The contribution of forest biomass to Canada’s energy production is small but growing. As the forest bioenergy industry in Canada expands, there is growing interest in more sustainably managing the wood ash that is generated as a by-product. Despite being rich in nutrients, wood ash is usually landfilled in Canada. Soil applications of ash in Canadian forests could be used to mimic some of the effects of wildfire, to replace nutrients removed during harvesting, to counteract the negative effects of acid deposition, and to improve tree growth. At present, the provincial and territorial processes for obtaining regulatory approval to use wood ash as a forest soil amendment can be challenging to navigate. Furthermore, the costs for obtaining approval and transporting and applying wood ash to the soil can render landfilling a more cost-effective method of ash management. To ensure that wood ash applications in Canadian forests are conducted safely, effectively, and efficiently, experience from European countries could provide a useful starting point for developing best practices. The results of Canadian research trials will assist policy makers and forest managers in refining management guidelines that encourage soil applications of wood ash as a forest management tool while protecting the ecology, water quality, biodiversity, and productivity of Canadian forests.
We tested the response of species composition of three dominant litter-dwelling arthropod taxa (carabid beetles, spiders, and rove beetles) to wildfire and harvest. This study was conducted in north-central Ontario (47°42′N, 83°36′W) in jack pine (Pinus banksiana Lamb.) dominated stands in 2013 using pitfall trapping. Using 222 species (12 015 individuals), we compared the effects of disturbance using recently burned (3 years since fire) and clearcut sites (3 years since harvest; tree length, full tree, stump removal, and blading), as well as older, closed-canopy stands that have regenerated following clearcutting (51 years since harvest) and fire (92 years since fire), with multivariate regression trees. Taxa were more similar in the three controls (including recent fire) than between controls and harvest treatments, with increased forest floor disturbance in harvested plots being a likely explanation. In addition, taxa were different in the younger (51 years) harvest-origin plots than in the older (92 years) fire-origin plots, suggesting that communities had not yet recovered from the harvest disturbance possibly due to insufficient coarse woody debris in the younger stand. These results indicate that forest management practices that match natural forest floor disturbance could ameliorate short-term effects, whereas the maintenance of more coarse woody debris could reduce the recovery time of epigaeic communities.
With a growing interest in the diversification (e.g., bioenergy, biochemicals) of the forest industry beyond the traditional product streams, concerns that higher harvest utilization levels may compromise site productivity have been heightened. This study reports on 15-year tree growth responses to varying levels of biomass removals conducted on four soil types: loamy tills, outwash sands, wet mineral, and peatlands. Experimental harvest treatments included stem-only, full-tree, full-tree chipping (a full-tree harvest with the roadside material chipped and returned to the site), and full-tree + bladed (a full-tree harvest followed by forest floor removal). Results indicated no significant effect on height growth on the loamy tills, a significant decline for the blading treatment on the sandy soils, and an increase when the blading treatment was applied to the peatland sites. At the stand level, better planted seedling survival and higher recruitment of naturals on the more extreme removal treatment (forest floor removal on sandy sites) tended to nullify any negative impacts identified in the individual-tree growth measurements. The more than doubling of the slash loading on the stem-only treatment plots compared with the full-tree plots did not result in differences in tree productivity levels between these two operational treatments. The stands, however, were just approaching crown closure by year 15, suggesting that ongoing monitoring will be required to confirm that the growth trajectories for the various harvest treatment -soil type combinations can be maintained.Résumé : Dans la mesure où l'industrie forestière est de plus en plus intéressée à diversifier ses activités (p. ex., bioénergie et produits biochimiques) au-delà de sa gamme traditionnelle de produits, les craintes que l'utilisation plus complète de la forêt compromette la productivité des stations augmentent. Cette étude rend compte des réactions en croissance des arbres, après 15 ans, à différents degrés de prélèvement de la biomasse sur quatre types de sol : till loameux, sable fluvio-glaciaire, sol minéral humide et tourbières. Les traitements expérimentaux d'exploitation incluaient tronc entier, arbre entier, copeaux d'arbres entiers (récolte d'arbres entiers mis en copeaux en bordure de route et redistribués sur le site), arbre entier + lame bineuse (récolte d'arbres entiers et enlèvement de la couverture morte). Les résultats ne révèlent aucun effet significatif sur la croissance en hauteur sur le till loameux, mais il y a une diminution importante avec le traitement arbre entier + lame bineuse sur les sols sablonneux et une augmentation avec le même traitement dans les tourbières. À l'échelle du peuplement, une meilleure survie des semis plantés et plus de recrues d'origine naturelle dans le traitement où l'enlèvement de la biomasse était le plus prononcé (enlèvement de la couverture morte sur les sols sablonneux) avaient tendance à annuler tous les impacts négatifs identifiés dans les mesures de croissance d'arbres individuels. Dans le trai...
Core Ideas Biomass removal trials targeted soils sensitive to nutrient removal (shallow to bedrock and infertile sands). 14 long‐term sites (42 plots per treatment) were used to evaluate C and nutrient reserves 20 years post‐harvest. After 20 years, soil C, N, and K reserves did not differ between pre‐harvest levels and SO and FT. Soil reserves of FTB treatments remained significantly lower than the pre‐harvest levels. Jack pine and black spruce declined in height on FTB on sandy sites; there were no differences between SO and FT. Here we report on 20‐yr soil (forest floor plus the upper 20 cm of mineral soil) carbon and nutrient reserves from 14 biomass removal trials established on coarse‐textured, nutrient poor sites. Harvest treatments included stem only (SO, delimbed at the stump), full‐tree (FT, entire trees with boles and branches removed), and full‐tree plus forest floor blading (FTB, full‐tree harvest followed by removal of the forest floor and approximately the upper 5 cm of mineral soil). After 20 yr, there were no significant differences in soil C, N, and K reserves between pre‐harvest levels and the SO and FT treatments. Only the soil reserves of the FTB treatment remained significantly lower than the pre‐harvest levels. Extractable soil Ca and Mg reserves increased in Year 5 in all treatments, followed by slow declines, but all treatments remained comparable to or exceeded pre‐harvest levels at Year 20. For P, harvesting (SO and FT) resulted in significant declines that remain after 20 yr. Both jack pine and black spruce showed reduced top height growth on FTB, but only on some of the sandy sites. There were no differences in top height for either species between SO and FT across all 14 study sites. Current results suggest there is no need for restrictions on full‐tree harvesting for traditional wood products on these nutrient poor sites. However, from a cautionary perspective, it seems prudent at this time to restrict more intensive bioenergy harvests to deep, finer‐textured sites that have larger soil C and nutrient reserves.
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