Browsing by Subject "rakennettu ympäristö"

Trees are the most visible part of urban vegetation, and they provide many ecosystem services which cannot be replaced. The ability to sequester and store carbon (C), balance peaks of storm water flows, regulate microclimate and provide shade in heat waves are dependent on the size and the vitality of a tree. Through the root system, abiotic and biotic factors in growing medium have a role in tree health and size. Tree fine roots and ectomycorrhizal (EcM) root tips, which are the most distal part of root system, have a crucial role in maintenance of tree vitality as they are responsible of water and nutrient uptake. Growing conditions in urban environments differ from those in natural environments. However, urban tree fine roots and EcM root tips are a scarcely studied subject. In this thesis I studied fine root growth, phenology, depth distribution, annual production, and the number of EcM root tips of three different tree species (Tilia cordata, Tilia × europaea and Betula pendula) growing in three different urban greenspaces (park, street site, unmanaged forest patch). In addition, I studied the effect of site, soil temperature, and soil moisture on root elongation. Fine root elongation was observed by a minirhizotron image system below ground from May until November 2020. Root production and the number of EcM root tips was studied by the ingrowth core method. Betula pendula had the highest fine root elongation among the three tree species, which can at least partially be explained by species-specific differences. Growing site had a statistically significant effect on root elongation, but also the thermal sum of soil temperature and the level of relative extractable water affected root elongation. Average height and trunk diameter between Tilias grown at the Garden and Tilias grown at the street side were different relative to their age. Tilias had clearly less EcM root tips on the street side, their fine roots elongated more, and the amount of dead roots was slightly higher than at Garden, indicating that root turnover rate was faster for street trees as they tried to absorb nutrient in a poorer environment. Based on previous studies, differences in fine root elongation between sites were expected, as e.g. rising of the temperature has been found to affect positively to root elongation. Additionally, the poor nutrient status of the growing medium has also previously been found to increase root growth. The site and the characteristics of the growing medium can has a significant effect on the fine roots and thus on the growth and vitality of the entire tree.