Recovery of forest soils from chronic acidification can be enhanced with the use of non-industrial wood ash (NIWA). Non-industrial wood ash is alkaline and contains high concentrations of macronutrients, but trace metal concentrations must be evaluated to limit risk of metal toxicity following application. Additionally, understanding how different forest ecosystem components respond to NIWA is essential to inform current policy regulating its use as a soil amendment. This study evaluated the response of sugar maple (Acer saccharum) sap yield and chemistry, the response of soils beneath maple, American beech (Fagus grandifolia) and mixed species canopies, and maple and beech fine roots, foliage, seedling abundance, and understory vegetation abundance and composition to an application of 6 Mg ha-1 NIWA. Eight 40 x 40 m plots were established in a hardwood stand in Bracebridge, Ontario and were sampled prior-to and up to two years following application of NIWA (n = 4). Non-industrial wood ash significantly increased organic horizon soil pH and macronutrient (Ca, Mg, and K) concentrations with increases in Mg and K extending to the mineral soils. Significantly higher concentrations of some trace metals (Al, Fe, Mn, Cd, Cu, Pb, Zn) were also observed, but these were restricted to the organic horizons. Sugar maple sap, pH, and sweetness were unaffected by NIWA application, and while increases were observed in nutrient and metal concentrations in sap, the differences were small and variable between years, and all concentrations were consistent with those commonly found in maple sap. Fine root biomass of maple and beech trees was not affected by NIWA application, but higher concentrations of K and Mg were observed in the roots of both species, consistent with higher concentrations observed in the mineral soil horizons beneath both species' canopies. Only significant increases were observed in K in sugar maple foliage. Both critical foliar concentrations and diagnosis and recommendation integrated system (DRIS) norms for sugar maple did not indicate mineral nutrient deficiencies at this site; although this site was acidic and nutrient-poor, this may account for the lack of differences observed, particularly between species. Changes observed in understory vegetation were driven by years rather than between treatments. These results suggest that moderate doses of NIWA can provide significant decreases in soil acidity and increase nutrient availability, with limited increases in metal concentrations that are primarily restricted to the organic horizons.
Author Keywords: American beech, metal toxicity, Non-industrial wood ash (NIWA), sap sweetness, sap yield, sugar maple