Maja Krzic

This study investigated the impacts of soil compaction and organic matter removal on soil properties and tree growth of white spruce (Picea glauca) and trembling aspen (Populus tremuloides) 22 to 26 years following treatment in a boreal ecosystem of Northeastern British Columbia (BC). The study was carried out on the white and black boreal spruce (BWBS) long-term soil productivity (LTSP) site located 34 km north of Dawson Creek, BC. Soil properties evaluated in this study included selected soil physical properties (bulk density, aggregate stability, aeration porosity) and soil chemical properties (total C, total N, pH, and polysaccharides) as well as forest floor thickness and depth of visible OM enrichment in the upper mineral layer. All of these were systematically analyzed utilizing linear mixed effects models, univariate parameters. Since at the BWBS LTSP site each plot is split between (planted) white spruce and (naturally regenerated) trembling aspen, data were analyzed separately for those two tree species.For both species, soil physical properties mainly experienced a negative impact due to compaction, while chemical properties were mainly adversely affected by the removal of organic matter. Specifically, compaction led to diminished aggregate stability parameters for spruce, highlighting the potential impediment to water movement and root penetration. Soil properties such as bulk density and air-filled porosity demonstrated signs of recovery after 22 to 26 years for both spruce and aspen. Soil organic matter removal negatively influenced nutrient content in the forest floor, emphasizing its importance for these two tree species in this northern boreal forest. For tree growth, trembling aspen exhibited a more pronounced hindrance compared to white spruce under the influence of study treatments. Both species responded with reductions in selected growth parameters, including height and diameter.The findings underscore the critical importance of limiting soil compaction during harvest and retaining site organic matter on long-term site productivity. The implications of this research extend beyond the immediate study area, offering valuable insights into forestry practices in boreal ecosystems. Addressing these concerns is imperative for the effective conservation and management of these ecosystems, ensuring the continued productivity of both soil and associated tree species.

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Majority of Canadian farmers are approaching retirement age with the average age of farm operators being 55 years (Statistics Canada, 2017a). Concomitantly, the dominant global- industrial agricultural model they are predominantly versed and engaged in threatens the sustainability of our food system via extensive detrimental environmental, economic and social impacts. ‘Alternative agriculture’ offers means of food production that protects or enhances natural resources and ecosystems, imbues climate resiliency, enhances local-regional food security and economies, and can enhance social equity. The transition to alternative agriculture, will require more farmers in absolute terms, and they must be trained in alternative (to the industrial model) farming practices. The objective of this study was to develop a curricular and pedagogical framework to support the training of new alternative agriculture farmers in the province of British Columbia (BC), Canada. A modified Developing a Curriculum (DACUM) process was used to identify the core duties, tasks and associated instructional techniques for the occupation of alternative farm operator in BC. Study results include a comprehensive DACUM chart describing the (15) duties and (213) tasks associated with the occupation of alternative farm operator in BC; a list of knowledge, skills and behaviours/attitudes associated with the occupation and detailed instructional techniques that describe effective methods for training new-entrants. The results of this study can guide and support existing and emergent alternative farmer training initiatives by providing a comprehensive framework for consistent curricula and program development and delivery grounded in the realities of alternative farming in the province.

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New Brunswick is one of the largest potato producing regions in Canada, which has experienced soil erosion and a decline in soil health due to intensive tillage from potato production. To address these concerns and the uncertainties of temperature and precipitation pattern changes from climate change, a new system has been proposed for soil and water conservation in Atlantic Canada. The landscape integrated soil and water conservation (LISWC) system combines diversion terraces, grassed waterways, tile drainage, water retention structures, supplemental irrigation, conservation tillage, and soil-landscape restoration. The objective was to evaluate the effects of diversion terraces, grassed waterways, and tile drainage relative to contour tillage on selected soil properties and greenhouse gas emissions over the initial three seasons of management implementation. The study site consisted of three land management practices (LMPs): contour tillage (CT), diversion terraces and grassed waterways (DTGW), and diversion terraces, grassed waterways, and tile drainage (DTGW+TD). Aggregate stability decreased in all LMPs, and LMP had a significant effect on labile carbon (POXC). CT led to a decrease of 11.2% POXC over the study period, while DTGW increased 19.8% and DTGW+TD increased 50.6%. Mineral associated organic matter (MAOM) carbon was affected by LMP: CT carbon concentrations decreased 3.75%, while DTGW+TD rose 9.7% and DTGW rose 15.8%.I also conducted a short-term incubation experiment in February of 2021 to quantify greenhouse gas fluxes in response to volumetric water content (20%, 27%, 35%, and 40%), nitrogen fertilizer application rates (0 and 170 kg N ha-1), and temperature (10°C and 25°C).Overall, both DTGW and DTGW+TD offer potential for improvement of soil health, relative to CT, in the second and third years of implementation, with increases in the labile C fraction POXC, a fraction significantly related to SOC, and increases in MAOM. This is the firststudy in the area measuring GHG emissions from erosion control structures. This study demonstrated that DTGW+TD significantly reduced the loss of CO₂ relative to DTGW, while also not emitting significantly more than CT, in the three years after implementation. Results were similar with respect to loss of nitrogen as N₂O.

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Soil and plant communities were examined across an elevation gradient of a grassland steppe ecosystem in the Southern Interior of British Columbia over 58 years (i.e., from 1961 to 2019). In 1961, three distinct zones were classified according to plant species composition and Chernozemic great groups. At the time, grasslands in the area had been in degraded states due to long-term overgrazing, but improved grazing management was put in place in mid-1970s. The objective of my study was to determine topographic, microclimate and soil variables that affect the distribution of Chernozemic great groups and associated soil carbon (C) (i.e., total, organic, active C) and plant communities over an elevation gradient at the Lac du Bois Grassland while reassessing the boundaries of three Chernozemic great groups as established in 1961 by the study of van Ryswyk et al. (1966). While soil C stock and plant composition at the lower grassland remained similar to 1961, the middle and upper grasslands have undergone notable changes. Both have progressed from early seral stage to late seral stage communities, showing recovery from the degraded state in 1961. The middle grassland, which used to be a unique grassland zone, has become a more mesic continuation of the lower grassland’s plant species composition with increased biomass and decreased bare soil. Similarly, soil C content only marginally increased from the lower to middle grasslands. Interestingly, during the 58-year period, soil C stock has not increased and may have even decreased in the middle and upper grassland despite the improved plant species composition. Soil organic C at the 0-15 cm depth showed a 7-fold increase (0.9% to 6.8%) from the lowest to highest elevation, while there was a 3-fold increase in C stock (2.87 to 8.51 kg m⁻²), indicating that elevation remains the primary factor that affects soil C distribution across this landscape due to its effect on effective precipitation and air temperature.

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Intensive cultivation, combined with poor drainage and heavy precipitation, has led to soil degradation in the lower Fraser River delta region (LFRD) of British Columbia, an important agricultural area of the province. The Delta Farmland & Wildlife Trust (DF&WT), a non-profit organization in the LFRD, partners with farmers to implement conservation practices such as grassland set-asides (GLSA). Farmers seed fields with grasses and clover and leave them to rest for one to four years. GLSA programs have been used worldwide, but program goals, GLSA duration, and the geographical contexts of these programs vary widely. The objectives of this study were to evaluate the effects of three- and four-year GLSAs on selected soil properties in the LFRD. Samples were collected from seven operating farm sites in 2018, and five in 2019. Sites were classified as productive or unproductive, and each comprised of a GLSA seeded in 2015 and an adjacent field under annual crop rotation (ACR). Previously collected data from 2015 and 2016 was included in the analyses. At depth 0–7.5 cm, GLSA had greater aggregate stability than ACR at productive and unproductive sites. GLSA had significantly lower bulk density and higher aeration porosity than ACR at depth 0–7.5 cm after the three years, but not after four years. The improvements to aggregate stability under GLSA were observed in 2015 and 2016 and were maintained thereafter. In 2018 and 2019, at depth 0–7.5 cm, aeration porosity decreased at ACR but not at GLSA. Total carbon and total nitrogen were significantly higher in GLSA than ACR after four years only at depth 30–45 cm. GLSA did not yield significant improvements in soil properties at depths below 7.5 cm, nor did they fully restore compacted soils. Still, GLSA remain a useful management practice for farmers in the LFRD and can improve soil quality in the first year of GLSA while protecting and maintaining soil structure from further degradation in the third and fourth years.

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Crop production is a known source of CO₂, N₂O, and CH₄ emissions, yet greenhouse gas (GHG) emissions data from crops in the Lower Fraser River Valley (LFRV) are limited. Potatoes are the most prominent cash crop in the LFRV and are often associated with excess nitrogen (N) fertilizer use, a primary source of N₂O emissions. Soils in this region have poor drainage, which is exacerbated by precipitation in the spring and fall. Consequentially, the variable soil workability impacts the timing of potato planting and harvest. The objective of this study was to assess how N fertilizer rates (0, 90, and 120 kg N ha⁻¹) and planting date (typical and late) influence GHG emissions, potato production, and soil properties. The field experiment was established in 2018 at two fields in Delta, British Columbia (BC); one was classified as productive and the other as unproductive. Yield increased with N fertilizer rate at the productive field, but a cost-benefit analysis showed that the increase in yield between the 90 and 120 kg N ha⁻¹ treatments did not significantly outweigh the additional fertilizer costs. The yield at the unproductive field did not respond to N fertilizer, likely due to pre-existing salinity and drainage issues. Planting date did not affect yield at either of the fields. Over the growing season (May to October), there were no differences in total GHG emissions with either N fertilizer rate or planting date. November sampling at the productive field, following a precipitation event, showed N₂O emissions increase with N fertilizer treatments. To supplement the field experiment, a soil incubation experiment was conducted to better understand the interactive effects of temperature (4ºC and 20ºC) and soil water content (20% and 40% volumetric water content) on GHG emissions and soil N dynamics in soils fertilized with inorganic N. Nitrous oxide emissions were near zero when temperature was 4ºC or volumetric water content was 20%. This study emphasizes the importance of reviewing N fertilizer management at fields with signs of soil degradation that will, most likely, respond differently to N fertilizers than productive fields.

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Since 1993, the Grassland Set-Aside (GLSA) Stewardship Program has incentivized farmers in the western Fraser River delta, British Columbia, Canada to plant a grass-legume mixture on active cropland and leave it fallow for 1-4 years to improve soil quality and provide wildlife habitat. Benefits to wildlife are well documented, but not well understood for soil quality. Study objectives were to quantify the effects of 2- and 3-year GLSAs on plant available nitrogen (N), crop production, soil quality, and greenhouse gas emissions. A field experiment was established in 2017 on a productive and unproductive field with fertilizer treatments (0 and 80-kg N ha⁻¹) compared across GLSA treatments (i) AC – GLSA biomass removed and (ii) 2G – 2-year-old GLSA biomass was incorporated, and seeded with beans. In 2018, fertilizer treatments (0 and 100-kg N ha⁻¹) were compared across the same GLSA treatments and (iii) 3G –3-year-old GLSA biomass was incorporated, and seeded with potatoes. Active carbon (POXC) and aggregate stability (MWD) were measured 3 times per growing season, plant available nitrogen (PAN) was sampled every 2 weeks from May-September, and carbon dioxide, methane, and nitrous oxide were measured weekly from May-September and every 3 weeks from October-April. MWD increased in 2G and 3G in the year of incorporation relative to AC and POXC increased for 3G relative to AC and 2G. Average seasonal PAN did not differ across treatments but was higher earlier in the season for 2G. Bean yields were greater in 2G compared to AC in the productive field, but otherwise crop yields did not respond to GLSA. N content of bean crops did not differ between treatments, was higher for 3G compared to AC in the unproductive field. 2G increased carbon dioxide emissions in 2018, but 3G only increased emissions in the 2018 production season. Nitrous oxide emissions treatments were higher in 2G treatments across all seasons, but lower in 3G treatments in the 2018 production season. Results suggest 2- and 3-year GLSAs do not increase average PAN to subsequent crops, but increase PAN earlier in the season, and increase crop yield and quality depending on subsequent crops.

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The Grassland Set-Aside Stewardship Program provides cost-share payments to agriculture producers in the Fraser River delta (FRD) region of British Columbia for placing active cropland under a grass and legume vegetation mix for a one to four-year period. While long-term grassland set-asides (GLSA) have been found to improve soil structure, reduce compaction, and increase soil organic matter; short-term set-asides (
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Biosolids have been shown to improve forage production and soil quality on semi-arid rangelands in the short-term. The objective of this study was to assess the long-term effects of a single, surface biosolids application on rangeland soil quality, forage production and plant community composition. In 2002, the experiment was established on a ranch in the central Interior of British Columbia, where two treatments were evaluated: surface biosolids application at 20 Mg ha-¹ and a control (no biosolids). Both treatments were replicated in four blocks, which were then excluded from grazing for 14 years. In 2016, soil samples were collected in April, June, August and October to assess various soil quality indicators, while forage quality indicators were assessed in June 2016. Fourteen years following the biosolids application, aboveground plant biomass was almost two times greater with biosolids application than on control. Exposed mineral soil was significantly decreased in biosolids plots. Despite differences in aboveground biomass there was no difference in total soil C, permanganate-oxidizable C, or aggregate-protected total C and polysaccharides contents between biosolids and control plots. However, biosolids amended soil did exhibit significantly greater aggregate stability, lower pH, increased spring soil water content, and increased availability of soil P, Fe, Zn and Cu. Forage grown on biosolids plots had lower protein concentrations than control plots, but greater total protein due to the greater biomass. The biosolids application resulted in higher cover of native bluebunch wheatgrass in the long-term, along with >25% cover of agronomic perennial, Kentucky bluegrass. These results offer a demonstration of the potential long-term improvement in forage production that can occur under biosolids application without grazing, which was accompanied by somewhat mixed effects on soil quality and plant species composition.

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Ammonia emissions from commercial broiler operations have been noted as one of the potential contributors to the nitrate contamination of the Abbotsford-Sumas aquifer in southwestern British Columbia (BC). The localized dry deposition of this emitted ammonia was of special interest and had not been measured in any comparable climate. Three barns, on two farms, located on the aquifer were assessed from July 2011 to June 2012. Ventilation, emission, and deposition samples were taken weekly throughout the seasons to accurately characterize the impact on the local environment. Ventilation was measured using a Fan Assessment Numeration System and timers that recorded individual fan activity. Acid impinger traps were used to measure the ammonia emitted by the sidewall fans. A methodology for measuring dry deposition by exposing air-dried soil was modified to use small Petri dishes and a 24-hr exposure time. The modified dry deposition method was found to be robust and effective for the requirements of this study. Dishes of soil were placed 2.1 and 3.6 m in front of and between each fan, as well as around the barns and farm properties. Ventilation rates for the barns were significantly and positively correlated with bird age and exterior temperature. Ammonia emissions were correlated with bird age and the emission factors for the three barns ranged from 0.19-0.37 g NH₃ bird-¹ day-¹ with annual ammonia emissions for each barn reaching 600 to 815 kg NH₃. Dry deposition levels on the two farms exceeded 50 kg NH₃ annually although this accounted for less than 10% of the ammonia emitted. The deposition levels were highest near the barns and were concentrated directly under the sidewall fan hoods. These levels of ammonia show significant potential to cause nitrate to leach into the groundwater and further contaminate the aquifer but future work and upscaling of data collection are needed.

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Given the functions of forest organic soil horizons in carbon sequestration, biodiversity and nutrient cycling, coupled with the fact that the forest floor is often not described in soil surveys, it is important that forestry professionals learn to classify organic horizons and humus forms. The current generation of undergraduate students appreciate having access to multimedia and online resources in their learning, and prefer active, collaborative experiences of the concepts they are learning in the classroom. With technological advances, modernizing curriculum by blending campus-based learning and multimedia is ever easier to accomplish. The objectives of this study were to: (1) develop blended-learning activities, combining campus based learning and multimedia web-based resources, to teach forest floor description and classification; and (2) conduct exploratory factor analysis of student survey responses to assess student opinions about the application of the blended-learning method. The Forest Floor web-based educational resource and campus-based activities were developed with the contributions of a team of experts in soil science, web and multimedia design, and science education. Ninety-four percent of students agreed or strongly agreed that the Forest Floor web-based resource was helpful for learning forest floor concepts, 79% that describing samples in class was essential for understanding the properties of organic horizons, and 81% that they were able to relate information in the Forest Floor web-based resource to their own samples used in an in-class activity indicating that students appreciated the blended learning methodology. Based on the survey responses five implicit factors were interpreted: (1) satisfaction with the web-based educational resources as learning enhancements; (2) success of presentation of concepts using a blended learning method; (3) student self-assessment of learning; (4) student learning preferences in accessing materials; and (5) website usability. Student feedback suggests that the blended learning activities were appreciated and met the learning objectives. This study also provides an example for conducting exploratory factor analysis of blended learning interventions and provides factors that may be verified through confirmatory factor analysis.

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Grassland set-asides (GLSAs) have been used to encourage environmental stewardship on agricultural land in the Fraser River delta of British Columbia (BC) since 1994. Through this Grassland Set-aside Stewardship Program, farmers plant a mixture of grasses and legumes in place of harvestable crops for a minimum of one full year and the farmers then receive payment for establishing these short-term grasslands. Grassland set-asides are typically established on degraded fields. Although improving long-term soil quality is a key objective in the GLSA Program, evaluations of GLSA management effects on the soil have been few and limited in scope. The objectives of this study were to determine the effects of GLSA management and GLSA age on selected soil properties in agricultural fields in the Fraser River delta. Three GLSA field sites – ranging in age from two, three, and six years – were compared to three adjacent cropped potato fields for the following soil properties: total soil C and N, mechanical resistance, bulk density, aeration porosity, and aggregate stability. Relative to the Cropped treatment, the GLSA treatment did not result in an increase in total soil C or N, but did result in lower soil mechanical resistance in the upper 30 cm depth, and higher aeration porosity, and aggregate stability. The differences observed between the Cropped and GLSA treatments were most pronounced on the site with the six-year-old GLSA, indicating reduced compaction and improved soil structure as a GLSA ages. Baseline measurements of the soil prior to GLSA establishment are recommended to track changes to the soil over time and to improve the efficacy of GLSA management as a remediation strategy by pinpointing underlying soil issues that could be addressed through other corrective management (i.e. sub-soiling, liming, etc.). Soil mechanical resistance, aeration porosity, aggregate stability, pH, salinity, and mineralizable N are suggested as valuable, responsive indicators of GLSA management effects on the soil.

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Although numerous studies have been conducted on rangeland soil quality in Alberta, Manitoba, Saskatchewan, as well as in the Great Plains, there has been little documentation of the response of soil properties to time of grazing and stocking rate treatments for the grasslands of the southern interior of BC. In the Lac Du Bois range in Kamloops, BC, the current moderate stocking rate of 2 AUM ha⁻¹ was based on a desired available forage use of 50%. Livestock is moved up and down an elevation and productivity gradient over the grazing season so that pastures located midway up the gradient are grazed either in the spring or fall. The objectives of this study were to determine (1) the effects of spring and fall grazing treatments on selected soil properties after periods of 20 and 30 years and (2) the effects of 0 and 2 AUM ha⁻¹ grazing rates on selected soil properties after periods of 20 and 30 years. The spring grazing treatment led to greater soil bulk density, mechanical resistance, pH, as well as lower polysaccharides and CEC relative to the fall grazing treatment. The grazing rate of 2 AUM ha⁻¹ led to greater soil mechanical resistance and pH, as well as lower soil polysaccharides and LOMF relative to the ungrazed control. After 30 years of grazing, soil bulk density was greater in the 0-7.5-cm depth under the 2 AUM ha⁻¹ treatment relative to the ungrazed exclosure in spring-grazed but not in fall-grazed areas, indicating that this stocking rate, when used for spring grazing, has led to soil compaction. Rangeland managers in the southern interior of BC should consider adjustments of time of grazing and stocking rate recommendations when these have been solely on vegetation responses, and should consider including soil properties in rangeland health assessments.

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Current studies of soil water repellency show that there are multiple contributing factors to its presence and persistence. Water repellency in soils of the Southern Interior of British Columbia has economic implications, as it can contribute to large scale landslides, and management implications as it affects hydrology and wildfire rehabilitation.The purposes of these studies were twofold. The first assessed three appropriate methods for testing soil water repellency of burned and unburned soils from eight areas in southern British Columbia. These tests were performed in laboratory conditions as well as in situ. The Concentration of Ethanol Drop (CED), Mini-Disk Infiltrometer (MDI) and Spatial Repellency Index (SRI) tests were all used, and the results compared to assess whether all were valid. The studies indicated that the MDI, CED and SRI tests are reliable to detect at least the presence or absence of water repellency in both field and laboratory conditions. The second study assessed whether wildfire would increase the presence and degree of water repellency in the soils one or two years after fire, and whether total organic content, texture and ambient moisture content could be used to predict this soil trait. Wildfire did not increase the presence or degree of water repellency, and soil texture, organic matter content and moisture content were not found to be reliable indicators of soil water repellency in these soils. This study showed that water repellency exists in burned and unburned forest soils in BC, and that various methods can be used to test for it. Further detailed studies are needed on the predictors on forest soils in British Columbia.

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No abstract available.