Browsing by Subject "urban ecology"

Urbanization is occurring at rapid rates worldwide. While the effects of urbanization are numerous, those on wildlife are of utmost concern in the continued fight for biodiversity conservation. Specifically, the focus on global pollinator declines is of interest due to the interconnectedness between pollinators and plant communities. It is feared that urban areas could become dead zones to these species, specifically bumblebees. Bumblebees are one of the native pollinators of Finland, and therefore were the focus of this study, which was conducted in Helsinki (southern Finland). This project's focus was on the influence of both local (i.e. flowering resources) and landscape (i.e. levels of urbanization) features on bumblebee communities. More specifically, I was interested in the effects of urbanization on bumblebee abundance and species richness. To study this question, community gardens (allotment gardens) were used as study sites along a gradient of urbanization from low to high (chosen by GIS mapping of the levels of impervious surfaces within 500 m of the sites). It is thought that these greenspaces could function as habitat for bumblebees in cities. This study was conducted during the summer of 2013 in 12 community gardens across the city of Helsinki. Two methods to survey bee populations were utilized, pan traps as well as sweep netting. Furthermore, a vegetation analysis was conducted to assess the level of resources present within the gardens, while GIS was used to measure a set of landscape variables in and around each garden. At the end of the season (June to September) the bees were identified and Generalized Linear Mixed Effects models were used to analyze the data. This study found that local variables more strongly predicted both bee abundance and species richness. Even though landscape variables were not strong predictors, this does not make them irrelevant in future conservation strategies. However, it is thought that as long as community gardens are planted appropriately (i.e. native flowers) the bees will be present in these gardens despite the surrounding matrix of inhospitable land (sealed surfaces). In conjunction with the investigation into the effects of local versus landscape determinants, this study also aimed to investigate the perception of gardeners towards bees. A questionnaire was utilized in order to gauge gardeners' opinions towards the bees in their plot and the garden as a whole. These results helped to evaluate the overall attitude towards bees, and in short, were very favorable. This extrapolates to a possibility of working in conjunction with gardeners to conserve habitat for pollinators in the continued effort for interconnected greenspaces in urban areas.

Promoting carbon sequestration and storage is an important part of climate change mitigation. Soils play a prominent role in this, as they contain the largest terrestrial carbon pools. Urban soils have been shown to contain significant amounts of carbon, and thus, urban green spaces have the potential to contribute to climate regulation through soil carbon sequestration and storage. Many green spaces in cities consist of managed lawns containing significant amounts of soil organic carbon, although management activities such as mowing can also be a source of carbon emissions. A low-maintenance alternative to lawns is urban meadows. The benefits in terms of soil carbon sequestration in urban meadows, however, are still poorly documented. This study aims to contribute to an increased understanding of the ecosystem services urban meadows provide, which is valuable in the planning of urban green infrastructure. I quantified soil organic carbon content in 140 urban meadows of different land use types in the Helsinki Metropolitan Area to determine their value in terms of carbon storage and to compare this with the soil carbon storage in highly managed urban lawns. The meadow types explored included valuable grasslands, which have special nature or cultural values, landscape meadows, road verge grasslands, and rocky outcrops. Soil samples were taken from a depth of 0–10 cm using a soil corer. The soil organic matter content and bulk density were measured. Existing data from the soils of city park lawns in Helsinki were used for comparison in the analysis. The soil organic carbon content in the different meadows, as well as in the lawns, was then analysed using land use type and site productivity as explanatory variables. Results show that park lawn soils have a significantly higher carbon density (kg C per square meter) than any of the meadow types. Out of the meadow sites, valuable grasslands had the highest carbon density. The higher carbon content in park lawn soils may be due to increased productivity due to frequent mowing, as well as the fact that these lawns were likely established on nutrient-rich soil. Interestingly, the highest %C was detected in rocky sites. However, the total carbon stocks of rocky sites are lower due to the soil cover being shallow and large portions of the sites not having soil cover at all. To answer the question of whether a lawn should be converted into a meadow in hopes of increasing carbon sequestration and storage, future studies should focus on meadows that were formerly lawns, and that had the same or similar initial conditions as a typical lawn.