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.
by Audrey Verreault | 25 January 2024
Published in Forest Ecology and Management 555(2024) : 121703. https://doi.org/10.1016/j.foreco.2024.121703
Mixedwood stands containing aspens (Populus tremuloides or P. grandidentata) often convert to hardwood-dominated stands after harvesting due to the rapid regeneration of aspen from root suckers, even when sites are promptly replanted with conifer seedlings. Without the use of herbicides, this problem is usually dealt with several passes of motor-manual (“manual”) release of overtopped seedlings. The aim of this study was to test a variation of thinning from below treatment (thinning; only 20% of the largest aspens are retained), and to compare it against two traditional release treatments: broadcast brushing (brushing; 100% removal of aspen) or crop tree release (CTR; removal of competing vegetation 60 to 90 cm around planted spruce) and an un-treated control. The thinning treatment left the 20% larger aspen stems in place, in order that they continue exerting apical dominance on smaller suckers and limit re-suckering of the treated plots. Aspen suckering and growth of planted black spruce seedlings (Picea mariana (Mill.) B.S.P) were measured two- and four-growing seasons following treatments. Results four years after release application showed that the thinning and CTR treatments reduced aspen density by 61% compared to the brushing treatment. In addition, aspen individual stem volume in the thinning treatment was almost 10 times larger than the brushing and twice that of the CTR treatments. Spruce height and ground collar diameter (GCD; 5 cm aboveground line) were both measured, and while height increment was similar in all treatments, diameter increment was greater in the thinning treatment (+42%) compared to the control, brushing and CTR treatments (+17%). Thinning yielded better short-term results than the brushing release in terms of aspen re-suckering and aspen sawlog potential, highlighting the need for adapted silvicultural treatments based on the species’ ecology.
by Audrey Verreault | 17 January 2024
Published in Biogeosciences 20(24): 5087-5108. https://doi.org/10.5194/bg-20-5087-2023
The carbon cycle in Arctic–boreal regions (ABRs) is an important component of the planetary carbon balance, with growing concerns about the consequences of ABR warming for the global climate system. The greatest uncertainty in annual carbon dioxide (CO2) budgets exists during winter, primarily due to challenges with data availability and limited spatial coverage in measurements. The goal of this study was to determine the main environmental controls of winter CO2 fluxes in ABRs over a latitudinal gradient (45∘ to 69∘ N) featuring four different ecosystem types: closed-crown coniferous boreal forest, open-crown coniferous boreal forest, erect-shrub tundra, and prostrate-shrub tundra. CO2 fluxes calculated using a snowpack diffusion gradient method (n=560) ranged from 0 to 1.05 g C m2 d−1. To assess the dominant environmental controls governing CO2 fluxes, a random forest machine learning approach was used. We identified soil temperature as the main control of winter CO2 fluxes with 68 % of relative model importance, except when soil liquid water occurred during 0 ∘C curtain conditions (i.e., Tsoil≈0 ∘C and liquid water coexist with ice in soil pores). Under zero-curtain conditions, liquid water content became the main control of CO2 fluxes with 87 % of relative model importance. We observed exponential regressions between CO2 fluxes and soil temperature in fully frozen soils (RMSE=0.024 ; 70.3 % of mean ) and soils around the freezing point (RMSE=0.286 ; 112.4 % of mean ). increases more rapidly with Tsoil around the freezing point than at Tsoil<5 ∘C. In zero-curtain conditions, the strongest regression was found with soil liquid water content (RMSE=0.137 ; 49.1 % of mean ). This study shows the role of several variables in the spatio-temporal variability in CO2 fluxes in ABRs during winter and highlights that the complex vegetation–snow–soil interactions in northern environments must be considered when studying what drives the spatial variability in soil carbon emissions during winter.
