Browsing by Subject "vegetation"

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  • Jukola-Sulonen, Eeva-Liisa; Salemaa, Maija (Suomen metsätieteellinen seura, 1985)
  • Caroppi, Gerardo; Västilä, Kaisa; Gualtieri, Paola; Järvelä, Juha; Giugni, Maurizio; Rowinski, Pawel M. (Elsevier, 2020)
    Data in Brief 32, (2020), 106080
    Vegetation, generally present along river margins and floodplains, governs key hydrodynamic processes in riverine systems. Despite the flow-influencing mechanisms exhibited by natural vegetation and driven by its complex morphology and flexibility, vegetation has been conventionally simulated by using rigid cylinders. This article presents a dataset obtained from hydraulic experiments performed for investigating the flow-vegetation interaction in partly vegetated channels. Vegetation was simulated by using both natural-like and rigid model plants. Specifically, two sets of experiments are described: in the first, vegetation was simulated with natural-like flexible foliated plants standing on a grassy bed; in the second, rigid cylinders were used. Experiments with rigid cylinders were designed to be compared against tests with natural-like plants, as to explore the effects of vegetation representation. The following experimental data were produced: 3D instantaneous velocity measured by acoustic Doppler velocimetry, vegetation motion video recordings, and auxiliary data including detailed vegetation characterization. These experiments are unique both for the use of natural-like flexible woody vegetation in hydraulic experiments and for the similarity achieved between the resulting observed vegetated shear layers. These data are expected to be useful in vegetated flows model development and validation, and represent a unique benchmark for the interpretation of the flow-vegetation interaction in partly vegetated channels.
  • Västilä, Kaisa; Väisänen, Sari; Koskiaho, Jari; Lehtoranta, Virpi; Karttunen, Krister; Kuussaari, Mikko; Järvelä, Juha; Koikkalainen, Kauko (MDPI, 2021)
    Sustainability 13, 16
    Conventional dredging of ditches and streams to ensure agricultural drainage and flood mitigation can have severe environmental impacts. The aim of this paper is to investigate the potential benefits of an alternative, nature-based two-stage channel (TSC) design with floodplains excavated along the main channel. Through a literature survey, investigations at Finnish field sites and expert interviews, we assessed the performance, costs, and monetary environmental benefits of TSCs in comparison to conventional dredging, as well as the bottlenecks in their financing and governance. We found evidence supporting the expected longer-term functioning of drainage as well as larger plant and fish biodiversity in TSCs compared to conventional dredging. The TSC design likely improves water quality since the floodplains retain suspended sediment and phosphorus and remove nitrogen. In the investigated case, the additional value of phosphorus retention and conservation of protected species through the TSC design was 2.4 times higher than the total costs. We demonstrate how TSCs can be made eligible for the obligatory vegetated riparian buffer of the European Union agri-environmental subsidy scheme (CAP-AES) by optimising their spatial application with respect to other buffer measures, and recommend to publicly finance their additional costs compared to conventional dredging at priority sites. Further studies on biodiversity impacts and long-term performance of two-stage channels are required.
  • Kuusipalo, Jussi (Suomen metsätieteellinen seura, 1985)
    The vegetation and some physical and chemical soil properties were studied in 410 sample plots in a random sample of stands by two-way indicator species analysis, discriminant analysis and analysis of variance. Understorey vegetation was dependent on site fertility and on the tree stand (especially species composition). Although the forest vegetation was distributed in a rather continuous way along a soil fertility gradient, relatively unambiguous site classification was possible based on the appearance of indicator species and species groups.
  • Hovi, Tiina (Helsingfors universitet, 2013)
    Finnish agriculture has faced radical changes since the mid-20th century due to intensification of agricultural production. These changes have resulted into considerable wildlife habitat loss and degradation of biodiversity. Open ditches and their boundaries are one such habitat. They were widely replaces by subsurface drainage. This thesis aims to understand the role open ditches for agricultural biodiversity; what kinds of plants live the ditch habitat and can ditches enhance agrobiodiversity? To answer these questions we surveyed the vegetation of ditch slopes and ditch banks. Both vegetation composition and species richness were studied. The survey concerns only vegetation, but it is assumed that plant species diversity supports diversity of other groups of organisms. The data was collected in summers 2008 and 2009 in Lepsämä river catchment in Southern Finland in co-operation with MYTVAS (Significance of the Finnish agri-environment support scheme for biodiversity and landscape) -project. Ditch habitat characterization was done by studying the most common species and their indicative values in the data. Also NMS-ordination graph was created. Environmental variables were analyzed too. According to the literature review ditches can have significant role in maintaining agrobiodiversity, and their existence has probably reduced biodiversity loss. However, the vegetation analysis shows that the study area was species-poor and homogenous. Probable explanations are the habitat’s humidity and high levels of nutrients alongside the dominance of few strong weed species. In order to improve ditches as wildlife habitats their quality should be enhanced. For example fertilizer and herbicide drifts should be reduced and ditch banks could be widened. Also tending the ditch habitat by cutting or grazing are highly recommendable methods to enhance biodiversity.
  • Kellomäki, Seppo (Suomen metsätieteellinen seura, 1977)
  • Nylund, Markku; Nylund, Liisa; Kellomäki, Seppo; Haapanen, Antti (Suomen metsätieteellinen seura, 1979)
  • Kyttälä, Christel (University of Helsinki, 1999)
  • Stam, Åsa Charlotta Sofia; Enroth, Johannes; Malombe, Itambo; Pellikka, Petri Kauko Emil; Rikkinen, Jouko Kalevi (2017)
    Transplant studies can provide valuable information on the growth responses of epiphytic bryophytes and lichens to environmental factors. We studied the growth of six epiphyte species at three sites in moist Afromontane forests of Taita Hills, Kenya. With 558 pendant transplants we documented the growth of the selected four bryophytes and two lichens over the time course of one year. The transplants were placed into the lower canopy of one forest site in an upper montane zone and two forest sites in a lower montane zone. Several pendant moss species grew very well in the cool and humid environment of the upper montane forest, with some transplants more than doubling their biomass during the year. Conversely, all transplanted taxa performed poorly in the lower montane zone, presumably because of the unfavorable combination of ample moisture but excessive warmth and insufficient light which characterizes lower canopy habitats in dense lower montane forests. The results demonstrate that transplantation studies with pendant transplants can be used for monitoring growth of nonvascular epiphytes in tropical forests. The start weight of 0.25 g for pendant transplants worked well and can be recommended for future studies.
  • Korpela, Ilkka; Haapanen, R.; Korrensalo, A.; Tuittila, E-S; Vesala, T. (2020)
    Boreal bogs are important stores and sinks of atmospheric carbon whose surfaces are characterised by vegetation microforms. Efficient methods for monitoring their vegetation are needed because changes in vegetation composition lead to alteration in their function such as carbon gas exchange with the atmosphere. We investigated how airborne image and waveform-recording LiDAR data can be used for 3D mapping of microforms in an open bog which is a mosaic of pools, hummocks with a few stunted pines, hollows, intermediate surfaces and mud-bottom hollows. The proposed method operates on the bog surface, which is reconstructed using LiDAR. The vegetation was classified at 20 cm resolution. We hypothesised that LiDAR data describe surface topography, moisture and the presence and depth of field-layer vegetation and surface roughness; while multiple images capture the colours and texture of the vegetation, which are influenced by directional reflectance effects. We conclude that geometric LiDAR features are efficient predictors of microforms. LiDAR intensity and echo width were specific to moisture and surface roughness, respectively. Directional reflectance constituted 4-34 % of the variance in images and its form was linked to the presence of the field layer. Microform-specific directional reflectance patterns were deemed to be of marginal value in enhancing the classification, and RGB image features were inferior to LiDAR variables. Sensor fusion is an attractive option for fine-scale mapping of these habitats. We discuss the task and propose options for improving the methodology.
  • Rankinen, Katri; Holmberg, Maria; Peltoniemi, Mikko; Akujärvi, Anu; Anttila, Kati; Manninen, Terhikki; Markkanen, Tiina (Molecular Diversity Preservation International (MDPI), 2021)
    Water 13 (2021), 472
    Climate change may alter the services ecosystems provide by changing ecosystem functioning. As ecosystems can also resist environmental perturbations, it is crucial to consider the different processes that influence resilience. Our case study considered increased NO3− concentration in drinking water due to the climate change. We analyzed changes in ecosystem services connected to water purification at a catchment scale in southern Finland. We combined climate change scenarios with process-based forest growth (PREBAS) and eco-hydrological (PERSiST and INCA) models. We improved traditional model calibration by timing of forest phenology and snow-covered period from network of cameras and satellite data. We upscaled the combined modelling results with scenarios of population growth to form vulnerability maps. The boreal ecosystems seemed to be strongly buffered against NO3- leaching by increase in evapotranspiration and vegetation NO3- uptake. Societal vulnerability varied greatly between scenarios and municipalities. The most vulnerable were agricultural areas on permeable soil types.
  • Winquist, Emelie (Helsingin yliopisto, 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 (Helsingin yliopisto, 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.
  • Eriksson, J.; Bergholm, J.; Kvist, K. (Suomen metsätieteellinen seura, 1981)
  • Mäki, Mari; Aalto, Juho; Hellen, Heidi; Pihlatie, Mari; Bäck, Jaana (2019)
    In the northern hemisphere, boreal forests are a major source of biogenic volatile organic compounds (BVOCs), which drive atmospheric processes and lead to cloud formation and changes in the Earth's radiation budget. Although forest vegetation is known to be a significant source of BVOCs, the role of soil and the forest floor, and especially interannual variations in fluxes, remains largely unknown due to a lack of long-term measurements. Our aim was to determine the interannual, seasonal and diurnal dynamics of boreal forest floor volatile organic compound (VOC) fluxes and to estimate how much they contribute to ecosystem VOC fluxes. We present here an 8-year data set of forest floor VOC fluxes, measured with three automated chambers connected to the quadrupole proton transfer reaction mass spectrometer (quadrupole PTR-MS). The exceptionally long data set shows that forest floor fluxes were dominated by monoterpenes and methanol, with relatively comparable emission rates between the years. Weekly mean monoterpene fluxes from the forest floor were highest in spring and in autumn (maximum 59 and 86 mu g m(-2) h(-1), respectively), whereas the oxygenated VOC fluxes such as methanol had highest weekly mean fluxes in spring and summer (maximum 24 and 79 mu g m(-2) h(-1), respectively). Although the chamber locations differed from each other in emission rates, the inter-annual dynamics were very similar and systematic. Accounting for this chamber location dependent variability, temperature and relative humidity, a mixed effects linear model was able to explain 79-88% of monoterpene, methanol, acetone, and acetaldehyde fluxes from the boreal forest floor. The boreal forest floor was a significant contributor in the forest stand fluxes, but its importance varies between seasons, being most important in autumn. The forest floor emitted 2-93% of monoterpene fluxes in spring and autumn and 1-72% of methanol fluxes in spring and early summer. The forest floor covered only a few percent of the forest stand fluxes in summer.
  • Tolvanen, Anne; Saarimaa, Miia; Tuominen, Seppo; Aapala, Kaisu (Elsevier, 2020)
    Global Ecology and Conservation, 23 (2020), e01160
    We used habitat suitability modeling to investigate whether the 15% ecosystem restoration target set in the previous Convention of Biological Diversity (CBD) and EU Biodiversity strategy targets, is sufficient to safeguard red-listed mire plant species. We assessed six theoretical restoration scenarios for drained peatland landscapes by altering the proportion of drained and undrained peatland area in 25-ha grid cells. The proportions represented steps when 15%, 30%, 45%, 60%, 75% and 100% of the drained peatland is restored. We modelled the habitat suitability for 48 red-listed plant species in the aapa mire region in boreal Finland. Model outcomes were assessed at the level of five species groups: calcareous species, rich fen species, decaying wood species, mesotrophic fen species, and spruce swamp species. The predicted distribution increased for 34 (71%) of the 48 red-listed plant species when 15% of drained peatland area was predicted to be restored. At the same time the potentially occupied area of species increased by 9%. In the scenario where all peatlands were restored, the predicted distribution of 43 (90%) of species increased, and on average the distribution of species quadrupled. According to our predictions, meeting the 15% ecosystem restoration target, set in the previous CBD and EU Biodiversity strategy targets would be beneficial for most of the boreal red-listed mire plant species, but a larger restoration area would expand their distribution considerably more. Our study shows that a landscape level approach is important to assess thresholds for the potential biodiversity benefits arising from peatland restoration. The models can also be used to select suitable areas for restoration.
  • Saarnia, Meri (Helsingin yliopisto, 2015)
    Conservation biological control is a strategy of biological control that aims to support natural enemies of pests. One of the potential ways to support natural enemies is to enhance diversity in agricultural landscapes. By establishing non-cultivated areas near crop fields natural enemies can be provided with many resources including food, shelter and overwintering sites. The availability of these resources potentially enhances the abundance and diversity of natural enemies and their efficiency to reduce pest populations. The goal of this study was to compare the effects of two different fallow strip types – meadow strip and grassland strip – on the abundance and species composition of predatory arthropods. To examine the differences between the strip types, data were collected from the strips and adjoining cereal fields. An experiment was conducted on two barley fields in Helsinki in summer 2014. Two fallow strips were established in the middle of each field. The strips were composed of four 3 m * 60 m-sized plots. Every other plot was sown with meadow seed mixture and every other with grassland mixture. Data on predatory arthropods were collected during June-July using pitfall traps. There were more predatory arthropods on the fallow strips than on the barley fields. However, there were no differences in the abundance of predatory arthropods between the fallow strip types. Moreover, the abundance of predatory arthropods on adjoining cereal field did not differ between the strip types. The species composition of predatory arthropods differed statistically significantly between barley fields and the fallow strips, and almost significantly between the strip types. The results indicate that the fallow strips succeeded to provide favorable habitats for predatory arthropods, which may be due to food or shelter that they provide. The lack of clear differences on the abundance and species composition of predatory arthropods between the strip types can be explained by the fact that the vegetation of the strips was not yet fully established in the first year. Other reasons include the substantial differences between the two study fields. However, it seems that fallow strips have potential to provide biodiversity benefits, which have previously been observed in environmental fallow fields, and to enhance ecosystem services such as biological control.
  • Kankaanpää, Outi (Helsingfors universitet, 2013)
    Loss of biodiversity in the Finnish agricultural environment has increased during the last decades due to the agricultural intensification. Accurate, efficient and repeatable sampling methods are important to follow the impacts of the measures to enhance biodiversity. This study focuses on the assessment of vegetation structure and species diversity. Vegetation cover is one of the most common measures to assess vegetation biodiversity. Cover data is usually collected by a point intercept method, a line intercept method or by visual estimation in quadrats. Traditional methods have been found to be laborious, time-consuming and subjective, and having poor repeatability. The main objective of this study was to find out if it is possible to improve vegetation surveys with digital photographs and an object-based image analysis. To answer this question, a visual method (VM) was compared with a photographic method (PM). The VM was based on ocular estimation of the total vegetation cover. In the PM, pictures of the top cover were taken vertically downward from 1.5 meters above the ground. Using a software program called Definiens, the photographs were divided into segments, which were then classified into bare ground, litter, monocots and dicots to estimate the covers for each category. The data was collected during the summer 2010 from environmental fallows and set-asides. There was a clear correlation between the cover measures in the VM and the PM, so it can be assumed that the PM is suitable for the assessment of the vegetation cover. However, using only the PM, it is not possible to get a reliable estimate of the vegetation structure or species diversity. It was faster to collect the data in the field with the PM than with the VM. The computer used in this survey was inefficient, thus the image analysis took more time than expected and as a result the PM was in its entirety slower than the VM. The study gave important theoretical and practical information about the photographic method, its strengths and weaknesses. Photographic methods are still under development and further research is needed but they hold promise for the future.
  • Häme, T.; Aulamo, O.; Gallego, J.; Hallikainen, M.; Kauppi, P.; Lahtinen, P.; Miller, N.; Pulliainen, J.; Saari, H.; Sephton, T.; Stenberg, J.; Warren, C. (VTT Technical Research Centre of Finland, 2006)
    This publication presents the results of a feasibility study on a proposed superhigh resolution satellite mission Kioto+. The study was conducted by an international consortium in response to the 2005 call for ideas for Earth Explorer missions of the European Space Agency (ESA). Kioto+ offers reliable and global data to near in-situ measurement accuracy on land cover and forest cover. It also gives information about their development over time. A super-high resolution optical instrument is proposed to achieve statistically representative and precise measurements. The information will greatly improve our understanding of the global carbon and water cycles, and the credibility of estimates of terrestrial carbon storage. The imagery will also give globally accurate training and validation data for wall-to-wall imaging instruments. The mission is named Kioto+ because the projected timescale of the mission (post-2011) means that it will primarily have relevance to successor treaties of the Kyoto Protocol to the FCCC of the United Nations.