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Browsing by Subject "vegetation"

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  • Winquist, Emelie (2021)
    The heath vegetation in the Jauristunturit study area is highly affected by the reindeer fence that was built in the mid-1950s between Finland and Norway, to prevent summer grazing in the Norwegian side. In the study area, the Finnish and Norwegian pastures are used during different seasons, causing differences in reindeer grazing history, and with time differences in vegetation. Additionally, local topography also impacts the vegetation composition and structure creating variation in local vegetation patterns. My research questions are: How vegetation patterns differ between summer- and winter- grazed areas, and which plant functional groups have the most significant difference? How local topography affects vegetation patterns, and does the effect of topography differ between summer and winter pastures? The data was collected from five 400 m long transects that crossed the fence and had vegetation plots with 10-m intervals. The %-cover and height of each vascular plant, bryophyte, and lichen species were estimated from 0.25 m2 plots. Later, species data was grouped into functional groups and general linear models were used to analyze differences in cover, height, species number, biomass, and leaf-area indices between countries. Topography indices were calculated in GIS for each plot and analyzed with random forest models to find out the most important topography indices explaining vegetation patterns. The vegetation data was collected by four teams, and therefore, the comparability in the collected data between teams was analyzed. Significant vegetation differences were found in the ground layer, with higher cover and biomass of bryophytes on the Finnish side (mean biomass 168.2 vs. 65.2 g m-2). Reindeer lichens were more abundant on the Norwegian side (mean biomass 197.0 vs. 2.9 g m-2) which is visible in aerial and satellite images and in the field. Among vascular plants, evergreen dwarf shrubs had higher biomass and leaf area index on the Finnish side and dwarf birch had higher cover and height on the Norwegian side. Topography indices had a higher level of variance explained on the Norwegian side, and higher at the ground layer compared to vascular plants. Elevation had the greatest impact on vegetation, and after that, topography protection index for 50 m and depth to water stream network for 2 and 10 ha. The differences between data collectors were not considered to have a major impact on the results. The results indicate that there are significant differences in vegetation between summer- and winter-grazed areas, mainly in the ground layer, and most differences are caused by differences in reindeer grazing history, but also local topography has an impact.
  • Finne, Hanna (2020)
    Boreal mires are natural sources of methane and contribute considerably to the global methane budget. Therefore, in order to comprehend the overall impact that these ecosystems have on climate change, it is essential to understand the factors that influence processes involved in methane production and consumption. Factors affecting methane flux vary between different mires, but there is also great spatial and temporal variation in flux within mires. In previous studies, temperature and water table position have been shown to influence methane flux, but vegetation could aid in explaining the small-scale variation. Vegetation can indicate spatial variation in water table position, but also affect methane flux directly by the transportation of methane through plant tissues, and by providing substrate for microorganisms through primary production. Furthermore, redox potential is a poorly studied factor that can reflect if chemical conditions in peat are suitable for methane production or consumption, making it a useful tool in predicting methane flux. In this thesis, I seek to identify if small-scale spatial variation in the methane flux occurs within the studied mire area. In addition, I strive to identify important controllers of the observed spatiotemporal variation in methane flux, with a specific focus on the effect of vegetation properties and redox potential. Methane and carbon dioxide fluxes were measured with the closed chamber technique at a boreal fen in Sodankylä (67°22'06.6"N 26°39'16.0"E) during the growing season in 2019. Flux measurements were carried out at nine measurement plots belonging to three different vegetation types: flark, lawn and string. Coverage and height of plant functional groups were followed during the summer and continuous redox potential was measured for each plot. CH4 fluxes of different plots and vegetation types were compared to study the spatial variation in methane flux. Generalized additive models (GAM) were used to determine which variables are best to explain spatiotemporal variation in methane flux over the growing season. Mean methane flux during the summer was 0.94 ug CH4 m-2 s-1 which is in the same magnitude as observed in a previous study at the fen. Some small-scale spatial variation in the methane fluxes was observed at the study site, with strings having lower flux than flaks and lawns. However, overall the spatial variation was small, while temporal variation in methane flux over the growing season was considerable. The best model, that was a combination of vegetation, redox potential and environmental variables, and it explained 72 % of the observed variation in methane flux. Vascular plant variables were the most important variables in the model, whereas moss functional groups were of lesser importance. Redox potential in deeper peat layers was also important in the model, but redox potential closer to the surface was not found to be significant. Vegetation is an important controller of methane flux, and this information could potentially be used when predicting methane flux over larger areas by using remote sensing to map vegetation characteristics. Redox potential, on the other hand, is relatively easy to measure, and the result suggests that it could provide a useful tool for improving the predictions of methane flux.
  • Lahti, Tuomas (2014)
    The purpose of this master's thesis was to study environmental impacts of nature-based tourism on vegetation, insect communities, birds and soil nitrogen levels in Käsivarsi wilderness area in the Finnish Lapland. Tourism is the largest industry in the world and nature-based tourism is the fastest growing segment of it. Nature-based tourism takes place in areas that holds great nature values. These areas are often protected to preserve significant nature values from negative impacts of human activities. This controversy creates disharmony between nature tourism and nature conservation. Most popular nature tourism destinations in Finland are state owned national parks and wilderness areas. Wilderness areas are not within strict nature conservation. They are areas defined by law for preserving the typical character of the remaining wilderness areas, preserving native Saami culture and for preserving and developing recreational use of these areas. Studies have shown that nature-based tourism has caused changes by erosion and human disturbance to vegetation, mammals and birds. The key study question was to examine if there are changes in the soil nitrogen levels around huts used by hikers. I was also a point of interest to discover what kind of bird, insect and plant communities occur around these huts. Main interest was to see if there are changes in these communities on a gradient from high human impact areas around the huts to more pristine mountainous areas. The study was performed around five huts with three study lines, which had study points 15, 30, 60, 120, 240, 480 and 960 meters away from the hut. Birds were observed from the same lines but with 200 meter point counting intervals. It was also studied whether the abundance of graminoids was affected by the soil nitrogen levels and if soil nitrogen levels or the abundance of graminoids influenced changes in insect or bird communities. Results show that nature-based tourism has an impact on soil ammonium and nitrate levels. This impact was visible in increased nitrate and ammonium levels on a 30 meter radius area around the huts. The observed fauna and flora around the huts were typical for the mountainous region in the northern Finland. There were no observed invasive species. No species was discovered to have a negative impact from nature-based tourism. Abundance of graminoids increased near the huts whereas plant species richness and vegetation biomass did not. The insect community was more diverse and abundant near the huts. Especially Amara brunnea ground beetle and rove beetles showed a clear increase in numbers near the huts. Birds were also more abundant and species rich near the huts. Especially insect eating bird species as a group were more abundant close to the hut compared to the surrounding study areas. The increased level of ammonium in the soil correlated with the increased graminoid and insect abundances. The increased graminoid abundance correlated also with the observed insect abundance. The influence between nature-based tourism and the changes in soils nitrogen levels and in the insect communities were scientifically demonstrated for the first time in this study. This thesis provides a comprehensive view of the effects that nature-based tourism has in the northern Finnish nature. The generalization of the result was weakened by the fact that the study was conducted only around five different huts and that the studied plant and animal communities were relatively diverse between these huts. The results are still substantial for the nature tourism in Käsivarsi wilderness area. The results can be useful for developing nature tourism infrastructure for the plausible new national park in the area.
  • Lindholm, Viivi (2022)
    Environmental factors are important tools in constructing methane flux models and estimations. Among the abiotic factors, plants and their functional groups have been noted to have significant effect on methane fluxes for three reasons. First, the vegetation community compositions express their abiotic environmental factors that affect not only the plants, but also local methanogen and methanotroph communities. Second, the vegetation itself might produce methane emissions and have a direct effect on methane balance. Third, the plant functional groups and species have differences in their chemical and physical properties that support different methanogen communities and therefore have an indirect impact on methane fluxes. In this study, methane fluxes of different plant communities were observed during one growing season in northern boreal catchment area in Muonio. Study focuses to determine the link between methane fluxes and abiotic and biotic environmental factors in different vegetation types. Closed chamber technique was used to measure methane and carbon dioxide fluxes from 23 plots every two weeks in period of June-August. Environmental data, such as moisture, temperature species composition etc. were collected from the plots. Vegetation types for each plot were determined via ordination analysis. Linear mixed-effects regression model and generalized additive model were applied and compared to observe the relationships of methane and environmental factors in different vegetation types. Dataset was divided into four vegetation types in clustering analysis: wet fen, pine bog, spruce swamp and forest. The greatest amount (average 5959 µg/m²/h) and biggest range (standard deviation 5285 µg/m²/h) of methane emissions were observed on wettest fen-like study sites. Peatland types in general acted as net methane sources. The driest, forest-like vegetation type acted as a net methane sink. The amount (average -107 µg/m²/h) and range (standard deviation 117 µg/m²/h) of methane fluxes were very moderate in comparison to peatland types. These effects intensified towards the climax of growing season. The most significant environmental factors were mostly abiotic on driest study sites and the whole plant biomass was more significant biotic methane flux regulating factor than plant functional groups. On wetter study sites, the role of abiotic factors decreased, and plant functional group increased. Graminoids were linked to bigger methane emissions especially on wetter study sites. Forest mosses and different shrub types seemed to have a link with lower methane emissions or methane absorption. The effect of other plant functional groups on methane fluxes varied more, and their role remains unclear. None of the environmental factors could estimate the methane flux alone, and the methane budget seems to be a sum of multiple variables in each vegetation type. The role of plant functional groups varied in different vegetation types and was dependent on surrounding vegetation. More research is needed to get better tools to estimate methane balance and to understand the underlying mechanisms in climate and environmental change.
  • Niemi, Johannes (2023)
    Suot ovat tärkeä osa maailmanlaajuista hiilen kiertokulkua, koska ne varastoivat suuria määriä hiiltä eloperäiseen materiaaliin turpeen muodossa, joka muodostuu biomassan hitaasta hajoamisesta kylmän, hapettoman ja matalan pH:n ympäristön vuoksi. Soista vapautuu myös metaania (CH4), joka on voimakas kasvihuonekaasu, jonka lämmityspotentiaali on 28 kertaa voimakkaampi kuin hiilidioksidin (CO2). Turvemaiden netto-C-päästöt riippuvat suotyypistä ja ympäristöolosuhteiden muutoksista, kuten pohjaveden korkeudesta tai turpeen lämpötilasta, ja niistä johtuvasta tasapainosta CH4-päästöjen ja turpeen muodostumisesta johtuvan hiilinielun välillä. Tämän tutkimuksen tavoitteena oli selvittää, miten kasviyhteisöt ja muut säätelevät tekijät, kuten lämpötila, pohjaveden korekus, LAI ja suotyyppi vaikuttavat sekä ilmakehän hiilivirtaan että turpeen CH4- ja CO2-pitoisuuksiin. Lisäksi tehtiin stabiiliin hiili-13 isotoopin mittauksia, jolla saadaan lisätietoa metanogeneesin biogeokemiasta. Mittaukset otettiin rahkasammalvaltaisista mättäistä ja saravaltaisista välipinnoista. Mittauspisteille tehtiin kolme kasvillisuuden manipulointia, joilla selvitettiin kasvillisuuden vaikutuksia hiilidynamiikkaan 1. putkilokasvien ja sammaleiden poisto, 2. pelkkä putkilokasvien poisto, 3. Kaikki kasvillisuus tallella. Tutkimuspaikka sijaitsee Etelä-Suomessa Siikanevan suoalueella. Mittaukset tehtiin vuonna 2018 touko-syyskuussa ombrotrofisessa keidasrämeessä ja oligotrofisessa saranevassa. Mittauskausi oli poikkeuksellisen kuiva ja pohjavedenkorkeus oli keskiarvoa matalammalla. Tästä johtuen monia aikaisemmin havaittuja korrelaatioita ei löytynyt. CH4-virtojen suuruus riippui suotyypistä ja kasvillisuuden manipuloinnista. Keskimääräiset turpeen CH4 ja CO2 pitoisuudet olivat hieman korkeammat mittauspisteissä saranavevalla. Pitoisuudet kasvoivat nopeasti syvyyden myötä, 50 cm:n syvyydessä pitoisuudet olivat useita suuruusluokkia suurempia kuin 7-20 cm:n syvyyksissä korkeimpien, mittausten ollessa yli 500 000 ppm. δ13C-CH4-arvot muuttuivat negatiivisemmiksi tyypillisesti syvyyden myötä, kun hydrogenotrofinen metanogeneesi yleistyi. Kasvillisuuden manipuloinneilla oli vaihtelevia vaikutuksia CH4-vuohon, eikä lehtipinta-alaindeksi osoittanut vahvaa lineaarista korrelaatiota CH4:n kanssa. CH4-virtaus oli myös epäherkkä pohjaveden korkeudelle, mutta kasvien välittämä CH4-kuljetus ei todennäköisesti ollut syynä, koska kasvillisuuden poistokäsitellyt mittauspisteet osoittivat myös samanlaista epäherkkyyttä veden korkeudelle. Putkilokasvien ja sammaleiden poistaminen vähensi yleensä CH4-virtoja. Mättäissä, joissa putkilokasvit oli poistettu, mutta sammaleita ei, oli alhaisimmat CH4-virrat. Yhteenvetona voidaan todeta, että useimmat ympäristömuuttujat eivät osoittaneet vahvaa korrelaatiota CH4:n kanssa. Mikään yksittäinen muuttuja ei selittänyt selvästi eroja CH4-vuossa. Turpeen CH4 ja CO2 pitoisuudet riippuvat voimakkaasti syvyydestä ja suotyypistä. Kasvillisuuden poistaminen tyypillisesti vähensi CH4-virtoja.