Browsing by Subject "δ15N"
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(2021)The present retreat of the Greenland Ice Sheet will increase the amount of fjords surrounded only by land-terminating glaciers in the future. As in the Arctic, productivity is generally lower at these kinds of fjord systems than in the ones surrounded by marine-terminating glaciers, this will most likely affect the productivity and ecosystem structure of coastal marine areas. Paleorecords of past coastal ecosystems can improve our understanding of the drivers of Arctic coastal ecosystem change and provide possible future scenarios. At present, there are not many high-resolution marine ecosystem reconstructions from the Arctic near-shore areas, and in particular those, which take into account land-derived inputs are lacking. To provide a detailed reconstruction of coastal marine ecosystem change over the Holocene and study its linkages to climate and terrestrial freshwater inputs, organic-walled palynomorphs (including e.g. dinoflagellate cysts and pollen) and some basic geochemistry (including e.g. total organic carbon, C:N ratio, biogenic silica and stable isotopes of carbon and nitrogen) were examined from two radiometrically dated sediment cores from Young Sound fjord, Northeast Greenland. The results indicate that the near-shore marine ecosystem in Young Sound is clearly influenced by local forcings, such as terrestrial freshwater and organic matter inputs, during the Holocene. The results also illustrate that these terrestrial inputs affect the ecosystem structure and at least some dimension of ecosystem productivity. This study demonstrates that increasing number of fjords with only land-terminating glaciers in the future will affect marine productivity and ecosystem structure in Greenland’s fjord systems, with potential impacts on biodiversity and important fisheries. Studying past ecosystem changes in different fjord systems, and complementing marine records with proxies for terrestrial inputs, would further help constrain the future scenarios along the Greenland shore.
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Soil nitrogen content and isotope ratios in urban remnant forests: What have dogs got to do with it? (2024)Keeping dogs (Canis familiaris) affects the environment. One significant effect of dogs in the environment is the production and deposition of urine. Unlike other waste, dog urine cannot be easily collected by owners, leading to unfiltered introduction into the soil. Dog urine is high in urea, which hydrolyzes to ammonium and nitrate. These soil nitrogen forms have the potential to change other soil properties that may cause harm in plant or microbial health, and contributing to eutrophication. In this thesis I investigate the impacts of dogs on soil nitrogen properties and their connection with human population density and closeness to walking paths in urban remnant forests. To evaluate the level of impact of dogs and to gain knowledge on the current nitrogen content and δ15N in urban remnant forests, five urban remnant forests were examined. Within each forest, soil nitrogen forms, δ15N in the soil and foliage samples, as well as total carbon and nitrogen content of the soil were compared, besides basic soil properties between dog-affected and control areas. The study revealed elevated levels of soil electrical conductivity, ammonium, and nitrate, as well as soil and foliage δ15N in dog-affected areas. Unexpectedly, soil acidity was lower in samples taken next to paths where dogs can potentially urinate. Organic matter content and total nitrogen and carbon content of the soils were higher where dogs are not frequent visitors, meanwhile the carbon-to-nitrogen ratio was also higher. These findings show that the impacts of dog urine on the soil should be considered in urban planning and further research is needed to understand the significance of it.
Now showing items 1-2 of 2