by Claire Morin | 30 January 2019
Published in Applied Geochemistry 26: 2181-2190
The concentrations and the isotopic compositions of S, N and C were studied in soils and in the dominant plant species of three forested watersheds (Québec, Canada) located along a latitudinal and atmospheric deposition gradient. Large increases in S, N and C isotope ratios (up to 3.9‰, 10‰, 2.6‰, respectively) were observed with increasing soil depth at the three watersheds. These increases were accompanied by a strong decrease in elemental concentrations resulting in a strong negative relationship between these two variables. Both S and N concentrations throughout the soil profile and d34S and d15N in the mineral soil appeared to increase with increasing S and N deposition rates and decreasing latitude. A strong positive linear relationship was found between d34S and d15N (R2 = 0.72) values and between organic S and N concentrations (R2 = 0.96) in soils. The slope of the linear relationship between d34S and d15N (d34S = f(d15N)) indicated that isotopic fractionation was almost 4 times higher for S than for N during transformations that occurred in soil. However, this difference might reflect a higher degree of openness of the S cycle compared to the N cycle rather than an isotope effect per se. Overall, the results suggest that N and S inputs significantly impact the isotope ratios and the concentrations of N and S in the soils, and that S and N were closely associated and subject to similar processes with the same isotopic effects throughout the soil profile. Contrary to most studies, d34S-SO4 in stream water of the most northerly site with the lowest S deposition rate was significantly higher than d34S-SO4 in atmospheric depositions but similar to the d34S of the bulk mineral soil. It suggests that the mineral soil actually contributes a large portion of the stream S-SO4 for this site.
by Marie-Claude Boileau | 30 January 2019
Published in Forest Ecology and Management 274: 210-221. https://doi.org/10.1016/jr.foreco.2012.02.020
Solar radiation, photosynthetically active radiation (PAR) and soil temperature were monitored during three summers following establishment of silvicultural gaps (1-ha square patch clearcut, 20- and 30-m diameter circular gaps) in yellow birch–conifer stands, in eastern Québec, Canada (47°N latitude, 72°W longitude). We assessed the effect of aspect, slope, opening size, and location within the opening on the microclimate in a foothill site characteristic of this forest type. Daily solar radiation averaged 9.7, 14.3, and 15.1 MJ/m2 in the patch clearcut, in 2001, 2002, and 2003, respectively, as compared to 1.7, 2.2, and 2.8 MJ/m2 in the understory of the uncut forest. We also determined that the ratio of PAR to broadband solar radiation was quite constant in the patch clearcut (1.67 mol/MJ), while it increased from 0.76 mol/MJ (June–September) to 1.49 mol/MJ (October) in the forest understory, as broadleaved trees in the main canopy lost their foliage. Circular gaps received intermediate levels of solar radiation (3.9, 6.3, and 7.3 MJ/m2) that were comparable for the 20- and 30-m gap diameters. Solar radiation was consistently lower in the southern portion of these gaps than in their central and northern portions, a relative shortfall of 40–50% on north-facing aspects, and 25% on east-southeast aspects. This microclimatic diversity among locations was confirmed by PAR measurements and soil temperature monitoring, which suggests that differing ecological niches may promote species coexistence in these mixedwood stands.
by André Boily | 30 January 2019
Published in Khasa, D., Y. Piché et A.P. Coughlan (eds.). Advances in mycorrhizal science and technology. NRC Research Press, Ottawa, Canada. p. 139-152.
Mycorrhizal symbioses are widespread and fundamental components of terrestrial ecosystems and have shaped plant evolution. Research in this field is rapidly evolving and recent findings have done much to improve our understanding of how these complex plant – fungal associations function. This volume, which is aimed at the scientific community, comprises 14 chapters written by more than 30 international experts from different fields of mycorrhizal research. The chapters provide either in-depth reviews or the results of previously unpublished scientific studies, and certain are illustrated with photos and line drawings. The topics covered are of global interest and include plant – fungal communication, the interaction of mycorrhizal fungi with other soil microorganisms, the use of mycorrhizal fungi in plant-production systems, and the commercial harvesting of edible mycorrhizal forest mushrooms.
by Claire Morin | 30 January 2019
Published in New Forests 42(2): 195-214. https://doi.org/10.1007/s11056-011-9247-y
To meet the needs for improved spruce seeds in the province of Québec, Canada, 17 first-generation white spruce seed orchards (SO) were established. These SOs are located in different bioclimatic domains and contain seed trees originating from geographically and genetically distinct sources. To evaluate the influence of SO on seedling growth and morphology, seedlings produced with seeds originating from the ten most commonly used first-generation white spruce SO in Québec were raised under similar nursery conditions. Tissue nutrient concentrations of seedlings evolved similarly among seed orchards during the second growing season. At the end of the growing season, only shoot phosphorus concentrations were significantly different. When modeled with a logistic function, there was a significant difference between height and diameter growth curve parameters of seedlings from distinct SO during the second growing season. These differences led to significant differences in the height and shoot dry mass of the seedlings at the end of their second growing season, but not in their diameter or root dry mass. The ten SOs were clustered in two groups according to the above-ground characteristics of their progeny. This limited amount of morphological diversity suggests that expanding the size of the present seed zones may be an appropriate course of action for white spruce seed production in Québec.
by Claire Morin | 30 January 2019
Published in Natural Areas Journal 31(3): 300-306
Worldwide, old-growth forest loss and fragmentation resulting from logging are considered major threats to biodiversity. In many regions of the boreal zone, remaining patches of old-growth forests left following logging are restricted to small areas exposed to edge effects. Our objectives were to evaluate, from a literature review, the distance of edge influence (DEI) induced by sharp logging-induced edges on adjacent old-growth residual forests and to compare, in order to exemplify edge effect influence, two contrasting scenarios of residual stand configurations (linear vs. agglomerated). Synthesis from studies conducted in boreal forests of Canada and Fennoscandia indicates a DEI of ~50 meters for residual old-growth forests located along recently (≤ 20 years) cutover areas. Based on the comparison of two contrasted scenarios, we demonstrate the strong relationship between residual forest configuration and area under edge influence. For a similar area of residual old-growth forest, linear strips scenario was > 2.5 times more affected by edge compared to agglomerated scenario. We thus recommend considering various types of dispersion strategies that result in large forest residual stands interconnected with remnants > 100 m wide in order to reduce edge influence on the remnant old growth stands, to mimic forest fire patterns, and to conserve associated biodiversity. To our knowledge, this study is the first meta-analysis to review and assess the DEI in boreal forest of North America and Fennoscandia. In addition, it quantifies, using a spatially explicit model, the impacts of logging-induced edges on the amount of interior forest for two common strategies of residual forest configuration that are well established in eastern Canada.
