Browsing by Subject "chlorophyll"

Sort by: Order: Results:

Now showing items 1-6 of 6
  • Kotamäki, Niina; Järvinen, Marko; Kauppila, Pirkko; Korpinen, Samuli; Lensu, Anssi; Malve, Olli; Mitikka, Sari; Silander, Jari; Kettunen, Juhani (Springer, 2019)
    Environmental Monitoring Assessment 191, 318 (2019)
    The representativeness of aquatic ecosystem monitoring and the precision of the assessment results are of high importance when implementing the EU’s Water Framework Directive that aims to secure a good status of waterbodies in Europe. However, adapting monitoring designs to answer the objectives and allocating the sampling resources effectively are seldom practiced. Here, we present a practical solution how the sampling effort could be re-allocated without decreasing the precision and confidence of status class assignment. For demonstrating this, we used a large data set of 272 intensively monitored Finnish lake, coastal, and river waterbodies utilizing an existing framework for quantifying the uncertainties in the status class estimation. We estimated the temporal and spatial variance components, as well as the effect of sampling allocation to the precision and confidence of chlorophyll-a and total phosphorus. Our results suggest that almost 70% of the lake and coastal waterbodies, and 27% of the river waterbodies, were classified without sufficient confidence in these variables. On the other hand, many of the waterbodies produced unnecessary precise metric means. Thus, reallocation of sampling effort is needed. Our results show that, even though the studied variables are among the most monitored status metrics, the unexplained variation is still high. Combining multiple data sets and using fixed covariates would improve the modeling performance. Our study highlights that ongoing monitoring programs should be evaluated more systematically, and the information from the statistical uncertainty analysis should be brought concretely to the decision-making process.
  • Viinikka, Arto; Hurskainen, Pekka; Keski-Saari, Sarita; Kivinen, Sonja; Tanhuanpää, Topi; Mäyrä, Janne; Poikolainen, Laura; Vihervaara, Petteri; Kumpula, Timo (MDPI, 2020)
    Remote Sensing 12 16 (2020)
    Sustainable forest management increasingly highlights the maintenance of biological diversity and requires up-to-date information on the occurrence and distribution of key ecological features in forest environments. European aspen (Populus tremula L.) is one key feature in boreal forests contributing significantly to the biological diversity of boreal forest landscapes. However, due to their sparse and scattered occurrence in northern Europe, the explicit spatial data on aspen remain scarce and incomprehensive, which hampers biodiversity management and conservation efforts. Our objective was to study tree-level discrimination of aspen from other common species in northern boreal forests using airborne high-resolution hyperspectral and airborne laser scanning (ALS) data. The study contained multiple spatial analyses: First, we assessed the role of different spectral wavelengths (455–2500 nm), principal component analysis, and vegetation indices (VI) in tree species classification using two machine learning classifiers—support vector machine (SVM) and random forest (RF). Second, we tested the effect of feature selection for best classification accuracy achievable and third, we identified the most important spectral features to discriminate aspen from the other common tree species. SVM outperformed the RF model, resulting in the highest overall accuracy (OA) of 84% and Kappa value (0.74). The used feature set affected SVM performance little, but for RF, principal component analysis was the best. The most important common VI for deciduous trees contained Conifer Index (CI), Cellulose Absorption Index (CAI), Plant Stress Index 3 (PSI3), and Vogelmann Index 1 (VOG1), whereas Green Ratio (GR), Red Edge Inflection Point (REIP), and Red Well Position (RWP) were specific for aspen. Normalized Difference Red Edge Index (NDRE) and Modified Normalized Difference Index (MND705) were important for coniferous trees. The most important wavelengths for discriminating aspen from other species included reflectance bands of red edge range (724–727 nm) and shortwave infrared (1520–1564 nm and 1684–1706 nm). The highest classification accuracy of 92% (F1-score) for aspen was achieved using the SVM model with mean reflectance values combined with VI, which provides a possibility to produce a spatially explicit map of aspen occurrence that can contribute to biodiversity management and conservation efforts in boreal forests.
  • Rankinen, Katri; Enrique, José; Bernal, Cano; Holmberg, Maria; Vuorio, Kristiina; Granlund, Kirsti (Elsevier, 2019)
    Science of The Total Environment 658 (2019), 1278-1292
    In Finland, a recent ecological classification of surface waters showed that the rivers and coastal waters need attention to improve their ecological state. We combined eco-hydrological and empirical models to study chlorophyll-a concentration as an indicator of eutrophication in a small agricultural river. We used a modified story-and-simulation method to build three storylines for possible changes in future land use due to climate change and political change. The main objective in the first storyline is to stimulate economic activity but also to promote the sustainable and efficient use of resources. The second storyline is based on the high awareness but poor regulation of environmental protection, and the third is to survive as individual countries instead of being part of a unified Europe. We assumed trade of agricultural products to increase to countries outside Europe. We found that chlorophyll-a concentration in the river depended on total phosphorus concentration. In addition, there was a positive synergistic interaction between total phosphorus and water temperature. In future storylines, chlorophyll-a concentration increased due to land use and climate change. Climate change mainly had an indirect influence via increasing nutrient losses from intensified agriculture. We found that well-designed agri-environmental measures had the potential to decrease nutrient loading from fields, as long as the predicted increase in temperature remained under 2 °C. However, we were not able to achieve the nutrient reduction stated in current water protection targets. In addition, the ecological status of the river deteriorated. The influence of temperature on chlorophyll-a growth indicates that novel measures for shading rivers to decrease water temperature may be needed in the future.
  • Wade, Andrew J.; Skeffington, Richard A.; Couture, Raoul-Marie; Erlandsson Lampa, Martin; Groot, Simon; Halliday, Sarah J.; Harezlak, Valesca; Hejzlar, Josef; Jackson-Blake, Leah A.; Lepistö, Ahti; Papastergiadou, Eva; Riera, Joan Lluís; Rankinen, Katri; Shahgedanova, Maria; Trolle, Dennis; Whitehead, Paul G.; Psaltopoulos, Demetris; Skuras, Dimitris (MDPI AG, 2022)
    Water
    Recent studies have demonstrated that projected climate change will likely enhance nitrogen (N) and phosphorus (P) loss from farms and farmland, with the potential to worsen freshwater eutrophication. Here, we investigate the relative importance of the climate and land use drivers of nutrient loss in nine study catchments in Europe and a neighboring country (Turkey), ranging in area from 50 to 12,000 km2. The aim was to quantify whether planned large-scale, land use change aimed at N and P loss reduction would be effective given projected climate change. To this end, catchment-scale biophysical models were applied within a common framework to quantify the integrated effects of projected changes in climate, land use (including wastewater inputs), N deposition, and water use on river and lake water quantity and quality for the mid-21st century. The proposed land use changes were derived from catchment stakeholder workshops, and the assessment quantified changes in mean annual N and P concentrations and loads. At most of the sites, the projected effects of climate change alone on nutrient concentrations and loads were small, whilst land use changes had a larger effect and were of sufficient magnitude that, overall, a move to more environmentally focused farming achieved a reduction in N and P concentrations and loads despite projected climate change. However, at Beyşehir lake in Turkey, increased temperatures and lower precipitation reduced water flows considerably, making climate change, rather than more intensive nutrient usage, the greatest threat to the freshwater ecosystem. Individual site responses did however vary and were dependent on the balance of diffuse and point source inputs. Simulated lake chlorophyll-a changes were not generally proportional to changes in nutrient loading. Further work is required to accurately simulate the flow and water quality extremes and determine how reductions in freshwater N and P translate into an aquatic ecosystem response.
  • Salmi, Pauliina; Eskelinen, Matti A.; Leppänen, Matti T.; Pölönen, Ilkka (MDPI AG, 2021)
    Plants 2021, 10(2), 341
    Spectral cameras are traditionally used in remote sensing of microalgae, but increasingly also in laboratory-scale applications, to study and monitor algae biomass in cultures. Practical and cost-efficient protocols for collecting and analyzing hyperspectral data are currently needed. The purpose of this study was to test a commercial, easy-to-use hyperspectral camera to monitor the growth of different algae strains in liquid samples. Indices calculated from wavebands from transmission imaging were compared against algae abundance and wet biomass obtained from an electronic cell counter, chlorophyll a concentration, and chlorophyll fluorescence. A ratio of selected wavebands containing near-infrared and red turned out to be a powerful index because it was simple to calculate and interpret, yet it yielded strong correlations to abundances strain-specifically (0.85 < r < 0.96, p < 0.001). When all the indices formulated as A/B, A/(A + B) or (A − B)/(A + B), where A and B were wavebands of the spectral camera, were scrutinized, good correlations were found amongst them for biomass of each strain (0.66 < r < 0.98, p < 0.001). Comparison of near-infrared/red index to chlorophyll a concentration demonstrated that small-celled strains had higher chlorophyll absorbance compared to strains with larger cells. The comparison of spectral imaging to chlorophyll fluorescence was done for one strain of green algae and yielded strong correlations (near-infrared/red, r = 0.97, p < 0.001). Consequently, we described a simple imaging setup and information extraction based on vegetation indices that could be used to monitor algae cultures.
  • Tolvanen, Kristiina (Helsingin yliopisto, 2020)
    Ecophysiology and ecology in plants are strongly affected by the conditions surrounding them. Adaptation aids plants to survive and to succeed in the prevailing conditions. Winter is a challenge to plants, particularly in northern latitudes and higher altitudes, because it exposes plants to cold and drought, for example. Plants survive from winter on species level with the help of genetic adaptations and as individuals also with the help of acclimation. Woodland strawberry (Fragaria vesca) has been observed to grow separate winter leaves. This allows it to continue photosynthesis in mild conditions during winter, thus improving its energy balance, and to start growing earlier than other species in the spring, which is beneficial in interspecific competition. Fragaria vesca is a species that has wide distribution in the northern hemisphere, and its genotypes are found from very different locations and conditions. However, adaptive traits such as producing a new set of leaves for winter can turn out to be a disadvantage if environmental conditions change rapidly. Climate change brings about changes that are difficult to predict, and these changes are advancing at a fast pace when compared to the developmental history of plants. The aim of this thesis was to study the effect of temperature on summer and winter leaf development, stolon formation and summer and winter leaf chlorophyll, flavonol and anthocyanin content in different Fragaria vesca genotypes. Leaf chlorophyll and secondary compound content give information about leaf development and stress reactions in plants. Plants are known to produce anthocyanins in order to protect the photosynthetic apparatus during chlorophyll recovery in leaf senescence. Anthocyanins are also produced as a response to low temperatures. Research increases knowledge of the ecophysiological and winter ecology-related processes in Fragaria vesca and in the commercially valuable Rosacea-family as well as provides information about the possible responses of these organisms to climate change. Material for the study consisted of twelve European Fragaria vesca genotypes, which had originally been collected from five countries: Norway, Finland, Germany, Italy and Spain. The genotypes had been collected from different latitudes, and they also expressed altitudinal differences. In this study, these genotypes were kept in two temperature treatments, warm (+16°C) and cold (+11°C/six weeks, after which +6°C/four weeks) at a greenhouse. Leaf development was studied by measuring summer and winter leaf middle leaflet width and length, and petiole length. Stolons from each plant individual were counted on a weekly basis and observations about stolon production in relation to the timing of summer leaf senescence and winter leaf development were made at the same time. Leaf chlorophyll and secondary compound content was measured with a Dualex-meter, which provided values for chlorophyll, flavonol and anthocyanin content. The underlying assumption was that cold temperature would induce winter leaf development and summer leaf senescence. The results show that there were differences in summer leaf size between genotypes. Winter leaves had differences between genotypes, but also within genotypes at different temperature treatments. Stolon count was lower and stolon production ceased slightly earlier in the cold treatment. Moreover, summer leaf chlorophyll content decreased in both treatments, but the summer leaves senesced earlier in the warm room. Summer leaf flavonol and anthocyanin values were generally higher in the cooler temperature treatment. Anthocyanins were also produced by winter leaves in the cooler temperature treatment. Based on the results, Fragaria vesca genotypes had differences related to their origin, but temperature also had an effect on winter leaf development, stolon production and the production of secondary compounds. The effect of cold temperature on the size of developing winter leaves was clear. In the cooler temperature treatment, the winter leaves were smaller than in the warmer treatment. The anthocyanin content of summer leaves was higher than in the winter leaves, and the summer leaf anthocyanin content was higher in the colder temperature treatment, where the stress related to the photosynthetic apparatus and low temperatures was combined. Nevertheless, lower temperature did not explain all the responses observed in the genotypes of the study, and thus it is likely that acclimation and winter leaf development in Fragaria vesca are affected by some other factor in addition to temperature, e.g. light regime. A possible continuation for this work would be to study the effect of light conditions or milder winters on winter leaf development in Fragaria vesca genotypes and on the physiology of the species.