Browsing by Subject "lajilevinneisyysmallinnus"
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(2023)The ongoing environmental change will cause changes in arctic-alpine environment affecting both abiotic and biotic processes and the distribution of arctic-alpine vegetation that has adapted to the cold environment. Former studies on the distribution of arctic-alpine vegetation have been conducted more from a macroclimatic point of view neglecting the microclimate perspective. Microclimate refers to radiation, temperature, humidity, and wind conditions near the Earth’s surface. These conditions vary notably in the topographically heterogenous mountain tundra. The effect of the microclimatic factors is particularly important when investigating low-growing arctic-alpine vegetation as the microclimatic variables can be expected to describe the climatic conditions of the biotically active layer better than the macroclimatic variables. The purpose of this thesis is to study how the microclimatic conditions vary across different biotopes within mountain tundra and to examine which microclimatic variables best explain the local distribution of the arctic-alpine vegetation. The microclimatic variation in the different biotopes of the mountain tundra was studied by examining the statistical key figures of air and soil temperature and soil moisture measurements. Species distributions modelling was used to examine the distribution of arctic-alpine vascular plants and species correspondence to the microclimate variables as well as the importance of those variables on the species distributions. The research material consists of the microclimate and species data collected on the field as well as data based on topography and remote sensing. The data for the study were collected around Rastigaisa mountain in northern Norway. The explanatory variables used in the species distribution modelling included freezing degree day (FDD), growing degree day, radiation, soil moisture, topographic position index and information on the snow cover persistence. Species distribution modelling was performed using generalized boosted regression. From the modelling results the relative importance of the predictor variables as well as the predicted distributions of the species were interpreted. Microclimate factors varied between biotopes. The biggest variation in air temperature was observed at mountain tundra heath. Soil moisture had a levelling effect on the minimum temperatures and the FDD’s. The species distribution modelling results show that snow and moisture variable have a significant impact on the distribution of the arctic-alpine vegetation. Snow controls both temperature and moisture conditions and hence affects the stress that vegetation undergoes as well as the supply of nutrients.
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(2020)Environmental conditions affect the occurrence of species and changes in conditions change distribution patterns of species. At the time of Last Glacial Maximum (LGM, ~ 21 ka), climate has been colder and drier and glaciers have spread over large areas of Europe, which has had a significant impact on the occurrence of plant and animal populations and biodiversity up to modern times. According to the traditional view, the Mediterranean peninsulas have acted as refugia for various species, but several paleoecological and phylogeographical evidence have challenged this notion, as they suggest that the more northern regions may also have had suitable habitats for both temperate and boreal species. The aim of this work is to study the potential distribution areas of terrestrial mammals and the distribution of potential species richness in Europe at the time of LGM using species distribution modelling (SDM). Presence/absence records of mammal species were collected by the Societas Europaea Mammalogica with a resolution of 50 x 50 km. After pre-processing, the data provided information on 107 species in Europe west of 32° E. Modelling was carried out using ensemble modelling and climate data was used as explanatory variable. Hindcasting was done separately with three different LGM climate simulations to allow the assessment of the geographical distribution of climatically suitable areas for the species. Maps of the potential species richness of different species groups were compiled from LGM projections of individual species belonging to the species group. There was variation in modelling success between different species, but consensus models could be made for each species and thus also distribution predictions for the LGM. The climatically potential distribution areas of the different species differed clearly in both size and location and were related to the species' current distribution. Overall, the potential species richness during the LGM was higher than average in the Mediterranean peninsulas, the southern Western Europe, the Black Sea region, and the Carpathian region. The focus of the distribution of southern species was in the areas south of the Alps and of the northern species north and east of the Alps. The potential ranges of northern species were also larger on average than those of southern species. For mammals, climatically potential distribution areas were modelled extensively across the glacial Europe. The results support the idea of several suitable refugia for temperate species, some of which are located on the southern peninsulas and some north of traditional southern refugia. Northern species, on the other hand, have been able to find suitable living conditions in much of central and eastern Europe and therefore have not necessarily been limited to certain refugia. In the light of the results, it appears that mammalian glacial distribution patterns may have varied greatly depending on the characteristics of the species and that the climate during the LGM may not have significantly limited the distribution of all species.
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