Browsing by study line "Physical Geography"
Now showing items 1-20 of 37
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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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(2021)Due to the harsh conditions in high latitude alpine and arctic regions, climate or land use changes make them very vulnerable. Thus, it is vital to study the habitats of these regions and increase our understanding of what factors impact species distributions. Species distribution modelling can be used to predict possible habitats for species and further inspect the relationships between different environmental variables and species. Generally, these species distribution models have been created using variables describing the topographical and climatic conditions of the study area. Recently there has been more evidence supporting the inclusion of biotic variables to species distribution models at all scales. Including biotic variables can be difficult, as these relationships can be challenging to quantify. This study uses the Normalized Difference Vegetation Index (NDVI) as a surrogate for plant biomass, thus representing biotic interactions. This study aims to answer what are the relationships between environmental variables and the predicted distributions and will including a biotic variable improve the species distribution models. The study data includes observational data from 683 arctic and alpine plant species from Norway, Sweden, and Finland. The observation data were collected from the three national databanks of Norway, Sweden and Finland and completed with observations from the Global Biodiversity Information Facility and observation data collected by the BioGeoClimate Modelling Lab. The cohesive study area was outlined with the biogeographical regions defined by the European Environment Agency. Overall, six environmental variables are used in this study: annual mean temperature, the maximum temperature of the warmest month, annual precipitation, elevation difference in a cell, bedrock class, and NDVI. The NDVI data was gathered by NASA’s MODIS sensors. The observations and the environmental variables were projected into a grid consisting of 1 x 1 km cells covering the whole study area. This study uses the ensemble modelling technique with four individual modelling methods: generalized linear models (GLM), generalized additive models (GAM), generalized boosted models (GBM) and random forests (RF). The modelling process consisted of two modelling rounds so that the impact of NDVI could be evaluated. The first modelling round included all the environmental variables except NDVI (the topoclimate model) and the second modelling round included all the environmental variables (the full model). The two temperature variables, annual mean temperature and the maximum temperature of the warmest month, had the highest mean variable importance values. With the topoclimate model, annual precipitation ranked third with the rest of the climate variables, but when NDVI was added to the models, it rose above annual precipitation. Overall, among the studied arctic and alpine species, the variable importance values of both the edaphic and topographical variables were low. In general, both the topoclimate models and full models performed very well. The mean AUC- and TSS-values were all higher for the full models, indicating that including a biotic variable improved the models. When the binary predictions of both modelling rounds were compared, it was clear that NDVI refined the projected distributions for most species. The results from this study confirm the discovery that including a biotic variable, such as NDVI, has the potential to increase the predictive power of species distribution models. One of the main problems with including biotic variables in species distribution models has been the difficulty of quantifying biotic interactions. NDVI can thus be a promising tool to overcome these difficulties, as it is one of the most direct variables to describe ecosystem productivity, can be acquired at various scales, and as remotely sensed data, it can also cover areas that are difficult to access.
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Design-based research : Supporting high school GIS education with a research-based learning activity (2022)The role of geographic thinking is essential in tackling topical challenges such as climate crisis, biodiversity loss and sustainable production of food. One powerful tool that helps to model and analyze these complex geographic phenomena is geographic information systems (GIS). Using GIS as part of geography high school education has many benefits when it is applied intentionally. However, many teachers still struggle to implement GIS in long-term classroom use even if they have gotten previous GIS training and have access to internet-based GIS, easy-access data and easier to use software. There is still a need for further research on how teachers can be supported in GIS education on a practical level. This thesis research aims to find solutions to this need. The research is conducted as design-based research that consists of problem analyses and a cyclic development process where a design solution, a GIS learning activity, is created. Problem analyses showed that combining new and existing knowledge, using multimodal learning environments, and supporting motivation and development of metacognitive skills are important to take into consideration in designing the learning activity. They also examined features that lead to successful GIS teacher training. Conducted interviews revealed that the biggest challenges with GIS education relate to scarcity of time, insufficient technical skills, and training that does not provide practical value. Teachers wished for very practical level support that is efficient timewise and offers them learning materials that are ready for easy classroom use. Based on these findings, a GIS learning activity was designed to answer the common challenges. The practical was tested consecutively by two geography teachers from a collaborative high school. Feedback revealed that the first teacher faced some challenges relating to time management during the lesson but found the activity useful. The second teacher tested the activity after some modifications had been made and the testing was overall successful. Both teachers expressed interest in using the material and the GIS software again in the future. The findings suggest that providing teachers this research-based GIS learning material has potential to support them in GIS education and to remove many common challenges. Some advantages of the practical were offering teachers a web-based GIS with simple user interface, preprocessed data already included in the service and a ready practical that can be completed in one lesson. The theme also supported the national core curriculum which is very valuable in creating new GIS materials for educational use. This study showed that relevant and inquiry-based GIS activities are still needed in high school geography education. It also serves as the first opening for new LUMA Taita -project that promotes international science education collaboration and brings research into schools in an inspiring way.
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Diatom species richness and community composition along an elevational gradient in subarctic ponds (2020)Subarctic ponds are important habitats for many freshwater species. The recent increase in global temperatures have stressed on the study of these habitats as rising water temperatures may have severe consequences to these cold and harsh ecosystems. Despite its importance, this topic has been largely overlooked in scientific research. Diatoms are microscopic, single-celled benthic algae, which are important indicators for environmental quality. Elevation is one of the main environmental variables controlling the composition and richness of diatom species as it shapes communities through several environmental variables such as temperature and water chemistry. The aim of this thesis was to illustrate the variability in diatom species richness and community composition along an elevational gradient in Kilpisjärvi and reveal the most important environmental drivers. As an additional focus, the applicability of the BenthoTorch sampling device was tested in measuring benthic algae biomass. Field and laboratory measurements were done using universal standards. Statistical analyses included multiple univariate and multivariate data analysis techniques. It was found that water pH, aluminium concentration and air temperature explained the variation in species richness and community composition the most. Elevation had only a secondary, non-significant role in shaping the diatom communities in subarctic ponds. Nearby sites showed similar compositions in terms of water chemistry and diatom communities. Biotope characterisation did not provide any further insight into the differences or similarities of diatom community composition or species richness. There were some differences in how genera responded to environmental variables. The centre of distributional range of many taxa was below the mid-point of the elevational gradient but species often occupied the whole elevational gradient. Rare taxa appeared at the ends of the elevational spectrum. The amount of singleton taxa was high (25.8%) and can be expected to increase with climate change. The BenthoTorch did provide reasonable results for benthic algae in the subarctic when compared to previous literature, but further research is required to grasp its full potential. More examination into the relationship between explanatory variables can be suggested (e.g. total phosphorus and ion balance) to gain better understanding on the changes in diatom species richness and community composition along elevational gradients.
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(2022)The subarctic ponds of northern Fennoscandia are often clear-water, fish-free and oligotrophic (relatively low primary production). The ponds in the area are useful physical geography research sites, as the human impact in these areas is relatively small. These ponds are often phosphorus-limited and serve as good indicators of air pollution. Understanding and anticipating changes in water chemistry is particularly important for both the people and the ecosystems in the region. Changes in these ecosystems due to the climate change, for example, can be harmful. The effects of the climate change are and will continue to be strongest in arctic and subarctic areas. The current relatively short growing season is lengthening, so habitats and vegetation zones will either relocate or, alternatively, organisms and plants will have to adapt to the changing conditions. Yet many of the cold-water endemic species worldwide will become extinct. The aim of this thesis was to focus on the biomass of benthic algae growing on the rocks of subarctic ponds. These cyanobacteria, green algae, and diatoms are important primary producers in subarctic ponds and an important part of the food web in these waters. The biomass in this thesis refers to the actual amount of benthic biomass expressed by the amount of dissolved nutrients (not their theoretical, potential amount). The aim of the thesis was to find out how well the physical variables (pond area, average water temperature of the last month of measurement and median solar radiation) and chemical variables (water metal and nutrient concentrations, pH, and conductivity) explain the benthic biomass of subarctic ponds. The Kilpisjärvi area is the only area in Finland that belongs to the old Caledonian orogeny range in the northern part of Fennoscandia. All these 39 ponds were studied, and they are located in Kilpisjärvi in Finnish Lapland, in the areas of about 30 km² of Malla Strict Nature Reserve and about 40 km² of Ailakkavaara, at altitudes of 486–882 m a.s.l. Some of the ponds are located above and some below the tree line. Water samples were collected in August 2020, when data from continuous temperature and radiation meters installed in the late summer of 2019 were also read. During the sampling of the ponds, the biomasses of epilithic, rock-bearing benthic algae groups were measured with a BethoTorch field device and a water pH with a YSI PRO field meter. Water samples were analyzed for metal concentrations by ICP-MS and nutrient concentrations by IC. The results obtained after this spectrometric and chromatographic laboratory analyzes were analyzed statistically, including by means of a generalized linear model (GLM). The water chemistry of the ponds and the biomass of benthic algae are affected by many biotic and abiotic factors. Among other things, geographical location, topography, and climate (in the polar region or the equator) affect both water chemistry and pond biomass. The total metal concentrations in the studied ponds ranged from about 20 to 220 μg/l and the nutrient concentrations from about 2 to 17 mg/l. Based on the results, the chemical variables explained the occurrence of 57 % diatoms, 56 % green algae, and 27 % cyanobacteria, and the physical variables explained 28 % diatoms, 8 % green algae, and 4 % cyanobacteria. According to the F-test, of the chemical variables, the metal concentrations in the water played the largest role in the biomass of benthic algae. The pond area had the largest impact from the physical variables. Surprisingly, nutrients did not appear to play much role in the benthic biomass, although the literature suggests that. The warmer the water, the more likely cyanobacteria are the dominant species and the colder the water more likely are diatoms. This is because the growth peak of cyanobacteria coincides with the warmest time of the year, late summer, and diatoms in springtime immediately after the break-up of ice. The advantage of the BenthoTorch instrument was it is ease of use and speed of measurement, but more specific results could have been obtained, for example, by microscopy of the abundance of the benthic species. In the future, special attention should be paid to the stabilization of chlorophyll-a concentrations in the measurement of benthic algae biomasses. This could produce results that are more consistent and comparable.
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(2021)Glaciers and ice caps (GICs) excluding Greenland and Antarctic ice sheets account for large proportion of potential future sea level rise and are losing great amount of their mass in high confidence by 2100. Glacier elevation change observations covering whole Greenland’s GICs are limited to the 21st century and regional geodetic mass balance estimates are scarce. Recent development of photogrammetric software and rediscovery of old aerial photographs has been increasingly used to extend temporal resolution of glacier change studies. Besides for extended mass balance observations, historical photographs may be used in observing glacier surge events to improve their coverage in glacier inventories. In this study, 320 historical aerial photographs from 1953/1954 were photogrammetrically processed to create new digital elevation model (DEM) of the 1953 surface. Comparing the 1953 DEM with 1985 and 2016 DEMs extended the geodetic mass balance records on Nuussuaq peninsula to 63 years. Moreover, differenced DEMs were used with orthophotomosaics to identify glacier surface changes and advances and their possible relation to glacier surges. The study also explored the usage of Open Global Glacier Model (OGGM) with user defined input data for simulating future glacier changes in small scale regional setting. The geodetic mass balance results showed clear change from near equilibrium mass balance in 1953-1985 to overall mass loss in 1985-2016. Glacier surface lowering was found to shift to higher elevations along with the change to negative mass balance and occurred throughout the elevation range in 1985-2016. In contrast to generally retreating glaciers, advancing and/or surface elevation increases at the glacier fronts with glaciomorphological evidence of surging were observed on 5 glaciers. OGGM model is easily applicable for smaller regions but correcting the OGGM calibration with a fit to the geodetic mass balance data didn’t provide explicit result of the re-calibration efficiency. Historical photographs provide source to extend geodetic mass balance estimates and means to observe past glacier changes in more detail. Therefore, their incorporation in glacier change studies should be continued and create consistent datasets over larger regions. More research is needed with additional reference data to assess the reliability of the OGGM performance on a region without the reference data from default reference glacier network and the effect of re-calibrating with geodetic fit.
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(2021)Geodiversity, the natural abiotic variety of the Earth’s surface, is an essential part of natural diversity and plays an important role in providing the abiotic ecosystem services that all life depends on. Geodiversity is increasingly threatened by human activities and climate change, and consequently there is a growing importance of including geodiversity in decision-making. However, there is still a lack of studies assessing the spatial variation and key drivers of geodiversity, especially in high latitude and altitude areas, and this study, therefore, aims to contribute to an improved understanding. In this study, the geodiversity of a subarctic mountainous area in Northern Norway was mapped using remotely sensed data and applying a grid-based approach. The spatial variation of geodiversity was assessed using five different measures, and the relationships between geodiversity and several topographical parameters were analysed using correlation analysis (Spearman’s rank correlation, RS) as well as both univariate and multivariate linear regression. The vertical variation of geodiversity was also examined to analyse the variation of geodiversity along altitudinal gradients. A total of 54 geodiversity elements were observed in the study area and the number of elements per grid cell varied from 7 to 36. Four of the geodiversity measures correlated strongly, resulting in relatively similar spatial patterns of diversity. Higher values tended to follow the valley systems and cluster in the vicinity of rivers and larger streams. Topographically diverse grid cells, containing both steeper slopes and smoother areas, also contained a higher diversity. Low diversity occurred mainly on the highest elevations as well as on the steepest slopes. The majority of the univariate relationships between the measures of geodiversity and the topographical parameters were statistically significant, although the correlations generally were relatively weak. The regression models further confirmed the relationship between topography and geodiversity, and revealed various statistically significant relationships, as well as the presence of both linear and unimodal relationships. Higher geodiversity generally occurred in topographically heterogeneous landscapes, as well as in the vicinity of rivers and larger streams, where both erosion and accumulation processes are prominent, leading to a great variety of geomorphological elements and soil deposits. The summits and slopes of the mountain massifs, on the other hand, displayed a lower geodiversity. In these areas, erosion is significant, but accumulation processes are lacking. Furthermore, the hydrological diversity is generally low there. The vertical patterns of geodiversity were related to the spatial patterns since total geodiversity decreased steadily as mean elevation rose above 600 m a.s.l. The influence of topography on geodiversity patterns could also be seen in the statistically significant relationships between several topographical parameters and the geodiversity measures. There was, however, some variation in the strength of the correlations, and the weaker relationships can partly be explained by the contradictory effect of slope angle and elevation on geodiversity. These patterns were further confirmed by the fact that the regression models revealed not only linear, but also unimodal relationships between the topographical parameters and geodiversity. Although topography seems to have an important effect on all geodiversity measures, there is some variation in which topographic parameters are the most important for the different measures. To conclude, this study of a northern high latitude mountainous area shows that high geodiversity occurs in the vicinity of rivers and larger streams, as well as in landscapes with a varied relief. Topography has a statistically significant influence on geodiversity, although the magnitude and direction of the effect varies between the elements of geodiversity. To facilitate the incorporation of geodiversity in education, land use planning, resource management and nature conservation, more research is still required about the patterns and drivers of geodiversity.
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(2023)Pääsääntöisesti maaperän keinotekoisen kuivattamisen seurauksena muodostuneet happamat sulfaattimaat ovat ympäristön kannalta erittäin ongelmallinen maaperätyyppi. Niiden ongelmallisuus johtuu sulfaattialueiden maaperässä esiintyvistä rautasulfideista, jotka vapauttavat hapettuessaan maaperään sulfaattia. Kun sulfaatti liukenee maaperän veteen, muodostuu hyvin hapanta rikkihappoa. Maaperän lisääntynyt happamuus liuottaa maaperästä runsaasti eri metalleja, joilla voi etenkin voimakkaaseen happamuuteen yhdistettynä olla hyvin haitallisia vaikutuksia esimerkiksi vesistöjen ekologiselle tilalle, ja akvaattisille eliöille. Sulfaattimailta huuhtoutuu happamuutta ja metalleja kuitenkin hyvin episodimaisesti, tyypillisesti korkean valunnan aikaan, syksyisin ja keväisin. Tämän seurauksena sulfaattimaiden aiheuttamat vesistövaikutukset vaihtelevat ajallisesti hyvin paljon. Jos sulfidipitoisia maaperäkerroksia ei alun perin kuivatettaisi, eivät maaperän rautasulfidit hapettuisi, eikä happamia sulfaattimaita tai niiden aiheuttamia ympäristöongelmia muodostuisi. Tämä tutkimus toteutettiin Etelä-Pohjanmaan alueelta, valuma-alueiltaan pääsääntöisesti joko osittain tai kokonaan mahdollisilta sulfaattimaa-alueilta sijainneista ojista ja puroista vuonna 2019 kerättyjen vesinäytteiden ja mitattujen veden fyysiskemiallisten suureiden pohjalta. Tutkimuksessa oli 42 näytepistettä, joille rajattiin valuma-alueet 10x10 metrin korkeusmalliin perustuen. Tilastollisessa tarkastelussa pyrittiin selittämään tutkittujen näyteuomien pH-arvon ja sinkin pitoisuuksien vaihtelua GLM-mallien ja korrelaatiopohjaisen tarkastelun avulla, etenkin tutkittujen valuma-alueiden eri maankäyttömuotojen, ojitusmuotojen ja sulfaattimaiden esiintymistodennäköisyyden näkökulmasta. Tutkimuksessa tarkasteltiin myös mitattujen vedenlaadun muuttujien selittävyyttä pH-arvon ja sinkin pitoisuuksien suhteen. Lisäksi tutkimuksessa kartoitettiin tutkituilta valuma-alueilta vapautuneen happamuuden voimakkuutta ja metallien pitoisuuksia, ja selvitettiin pH-arvon kykyä selittää 14 eri metallin pitoisuuksien vaihtelua GLM-mallien avulla. Tutkimuksessa havaittiin, että tutkituilta valuma-alueilta vapautui tiettyjä metalleja (Fe, Mn, Zn, Ni, Co) korkeina pitoisuuksina, ja joidenkin tutkittujen uomien vesi oli myös hyvin hapanta (pH 3–4). GLM-mallinnuksessa eri maankäyttömuuttujat, ojitusmuodot ja sulfaattimaan esiintymisen todennäköisyys selittivät kuitenkin vain pienen osan pH-arvon vaihtelusta, kun taas veden sähkönjohtavuuden ja liuenneen aineksen pitoisuuden tilastollisesti hyvin merkitsevä kyky (p < 0,001) selittää pH-arvon vaihtelua viittasi sulfaattiperäiseen kuormitukseen tutkituilla valuma-alueilla. Sinkin pitoisuuksien vaihtelua pystyttiin selittämään pääosin vahvemmin kuin pH-arvon vaihtelua, mutta tulokseen vaikutti sinkille ennen GLM-mallinnusta suoritettu logaritmimuunnos. Sinkin pitoisuuksien vaihtelua selittivät parhaiten valuma-alueen muuttujista peltojen ja suuren/kohtalaisen todennäköisyyden sulfaattimaiden osuus valuma-alueen pinta-alasta, sekä salaojien määrä. Vedenlaadun muuttujista sinkin vaihtelua selittivät parhaiten liuenneen aineksen pitoisuus, veden pH-arvo ja sähkönjohtavuus, mikä osoitti sinkin korkeiden pitoisuuksien olleen sulfaattiperäisen happamuuden mobilisoimia. pH-arvon vaihtelulla voitiin myös selittää suuri osuus tutkimuksessa tarkasteltujen 14 eri metallin pitoisuuksien vaihtelusta, ja molybdeenia lukuun ottamatta kaikkien tutkimuksessa tarkasteltujen metallien pitoisuudet kasvoivat pH-arvon laskiessa. Tutkimuksen tulokset osoittivat selkeän yhteyden sulfaattimaiden aiheuttaman happamuuden ja metallipitoisuuksien välillä Etelä-Pohjanmaan sulfaattialueilla sijaitsevissa uomissa. Vaikka pH-arvon tai sinkin pitoisuuksien vaihtelusta ei voitu selittää suurta osuutta valuma-alueen muuttujilla, viittasivat tulokset sulfaattiperäiseen kuormitukseen ja siihen, että etenkin pohjaveden pinnan tasoa laskeva salaojitus ja peltojen osuus valuma-alueesta kasvattivat happaman ja metallipitoisen huuhtouman määrää. Tulokset korostavat happamien sulfaattimaiden aiheuttamaa kuormitusta ja niistä seuraavien ympäristövaikutusten merkitystä vesistöille ja niiden ekologiselle tilalle. Kokonaisuudessaan tutkimuksen tulokset tuovat esiin tarvetta löytää sulfaattialueiden viljelyyn kestäviä ratkaisuja, jotka voisivat rajoittaa sulfaattiperäisen kuormituksen muodostumista ja edistää vesiekosysteemien terveyttä ja ekologista tasapainoa.
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(2022)Glacial meltwater potholes are cylindrical and often remarkably smooth-walled pits in the bedrock, formed as a result of the evorsion caused by eddy currents of water released by the melting of the continental glacier, and possibly also by the cavitation due to the meltwater rushing to a glacial moulin or crevasse. This study examines how the location, topography, orientation according to the direction of ice movement, bedrock and the distance from the fault lines and eskers explain the occurrence and abundance of potholes in the province of Uusimaa in southern Finland. This study also provides a unified database of potholes that have been found in Uusimaa, which have not been compiled to this extent before. The research material with location and characteristic data was collected in July-October 2020 and in May-June 2021. A total of 320 potholes were selected for the research group, of which 206 were determined from fieldwork and 114 from source data. There were a total of 116 sites around Uusimaa, where the number of potholes varied from one to twenty (1–20). Moreover, especially in the archipelago spreading off the southern coast of the study area, there are numerous potholes marked only in sporadic old articles. As some potholes were located in areas that were too difficult to reach or in private yards, for example, the work also required the use of databases and reports published by research institutes and municipalities. The above-mentioned sources were also utilized in the field when searching for potholes and later in slope and distance analyses. In addition, one hundred (100) comparison sites were drawn from somewhat evenly across the study area in order to interpret how the location and characteristic data of pothole sites differ from rock formations where potholes are not known to occur. The location and characteristic data of pothole and comparison sites were compiled into a material. Based on the data, diagrams as well as regression and correlation analyses were made to visualize the results and their interrelationships, and statistical models (generalized linear model, GLM) were used to model several variables simultaneously. The results showed that many physical geography-related factors simultaneously affect the occurrence and abundance of potholes. Since potholes are glaciofluvial landforms, they often occur in north-south or northwest-southeast queues because these directions are equivalent to the direction of ice movement. The proximity of bedrock faults of tectonic origin strongly explains the occurrence of potholes, as the faults, like glacial moulins and crevasses, were favourable locations for meltwater flows. On average, there are more potholes in the sites located on the lee sides (downstream sides) compared with those on the stoss sides or central parts, because there were cavities and cracks as well as more space between the ice and the rock in the rough and plucked lee sides. The thin, non-uniform soil and the abundance of rock outcrops have led to the discovery of many more potholes in the lower southern parts of the study area and especially in the archipelago than in the higher northern parts. A significant proportion of potholes, which were not known to be located near bedrock faults, were located in the archipelago. In contrast, inland potholes typically occurred in steeper and rugged terrain near the fault lines. However, there was a weak negative correlation between the proximity of the eskers and the occurrence of potholes, which is probably due to the fact that the formation of potholes requires faster flows in glacier rivers than the formation of eskers. Most of the potholes in Uusimaa are quite small, up to about 120 centimetres in diameter and depth, but approximately one in eight potholes were more than three (3) meters deep or wide. The steepness of the slope was most strongly associated with the occurrence of large potholes. Potholes formed on rock consisted of granodiorite were, on average, larger than potholes formed on microcline granite, probably due to the granodiorite minerals are more prone to dissolve.
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(2020)Arctic peatlands are globally extensive and long-lasting storages of carbon and are therefore important ecosystems controlling global carbon cycling. Changes in climate affect peatlands’ ability to accumulate carbon through changes in hydrology and water table level, vegetation, soil temperature and permafrost thaw. As climate warming is projected mostly to northern and arctic regions, it may change the peatlands’ capacity to sequester and release carbon as carbon dioxide and methane. In this Master’s Thesis I studied how the past climate changes are reflected in carbon accumulation rates over the past millennia. Known climate anomalies, such as the Medieval Climate Anomaly, Little Ice Age and the last rapid warming starting from 1980, and their impact on average long-term apparent rate of carbon accumulation were studied from the peat proxies. 15 peat cores were collected from northern subarctic Swedish Lapland and from North-East European Russia. Cores were collected from the active peat layer above permafrost that is known to be sensitive to climate warming. Cores were dated with radiocarbon (14C) and lead (210Pb) methods and peat properties and accumulation patterns were calculated for one centimeter thick subsamples based on chronologies. The Little Ice Age and the last rapid warming affected the carbon accumulation rate considerably whereas for Medieval Climate Anomaly period the peat records did not show very distinctive response. During the Little Ice Age the carbon accumulation rates were low (median 10,5 g m-2v-1) but during the post-Little Ice Age and especially during the last warm decades after 1980 carbon accumulation rates have been high (median 48,5 g m-2v-1). Medieval Climate Anomaly had only a minor positive effect on accumulation rates. On average, the long-term apparent rate of carbon accumulation during the past millennia was 43,3 g m-2v-1 which is distinctly higher than the previously studied rate of 22,9 g m-2v-1 for northern peatlands (p-value 0,0003). Based on results it can be concluded that warm climate periods accelerated the carbon accumulation rate whereas during cold periods accumulation decelerated. Warm climate prolongs the growth period and accelerates the decomposition of peat; cold climate shortens the period of plant growth and thickens the permafrost layer in peatlands, respectively. However, peat layers that are formed after the Little Ice Age are incompletely decomposed which amplifies the carbon accumulation rate partly. Nevertheless, permafrost thawing has been shown to increase accumulation rates, as well. Studying past carbon accumulation rates helps to understand the peatland and carbon cycling dynamics better. Even though accumulation rates reveal a lot about carbon sequestration capabilities of peat, it does not indicate whether a peatland has been a carbon sink or a source.
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(2023)Aapa mires are northern peatlands of high conservation value that are currently threatened by hydrological changes caused by land use and climate change. In pristine hydrological state they are characterized by wet fens and waterflows from surrounding landscape, particularly during the snow melt time in spring. In future climate conditions, increased summer evapotranspiration and earlier spring floods can possibly reduce summertime water availability in aapa mires. It is however unclear, how strong effect the changes in the different climatic hydrological components exactly have on aapa mire wetness on regional level. Particularly spatial information of climatic sensitivity of mires is lacking. Current knowledge and large-scale hydrological predictions are based mainly on measurements at individual sites, modeling and generalization, even though climate-wetness relationships seem to vary largely from site to site. In this study, Sentinel-2 satellite imagery from 2017-2020 was used to produce regionally representative information of interannual summer wetness variability in Finnish aapa mires, and to quantify with statistical modeling the relationships to interannual climatic variation based on the observations. Monthly values for optical metrics of surface moisture and areal extent of the wettest mire surfaces were extracted for wet fen mires of the Natura 2000 conservation network (n=2201), covering the whole aapa mire zone of Finland. Wetness metrics from June and July in a regionally representative sample (n=400) of mires were linked to the respective yearly climatic data of summer-time water balance (WAB, precipitation - evaporation), day of snowmelt and snow water equivalent maximum. Climate-wetness relationships were estimated regionally for the eight aapa mire zone sub-regions with mixed effects models. The resulting satellite-derived metrics revealed high interannual variability of the surface moisture conditions and the areal extent of wet surfaces in aapa mires, and this variability was shown to be significantly connected to variation in the climatic variables. Regional variation in climatic sensitivity was remarkable. Mires in the most sensitive regions had twice as strong responses to varying WAB conditions and drought-periods than mires in the least sensitive regions. If the short-term responses are assumed to reflect the sensitivity to climatic changes in the long-term, these effects imply that aapa mires might experience remarkable hydrological changes in the future, especially in the most sensitive areas in the southern and the western parts of the Finnish aapa mire zone. The results emphasize the important role of yearly snow conditions alongside summertime WAB as a driver of aapa mire wetness, especially in June but also later in the summer.
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(2022)Kasvi- ja eläinplanktonia esiintyy käytännössä kaikissa boreaalisissa järvissä ja lammissa. Kasviplankton on koko järviekosysteemille tärkeä perustuottajaryhmä, kun taas eläinplankton on tärkeä kasviplanktonin kuluttajaryhmä. Ne siirtävät energiaa korkeammille trofiatasoille. Lisäksi ne toimivat ympäristöntilan indikaattoreina, sillä erityisesti kasviplankton reagoi herkästi elinympäristönsä muutoksiin. Tämän vuoksi kasvi- ja eläinplanktonin esiintymiseen ja levinneisyyteen vaikuttavien tekijöiden tunteminen on tärkeää. Tässä maisterintutkielmassa selvitettiin kasvi- ja eläinplanktonin levinneisyyttä boreaalisissa järvissä viidellä eri valuma-alueella Suomessa. Levinneisyyttä tarkasteltiin kolmen selittävän tekijän avulla, jotka olivat runsaus, ekolokeron koko ja lajipiirteet. Nämä selittävät muuttujat valittiin, koska kirjallisuuden perustella ne vaikuttavat merkittävästi lajin levinneisyyteen. Runsaus kuvaa lajin paikallista esiintymistä, ekolokeron koko puolestaan vuorovaikutusta muiden lajien kanssa ja lajipiirteet vaikuttavat pääasiassa leviämiskyvyn lisäksi saalistuspaineeseen. Tutkimuksen aineisto sisälsi yhteensä 100 järven kasvi- ja eläinplanktonlajien yksilöiden määrän kussakin järvessä sekä fysikaalis-kemiallisten ominaisuuksien mittaustulokset. Lajipiirteistä valittiin tutkittavaksi solukoko, jonka arvot pohjautuivat kirjallisuuteen. Levinneisyyden yhteyttä selittäviin muuttujiin tutkittiin regressioanalyysin avulla sekä tärkeimmille järvien fysikaalis-kemiallisille muuttujille tehtiin pääkomponenttianalyysi (PCA). Runsaus sekä ekolokeron koko korreloivat merkitsevästi levinneisyyden kanssa. Solukoolla ei havaittu lainkaan yhteyttä kasviplanktonin levinneisyyden kanssa. Eläinplanktonilla yhteys näiden muuttujien välillä havaittiin, mutta tulos ei ollut merkitsevä. Tulokset levinneisyyden ja solukoon välillä eivät kuitenkaan olleet luotettavia tai vertailukelpoisia, koska aineiston lajeilla oli liian pieni otanta. Aiempien tutkimusten perusteella voidaan kuitenkin sanoa, että solukoolla olisi käänteinen suhde levinneisyyden kanssa. Lajisto ja järvien fysikaalis-kemialliset olosuhteet olivat samankaltaisempia mitä lähempänä valuma-alueet olivat toisiaan.
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(2021)Large amounts of carbon is stored in the soil and vegetation of the tundra ecosystem. Carbon dioxide is stored in the vegetation in photosynthesis and is released into atmosphere from the soil and vegetation in ecosystem respiration. Rising temperatures can cause considerable changes to the delicate tundra ecosystem and create new potential feedbacks to global warming as the environment changes. There are several factors regulating carbon dioxide fluxes and their interactions and temporal changes are not yet fully known. Understanding carbon dioxide fluxes and the factors contributing to them is important in order to study and predict temporal and local changes. This research focuses on describing changes in net ecosystem exchange, primary production, and ecosystem respiration in the tundra as well as the factors contributing to them. The measurements were made with the chamber method in Saana fell, Kilpisjärvi in Finnish Lapland. This study includes 14 nivations with a total of 84 study points that were measured three times during the growing season in the summer of 2019. In addition to flux the measurements, information about controlling environmental variables were collected. These included vegetation, air temperature, soil moisture and soil temperature. The impact of the explanatory variables on fluxes at different times in the growing season was studied using mixed effects model and an estimated carbon budget was calculated for the region. The largest fluxes were measured mid-July during the peak growing season. Ecosystem respiration and primary production declined from the peak of the growing season in August towards the end of the growing season, but net ecosystem exchange increased slightly due to imbalances in the other two fluxes. Vegetation was an important explanatory variable (p ≤ 0,001) in every flux and during different times of the growing season. Air temperature had the greatest impact on net ecosystem exchange and ecosystem respiration, but the intensity of its response varied during different periods of the growing season. In both of these fluxes, higher temperatures increased the flux into the atmosphere. In primary production, the response changed in the middle of the growing season from positive to negative due to high temperatures. Soil moisture had a positive effect especially on ecosystem respiration, but its significance varied during the growing season (p = 0,0012; 0,02; < 0,001) and the response increased towards the end of the growing season. Also in primary production, response intensity and significance (p = 0,02) increased at the end of the growing season and in net ecosystem exchange the response changed from negative to positive at the end of the growing season. The response of soil temperature increased with all fluxes from the beginning of the growing season and decreased with ecosystem respiration and net ecosystem exchange towards the end of the growing season. Soil temperature was only significant in the second measurement campaign for net ecosystem exchange (p = 0,01) and ecosystem respiration (p = 0,005). During the growing season, carbon dioxide fluxes changed considerably and their explanatory factors also varied in time. The responses to soil moisture and air temperatures also turned negative or positive during the growing season. These changes and studying them is very important to understanding the processes behind different fluxes. The change in carbon dioxide fluxes and the variables that affect them in the tundra environment affects the region's carbon budget.
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(2021)Korkeuden vaikutusta eliöiden esiintymiseen on tutkittu eri alueilla jo 1800-luvulta lähtien, mutta vasta viimeisten vuosikymmenien aikana korkeuden vaikutuksen on tunnistettu olevan monimutkainen. Eri eliöryhmien lajirunsaushuiput saavutetaan korkeusgradientin eri vyöhykkeissä eri alueilla. Lintuihin korkeuden ja lajirunsauden välille on tunnistettu neljä toisistaan poikkeavaa trendiä. Korkeuden vaikutusta on tutkittu pääosin lauhkeilla ja trooppisilla alueilla, kun taas korkeiden leveyspiirien alueilta on tutkimusta vähän. Korkeuden lisäksi elinympäristöjen on todettu vaikuttavan merkittävällä tavalla lintujen esiintymiseen, mutta elinympäristöjen vaikutusta on tutkittu lähinnä metsissä, maatalousympäristöissä ja kaupungeissa. Ilmastonmuutos vaikuttaa pohjoisten alueiden elinympäristöihin erityisen voimakkaasti, mikä tekee näistä alueista tärkeitä tutkimuskohteita. Tämän tutkielman tarkoituksena on selvittää, miten korkeus ja elinympäristöt vaikuttavat lintujen esiintymiseen ja runsauteen tunturiympäristössä. Korkeuden ja elinympäristöjen vaikutusta tutkittiin tuottamalla alueellisia malleja kahdella eri mallinnusmenetelmällä (GLM ja GAM) lintuaineiston, korkeuden ja elinympäristöjen välille. Lintuaineisto kerättiin kesän 2019 aikana pistelaskennalla 420 tutkimuspisteeltä Pohjois-Norjassa Rásttigáisá-tunturin ympäristössä noin 180 km² kokoiselta alueelta. Lintuaineiston lajit luokiteltiin taksonomian mukaan lintulahkoihin varpuslintuihin, rantalintuihin, kanalintuihin ja päiväpetolintuihin. Tutkimuspisteet luokiteltiin viiteen eri elinympäristöluokkaan (metsä, metsänraja, kuiva avotunturi, kostea avotunturi, karukko) NDVI-aineiston ja ilmakuvien perusteella. Lintulajeille laskettiin Shannonin habitaatti diversiteetti-indeksi (SHDI), jonka avulla tutkittiin lajien esiintymistä eri elinympäristöissä. Sekä korkeus että elinympäristöt selittävät lintujen esiintymistä tunturiympäristössä. Korkeuden ja elinympäristöjen välillä havaittiin merkittävä suhde ja elinympäristöt sijoittuvat verrattain selvästi korkeusgradientille. Korkeuden ja lajirunsauden suhteen todettiin olevan huipukas, korkeimmat lajirunsaudet havaittiin 300–500 metrissä metsänrajalla ja sen yläpuolella. Korkeus selitti 30,3 % kokonaislajirunsauden, 30,8 % varpuslintujen ja 28,0 % rantalintujen lajirunsauden vaihtelusta (GAM). Elinympäristöluokat selittivät korkeutta paremmin etenkin esiintymisen muutoksia 50 metrin skaalalla. SHDI-arvon mukaan elinympäristöön erikoistuneimmat linnut ovat kosteiden avotuntureiden rantalintuja, kun taas varpuslinnuissa esiintyy enemmän generalistilajeja. Elinympäristöluokat selittivät tarkan skaalan lisäksi erityisen hyvin elinympäristöön erikoistuneiden rantalintujen lajirunsautta (35,5 %). Tulevat muutokset ilmastossa uhkaavat etenkin avotunturissa esiintyviä lajeja, joista monet esiintyvät vain tietyssä elinympäristössä. Korkeuden ja elinympäristöjen vaikutusten syvempään ja tarkempaan ymmärtämiseen tarvitaan lisää tutkimusta. Jatkotutkimusta tarvitaan useammalta korkeusgradientilta ja tarkemmalla elinympäristöluokituksella.
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(2022)Climate change is going to bring a change for ecosystems and their abiotic and biotic processes. Relationship between climate and ecosystems is usually studied using macroclimatic data, but plants have been found to be more closely associated with changes in microclimates. Microclimates involve temperature, wind, radiation, and humidity conditions near the ground surface. Microclimates can change over short distances creating differences for areas general climatic conditions. Microclimates can help plants to survive in the edge of their dispersal area or create stronger variations in temperatures. Not much research conducted on microclimates in boreal ecosystems yet. The aim of this thesis is to illustrate how environmental variables affect temperatures in different seasons inside boreal biome. Microclimates are a combination of physical processes and environmental variables. Main physical processes are energy released and bound by changes in the state of water, heat flux between soil and air, and radiation balance. Environmental variables are key components on defining how physical processes occur in the area affecting the microclimatic temperatures. Topography creates change in the lapse rates via altitude variations, and slope curves and orientation change radiation and moisture conditions. Radiation and moisture conditions also vary according to the vegetation factors, for example in the forest where canopy cover and vegetation height create differences in physical processes. Water masses and mires affect the area’s moisture conditions and heat flux between air and water. Heat flux between air and soil on the other hand is affected by quality of soil and wind conditions. Wind currents affect the mixing of different layers of air and the cold air pooling together with local topography. Relative influence of the environmental variables was studied using 8 study areas located in different boreal climatic zones. Study sites included 50 to 100 temperature meters, covering different environmental conditions in the area. Temperature data were collected at a height of 15 cm above the ground over a two-year period. In this thesis explanatory variables where canopy cover, radiation, slope, wind, distance to forest edge, TWI, and water and wetland portions. GAM-models were generated for different temperature variables for different months and years. Explanation ability of the model was evaluated with bootstrap-method. Relative influence of the explanatory variables was examined by variable randomization. Models explanatory power was highest in the southern study areas and decreased slightly when moving to the northern sites. There was a positive correlation between model explanatory power and its stability. Based on this the results are more reliable in the southern sites and during the summer. Temperatures observed in microclimates followed the changes in the macroclimatic conditions. In the northern areas, the main environmental factors explaining temperature variations were mainly topographic variables such as slope, wind, and TWI. In the southern areas vegetation variables like canopy cover, distance to forest edge and wetland portion were more relevant in explaining the temperature variations. Results also suggest that topography driven wind conditions are an important variable in the northern areas. Wind was found to decrease temperatures in winter months and increase temperatures in summer. The influence of wind has not yet been taken into consideration in many previous studies, as it is affected by several different factors. Further research into the factors affecting microclimatic temperatures is important in order to determine more precisely the differences between the environmental factors influencing the temperatures and their relative significance in different years. However, the temperature variables occurring in the boreal zone can be explained by examining the topographic and vegetation variables.
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(2022)Diatoms, green algae, and cyanobacteria react fast to changing environmental conditions. Algae are important primary producers in stream ecosystems, thus changes in periphyton can influence the whole stream ecosystem. There have not been many studies where algae biomass variation has been explained with a large water chemistry data. Furthermore, there is lack of studies where metal concentrations in the water are near to natural concentration levels. In this master’s thesis I examine how environmental variables affect the changes in algae biomass. Furthermore, the aim of this study is to examine do diatoms, green algae and cyanobacteria have different responses to environmental variables. Competition between three algae biomass groups is also researched. In this study research points were classified to three land use types. The aim of the classification was to enable variation as much as possible in shading and water chemistry variables in the study area. Eventually 51 research points were selected. Algae biomass was measured with BenthoTorch. Total phosphorus, total nitrogen, anions, cations, solid matter, dissolved matter and dissolved metals were measured in laboratory. Total biomass’ and algae groups’ response shapes where analyzed with GAM. Furthermore, competition between different algae groups were studied with Spearman’s correlation. The average total algae biomass was 2.94 μg cm-2 in the study area and diatoms were the most dominant group. Surprisingly the amounts of light and total phosphorus were sufficient in the study area and had no significant effect on the total algae biomass variation. However, total nitrogen, calcium, zinc, iron, and nickel were significant environmental variables in total biomass model. Total nitrogen, calcium, zinc and nickel where significant environmental variables for explaining diatom biomass variation. Total phosphorus and nitrogen were significant in cyanobacteria’s model and only zinc was significant in green algae’s model. Green algae had a weak but a significant negative correlation with diatoms and cyanobacteria. Total algae biomass growth was notable restricted in study area. The average amount of biomass matched a biomass volume in an oligotrophic stream. There were enough of light and total phosphorous in the study area, thus they had no significant effect on algae biomass. At high total nitrogen concentration levels biomass growth was inhibited. In addition, iron and nickel had a significant negative effect on total biomass. Zinc was an important mineral for algae biomass growth, specially to diatoms and green algae. Strong competition on resources did not occur between the algae groups. Negative correlations between algae groups where most likely explained with different responses to iron, nickel, and calcium. There is need for more studies to explain algae biomass in different natural stream ecosystems. For understanding better how different concentrations change algae biomass, more variation on environmental variables is needed. Furthermore, water hydrology and grazing should be measured. In addition, research on how water chemistry changes affect species composition in periphyton is recommended.
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(2021)Urban stormwater systems effectively connect harmful substances from urban areas to more natural waters. The goal of this study was to determine whether stormwater sumps served as purifying elements of urban waters or whether urban stormwater and its harmful substance load passes through the system into nature. In addition, the study examined if significant quantities of harmful heavy metals are deposited in the stormwater sump sediment traps, and if the intensity of land use affects the quality of sediment in these traps. The study analyzed sediment samples from 30 stormwater sump traps in Helsinki, Finland. The stormwater sumps were selected from areas representing different land use intensities. For each sump, a catchment area and the magnitude of built area were determined by using geoinformatic data. From the sediment samples taken from the stormwater sump traps, metal concentrations (Al, P, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Mo, Cd, Pb and U), susceptibility, organic matter as well as dry matter and grain size distribution were analyzed. The study looked at the statistical significance of correlations between different variables. All measured variables were also studied by primary component analysis. The differences in metal concentrations of land use classes were assessed by one-way variance analysis. The harmfulness of the sediments in the stormwater sump traps was assessed based on the regulations of the Ministry of the Environment’s degraded soil and sediment slapping guidelines. The results show that stormwater sump traps had harmful concentrations of heavy metals. Concentrations of nickel, copper, and zinc harmful to water nature were found in the sediment samples. In addition, concentrations of zinc and copper exceeding the soil pollution limits were found. Metal concentrations in sediments were generally highest in the stormwater sump traps in traffic areas. Statistically highly significant correlations were observed with the increase in land use intensity and the concentrations of heavy metals. As land use intensity increased, concentrations of metals referring to human activity increased in stormwater sump traps. However, the metal concentrations in the sediments of the stormwater sump traps were not higher than the metal concentrations in stream sediments studied in the Helsinki region. The minor amount of fine sediment present in the stormwater sump traps also suggests that the particles that move with stormwater do not sediment into the sump traps in large quantities. This study indicates that stormwater sumps in the Helsinki region could have significant amounts of harmful metals. Based on the results of this study, when draining stormwater sumps, sediment treatment should be considered prior to its possible deployment into the watershed or reuse as filling soil or mull. In particular, reusing untreated sediments from stormwater sumps in traffic areas can be detrimental to nature. The fine material sedimentation capacity of stormwater sumps should be improved to minimize the load of harmful substances passing through the stormwater system into nature. More research is needed on the sedimentation processes of stormwater sumps suitable for Finnish conditions.
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(2020)The Arctic is warming with an increased pace, and it can affect ecosystems, infrastructure and communities. By studying periglacial landforms and processes, and using improved methods, more knowledge on these changing environmental conditions and their impacts can be obtained. The aim of this thesis is to map studied landforms and predict their probability of occurrence in the circumpolar region utilizing different modelling methods. Periglacial environments occur in high latitudes and other cold regions. These environments host permafrost, which is frozen ground and responds effectively to climate warming, and underlays areas that host many landform types. Therefore, landform monitoring and modelling in permafrost regions under changing climate can provide information about the ongoing changes in the Arctic and landform distributions. Here four landform/process types were mapped and studied: patterned ground, pingos, thermokarst activity and solifluction. The study consisted of 10 study areas across the circumpolar Arctic that were mapped for their landforms. The study utilized GLM, GAM and GBM analyses in determining landform occurrences in the Arctic based on environmental variables. Model calibration utilized logit link function, and evaluation explained the deviance value. Data was sampled to evaluation and calibration sets to assess prediction abilities. The predictive accuracy of the models was assessed using ROC/AUC values. Thermokarst activity proved to be most abundant in studied areas, whereas solifluction activity was most scarce. Pingos were discovered evenly throughout studied areas, and patterned ground activity was absent in some areas but rich in others. Climate variables and mean annual ground temperature had the biggest influence in explaining landform occurrence throughout the circumpolar region. GBM proved to be the most accurate and had the best predictive performance. The results show that mapping and modelling in mesoscale is possible, and in the future, similar studies could be utilized in monitoring efforts regarding global change and in studying environmental and periglacial landform/process interactions.
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(2020)Methane (CH4) is a greenhouse gas with a great impact on global climate. In the soil, it is produced in anoxic and consumed in oxic conditions by microbes. Together with different methane transport mechanisms, methane production and consumption directly regulate the resulting soil methane flux. Boreal upland forests are generally considered to act as methane sinks due to high methane consumption. However, some studies have shown a boreal upland forest soil turning from a methane sink to a source after long-term abundant precipitation. This study aimed to examine the effects of soil moisture on CH4 flux from simulated increase in rainfall in a northern boreal upland forest soil, and how simultaneous soil temperature increase, organic litter addition and organic litter and root exclusion affect the temporal changes in flux. The study was conducted in Kenttärova forest in Kittilä, Finland in summer 2018. Split-plot design was used in the experiment with soil moisture being the main treatment variable and soil warming (T), organic litter addition (A) and organic litter and root exclusion (E) subtreatment variables. The design included two main plots: irrigation (I) and control (C), within which each subtreatment was replicated three times. In addition to the T, A and E manipulations, plots without additional manipulations (O) were included for the assessment of the effect of only soil moisture increase, and were replicated four times within both main plots. Methane flux was measured at least once a week using chamber method. Soil moisture and temperature were also continuously measured. The treatment effects were analysed using both autoregressive heterogeneous and autoregressive two-way analyses of variance, TukeyHSD method, variable correlations and Generalized Linear Models. The soil did not turn into a methane source but the results showed significant differences between the irrigation and control site, indicating a strong decreasing effect of soil moisture on soil CH4 sink in all treatment levels. All treatments had lowest uptake rates in August, possibly as a result from highest soil moisture levels. IA treatment was the most effective in producing low uptake rates possibly due to the reduction in gas diffusion. E treatments had contrasting results, IE showing increases in uptake rate by increases in soil moisture but the causes remained unsolved and the results were highly uncertain. T treatment had no effect on uptake likely due to a failure to create soil temperature differences and thus the interactions were not reliably analysed. The results suggest that the changes may have been more related to changes in methane consumption than production. Further research is needed especially for examining the combined effect of litter addition, soil moisture and soil temperature increase on methane flux with multiple temporal replications of the experiment.
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(2023)Bioklimaattinen mallinnus on keskeinen biogeografinen menetelmä, jolla tutkitaan lajilevinneisyyden ja ilmaston välistä yhteyttä. Tutkimuksessa tarkasteltiin, kuinka hyvin lämpö- ja kosteusolosuhteita kuvaavat bioklimaattiset muuttujat selittivät tundran putkilokasvilajien levinneisyyttä kahdella mittakaavatasolla ja mitkä muuttujat olivat suhteellisesti tärkeimpiä eri lajeille. Lisäksi tarkasteltiin muuttujien alueellista vaihtelua. Biogeografinen tutkimus on erityisen tärkeää tundralla – esimerkiksi Suomen tunturipaljakan putkilokasvilajeista 16 % on uhanalaisia, ja tämän luvun odotetaan kasvavan ilmaston lämpenemisen myötä. Tutkimus sijoittui Mallatuntureiden ja Ailakkavaaran alueille Luoteis-Lappiin. Mallinnettavia putkilokasvilajeja oli 26, joista kahdeksan on arktis-alpiinisia ja muut boreaalisia. Bioklimaattisia muuttujia johdettiin kahdesta ilmastoaineistoista: hienon mittakaavan mikroilmastoaineistosta sekä mesomittakaavan sääasemien mittauksista interpoloidusta aineistosta, joka kuvaa makroilmastollisia olosuhteita. Bioklimaattisten muuttujien alueellista vaihtelua tutkittiin karttatarkastelun avulla ja aineistojen erojen tilastollista merkitsevyyttä arvioitiin tilastollisin tunnusluvuin. Malleja rakennettiin kolmella menetelmällä: yleistetyt lineaariset ja addittiviset mallit sekä yleistetyt luokittelupuut. Mikroilmastomallien muuttujia olivat kasvukauden lämpöolosuhteita kuvaava tehoisa lämpösumma, talven olosuhteita kuvaava helmikuun minimilämpötila ja kesän kosteusolosuhteita kuvaava heinäkuun maaperän kosteus. Makroilmastomalleissa oli muuttujina lämpösumma, helmikuun minimilämpötila ja kesän sademäärä. Mallien suorituskykyä arvioitiin AUC-arvojen avulla ja muuttujien tärkeydet selvitettiin yleistetyt luokittelupuut -menetelmällä. Hienon mittakaavan bioklimaattiset muuttujat kuvasivat selkeästi tarkemmin lämpö- ja kosteusolosuhteiden alueellista vaihtelua lyhyillä etäisyyksillä kuin karkeamman mittakaavan muuttujat. Eri mittakaavojen muuttujien erot olivat myös tilastollisesti merkitseviä. Vaikka bioklimaattisten mallien suorituskyky oli keskimäärin heikko, mikroilmastomallien AUC 0,69 oli korkeampi kuin makroilmastomallien AUC 0,63. Ero suorituskyvyssä oli siis tilastollisesti merkitsevä. Mikroilmastomallit selittivät paremmin yksittäisten putkilokasvilajien levinneisyyttä kuin makroilmastomallit, sillä suorituskyvyltään hyviä tai erinomaisia malleja oli enemmän. Alle puolelle lajeista suhteellisesti tärkein bioklimaattinen muuttuja oli sama eri mittakaavoilla. Tehoisa lämpösumma oli tärkein muuttuja useimmille arktis-alpiinisille ja boreaalisille lajeille karkeammassa mittakaavassa, kun taas heinäkuun keskimääräinen maaperän kosteus oli tärkein muuttuja useimmille arktis-alpiinisille lajeille hienossa mittakaavassa. Tehoisa lämpösumma oli tärkein muuttuja useimmille boreaalisille lajeille myös hienossa mittakaavassa. Tutkimuksen perusteella tundran mikro- ja makroilmastolliset lämpö- ja kosteusolosuhteet eroavat merkittävästi toisistaan, millä on merkitystä esimerkiksi lajien suojelusuunnittelua kehitettäessä ilmaston lämmetessä. On tärkeää huomioida, millaisia ilmasto-olosuhteita bioklimaattisten mallien aineistot kuvaavat, kun tutkitaan tundran putkilokasvilajien suhdetta ympäristöönsä hienossa mittakaavassa.
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