Soil freezing effects on a grass-dominated old field ecosystem under current and future rates of atmospheric nitrogen deposition

Climate change is expected to alter the intensity and dynamics of soil freezing as a result of increased air temperatures and reduced snow cover. Soil freezing can influence ecosystem nitrogen (N) cycling by damaging plants and soil microorganisms, but little is known about how soil freezing effects on ecosystem N cycling may combine or interact with increased atmospheric N deposition, which is also expected to exert a strong influence on terrestrial ecosystems in the coming decades. The objective of my thesis was to examine the combined and possibly the interactive effects of climate induced changes in soil freezing and N addition on plant productivity, soil microorganisms, and soil nutrient cycling in a grass-dominated temperate old field ecosystem. First, using 15N tracer, I investigated N retention by different nitrogen pools (plant, litter, roots, soil and simulated N deposition) in response to soil freezing under current and projected future atmospheric N deposition rates. My results indicated that soil freezing can increase N losses from soil over the winter and from atmospheric N deposition during the growing season, with the latter occurring due to decreased plant productivity. Second, I combined increased freezing (both in controlled environment chambers and in response to snow removal in the field) with N addition to explore whether soil freezing effects are mostly transient (i.e. over winter and spring melt), or whether there are legacy effects of freezing that continue over multiple years. My results indicated that the legacy effect of soil freezing reduced plant productivity over multiple years, but that N addition counteracted these declines in plant productivity. With respect to soil responses, freezing only caused short term (over winter) increases in extractable nitrogen pools, although there were also declines in fungal biomass during the second growing season as a legacy effect of freezing. Overall, my results indicate that intense soil freezing and increased atmospheric N deposition can both alter plant productivity and ecosystem N retention, although there were few significant interactions between these two factors

On the K(1)-local homotopy of tmf boolean AND tmf

As a step towards understanding the $\mathrm{tmf}$-based Adams spectral sequence, we compute the $K(1)$-local homotopy of $\mathrm{tmf} \wedge \mathrm{tmf}$, using a small presentation of $L_{K(1)}\mathrm{tmf}$ due to Hopkins. We also describe the $K(1)$-local $\mathrm{tmf}$-based Adams spectral sequence

The impact of peer mediation training on conflict

vii, 73 leaves : charts ; 28 cm. --The problem investigated in this study relates specifically to high school students and their response to conflict. The purpose of this study is to determine whether or not there is an improvement for peer mediators in handling inter-personal conflict situations after receiving peer mediation skills training. The effectiveness of this training was measured by using both the quantitative and qualitative methods. Cross-sectional surveys were distributed to a cluster sample of 18 grade 11 and grade 12 peer mediators and the resulting data were analyzed. Interviews with 7 peer mediators were also conducted. Although the sample group size may be too small to make conclusive statements, a relationship between peer mediation training and constructive outcomes in conflict situations was indicated for trainees in their inter-personal associations.Page numbering may be wrong - page 73 appears after page 74

Increased Soil Frost Versus Summer Drought as Drivers of Plant Biomass Responses To Reduced Precipitation: Results from A Globally-Coordinated Field Experiment

Reduced precipitation treatments often are used in field experiments to explore the effects of drought on plant productivity and species composition. However, in seasonally snow-covered regions reduced precipitation also reduces snow cover, which can increase soil frost depth, decrease minimum soil temperatures and increase soil freeze-thaw cycles. Therefore, in addition to the effects of reduced precipitation on plants via drought, freezing damage to overwintering plant tissues at or below the soil surface could further affect plant productivity and relative species abundances during the growing season. We examined the effects of both reduced rainfall (via rain-out shelters) and reduced snow cover (via snow removal) at 13 sites globally (primarily grasslands) within the framework of the International Drought Experiment, a coordinated distributed experiment. Plant cover was estimated at the species level and aboveground biomass was quantified at the functional group level. Among sites, we observed a negative correlation between the snow removal effect on minimum soil temperature and plant biomass production the next growing season. Three sites exhibited significant rain-out shelter effects on plant productivity, but there was no correlation among sites between the rain-out shelter effect on minimum soil moisture and plant biomass. There was no interaction between snow removal and rain-out shelters for plant biomass, although these two factors only exhibited significant effects simultaneously for a single site. Overall, our results reveal that reduced snowfall, when it decreases minimum soil temperatures, can be an important component of the total effect of reduced precipitation on plant productivity

The Arctic plant aboveground biomass synthesis dataset

Abstract Plant biomass is a fundamental ecosystem attribute that is sensitive to rapid climatic changes occurring in the Arctic. Nevertheless, measuring plant biomass in the Arctic is logistically challenging and resource intensive. Lack of accessible field data hinders efforts to understand the amount, composition, distribution, and changes in plant biomass in these northern ecosystems. Here, we present The Arctic plant aboveground biomass synthesis dataset, which includes field measurements of lichen, bryophyte, herb, shrub, and/or tree aboveground biomass (g m−2) on 2,327 sample plots from 636 field sites in seven countries. We created the synthesis dataset by assembling and harmonizing 32 individual datasets. Aboveground biomass was primarily quantified by harvesting sample plots during mid- to late-summer, though tree and often tall shrub biomass were quantified using surveys and allometric models. Each biomass measurement is associated with metadata including sample date, location, method, data source, and other information. This unique dataset can be leveraged to monitor, map, and model plant biomass across the rapidly warming Arctic

An investigation into induction stovetops for the new SUB

The following report outlines a comparison between induction stovetops and conventional gas stovetops using a triple bottom line analysis approach. The purpose of this comparison was to identify the most suitable type of stovetop technology for the kitchens in the new Student Union Building. The triple bottom line analysis consists of an economic, social, and environmental assessment. Research on these three topics was gathered through websites, government documents and academic papers. The main economic results from the analysis are that induction stoves have an increased initial capital investment, but that they have lower operating costs. In the model we developed for our research, the payback of the initial increased cost is approximately twenty three years. Although this seems like a large investment, twenty three years is not that long for a company to make a return, especially considering the life time of the new SUB. The main social result is that an induction kitchen stays at a much cooler temperature than a kitchen that operates gas stovetops. Higher temperatures in kitchens with gas stoves have been linked to high heart rates, high skin temperatures and high blood pressures for the workers. Heat stress for cooks is also a huge issue and this will be minimized with the installation of induction stoves. Increased cooking times, lower noise output, immediate heat response and ease of cleaning are also social impacts related to induction stoves. The environmental research found that running induction stoves produces approximately 13 times less greenhouse emissions than natural gas stoves. Not only does the reduction in greenhouse gases have a direct positive environmental impact, but this reduction could be a major contributor to earning LEED Platinum Plus certification, the merit that the new SUB is aiming to achieve. In conclusion, based on the points outlined above, we believe that induction stove tops have an advantage over gas stoves and therefore our recommendation is to install induction stove tops in the kitchens of the new SUB. Disclaimer: “UBC SEEDS provides students with the opportunity to share the findings of their studies, as well as their opinions, conclusions and recommendations with the UBC community. The reader should bear in mind that this is a student project/report and is not an official document of UBC. Furthermore readers should bear in mind that these reports may not reflect the current status of activities at UBC. We urge you to contact the research persons mentioned in a report or the SEEDS Coordinator about the current status of the subject matter of a project/report.”Applied Science, Faculty ofUnreviewedUndergraduat