Browsing by Subject "soil properties"
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(2022)More than half of the global population lives in urban areas. Urban sprawl and densification have affected urban ecosystems and the services they provide. Urban vegetation is one of the most important providers of ecosystem services. Previous studies have shown that plant functional type and age of parks/trees affect soil properties in urban environments. However, knowledge on the effects of plant roots on ecosystem services is limited. In this thesis I focused on exploring the contribution of root biomass to soil carbon and nitrogen accumulation under evergreen and deciduous trees in urban greenspaces. In addition, I explored how soil properties differ based on tree type and age of the park/tree, and how sampling distance from the tree affects root biomass and soil properties. Soil samples were taken at five distances: 1) under the canopy (midway between the trunk and the canopy edge), 2) at the canopy edge, and 3)–5) 1 m apart, starting from the canopy edge. This transect of five distances was replicated three times per tree (30 trees in total). Trees belonging to two functional types were sampled, evergreen (mostly Norway spruce, Picea abies (L.) H. Karst.) and deciduous (Linden, Tilia x europaea L.) trees. Sampling was done in young (ca. 15 years) and old (>70 years) urban parks in Lahti and Helsinki. The results show higher root biomass under young trees than old trees, and spruces had higher root biomass compared to lindens. Root biomass was positively correlated with soil organic matter, soil carbon and soil nitrogen. Sampling distance from the tree affected both root biomass and soil properties in young and old parks. Plant functional type affected soil organic matter, soil carbon, C/N ratio and acidity, but not soil nitrogen. Irrespective of tree type, soil properties varied less in old parks than in young parks between the sampling distances. Soils under old spruces had higher total carbon content compared to young spruces, whereas for lindens, tree age affected soil carbon less on. Total nitrogen content was higher in old parks than in young parks for both tree types. My study provides new information about how park tree roots affect urban park soil carbon and nitrogen accumulation. There are no previous studies on how far this root effect extends, and my study fills this knowledge gap. My results show that tree roots are an important factor in urban park carbon stocks. I also showed that age of the park/tree has an evident effect on urban soil properties. In the light of my research findings, it seems that a significant portion of ecosystem services provided by urban vegetation is produced underground.
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The Effects of Soil Treatments and Yellow Rattle on the Soil Properties of Newly Established Meadows (2024)My master’s thesis aims to determine the impact of soil treatments and the hemi-parasite Rhinanthus minor (yellow rattle) on the soil properties of newly established perennial wildflower meadow. As urbanization and urban green spaces increase, the need for viable methods for establishing biodiverse meadows on existing lawns grows. I joined a lawn to meadow project based at Lammi Biological Station wherein four soil treatments (untreated, scarified, overturned, and replaced with meadow substrate) were employed in eight meadow blocks. Within those blocks, yellow rattle was sown into half of the plots to determine if it can hamper the growth of competitive grass species. My aim was to explore the meadow blocks’ chemical soil properties (phosphate, nitrate + nitrite, ammonium, total carbon, total nitrogen, and pH). The soil properties were measured using LECO analysis, photometric analysis, and a pH meter. In the newly established meadows at Lammi biological stations, there is evidence that soil properties do change as a result of different soil treatments and the introduction of a hemi-parasitic plant. The initial soil properties show that soil turnover results in increased nitrate + nitrite and decreased total nitrogen compared to untreated meadow soil and lawn controls, respectively. Meadow soils replaced with a substrate exhibited nutrient poor conditions typical of low nutrient preferring meadow plants. The effects of yellow rattle on aboveground community structure are not investigated here, but after the first growing season, its presence increased nitrate + nitrite in the first ten cm of soil. Nitrogen mineralization as a result of grass introduced to soil microbes and nutrient dense yellow rattle leaves may be the cause of these changes to the soil properties. Meadow establishment can take 3 – 5 years, so the use of these methods should continue to be observed. I would expect larger differences to manifest as the experiment continues, namely, decreased soil nutrients as more growing seasons pass.
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