by Marie-Claude Boileau | 12 March 2024
Published in Applied Geochemistry 160: 105855. https://doi.org/10.1016/j.apgeochem.2023.105855
The use of tree rings to record changes in lead (Pb) deposition levels and pollution sources has produced contrasted results depending on tree species and sites. In this study, Pb concentrations and isotopic ratios (206Pb/207Pb, 208Pb/206Pb and 206Pb/204Pb) were analyzed in the exchangeable (0.05M HCl extraction) and the residual (concentrated HNO3 extraction) fractions of sugar maple’s tree rings at four eastern Canada forest sites. Above 90% of tree ring Pb was associated with the residual fraction, reflecting strong binding to wood, thus suggesting low radial mobility in sugar maple. After an increase in the first part of the 20th century, wood Pb concentration declined from the 1970s–80s to nowadays for most sampled trees to reach levels similar or even lower than in the early 20th century. This decline was paralleled by a slight decrease in 206Pb/207Pb ratio, reflecting a decrease in Pb pollution in the last decades. Our isotopic data suggest the contribution of USA sources declined by 20–40% at three out of the four study sites since the early 1900’s. These observed trends align with findings reported in previous studies and reveal that sugar maple may be a good tree species model to record Pb atmospheric pollution. Further study must be conducted to validate these findings, especially to estimate the contribution of root vs. aboveground biomass to Pb uptake.
by Audrey Verreault | 12 March 2024
Published in Forest Ecology and Management 558: 121785. https://doi.org/10.1016/j.foreco.2024.121785
Despite the need for climate change mitigation and altered forest management practices, little is known about the impacts of silvicultural practices such as partial-cuts and clear-cuts on forest ecosystem carbon (C) dynamics. Specifically, the effect of these two overstory treatments on C pools other than the aboveground biomass of trees remains poorly understood. Here, C stocks were estimated for a northern temperate mixed forest located in eastern Québec, Canada, five years after clear-cutting and partial-cutting, either with or without a brushing treatment to control the competing vegetation. The biomass of the aboveground vegetation (trees, saplings, understory), litter and woody debris (coarse, small, fine), as well as the roots (diameter ≤ 1.5 cm) was evaluated. Additionally, soil C pools up to a depth of 35 cm of the mineral soil were assessed. Total ecosystem C stocks were influenced by the overstory treatments reflecting harvest intensities. Although the belowground C pools were major contributors to total ecosystem C stocks, silvicultural treatments only influenced forest floor and aboveground C stocks. However, assessments like the one presented here capture contemporary C stocks, which highlights the need for monitoring to build suitable forest ecosystem C models and to understand long-term C dynamics.
by Audrey Verreault | 28 February 2024
Published in Proceedings of the first biennial Northern Hardwood Conference 2021: Bridging science and management for the future. Gen. Tech. Rep. NRS-P-211. Madison, WI . U.S. Department of Agriculture, Forest Service, Northern Research Station: 48-51. https://doi.org/10.2737/NRS-GTR-P-211-paper11
In Quebec, Canada, multicohort forest management in hardwood and mixedwood stands include group selection cutting and patch cutting. We assessed the success of these cuts in regenerating the intermediate shade tolerant yellow birch (Betula alleghaniensis Britt.; YB) at an operational scale and over a large territory using surveys conducted at 2, 5, 10, and 15 years after harvest. Regeneration of the target species was successful, with YB showing a mean stocking around 60 percent and a mean sapling density around 3,400 stems ha-1 after 15 years. The relative presence of YB in 15-year-old canopy openings—a proxy for future species composition—was best predicted by that species’ relative abundance, stocking based on one stem per sampling unit, and mean maximum height measured in year five (rather than year two) using smaller sampling units (6.25 m2 rather than 25 m2). See Bilodeau-Gauthier et al. (2020) for further details.
by Audrey Verreault | 26 February 2024
Published in Scandinavian Journal of Forest Research 39(2): 101-109. https://doi.org/10.1080/02827581.2024.2305186
Uncertainties remain regarding the carbon (C) loss due to scarification in afforested lichen woodlands (LW), which originate from regeneration failures of closed-crown black spruce- feathermoss stands due to compounded disturbances. Therefore, the objective of this study was to characterize the C stock changes in the forest floor of scarified, unharvested LWs. Ten afforestation trials were established from 1999 to 2014 in LWs in the managed boreal forest of Québec. Ground surface layers were sampled in 2017 for different microsites. From 3 to 18 years after treatment, scarified floors exhibited ≈ 2 Mg ha−1 C loss, due to opposite trends in the furrow and ridge microsites. Both gradually approached the undisturbed C density level of forest floor between furrow pairs and between skidder trails microsites without reaching it after 18 years. This suggests that microsite C density continued to evolve afterward, and that losses due to scarification might be recovered, due to a higher potential gain in the furrow microsites combined with a lower expected loss in the ridge microsites. Carbon managers should use a permanent 2 Mg ha−1 C loss in the forest floor due to scarification in LWs, acknowledging that this is offset by the growth of planted trees.
by Audrey Verreault | 26 February 2024
Published in Forestry Chronicle 100(1). https://pubs.cif-ifc.org/doi/10.5558/tfc2024-004
This paper consolidates the most current information available on tree improvement in Canada and provides a summary of key historical events leading to its development and expansion across the country. The most recent publication on the topic was by Fowler and Morgenstern (1990) compiled over 30 years ago. Since that time, many things have changed and new technologies, such as the increasing use and adoption of genomics, have become part of the tool-box of tree breeders in forestry and natural resource management. This paper provides information on the status of tree improvement programs including their history, objectives, seed production, future outlook and other performance measures by province across Canada.
