Browsing by Subject "maaperän lämpötila"

The arctic-alpine tundra environment, located above treeline at mountainous areas in high latitudes, is a varying fine-scale mosaic of landscapes and biotopes driven by harsh and extreme environmental conditions. Soil moisture and temperature play a key part in the environmental processes of the area, as they regulate especially vegetation and soil microbial activity. Both soil moisture and temperature vary greatly in spatial as well as temporal scales even in small scale environments. Despite their variability and importance, the mechanisms driving these variables have been scarcely studied. In this study the focus was how soil moisture and temperature vary in the different biotopes of arctic-alpine environment in the Kilpisjärvi region. The study area is located in the slopes and valley between the fjells Saana and Korkea-Jehkas, where 1 200 study plots, 1 square meter in size and 50 meters from each other, were placed systematically. Soil moisture and temperature were measured from the plots three times during the growing season: in June, July and August. A vast collection of field measurements was gathered from the plots and then supplemented with variables extracted from a digital elevation model. The next step was to use statistical models to determine how topographic, soil and vegetation variables affect the spatial variability of soil moisture and temperature during the growing season. The methods used were Generalized Additive Models (GAM), Generalized Boosted Methods (GBM) and Random Forest (RF). The effect of the variables was studied by how adding different variable groups affected the explanatory and predictive powers of the different models. In addition the effect of individual explaining variables was examined by their relative influence on GBM-models. Soil moisture and temperature varied significantly during entire growing season and not only in the entire study area but also within biotopes as well. Soil temperature values increased throughout the growing season, whereas soil moisture values were highest in July and lowest in August. Modelling results suggest that topography and soil variables have stronger effect in June and July and the effect of vegetation variables strengthens in August. GBM-models suggest that the best individual variable in explaining soil moisture´s spatial variation during all field measurement periods is biotope class and organic layer depth. The best individual variable explaining soil temperature´s spatial variation during all field measurement periods is potential solar radiation. In addition elevation has a strong effect in June and July and soil moisture in August. In principle, the moisture models´ explanatory and predictive powers decrease during growing season due to drying soil while temperature models´ explanatory and predictive powers increase due to warming soil. The results of this study support and expand the findings of former studies on spatial and temporal variation of soil moisture and temperature modelling in arctic-alpine environment. In future studies it is important to consider the impact of using different variables in soil moisture and temperature in a versatile way. It is also important to study the temporal variation of soil moisture and temperature more thoroughly to understand the effects of climate change on arctic-alpine biotopes better.