Maxime C. Paré

Soil organic matter quality influences mineralization and GHG emissions in cryosols: a field‐based study of sub‐ to high Arctic

Arctic soils store large amounts of labile soil organic matter (SOM) and several studies have suggested that SOM characteristics may explain variations in SOM cycling rates across Arctic landscapes and Arctic ecosystems. The objective of this study was to investigate the influence of routinely measured soil properties and SOM characteristics on soil gross N mineralization and soil GHG emissions at the landscape scale. This study was carried out in three Canadian Arctic ecosystems: Sub-Arctic (Churchill, MB), Low-Arctic (Daring Lake, NWT), and High-Arctic (Truelove Lowlands, NU). The landscapes were divided into five landform units: (1) upper slope, (2) back slope, (3) lower slope, (4) hummock, and (5) interhummock, which represented a great diversity of Static and Turbic Cryosolic soils including Brunisolic, Gleysolic, and Organic subgroups. Soil gross N mineralization was measured using the (15) N dilution technique, whereas soil GHG emissions (N2 O, CH4 , and CO2 ) were measured using a multicomponent Fourier transform infrared gas analyzer. Soil organic matter characteristics were determined by (1) water-extractable organic matter, (2) density fractionation of SOM, and (3) solid-state CPMAS (13) C nuclear magnetic resonance (NMR) spectroscopy. Results showed that gross N mineralization, N2 O, and CO2 emissions were affected by SOM quantity and SOM characteristics. Soil moisture, soil organic carbon (SOC), light fraction (LF) of SOM, and O-Alkyl-C to Aromatic-C ratio positively influenced gross N mineralization, N2 O and CO2 emissions, whereas the relative proportion of Aromatic-C negatively influenced those N and C cycling processes. Relationships between SOM characteristics and CH4 emissions were not significant throughout all Arctic ecosystems. Furthermore, results showed that lower slope and interhummock areas store relatively more labile C than upper and back slope locations. These results are particularly important because they can be used to produce better models that evaluate SOM stocks and dynamics under several climate scenarios and across Arctic landscapes and ecosystems.

Optimum liquid density in separation of the physically uncomplexed organic matter in Arctic soils

Paré, M. C. and Bedard-Haughn, A. 2011. Optimum liquid density in separation of the physically uncomplexed organic matter in Arctic soils. Can. J. Soil Sci. 91: 65-68. Using an appropriate density to separate the soil light fraction (LF) and heavy fraction (HF) is an important aspect of the density fractionation technique. The effect of liquid density when separating the physically uncomplexed Arctic soil organic matter (SOM) was tested on three Arctic sites: High-Arctic, Low-Arctic, and Sub-Arctic. Our results showed that selecting the right density to use for Arctic soils is not unequivocal. Nevertheless, based on these two criteria: (1) the difference between the C:N values of the LF and HF needs to be as large as possible, and (2) the C:N value of the whole soil needs to be different from the C:N values of the LF and HF, the optimum density for all of our Arctic sites was between 1.49 and 1.55 g mL-1. We concluded that 1.55g mL-1 was the conservative optimum liquid density to use to separate Arctic SOM light and heavy fractions.

Surface Soil Organic Matter Qualities of Three Distinct Canadian Arctic Sites

Abstract Cryosolic soils store large amounts of carbon (C) because soil organic matter (SOM) decomposition is slower than plant growth. The response of arctic SOM to climate change is likely to depend not only on temperature, but also upon complex interactions between soil properties and SOM chemistry. We hypothesized that organic surface soils (>17% carbon) have more labile SOM than mineral surface soils (<17% carbon). Furthermore, we hypothesized that high arctic soils have more labile SOM than soils from the Low Arctic and subarctic. This study was conducted in 3 arctic ecosystems: subarctic (Churchill, Manitoba; n = 138), Low Arctic (Daring Lake, Northwest Territories;n = 60), and High Arctic (Truelove Lowlands, Nunavut; n = 54). The 0–10 cm depth of several different Cryosolic soils was sampled. The results from density fractionation and solid-state 13C cross polarization and magic angle spinning (CPMAS) nuclear magnetic resonance (NMR) spectroscopy showed that organic surface soils contained relatively more labile C than mineral surface soils. Organic soils contained about 13% more O-Alkyl-C and 30% less Aromatic-C than mineral soils. Furthermore, for Churchill, Daring Lake, and Truelove organic soils, 53, 73, and 20% of the C was included in the light fraction of SOM [LF (LF < 1.55 g mL-1)], whereas 24, 19, and 14% of the C was included in the LF of mineral soils, respectively. Organic surface soils of subarctic and low arctic sites contained relatively more labile C than the high arctic site. Results showed that the subarctic and low arctic sites store about 15% more O-alkyl-C and 35% less Aromatic-C than high arctic organic soils (P < 0.001).

Improving Physical Properties of Organo-Mineral Fertilizers: Substitution of Peat by Pig Slurry Composts

Some granulated organo-mineral fertilizers (OMF) are made with peat and their utilization is expected to increase mostly because of their advantages over mineral fertilizers. However, peat is a non-renewable resource and could be replaced by sustainable organic materials such as stabilized composted pig slurry. The objectives of this study were to determine the changes of OMF physical properties when 1) substituting peat by composted pig slurry mixtures, 2) changing source of composted mixtures, and 3) increasing the level of organic material in the OMF. Thirty-four mixtures of compost, monoamonium phosphate (MAP), diammonium phosphate (DAP), and peat were granulated in OMF at different proportions. The increase of the compost proportion and the decrease of organic material input (30% vs. 60% of organic materials) improved most physical properties of OMF granule such as bulk and granule densities, total and granular porosities, water content, abrasion fragility, crushing strength, critical relative humidity, and water sorption from moist porous media. In addition, most compost types resulted in similar physical properties of OMF granules. Finding the appropriate organic matter content requires more research and the optimum OMF mixture should be chosen as a function of its combined physical, chemical, and plant response properties.

Hydrocarbons, Pb-Concentrations, and Pb-Isotope Ratios in Contaminated Alluvial Soils (Southern Québec, Canada)

Hydrocarbon-contaminated layers found over 100 kilometers of riverbanks (southern Québec) were investigated. Analytical results for hydrocarbons, trace metals, Pb concentrations, and Pb isotopic signatures (206Pb/207Pb, 208Pb/206Pb, 204Pb/206Pb) of contaminated soil are presented. Soil samples show hydrocarbon concentrations (C10-C50) ranging from <60 to 660 mg kg−1. Higher concentrations were found in the Richmond site (southern Québec). The values for Pb-concentrations ranged between 7 and 149 mg kg−1 with median value of 23 mg kg−1. For the Pb isotope ratios, the values obtained in the hydrocarbon layer range from 1.124 to 1.175 ± 0.011 (206Pb/207Pb), 2.085 to 2.126 ± 0.011 (208Pb/206Pb), and 0.054 to 0.057 ± 0.000 (204Pb/206Pb). The combination of various techniques used allows us to distinguish the various sources of contaminants. The study also reveals that Pb and other trace metal elements continue to be found in the fluvial environment, even after many years, and this soil pollution could affect the quality of streams and living organisms.

The importance of characterizing residual household waste at the local level: A case study of Saguenay, Quebec (Canada)

Knowledge of the quantity and the type of residual household waste (RHW) generated by a population within a given territory is essential for developing affordable, effective, and sustainable management strategies for waste. This study aims to accurately describe the composition of residential residual materials collected directly from households over the course of a year. Household waste was collected from urban and rural sectors that were representative of the study territory. Samples were collected during the winter, summer, and fall of 2014. A total of 3039 kg of RHW was collected and sorted into 9 categories and 39 subcategories. Statistical analysis showed, except for organic matter, that the weight percentage of each category of material did not significantly differ among sampling periods or locations. Therefore, the results for a category were compiled to generate a single value to calculate the relative abundance of each type of residual material. Organic matter made up the majority fraction of the RHW (53% to 66%). This was followed by plastics (9%), bulky items and renovation/demolition debris (6%), textiles (5%), metals (4%), paper and cardboard fiber (4%), glass (2%), and household hazardous waste (2%). This approach has allowed us to improve the accuracy of the data used in MRM, contribute to the creation of a regional dataset for waste, and develop a methodology more applicable to local realities. Specific to the immediate needs of municipal MRM, we updated knowledge regarding the generation, recovery, and disposal of the contents of the residential sector, and tracked the evolution and the variation of contents over a given period. We believe our methodology is applicable to other regions having similar characteristics in terms of climate, socio-economic status, and other parameters that affect the composition of RHW.

A Call For Improving Winter Windbreak Design for Lowbush Blueberry Production in the Saguenay–Lac-Saint-Jean Region of Québec, Canada

ABSTRACT Wind exposure may reduce the snowpack and increase frost damage to lowbush blueberry (Vaccinium angustifolium Ait.). Farmers in the Saguenay-Lac-Saint-Jean region (Québec) have therefore installed natural windbreaks to maintain a deep snow cover. We verified the efficiency of 39 windbreaks distributed over two farms. Over two consecutive years, snow depth was measured along transects established perpendicular to these windbreaks. In the first summer, frost damage and yields were assessed at each point where snow depth had been measured. We found large fluctuations in snow depth along most transects, with deeper snow occurring within 20 m on either side of windbreaks. Relative snow depth distribution was correlated between years on 19 transects. On one farm, one third of total transect length was below the recognized critical depth of 30 cm. On this farm, the proportion of damaged stems, the mean length of stem damage and the damaged-to-total stem length decreased exponentially with increasing snow depth. Likewise, the number of fruits per stem decreased exponentially with the length of stem damage and increased linearly with snow depth. Given current trends in climate change, our results serve as a timely call for improving winter windbreak design in the Saguenay-Lac-Saint-Jean region.

Canadian goldenrod residues and extracts inhibit the growth of Streptomyces scabiei, the causal agent of potato common scab

Abstract Common scab is one of the most important diseases affecting potato crops worldwide. Using fresh residues and/or bio-products of Canadian goldenrod (Solidago canadensis) may offer an alternative to harmful conventional fumigants. In this study, we aimed to: (i) conduct a preliminary investigation of the utilization of S. canadensis to reduce common scab severity (Experiment 1), and (ii) determine the allopathic potentials of S. canadensis extracts on Streptomyces scabiei (also known as S. scabies), the most important soil pathogen responsible for causing common scab in North America (Experiment 2). Compared with control plants, preliminary results showed that adding 1.2 kg of fresh S. canadensis residue per m2 reduced scab severity by about 45% (Experiment 1). Furthermore, hexane and dichloromethane extracts of S. canadensis, at a concentration of 200 µg·mL−1, inhibited the growth of S. scabiei by about 97% (Experiment 2). These results were comparable with those using tetracycline (2.5 µg·mL−1), a known inhibitor of S. scabiei. Both experiments suggested that S. canadensis may represent a new approach for controlling potato common scab. More studies are required to better understand the mechanisms involved in S. canadensis induced reduction of common scab in order to standardize the approaches.