlogged natural mixed forest areas were used as a reference. Analysis of soil nutrients, abundance of bacteria and gas exchanges unveiled no significant difference among the plots. However, inverting site preparation resulted in higher variations of gas exchanges when compared with trenching, mounding and unlogged natural forest. A combination of the biological and physicochemical variables was used to define a multifunctional classification of the soil samples into four distinct groups categorized as a function of their deviation from baseline ecological conditions. According to this classification model, simple trenching was the approach that represented the lowest ecological risk potential at the microsite level. No relationship was observed between MSP method and soil bacterial community structure as assessed by high-throughput sequencing of bacterial 16S rRNA gene; however, indicator genotypes were identified for each multifunctional soil class. This is the first identification of multifunctional molecular indicators for baseline and disturbed ecological conditions in soil, demonstrating the potential of applied microbial ecology to guide silvicultural practices and ecological risk assessment.
by Claire Morin | 30 January 2019
Published in PeerJ 4: e1767 https:/doi.org/10.7717/peerj.1767
Biological carbon sequestration by forest ecosystems plays an important role in the net balance of greenhouse gases, acting as a carbon sink for anthropogenic CO2 emissions. Nevertheless, relatively little is known about the abiotic environmental factors (including climate) that control carbon storage in temperate and boreal forests and consequently, about their potential response to climate changes. From a set of more than 94,000 forest inventory plots and a large set of spatial data on forest attributes interpreted from aerial photographs, we constructed a fine-resolution map (~375 m) of the current carbon stock in aboveground live biomass in the 435,000 km2 of managed forests in Quebec, Canada. Our analysis resulted in an area-weighted average aboveground carbon stock for productive forestland of 37.6 Mg ha-1, which is lower than commonly reported values for similar environment. Models capable of predicting the influence of mean annual temperature, annual precipitation, and soil physical environment on maximum stand-level aboveground carbon stock (MSAC) were developed. These models were then used to project the future MSAC in response to climate change. Our results indicate that the MSAC was significantly related to both mean annual temperature and precipitation, or to the interaction of these variables, and suggest that Quebec’s managed forests MSAC may increase by 20% by 2041-2070 in response to climate change. Along with changes in climate, the natural disturbance regime and forest management practices will nevertheless largely drive future carbon stock at the landscape scale. Overall, our results allow accurate accounting of carbon stock in aboveground live tree biomass of Quebec’s forests, and provide a better understanding of possible feedbacks between climate change and carbon storage in temperate and boreal forests.
by Marie-Claude Boileau | 30 January 2019
Published in Forest Science 62(2): 227-236 http://dx.doi.org/10.5849/forsci.15-023
Since two decades, patch cutting systems have been applied in Eastern Canada to regenerate uneven-aged yellow birch (Betula alleghaniensis Britton) – conifer stands. Yet, we still know very little about how the trees located in the between-patch matrix respond to treatments. This study compares growth, recruitment and tree mortality of yellow birch, red maple (Acer rubrum L.), balsam fir (Abies balsamea [L.] Mill.) and red spruce (Picea rubens Sarg.) in three 50% patch cutting treatments with 20-, 30-, 40-m diameter circular gaps combined with 33% single-tree cutting in the matrix between patches, and an uncut control. After 10 years, positive effects of cutting treatments on recruitment and growth were nullified by mortality, resulting in non-significant changes in stand net merchantable basal area. Mortality rate modeled at the tree-level was higher for trees with larger diameters, defects, and high crown ratios. Trees with small diameter and those located along the border of harvest gaps had the largest increments in basal area. This study questions the use of patch cutting in mixed uneven-aged stands comprising an important component of short-lived balsam fir. Silvicultural systems utilizing non-systematic placement of variably-sized gaps may prove more beneficial for managing wood production and complexity in yellow birch – conifer stands.
by Claire Morin | 30 January 2019
Published in PLOS ONE 10(12): e0144844. https://doi.org/10.1371/journal.pone.0144844
Maple syrup production is an important economic activity in north-eastern North-America. The beginning and length of the production season is linked to daily variation in temperature. There are increasing concerns about the potential impact of climatic change on this industry. Here, we used weekly data of syrup yield for the 1999–2011 period from 121 maple stands in 11 regions of Québec (Canada) to predict how the period of production may be impacted by climate warming. The date at which the production begins is highly variable between years with an average range of 36 days among the regions. However, the average start date for a given region, which ranged from Julian day 65 to 83, was highly predictable (r2 = 0.88) using the average temperature from January to April (TJ-A). A logistic model predicting the weekly presence or absence of production was also developed. Using the inputs of 77 future climate scenarios issued from global models, projections of future production timing were made based on average TJ-A and on the logistic model. The projections of both approaches were in very good agreement and suggest that the sap season will be displaced to occur 15–19 days earlier on average in the 2080–2100 period. The data also show that the displacement in time will not be accompanied by a greater between years variability in the beginning of the season. However, in the southern part of Québec, very short periods of syrup production due to unfavourable conditions in the spring will occur more frequently in the future although their absolute frequencies will remain low.
