Watmough, Shaun SW

Nutrient losses from forest soils caused by decades of acid deposition and intensive tree harvesting have affected tree growth and forest health in North America and Europe. Non-industrial wood ash (NIWA), a substance rich in macronutrients, may be a potential remediation strategy to return lost nutrients to forest. However, the chemical composition of NIWA and its effects on soil and tree growth are poorly understood. This thesis evaluated the chemical variability of non-industrial wood ash, and its short-term effects on soil properties, sugar maple (Acer saccharum) foliar chemistry, tree growth, and understory vegetation community composition at three sugar bushes in Muskoka, Ontario. The chemical analysis of NIWA samples obtained from the residents of Muskoka, showed that NIWA contains high levels of macro nutrients such as calcium, magnesium, and potassium and contains relatively low concentrations of trace metals. Ash mixtures amalgamated in the field were relatively homogenous in their chemical composition and metal concentrations were generally below Ontario NASM regulation guidelines for land application. Concentrations of copper and zinc exceeded CM1 guidelines, however, were always below restricted metals land application limits (CM2). Ten months after NIWA application to three sugar bush sites, soil pH and exchangeable base cations increased significantly in the litter and FH horizons at all treatment plots compared with control plots. Few treatment effects were recorded for the surface (0 – 10 cm) mineral horizon, with only potassium increasing in mineral soil at all three study sites. Elevated concentrations of most metals and metalloids (aluminum (Al), boron (B), cadmium (Cd), copper (Cu), Iron (Fe), manganese (Mn), nickel (Ni), lead (Pb), zinc (Zn)) were recorded in soil at all treatment plots, however these effects were generally restricted to the litter horizon. Diagnosis and recommendation integrated system analysis (DRIS) conducted on the sugar maple foliage indicated that potassium was the most limiting nutrient at all three study sites, and significant increases were recorded in foliar potassium concentrations ten months after ash application in sapling and mature trees at all treatment plots. Increases in foliar calcium and magnesium concentrations were small and variable amongst the study sites. No significant treatment effects of NIWA application were observed on sugar maple tree growth two years after ash application, while changes in understory composition were generally limited, but these also varied among sites.

Author Keywords: Acer saccharum, Base cations, Calcium decline, Forest soil amendment, non-industrial wood ash, Trace metals

Recent agricultural land use change in east-central Ontario, including the expansion of intensive agriculture (corn and soybean crops) and tile drainage (TD) infrastructure, may alter the fluxes of both phosphorus (P) and nitrogen (N) to the Lower Great Lakes. Through intensive monitoring of several sub-watersheds that encompassed a range of row crop and TD extents, this study examined differences in stream N and P concentrations both seasonally and during variable flow conditions, to better understand land use/land cover (LULC) relationships with nutrient export. There was no clear relationship between total P (TP; concentration or export) and agricultural LULC, and instead, TP delivery was highly sensitive to flow events, and TP concentrations (especially particulate P; PP) were significantly higher during event flow compared with baseflow. In contrast, the dissolved fraction of P (total dissolved P; TDP) and dissolved nitrogen as nitrate (NO3-N) were not sensitive to flow, but were instead positively related to row crop agriculture, and associations between NO3-N concentrations/export and tile-drained row crop area were particularly strong (concentration r2 = 0.93; export r2 = 0.88). Regression relationships showed that with every 10% increase in row crop area in watersheds, NO3-N and TDP flow-weighted concentrations increased by 0.34 mg/L and 1.5 µg/L, respectively. As well, the same 10% increase in row crop agriculture translated to an increase of NO3-N export of as much as 130 kg/km2. Geospatial records of TD are incomplete in east-central Ontario, which presents challenges for evaluating the contribution of TD to nutrient export. Understanding the response of nutrients to changes in agriculture and agricultural practices is an integral part of watershed management as rapid changes in both urban and agricultural LULC continue to put pressure on water quality in the Lower Great Lakes.

Author Keywords: East-Central Ontario, Nutrient Export, Row crops, Streams, Tile Drainage, Water Quality

Peatlands can be found widely across all latitudes and play a significant role in global cycles within the earth's biosphere. The anoxic conditions in peatlands promotes the accumulation of organic matter through decreased rates of decomposition and the storage of certain elements, which have received contaminant loading over the course of human existence, with significant increases occurring during the period of industrialization. We assessed global patterns of metal enrichment in peatlands in 439 cores distributed across 5 continents and 21 countries and measured 35 elements by depth increments and by peatland type. Global patterns in enrichment factors (EF's) were determined for all metals with the majority of metals being found to have a median EF < 2 indicating relatively minor enrichment. Principal component analysis indicated EF's of 6 metals (Cd, Co, Cu, Ni, Pb, and Zn), 2 metalloids (As and Sb) and Se in the upper peat horizon had similar spatial patterns among peatlands and these elements had generally the highest EF's with many cores exceeding EF >10 and some having EF values >100. Significant differences in EF's were found for these 9 "pollution" elements by peatland type and to a greater extent by geographic region, with higher EF values typically occurring in Europe and North America. Enrichment factors for most elements exhibited weak but significant positive correlations with modelled [1850 – present] S deposition. Estimated pools for the "pollution metals" within the 0 - 40 cm depth varied considerably, with median global pools in peat ranging from 12.9 mg m-2 (Sb) to 439 mg m-2 (Zn) for these 9 metals. Climate changes presents a significant risk to global peatland geochemistry due to expected changes in hydrologic regimes, resulting in potentially increased metal mobility though drought-induced peatland acidification, with historic areas previously impacted by industrial activities presenting the greatest risk of metal release to downstream receiving environments. Using a case study, we examined the impact of simulated 30-day drought on pore water chemistry at six sites in a peatland complex in Elliot Lake Ontario that were historically impacted by uranium (U) mining activities. All sites responded similarly to simulated drought with pore water pH significantly declining. The decline in pore water pH was likely due to increasing sulphate (SO42-) concentrations, which accompanied large increases in Al, Ni, Cu, Pb, Zn, and U. Dissolved organic carbon (DOC) increased, which may further enhance Al, Cu, and U mobility as these metals are strongly complexed by organic acids. Metal partitioning (Kd) values could be significantly predicted by pH and DOC although the strength of the relationship varied considerably among sites. Multiple linear regression and the inclusion of SO4-2 improved predictions, indicating that declines in pH as a result of SO4-2 and H+ production primarily governs metals and U partitioning in peatland soils. The results from both studies show that metal enrichment in global peatlands is highly variable, with northern peatlands in industrialized areas presenting the greatest risk of metal release to downstream surface waters based on expected hydrologic impacts from climate change due to historical and on-going metal and S deposition.

Author Keywords: Acidification, Climate Change, Drought, Enrichment Factors, Global, Peatlands