by Marie-Claude Boileau | 30 January 2019
Published in Forest Ecology and Management 312: 203-215
We quantified the effects of different loads of forest logging residues on the microenvironment (soil temperature, soil volumetric water content, competing vegetation cover, and available nutrients) of planted hybrid poplars one year after planting, and assessed the corresponding seedling growth until the third growing season. In four experimental plantations across Quebec (Canada), we used a factorial design of four residue loads that were applied at the tree-level over three planted species: hybrid poplars (Populus spp.), black spruce (Picea mariana (Mill.) BSP), and either jack pine (Pinus banksiana Lamb.) or white spruce (Picea glauca (Moench) Voss), depending upon the site. Logging residues linearly decreased competing vegetation cover on two of four sites and reduced fluctuations in soil temperature on all sites. Logging residues also decreased summer soil temperatures at all sites through a negative quadratic effect. On one site, the frequency of freeze–thaw cycles increased under logging residues, while logging residues increased soil water content on another site, for certain measurement events. Logging residues did not affect available nutrients. Seedlings showed no consistent growth response to logging residues for three years after planting, except for a beneficial effect of logging residues on hybrid poplar growth on one site. Because logging residues affected seedling microclimate and competing vegetation, their maintenance and on-site spatial arrangement on site could be used to manipulate the growing conditions for planted trees.
by Claire Morin | 30 January 2019
Published in Forest Ecology and Management 310: 167-172. https://doi.org/10.1016/j.foreco.2013.08.020
Ammonium nitrate was added annually at 3- and 10-fold the ambient wet atmospheric deposition rate (8.5 kg ha-1 year-1) during 8 years in a base-poor northern hardwood forest of Québec, Canada. Soil chemistry and foliar chemistry, crown dieback and basal area growth of sugar maple (Acer saccharum Marsh.) were measured after 8 years of treatments. Despite repeated N additions, N concentrations in all soil layers remained similar between treatments. However, the treatments significantly reduced exchangeable Ca, Mg, Mn and K compared to the untreated plots, at least for one of the top organic soil layers. The most significant and substantial differences were observed for Ca between the control and the high N treatment, with the L and the H layers showing decreases of 29% and 72%, respectively. Foliar Ca and Mn concentrations decreased with increasing levels of N addition, while foliar N increased. Foliar Ca in the high N treatment decreased by 79% compared to the control and reached 0.24%, the lowest foliar Ca concentration ever reported for sugar maple. No significant treatment effects were observed for dieback rate or basal area growth, although mean dieback rate of sugar maple in the high N treatment was 43% higher than in the control. Our results show that increased N deposition, even at relatively low rates, can strongly affect Ca nutrition of sugar maple at sites with low base cation saturation. This raises concerns about the sustainability of sugar maple in acidic, base-poor forest soils.
by Claire Morin | 30 January 2019
Published in Annals of Forest Science 70(8): 825-834. https://doi.org/10.1007/s13595-013-0329-1
Context – Warmer temperatures and anthropogenic N depositions are altering soil nutrient cycles and plant nutrition worldwide and are projected to rise dramatically in the future, particularly at the high latitudes. How much will such alterations affect symbiotic organisms such as ectomycorrhizae (ECM)?
Aims – The aim was to investigate the short-term effects of warmer soil temperatures and N-enriched precipitations on roots and ECM.
Methods – A field experiment was established during 2008–2010 in two black spruce (Picea mariana) stands of the boreal forest of Quebec, Canada. The ECM of 12 trees per site were counted and identified by morphotyping.
Results – After 3 years, soil heating markedly modified the proportions of vital root tips and ECM in the colder stand, while no effect of the N-enriched rain was observed on soil chemistry and consequently on roots and ECM. Density and ramification of root tips were not affected by the treatments.
Conclusion – The hypothesis that the treatments would alter the ECM was confirmed only partially in the colder stand. The type of application and amount of N supplied were unable to substantially modify in the short-term growth conditions of roots and ECM, explaining the observed results.
by Marie-Claude Boileau | 30 January 2019
Published in Canadian Journal of Forest Research 44: 750-759. https://doi.org/10.1139/cjfr.2013.0407
The identification of low-vigor trees with potential for sawlog production is a key objective of tree marking guidelines used for partial cuts in northern hardwoods. The aim of this study was to measure the impact of various vigor-related defects on the monetary value of hardwoods. To achieve this, we sampled 64 sugar maple (Acer saccharum Marshall) and 32 yellow birch (Betula alleghaniensis Britton) trees from two locations in southern Quebec, Canada. We identified over 420 defects, which were grouped into 8 categories. The trees were then harvested and processed into lumber, and the value per unit volume of each stem was calculated from the value of the product assortment (lumber, chips, and sawdust). We found that visible evidence of fungal infections (sporocarps and (or) stroma) and cracks had the largest negative influence on value in both species. A model that included these defects was almost as good at predicting value as one that included a specifically designed quality classification. A more accurate assessment of value could be achieved using wood decay assessment tools and (or) by considering site-specific variables. Results from this study showed that visual identification of fungal infections and cracks could be used to enhance tree marking guidelines for hardwoods. This would meet both the silvicultural objective of selection cuts, by removing low-vigor trees, and the wood supply objective, by improving stem quality assessment prior to harvest.
by Audrey Verreault | 30 January 2019
Published in Forest Ecology and Management 318: 270-273
Liming, the application of calcitic materials to soil, is increasingly used in acidic, base-poor sugar maple stands of eastern North America to restore nutritional status and vigor of sugar maple trees. However, few studies have evaluated the effect of base cation addition on other components of these ecosystems. The eastern red-backed salamander (Plethodon cinereus) is one of the most abundant vertebrates in forests of eastern North America, and is commonly used as an indicator of forest disturbances. So, it is important to know how it might be affected by soil liming. This is the first study dealing with the potential direct and short-term effect of liming on amphibians of North America. Lime, in the form of CaCO3 (3 Mg ha-1), was added at the surface of microcosms containing a low buffered soil and forest floor from a sugar maple stand to evaluate the short-term effect of this treatment on this amphibian species. Two grades of lime were used in this study: finely ground and sandy CaCO3. Finely powdered lime was included to verify if it could clog salamander skin pores, since this could negatively affect health and growth, and consequently induce mortality. The results suggest that, even when applied in finely ground form, direct contact with lime had no short-term effect on the species’ health and survival rate. Given this, and the fact that it can be found in a wide range of soil pH conditions, the redbacked salamander is thus unlikely to be affected by the use of liming to restore acidic, base-poor sugar maple bushes. Some old liming trials carried out in forests of eastern North America could be used in the next years to verify the long-term effects of liming on this species. This should help foresters decide whether or not liming treatments are compatible with conservation, ecological and management objectives.
