by Marie-Claude Boileau | 27 March 2024
Published in Silva Fennica 58(2): 2309. https://doi.org/10.14214/sf.23029
Mechanical site preparation (MSP) is used prior to planting to control competing vegetation and enhance soil conditions, particularly in areas prone to paludification. Tree planting density can be adapted to the management context and objectives, as it influences yield and wood quality. However, the combined effects of MSP and planting density on understory vegetation composition, functional traits, and diversity remain uncertain. We thus conducted a study in the Clay Belt region of northwestern Quebec, Canada. After careful logging, the study area was divided into nine sites, each receiving one of three treatments: plowing, disc trenching, or no preparation. Sites were further divided into two, with black spruce (Picea mariana [Mill.] Britton, Sterns & Poggenb.) seedlings planted at either a low planting density of 1100 seedlings ha–1 or a high planting density of 2500 seedlings ha–1. After nine years, we assessed understory composition, diversity, key functional traits, sapling density and growth of planted trees. Careful logging alone led to a higher density of naturally established conifers compared to plowing or disc trenching. The interaction between planting density and MSP significantly influenced understory diversity and composition in plowed plots. Understory composition was affected by the soil C/N ratio, coniferous species, and deciduous species density. The growth of black spruce was notably enhanced with higher planting density in the plow treatment only. Neither planting density nor MSP alone affected tree height and diameter. Our results suggest that combining plowing with high-density planting can enhance stand growth and improve forest productivity. These findings guide future research on paludified forests.
by Claire Morin | 27 March 2024
Order made under the Quebec Fishery Regulations (1990) which modifies the content of this Regulation with regard to the periods, quotas, fishing gear and methods and the length or weight limits for fish applicable to the sport fishing for an area or part of it.
by Marie-Claude Boileau | 14 March 2024
Published in Ecological Applications e2958. https://doi.org/10.1002/eap.2958
The boreal forest is one of the world’s largest terrestrial biome and plays crucial roles in global biogeochemical cycles, such as carbon (C) sequestration in vegetation and soil. However, the impacts of decades of N deposition on N-limited ecosystems, like the eastern Canadian boreal forest, remain unclear. For 13 years, N deposition was simulated by periodically adding ammonium nitrate on soils of two boreal coniferous forests (i.e., balsam fir and black spruce) of eastern Canada, at low (LN) and high (HN) rates, corresponding to 3 and 10 times the ambient N deposition, respectively. We show that more than a decade of N addition had no strong effects on mineral soil C, N, P, and cation concentrations and on foliar total Ca, K, Mg, and Mn concentrations. In organic soil, C stock was not affected by N addition while N stock increased, and exchangeable Ca2+ and Mg2+ decreased at the balsam fir site under HN treatment. At both sites, LN treatment had nearly no impact on foliage and soil chemistry but foliar N and N:P significantly increased under HN treatment, potentially leading to foliar nutrient imbalance. Overall, our work indicates that, in the eastern Canadian boreal forest, soil and foliar nutrient concentrations and stocks are resilient to increasing N deposition potentially because, in the context of N limitation, extra N would be rapidly immobilized by soil micro-organisms and vegetation. These findings could improve modeling future boreal forest soil C stocks and biomass growth and could help in planning forest management strategies in eastern Canada.
by Marie-Claude Boileau | 14 March 2024
Published in BioInvasions Records 13(1): 1-8. https://doi.org/10.3391/bir.2024.13.1.01
The presence of non-native Asian earthworms in northeastern North America has raised concerns in the last decades following the observation of how intensely they can disturb the soil and initiate cascading effects in invaded areas. A recent study showed that the known northern distribution of these earthworms in northeastern North America reached the southern parts of the province of Ontario (Canada) as well as the northeastern states in the U.S.A. that border the province of Québec (Canada). In 2021, more specimens were found in southern Ontario and in the province of New Brunswick. Here we report the first record of a non-native Asian earthworm (Amynthas tokioensis) in the province of Québec, which confirms the progression of the invasive Asian earthworms in Canada.
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.
