Search

Wood ash amendment to forest soils contributes to the sustainability of the growing bioenergy industry, not only through decreased wood ash waste disposal in landfills but also by increasing soil/site productivity and tree growth. However, tree growth studies to date have reported variable responses to wood ash, highlighting the need to identify proper application rates under various soil/site conditions to maximize their benefits. We explored the influence of tree species, wood ash nutrient application rates, time since application, stand development stage, and initial (i.e., before wood ash application) soil pH and N on short‐term tree growth response to wood ash amendment across eight unique study sites spanning five Canadian Provinces. Jack pine (Pinus banksiana Lamb) had the most positive response to wood ash amendment compared to white (Picea glauca Moench), hybrid (Picea engelmannii x glauca Parry), and black spruce (Picea mariana Miller), where increasing nutrient application rates increased height growth response. In comparison, black spruce had the most negative response to wood ash amendment, where increasing nutrient application rates slightly decreased height growth response. Site as a random effect explained additional variation, highlighting the importance of other unidentified site characteristics. By examining trends in short‐term growth response across multiple studies with variable site characteristics, we found growth response differed by tree species and nutrient application rates, and that jack pine is a promising candidate for wood ash amendment. These results contribute to our knowledge of optimal wood ash amendment practices and environmentally sustainable bioenergy production. [ABSTRACT FROM AUTHOR]

• Hemlock is a foundation species that supports distinct forest ecosystems. • The invasive hemlock woolly adelgid (HWA) has decimated hemlock in the eastern US. • HWA continues to spread north and has begun causing hemlock mortality in Nova Scotia. • We provide a decision framework to inform HWA management plans in eastern Canada. • Current lack of HWA control highlights the importance of an ecosystem restoration plan. The invasive hemlock woolly adelgid (HWA) has decimated hemlock stands across much of the eastern United States, and presents a significant threat to all eastern hemlock in Canada across Ontario, Quebec, New Brunswick, Nova Scotia, and Prince Edward Island, especially since the recent detection of its widespread establishment in southwest Nova Scotia. The spread and rising infestation level and impacts of HWA in this region serve as a warning for forest managers across eastern Canada to develop appropriate management plans and priorities. The HWA decision framework presented here aims to prepare forest managers in eastern Canada for the decisions and challenges that they will face, from prevention, detection, and control, to hemlock ecosystem restoration and management program evaluation. We review the strategies and tactics that are currently available, that are being developed, and that show the most promise to date. Given the nature of HWA, the long-term outlook for eastern hemlock in Canada will likely feature HWA as a component of hemlock ecosystems across much of the region, necessitating a comprehensive, adaptive management program to mitigate its ecosystem consequences. [ABSTRACT FROM AUTHOR]

Defoliation by eastern spruce budworm is one of the most important natural disturbances in Canadian boreal and hemi-boreal forests with annual area affected surpassing that of fire and harvest combined, and its impacts are projected to increase in frequency, severity, and range under future climate scenarios. Deciding on an active management strategy to control outbreaks and minimize broader economic, ecological, and social impacts is becoming increasingly important. These strategies differ in the degree to which defoliation is suppressed, but little is known about the downstream consequences of defoliation and, thus, the implications of management. Given the disproportionate role of headwater streams and their microbiomes on net riverine productivity across forested landscapes, we investigated the effects of defoliation by spruce budworm on headwater stream habitat and microbiome structure and function to inform management decisions. We experimentally manipulated a gradient of defoliation among 12 watersheds during a spruce budworm outbreak in the Gaspésie Peninsula, Québec, Canada. From May through October of 2019-2021, stream habitat (flow rates, dissolved organic matter [DOM], water chemistry, and nutrients), algal biomass, and water temperatures were assessed. Bacterial and fungal biofilm communities were examined by incubating six leaf packs for five weeks (mid-August to late September) in one stream reach per watershed. Microbiome community structure was determined using metabarcoding of 16S and ITS rRNA genes, and community functions were examined using extracellular enzyme assays, leaf litter decomposition rates, and taxonomic functional assignments. We found that cumulative defoliation was correlated with increased streamflow rates and temperatures, and more aromatic DOM (measured as specific ultraviolet absorbance at 254 nm), but was not correlated to nutrient concentrations. Cumulative defoliation was also associated with altered microbial community composition, an increase in carbohydrate biosynthesis, and a reduction in aromatic compound degradation, suggesting that microbes are shifting to the preferential use of simple carbohydrates rather than more complex aromatic compounds. These results demonstrate that high levels of defoliation can affect headwater stream microbiomes to the point of altering stream ecosystem productivity and carbon cycling potential, highlighting the importance of incorporating broader ecological processes into spruce budworm management decisions., (© 2024 His Majesty the King in Right of Canada. Ecological Applications published by Wiley Periodicals LLC on behalf of The Ecological Society of America. Reproduced with the permission of the Minister of Natural Resources Canada.)