by Marie-Claude Boileau | 11 March 2021
Published in For. Ecol. Manage. 489: 119062. https://doi.org/10.1016/j.foreco.2021.119062
Wood ash as soil amendment is increasingly being used globally to counter forest soil acidity, increase base cation availability, especially Ca, and correct foliar nutritional deficiencies/imbalances. Knowledge remains limited regarding the effects of wood ash in temperate hardwood forests dominated by sugar maple and supported by acidic soils with low availability of base cations. The main objective of this study was to determine short-term effects of wood ash application on the soil’s acid base-status and nutrient availability, foliar nutrition, and growth of seedlings and mature sugar maple trees. A first experiment was established in 15 stands across southeastern Quebec, which included an unamended control and a 20 Mg ha−1 treatment. A layer of naturally regenerated sugar maple seedlings was present in these stands. A second experiment was conducted on four other sites, which included an unamended control and three ash treatments (5 Mg ha−1, 10 Mg ha−1, 20 Mg ha−1); sugar maple seedlings were then planted at high density (50 × 50 cm). In Experiment 1, ash application resulted in increased pH and concentrations of P, Ca and Mg in the forest floor after 3 years. Only marginal treatment effect was detected in the upper mineral soil, where pH and Ca and Mg concentrations tended to be higher under the ash treatment. Nutritional diagnoses using the DRIS approach revealed that the different ash treatments were associated with a decrease in Ca deficiency and N excess in sugar maple (seedlings and mature trees). Using dendrochronological data from 288 trees, we measured a positive effect of the 20 Mg ha−1 ash treatment on the basal area increment (BAI) of mature sugar maple from the first year after application. Within 3 years following ash application, mean annual BAI of sugar maple in the ash treatment was 20% higher (+1.9 cm2 y−1) than that of the control. The ash treatments exerted no effect on sugar maple seedling growth. Varying wood ash doses had weak effects on seedling nutrition in Experiment 2. Our results indicate that ash application may exert positive short-term effects on the soil acid-base status, foliar nutrition, and diameter growth of mature sugar maple trees.
by Marie-Claude Boileau | 11 March 2021
Published in Ecological Indicators 125: 107516. https://doi.org/10.1016/j.ecolind.2021.107516
Many jurisdictions have put forward guidelines to identify sites at risks of soil degradation with the extraction of logging residues. Most guidelines are based on expert opinion and use the precautionary principle because of the lack of strong understanding of what makes a site sensitive to intensive biomass removal. Two main approaches are used: 1-identifying thresholds for specific site properties 2- developing nutrient budget indicators to rate the potential for nutrient deficit. Thanks to the development of digital soil mapping, it is becoming easier to develop maps for such indicators. A crucial question is the reliability of the different indicators. One way of evaluating their reliability is to test the coherence between the geographic locations of sites rated as sensitive by different indicators. In this study, we developed maps of key soil properties and of biogeochemical fluxes for the managed forest land of Canada at a resolution of 250 m. We used three site properties (slope, pH and sand content), as well as three nutrient budget indicators (N Budget, Base cation (BC) Budget and N Stability ratio) that were mapped and compared. The results indicated very little overlap between the areas identified as sensitive by the three site property indicators and very little concordance between sites rated as sensitive by site property indicators and those identified as sensitive by nutrient budget indicators while nutrient budget indicators showed coherence among themselves. Because nutrient budget indicators were found to be more dependent on the amount of nutrient extracted in the harvested biomass, than on the rates of nutrient inputs from the soil or the atmosphere, they tended to rate productive sites as sensitive, to the opposite of site property indicators. These results suggest that different indicators are assessing different processes and different aspects of site sensitivity. Because of the lack of coherence amongst the indicators, it is advisable 1) to use indicators based on the results of long-term monitoring plots, 2) to maintain such long-term observations and 3) to leave on the ground a substantial proportion of harvest residues, especially on sites evaluated as sensitive.
by Audrey Verreault | 3 March 2021
Published in Eur. J. For. Res. https://doi.org/10.1007/s10342-020-01349-6
New silvicultural practices to meet the requirements of ecosystem-based forest management are being adopted operationally, even if the long-term outcomes remain unknown. In eastern Quebec, Canada, the conversion of plantations from even-aged to irregular or uneven-aged stands is being carried out in 10% of commercial thinning operations. Existing growth and yield simulators cannot be used to forecast stand development. Here we apply a novel individual tree-level simulator to plantations characterized by high levels of natural regeneration ingrowth, such as those observed in Quebec. The simulator user can either choose distance-dependent or distance-independent competition indices, depending on user preference or simulation needs. Calibration statistics and validation results indicate that both versions perform very well. When applied to operational silvicultural scenarios, the simulator shows that thinning does not influence total stand yield; however, tree spatial aggregation does change. Moreover, the variability among the different simulation runs is greater for spatial statistics than for stand yield. Overall, thinning from below has the greatest effect on stand structure, whereas the smallest is from early crop tree release, used as the initial conversion step. This pattern implies that the first and second thinnings of the conversion process towards irregular or uneven-aged stands may not have a major effect on stand structure. In the case of the conversion process, the consequences for stand structure must thus be viewed as a longer-term issue. More importantly, the conversion process does not reduce stand yield, thereby reducing one of the key concerns of forest managers.
by Audrey Verreault | 2 March 2021
Published in Trees 35(1). https://doi.org/10.1007/s00468-020-02001-x
Some studies suggest that tapping sugar maple (Acer saccharum Marshall) trees can cause their growth to decline, particularly on poor and acidic soils. We tested this hypothesis in seven sugar bushes located in the Quebec Appalachians by comparing the growth of tapped trees with nearby untapped trees. The sites represented a range of soil fertility, from very good for sugar maple to strongly deficient in calcium. Trees were cored, and individual dendrochronology series were used to analyze trends in basal area growth, from a period of 10 years before, to 8–10 years after tapping began. Basal area growth of sugar maples did not appear to be influenced by tapping (p ≥ 0.134), except at one site (p < 0.001), where the growth of tapped trees decreased by 33% over 10 years. This decline could not be explained only by the poor soil fertility observed at the site. Although a tree biomass distribution budget indicated that maple syrup production represented only 4–6% of the carbon allocated annually to net primary production, the long-term relationship between maple syrup production and tree growth requires further study.
by Audrey Verreault | 2 March 2021
Published in Energies 14(1): 93. https://doi.org/10.3390/en14010093
Unharvested hardwoods are abundant in eastern Canada, due to the low quality of their fiber and the absence of outlets in conventional wood transformation industries. The objective of this study was to assess the biochemical and thermochemical energy conversion potential of decaying hardwoods and compare their relationships with external and internal indicators of tree degradation. We characterized how wood-decay processes altered the physical and chemical properties of these woods and affected their digestibility yield and their performance according to indexes of stability and efficiency of combustion. DNA analysis on wood samples was also performed to determine the relative abundance of white-rot fungi compared to that of other saprotrophs. All properties stayed within the range of variations allowing the wood to remain suitable for conversion into bioenergy, even with increased decay. We found no significant differences in the physical and chemical properties that are crucial for energy production between wood from externally-assessed live and decayed trees. However, the proportion of wood area affected by rot was significantly associated with increased digestibility yield, and with decreased combustion reactivity. We could not detect any specific effect associated with increased relative abundance of white-rot fungi. These results suggest that the utilization of biomass from decayed hardwoods instead of live trees for bioenergy production should not alter the conversion efficiency and even potentially increase the performance of biochemical pathways, and hence, support their use as feedstock for bioenergy production.
