Browsing by Subject "ilmaston lämpeneminen"
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(2020)Global warming caused by the warming effect of greenhouse gases (GHGs) induces permafrost thaw, which could alter Arctic ecosystems from prominent carbon sinks to potential sources of GHG emissions when polar microorganisms become metabolically more active and have access to carbon compounds that were previously largely unavailable. Polar microbes can have significant contributions to the growing emissions of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) and therefore, studies on their metabolism are important. The aim of my study was to investigate polar microbial community composition and diversity as well as functional potential that was related to GHG-cycling in a subarctic environment with genome-resolved metagenomics. Soil cores were collected at the Rásttigáisá fell that is located in Northern Norway. After DNA extraction, ten mineral soil samples were sequenced. Metagenome-assembled genomes (MAGs) were reconstructed using either the combination of human-guided binning and automatic binning or human-guided binning only. Taxonomy was assigned to the MAGs and the functional potential of the MAGs was determined. I recovered dozens of good-quality MAGs. Notably, the MAGs from the mostly unknown phyla Dormibacterota (formerly candidate phylum AD3) and Eremiobacterota (formerly candidate phylum WPS-2) were reconstructed. There were MAGs from the following bacterial phyla as well: Acidobacteriota, Actinobacteriota, Chloroflexota, Gemmatimonadota, Proteobacteria and Verrucomicrobiota. In addition to the bacterial MAGs, MAGs from the group of ammonia-oxidizing archaea were recovered. Most of the MAGs belonged to poorly studied phylogenetic groups and consequently, novel functional potential was discovered in many groups of microorganisms. The following metabolic pathways were observed: CO2 fixation via the Calvin cycle and possibly via a modified version of 3-hydroxypropionate/4-hydroxybutyrate cycle; carbon monoxide oxidation to CO2; CH4 oxidation and subsequent carbon assimilation via serine pathway; urea, ammonia and nitrite oxidation; incomplete denitrification as well as dissimilatory nitrate reduction to ammonium. My study demonstrates how genome-resolved metagenomics provides a valuable overview of the microbial community and its functional potential.
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(2014)Boreal peatlands are diverse ecosystems and globally significant carbon sinks. Changes in environmental conditions might alter their vegetation and the amount of carbon fixation. The amount and composition of peatland vegetation is determined by air and peat temperature and hydrology. The air temperature is expected to rise on average by 1,2 – 4,8 °C, increasing the amount of droughts and lowering the water table level of fens by 8 – 14 cm. Fens may be especially vulnerable to changes in environmental conditions because they receive most of their nutrient input through groundwater flow and run-off. The aim of the research was to study the effect of warming and drying on the leaf area, phenology, leaf biomass production and composition of the plant community. The study site was an oligo-mesotrophic fen situated in central Finland. Vegetation was monitored throughout the growing season. The site was divided into a ditched area where the water table was lowered on average by 8 cm and to a pristine area where the water table remained at its natural state. Vegetation monitoring plots were warmed with plastic open top chambers. The walls were tilted inward in order to trap solar radiation inside the chamber, warming the air temperature on average by 2,3 °C. The results indicated that climate warming will affect the vegetation mostly through water level drawdown. Water table drawdown had no effect on the leaf biomass production of the whole plant community but it changed its composition. The amount of sedges remained unchanged and they continued to be the dominant plant group. Lowering of the water table increased the amount of evergeen shrubs and promoted the emergence of decidious shrubs. The amount of herbs dropped significantly because they require a more moist environment. Warming had no effect on leaf biomass production or species composition but it increased the development rate of leaf area until peak leaf area was reached. Water level drawdown on the other hand slowed down the development rate of leaf area. Together warming and water table drawdown increased the length of the growing season of sedges and the whole community. The ecosystem seems to adapt to changing environmental conditions through changes in the plant community composition, leaving the amount of leaf biomass production and carbon fixation unchanged despite the changes. The decrease of the more nutrient dependent species and the increase of species accustomed to more nutrient poor habitats might imply the beginning of gradual ombrotrophication of fens as the climate changes.
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(2022)The Arctic is facing a major turning point with climate change and the region's climate will experience a particularly sharp rise in temperature. Subarctic ponds are important habitats and shelters for many organisms in the area but are nevertheless poorly known compared to larger water bodies. Along with climate change, the importance of studying ponds becomes more important as they are the first to manifest a changing climate. Factors affecting the water properties of subarctic ponds include the characteristics of the catchment area, such as its location relative to the sea, altitude, bedrock, and soil. Of the climatic factors, the temperature in the summer months and the amount of precipitation are of great importance. The purpose of the thesis was to find out the factors influencing the water properties of ponds in the Kilpisjärvi region and how the water properties vary between ponds. Water samples were collected from 94 tundra ponds in and around Malla Strict Nature Reserve and in the areas around Ailakkavaara in August-September 2018 and 2019. The collected samples were later analyzed in the laboratory of the Department of Geosciences and Geography in University of Helsinki. The hydrochemical variables studied were metals dissolved in water, major ions, and total phosphorus and nitrogen. Variables describing catchment characteristics such as the Normalized Difference Vegetation Index (NDVI), TWI (Topographic Wetness Index) and climatic variables such as precipitation during the summer months and average temperature in July were collected from open spatial data sources. Based on the results of the principal component analysis (PCA), the chemical properties of pond waters vary slightly on average between Malla and Ailakkavaara, but there is more variation within the regions. The characteristics of the catchment areas and the climate clearly influenced the vegetation type surrounding the ponds, but these factors were not as strongly reflected in the characteristics of the pond waters. The absolute amounts of nutrients and water-dissolved metals are small, but the relative variation between ponds is substantial. Based on GAM-modeling, influence of groundwater (deuterium excess) was the single most significant factor influencing water quality, which was the explanatory variable for several water properties. The drier-than-average summer months in the study years emphasize the importance of runoff to water quality. Rainfall during the summer months, altitude, mean temperature in July, and amount of vegetation (NDVI) were the main factors influencing the subarctic ponds in the study. The increase in temperature caused by climate change will raise the temperature of pond waters and increased precipitation will increase the runoff of metals dissolved in ponds.
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(2019)In nutrient poor boreal peatlands, a significant proportion of photosynthesis-derived carbon of mycorrhizal plants is allocated to their fungal symbionts in exchange for nutrients. The soil carbon cycle is intertwined and affected by inputs of e.g. nitrogen and sulfur, whose amounts both in the soil and atmosphere have increased since the Industrial Revolution. In addition, as stated in the recent Global Warming of 1.5 °C -report (IPCC 2018) global warming is likely to reach 1.5 °C above pre-industrial levels before 2052. In this study, data from ericoid mycorrhizal fungi (ErMF) abundance, enzyme activities and the fungal taxa associated with them under increased warming and nutrient depositions were connected. This thesis is part of the Nitro-Erica -project of Natural Resources Institute Finland (LUKE) and it has been funded by the Academy of Finland (SA286731). Root fragments of Vaccinium oxycoccos L. and Andromeda polifolia L. were observed under a light microscope to determine the abundance of all root associated fungi, ErMF and dark septate endophytes (DSE). Fluorometric and photometric assays were used to study the ability of the fungi to degrade organic material and scavenge nutrients. Finally, direct PCR and Sanger sequencing were used to learn the dominant fungal taxa in the roots. A decrease in the abundance of ErMF and DSE was observed, indicating the possibility of a reduction in the carbon sink potential of peatlands through a decrease in the number of fungi. An increase in acid phosphatase activity under nitrogen deposition was observed in the two plants, which was expected as boreal peatlands are often nitrogen limited. In contrast, sulfur deposition suppressed the activity of all carbon acquiring enzymes which we concluded was likely to be the result of the sulfur inhibiting the growth of two parasitic fungi that greatly contributed to the overall high activity of carbon acquiring enzymes. More research is needed to gain a comprehensive understanding of the fungal abundance, communities and their functioning in peatlands under the changing environmental conditions.
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