3. Doktoritööd

Selle kollektsiooni püsiv URIhttp://hdl.handle.net/10492/2490

Sirvi

Nüüd näidatakse 1 - 20 158

Effects of light availability on moss canopy structural, chemical and physiological traits
(Estonian University of Life Sciences, 2025) Tobias, Mari; Niinemets, Ülo (advisor); Institute of Agricultural and Environmental Sciences; Zotz, Gerhard (opponent)
ABSTRACT. Light is essential to all green plants for photosynthesis, but it is highly variable environmental factor. It varies at temporal and spatial scales, both across the habitats and within the plant canopies. The plant canopy is adapted to light harvesting, interception and photosynthetic production, but it can only acclimate to changing light conditions within certain limits. The overall objective of this thesis was to gain insight into how the moss canopy as a whole responses to variations in light availability. Leaf area index (LAI) is one of the most widely used measurements for describing vascular plant canopy structure, and it characterizes the capacity of canopies to exchange energy and matter with the environment. The LAI and its underlying structural canopy traits were investigated in eleven moss species, eight acrocarpous species (Aulacomnium palustre, Ceratodon purpureus, Dicranum polysetum, D. scoparium, Hedwigia ciliata, Polytrichum commune, Racomitrium canescens and Syntrichia ruralis) and three pleurocarpous species (Hypnum cupressiforme, Pleurozium schreberi and Pseudoscleropodium purum). We found that structural traits were highly variable while LAI variability was low due to the underlying trait trade-offs (leaf size vs. leaf number and total shoot leaf area vs. shoot number) as in vascular plants. Despite this, moss LAI values were higher than typical vascular plants. The great structural variability found in every level (leaf, shoot and canopy) indicate that the structural differentiation serves multiple roles: maintenance of moss hydration, avoidance of photoinhibition and efficient light harvesting for photosynthesis. Using P. schreberi as an example we demonstrate how further there are major variations in moss chemical and physiological traits across the habitats and from top to bottom of the moss canopies. At the same time across-habitat variation in photosynthesis was low as is characteristic to shade plants and within-canopy trait acclimation to reduction in light availability was strongly curbed by an interacting age gradient. Overall, the data shown in this thesis collectively highlight that moss canopy functioning profoundly differs from vascular plant canopies.
Uncovering the patterns of woody plants’ adaptations to tolerate multiple abiotic stresses
(Estonian University of Life Sciences, 2025) Pavanetto, Nicola; Laanisto, Lauri (advisor); Puglielli, Giacomo (advisor); Institute of Agricultural and Environmental Sciences; Pugnaire, Francisco (opponent); Davison, John (pre-opponent)
ABSTRACT. Identifying the ecological constraints on plants' adaptive strategies to tolerate multiple abiotic stresses is fundamental to plant ecology. Recently, a stress tolerance trade-off space (STS) was formalized, defining the limits of abiotic stress tolerance strategies of woody plants of the Northern Hemisphere. This thesis aimed to establish the STS as both a conceptual and practical tool for characterising woody plant adaptations to abiotic stress through the integration of multiple ecological dimensions, including functional traits and environmental conditions at species' habitats. To support the analysis, a new R package, funspace, was developed for multivariate trait-space analysis and visualisation. Species positions within the STS were linked to six key plant traits - plant size, wood density, seed mass, and leaf-economic traits - as well as species occurrence records with associated climatic and soil variables. Generalised additive models and clustering analyses were used to identify trait–tolerance relationships and reveal global geographic patterns of stress tolerance strategies. Distinct stress-tolerance strategies were related to contrasting plant functional trait syndromes that depended on plant functional type considered. Macroecological analyses showed that size-related traits and soil fertility were the primary determinants of drought and waterlogging/cold tolerance strategies, whereas climatic factors primarily shaped shade tolerance. These findings led to the identification of "stress tolerance biomes"—geographic regions characterised by specialized stress tolerance syndromes—and "polytolerance hotspots," regions with frequent coexistence of multiple tolerance strategies. Collectively, this thesis provides a comprehensive synthesis of woody plant adaptations to multiple abiotic stresses, offering a robust conceptual framework and practical tools for understanding and exploring the multidimensional nature of plant stress tolerance strategies.
Multi-scale modelling and upscaling ecosystem function dynamics in Boreal Baltic coastal meadows using remote sensing platforms
(Estonian University of Life Sciences, 2025) Martínez Prentice, Ricardo; Sepp, Kalev (advisor); Villoslada Peciña, Miguel (advisor); Ward, Raymond David (advisor); Institute of Agricultural and Environmental Sciences; Muro, Javier (opponent); Kmoch, Alexander (pre-opponent)
ABSTRACT. Boreal Baltic Coastal Meadows face degradation caused by agricultural intensification and the abandonment of traditional management practices. In Estonia, they have been in decline over the past century, with 82% of managed coastal meadow areas lost by the year 2000. Since Estonia’s accession to the European Union, restoration efforts supported by EU agricultural funding have led to a noticeable recovery. By the end of 2019, 10700 hectares were restored. However, these coastal meadows remain under pressure from both abandonment and intensive grazing. Previous studies aimed at assessing the current state of preservation and restoration efforts for coastal meadows have accounted for their multi-faceted dynamics. High-precision Remote Sensing (RS) technologies detect those dynamics by capturing the variety of features in multispectral wavelengths, being able to retrieve key parameters such as plant community distribution and biophysical variables—supported by UAVs and field sampling. In this way, monitoring coastal meadows has evolved from static, site-limited surveys to spatially continuous approaches that reflect ecological variability across scales. The integration of UAV data with satellite imagery allows for both fine-scale resolution and landscape-scale coverage. The information retrieved by these platforms support evidence-based decision-making for restoration planning, agri-environmental policy implementation, and adaptive management, particularly in regions facing pressures from climate change and land-use transitions. The present thesis contributes to the monitoring of coastal meadows by extending high-precision mapping approaches to satellite-based imagery at coarser spatial resolutions. It tests the correspondence between UAV-mounted cameras and the sensors on board two well-known, medium-resolution, and publicly available satellite platforms: the European Space Agency's Sentinel-2 (S2) and the NASA–U.S. Geological Survey Landsat 8 (L8), both of which provide continuous Earth Observation (EO) data. The goal is to leverage UAV-based studies and make it feasible to expand monitoring efforts across larger areas of coastal meadows, particularly those protected under the EU Habitats Directive, Annex I (92/43/EEC). The use of publicly available satellite data also will facilitate the rapid automating and integration of UAV data with satellite data provided from Estonia’s national EO platforms. This can offer rapid decision-support tools for farmers receiving national subsidies to preserve the ecological state of coastal meadows. This work states three hypothesis. The first posits that pixel-based classification of very high-resolution UAV imagery yields more accurate maps of plant community distribution in coastal meadows than object-based methods. The second and third hypotheses propose that very high-resolution UAV data can be effectively upscaled to estimate Plant Fractional Cover (PFC) and Surface Soil Moisture (SSM) at the spatial resolutions of Sentinel-2 (10 m) and Landsat 8 (30 m), respectively, based on the spectral compatibility between sensors and calibration procedures. To enhance predictive performance, the study employs Random Forest (RF) and XGBoost algorithms, both of which demonstrate strong capabilities in handling complex, non-linear relationships. Their non-parametric and ensemble-based nature makes them particularly effective in modeling the spatial heterogeneity typical of coastal meadow ecosystems. Pixel-based classification proved more accurate than object-based methods for mapping Plant Communities, as it better captured the heterogeneous spectral variation typical of coastal meadows. On the other hand, upscaled UAV-derived Plant Community classification values were used both to assess the spectral correspondence between S2 and Parrot Sequoia (PS) images and to train S2-based RF models for estimating PFC. SSM was estimated at L8 scale using calibrated Temperature Vegetation Dryness Index (TVDI) values derived from UAV imagery and ground-based volumetric water content (VWC) measurements, resulting in very high-resolution SSM maps that were upscaled to L8 scale to train XGBoost models in three different months. The resulting predictions outperformed existing medium-resolution SSM estimation methods reported in the literature. The models yielded moderate to high performance, underscoring the importance of integrating vegetation indices (VIs) with auxiliary variables such as Digital Elevation Models (DEMs) and Land Surface Temperature (LST). Collectively, these results demonstrate the potential for scalable and automated monitoring frameworks that can inform both ecological research and the implementation of policy instruments—including agri-environmental subsidies and restoration programs—aimed at supporting the sustainable management of coastal meadows.
Non-native species invasion strategies and effects on freshwater native communities
(Estonian University of Life Sciences, 2025) Teesalu, Paul; Ercoli, Fabio (advisor); Tuvikene, Arvo (advisor); Institute of Agricultural and Environmental Sciences; Tricarico, Elena (opponent)
ABSTRACT. The spread of invasive species has been forecasted to increase, particularly in freshwater ecosystems due to anthropogenic and environmental changes taking place at increasing rates. Invasive species generally adapt quickly to new environments, have high reproductive rates and can tolerate a wide range of conditions. This thesis studied three invasive species in the Narva reservoir area and found that their success is linked to dietary flexibility, behaviour, and tolerance to temperature changes. The Amur sleeper fish (Percottus glenii) can inhabit various waterbodies, for example, we found it in a warm-water channel, a large reservoir and a small pond. The Amur sleeper demonstrated great dietary plasticity, or the ability to consume a wide range of prey items. As Amur sleeper individuals grew, their diet shifted from a benthivorous diet to a piscivorous diet. The small amphipod Gmelinoides fasciatus, which has outcompeted and displaced native gammarid Gammarus lacustris in Lake Peipsi, exhibits superior predator avoidance and shows a more pronounced behavioural response to predators than its native counterpart, increasing its survivability. Marbled crayfish (Procambarus fallax virginalis) can shift from a protein rich macroinvertebrate based diet to a macrophyte based diet, indicating great dietary plasticity. Additionally, marbled crayfish, despite being considered a warm-water species, could withstand a wide range of water temperatures ranging from 0-30 °C over an extended period at our study site. During the implementation of invasive species management programs, it is important to consider their environmental tolerance, dietary adaptability and behavioural traits. As conditions change in our freshwater lakes and reservoirs, it is likely that invasive species will continue to be a problem, highlighting the need to understand and manage their spread to protect native freshwater ecosystems.
Weeds in different cropping systems
(Estonian University of Life Sciences, 2025) Madsen, Helena; Talgre, Liina (advisor); Luik, Anne (advisor); Institute of Agricultural and Environmental Sciences; Romaneckas, Kęstutis (opponent)
ABSTRACT. Weeds play multiple roles in an agroecosystem. On the one hand they compete with crops for water and nutrients and on the other hand they enhance biodiversity within the field community, thereby providing environmental benefits. The aim of this study was to investigate weed occurrence in a long-term crop rotation experiment. The five-field rotation (barley undersown with clover, clover, winter wheat, pea, potato) was conducted under five different cropping systems. In two conventional systems herbicides were used for weed control, one of them also used mineral fertilizers. One organic system followed the crop rotation as a control variant. The remaining two systems used winter cover crops; composted manure was additionally applied to one of the systems. Weed occurrence and species composition depended on both the cropping system and the crop. In the first rotation the study of weed seedbank in the soil revealed that the number of weed seeds in organic cropping remained at a similar level compared to conventional systems, but species diversity was higher in organic systems. The highest number of weed seeds was found in the soil of pea fields across all systems except in organic system with winter cover crops. The lowest seed count was found in the soil of barley undersown with clover fields in conventional system with mineral fertilizers and in organic system with manure. In the second rotation, studies showed that weed biomass and density of occurrence was increased in all cropping systems, but significantly more in organic systems than in conventional ones. Also, weed diversity increased more in organic systems, being highest in the organic system with winter cover crops. Among the crops, weed biomass and density were high in pea and low in barley. Among the winter cover crops winter rye suppressed weeds most. However, likely due to their low biomass, winter cover crops did not achieve weed suppression comparable to herbicides. Nevertheless, winter cover crops improved soil properties and had a yield-enhancing effect.
The effect of land use and agricultural management systems on earthworm communities and soil quality
(Estonian University of Life Sciences, 2025) Sutri, Merit; Reintam, Endla (advisor); Shanskiy, Merrit (advisor); Ivask, Mari (advisor); Institute of Agricultural and Environmental Sciences; Garré, Sarah (opponent)
ABSTRACT. The loss of soil biodiversity is considered one of the greatest threats to soil functioning in Europe. Due to their significant role in the soil, their abundance is considered one of the most suitable indicators of soil quality. To prevent the loss of soil quality and the decline of biological diversity, several sustainable agricultural practices have been proposed. However, it is still unclear whether these practices help maintain soil quality and earthworm communities in Estonia. The aim of this doctoral thesis was to investigate how land use and agricultural practices affect earthworm communities and soil quality in Estonia under field conditions. To assess soil quality, eight farm fields were selected, differing in tillage and land use, including grassland, no-tillage, minimum and conventional tillage fields. To determine how land use and agricultural practices affect earthworm communities, data on earthworm species abundance from research projects conducted in Estonia were compiled. The results showed that soil quality was better in fields with minimum tillage. The latter had lower penetration resistance, and higher porosity, water holding capacity, and water permeability compared to no-tillage and conventional tillage fields. The no-tillage system created the most favourable habitat conditions for earthworms compared to minimum and conventional tillage systems. Although the fields under organic farming had a higher Shannon diversity index, no significant effect of farming system on earthworm abundance was found. Natural and semi-natural grasslands had higher earthworm abundance and diversity compared to arable land. Overall, the natural variation in soils can have a greater impact on earthworm species diversity than the agricultural management used in the field. Therefore, the effect of the environmentally friendly practices can be modest, although these practices can still improve other parameters of soil quality.
Dietary fiber content of cereal grains influenced by weather, fertilization and cropping system
(Estonian University of Life Sciences, 2025) Khaleghdoust, Banafsheh; Loit-Harro, Evelin (advisor); Korge, Mailiis (advisor); Värnik, Rando (advisor); Institute of Agricultural and Environmental Sciences; Stoddard, Frederick (opponent)
ABSTRACT. Cereal grains like wheat, barley, and oats are crucial for global nutrition, providing essential dietary fibers such as arabinoxylans (AX) and beta-glucans (BG). This thesis examines how weather conditions, nitrogen fertilization, and intercropping affect AX and BG content in cereal grains grown in Estonia. It aims to identify best practices for enhancing nutritional value and sustainability in cereal production, supporting global health and environmental resilience. The thesis is based on three field experiments in Estonia: two at the Estonian University of Life Sciences in Tartu County and one at the METK in Jõgeva County. The first experiment (2014-2021) analyzed winter wheat and spring barley grains under various fertilization regimes and weather conditions and the second (2021) evaluated the genotype effect on AX and BG content in different wheat and barley varieties. The third experiment (2022-2023) compared barley and oat grains dietary fiber content in mono-cropping and intercropping systems. AX and BG contents were determined enzymatically and statistical analyses were performed to assess treatment effects. The study found that weather conditions significantly influenced dietary fiber content in cereal grains. Higher temperatures during the grain-filling period increased AX and BG content in winter wheat and spring barley. Moreover, nitrogen fertilization effect on AX and BG content in cereal grains was limited. Winter wheat AX content in organic system was higher only at lower grain filling temperatures when compared to conventional systems. Intercropping had mixed effects on dietary fiber content, with decreasing BG content in intercropped barley and unaffected content of AX in barley and oats. Genotypic variation in both fiber content was less when compared to the impact of species. In conclusion findings of this thesis demonstrate the possibility to enhance the dietary fiber content of cereal grains while promoting sustainable agriculture.
Phenotypic traits influencing changes in potato late blight pathogen Phytophthora infestans populations in Europe
(Estonian University of Life Sciences, 2025) Puidet, Britt; Mänd, Marika (advisor); Koppel, Mati (advisor); Kiiker, Riinu (advisor); Institute of Agricultural and Environmental Sciences; Andersson, Björn (opponent)
ABSTRACT. Potato late blight, caused by Phytophthora infestans, remains a substantial threat to global food security. European P. infestans populations are generally divided into Northern (genetically diverse) and Western (mainly clonal) populations. However, new genotypes have recently emerged and successfully established themselves in Northern Europe. Additionally, new strains that are more aggressive and more virulent or exhibit fungicide sensitivity to widely used active ingredients emerge frequently. The main objectives of this thesis were to study the drivers of new invasive lineages of P. infestans in Europe and the reason behind the shift in Northern European populations. Samples were collected from potato plants from conventional production fields, organic fields and trap nurseries in Estonia, Denmark, Norway, the UK, and France in ten growing seasons (between 2005-¬2022). DNA acquired from all the samples was genotyped through simple sequence repeat analysis. Phenotypic experiments were performed for samples collected in 2016 and 2017 and involved testing the isolates’ fungicide sensitivity to active ingredients widely used in Europe and evaluating their virulence to assess the ability of P. infestans to damage potato plants. Various population genetic indices were calculated to characterise the genetic diversity and dynamics of the pathogen in Estonia. Results showed that the Western European genotype EU_37_A2 exhibits fluazinam resistance, likely aiding its invasiveness. Genotype EU_41_A2 has successfully been established in Northern Europe, possibly due to higher virulence combined with other fitness traits or changes in environmental conditions not examined in this study. Substantial genetic and genotypic diversity persists in Estonia, suggesting a high likelihood of random mating. Still, monitoring results showed introductions of clonal lineages to the country, which creates a potential risk for future establishment. Our findings underscore the importance of continuous pathogen population monitoring to enable timely adjustments in control strategies.
Factors affecting beekeeping sustainability: pathogen spread, diagnostics and queen breeding
(Estonian University of Life Sciences, 2025) Naudi, Sigmar; Mänd, Marika (advisor); Karise, Reet (advisor); van der Steen, Jozef (opponent)
ABSTRACT. The decline of pollinators is a global issue caused by diseases, parasites, poor nutrition, pesticides, habitat loss, and climate change. The honeybee (Apis mellifera Linnaeus) is a vital pollinator that helps maintain ecosystem balance and ensure food security. Although the number of managed bee colonies has increased in recent decades, beekeepers continue to face various challenges, including the spread of diseases, the impact of pesticides, and bee health issues. This doctoral theses focuses on identifying several of these threats, investigating major bee diseases, the effects of pollutants, their interactions, and developing potential protection methods. The study assessed the prevalence of the pathogenic microsporidians Nosema apis and N. ceranae in Estonian and Latvian apiaries. The results revealed that in cooler climates, the recently discovered N. ceranae is beginning to replace N. apis, which may lead to differences in the nature, spread, and control of the disease. Additionally, it was found that the simultaneous presence of both pathogens in bees increases infection levels, indicating a synergistic interaction. Research on Paenibacillus larvae, the pathogen responsible for American foulbrood, highlighted the hidden nature of the disease and its spread's dependence on bee density and climatic conditions. The use of qPCR technology proved effective for early disease detection, helping to reduce the severity and extent of infections. To ensure the sustainability of beekeeping, it is crucial that queen bees are healthy and their development is not disrupted. Studies on the fungicide active ingredient tebuconazole showed that, while the substance accumulates in beeswax, its transfer to other hive matrices, including royal jelly and developing bees, is minimal. This suggests the presence of a so-called barrier system within the colony that limits potential exposure to contaminants. However, further research is needed to understand the internal movement of pollutants within the hive and their long-term effects. Additionally, the impact of Nosema species on queen bees was investigated, revealing that infected royal jelly caused only minimal developmental disturbances in queens. Future studies should further analyze the effects of pathogens on different members of the bee colony.
Assessing behavioural traits and ecological impacts of invasive crayfish species in freshwater ecosystem
(Estonian University of Life Sciences, 2024) Ghia, Daniela; Sacchi, Roberto (advisor); Ercoli, Fabio (advisor); Institute of Agricultural and Environmental Sciences; Department of Earth and Environmental Sciences, University of Pavia; Maguire, Ivana (opponent); Kozák, Pavel (opponent)
ABSTRACT. Biological invasions occur when species spread to new areas, causing ecological, economic, and social problems. Invasive species can be found in various ecosystems, but freshwater ecosystems are particularly vulnerable due to human activities and environmental changes. It has been forecasted that the invasion of alien species will increase by up to 36% by 2050, particularly in Europe. Among these invaders, crayfish are expected to see significant increases globally, representing major threats. These large freshwater invertebrates have attracted the attention of freshwater biologists and ecologists because of their ability to travel long distances, high reproductive rates, and adaptability. To better manage invasive species and conserve native ones, it's crucial to understand their behaviour and impacts on ecosystems. This research study has focused on understanding the behaviour of invasive crayfish and their impacts on freshwater ecosystems. Results highlighted the high adaptability of signal crayfish, which can vary their diet by season and age and, when coexist with native crayfish, they adjust their feeding habits, likely to reduce competition. The study also revealed that signal crayfish individuals coexisting with native crayfish at the invasion front are stronger than those living alone, suggesting a more successful invasion. It has also been found that invasive crayfish have a remarkable ability to disperse over land during droughts, showing their resilience and potential to spread. Additionally, experiments on their reproductive behaviour and the effects of removing female reproductive parts showed that this method could effectively reduce their reproductive capacity. These findings show the importance of considering behavioural traits in managing invasive species. Implementing control programs for invasive crayfish is crucial to preserving biodiversity and maintaining healthy freshwater ecosystems worldwide.
Role of leaf anatomy in photosynthetic modifications during plant ontogeny and upon environmental acclimation
(Estonian University of Life Sciences, 2024) Kuusk, Vivian; Niinemets, Ülo (advisor); Institute of Agricultural and Environmental Sciences; Fernández-Marín, Beatriz (opponent)
ABSTRACT. To cultivate plant species and varieties best suited to our future environment, it is essential to gain a deep understanding of how plants acclimate to their surrounding conditions and which changes do they undergo during their life. The internal structure of plants, plant anatomy, plays a crucial role in this acclimation. This study focuses on investigating the anatomical and physiological changes that occur during plant aging and in response to high growth temperatures. Plants are the most important component of Earth's ecosystem, as the existence of all other living organisms depends on them. Since plants cannot change their location, they have evolved the ability to adapt to environmental conditions and modify themselves as needed. For young plants, survival and sufficiently rapid growth, including the development of a strong root system and foliage, are of utmost importance. Using three Mediterranean pine species (Pinus halepensis, P. pinea, P. nigra) as examples, we demonstrate how their photosynthetic capacity changes over time depending on the anatomy of their needles and what causes these changes. What makes this study unique is the precise mapping of the changes occurring in the needles as they age and their correlation with photosynthetic capacity. The second aim of this study is to investigate the effects of elevated growth temperatures on plant anatomy and isoprene emission. Almost all plant leaves emit isoprene, the most abundant volatile compound globally, whose emission is strongly influenced by the plant's growth environment. Isoprene is highly chemically reactive and significantly impacts atmospheric chemistry. Given its widespread importance, a detailed understanding of all aspects of its emission is essential to ensure more accurate models and future predictions related to isoprene. This study demonstrates that elevated growth temperatures substantially alter leaf anatomy, which in turn affects photosynthesis and isoprene emission per leaf area. The research aims and succeeds to gain a better understanding of the anatomical changes in plants under challenging conditions: when a young plant establishes itself in its habitat and when it grows under temperatures higher than normal for the species.
Suitability of cruciferous oilseeds as cover crops, their disease resistance and optimized cultivation technologies for improved overwintering and yield
(Estonian University of Life Sciences, 2024) Lääniste, Peeter; Runno-Paurson, Eve (advisor); Niinemets, Ülo (advisor); Institute of Agricultural and Environmental Sciences; Kadžienė, Gražina (opponent)
ABSTRACT. Cruciferous field crops are important as oil crops and inhibitors of some soil pathogens. At the same time they can be susceptible to various other diseases, as they have been intensively cultivated in short rotations. There are lot of problems with the cultivation of the main oil crop - winter rapeseed in Estonia, mostly evident through instability of seed yields. Previous studies have indicated that the cultivation of winter rapeseed as a cover crop reduces the presence of pathogen, that is causing the potato late blight; different cruciferous species have large variation in resistance to crop diseases; and the successful overwintering of winter rapeseed is related to weather conditions, sowing time and seed rates. Therefore, following hypotheses were set at the start of present research: 1) The cultivation of winter rapeseed as a cover crop has positive effect on controlling the abundance of pathogen that is causing late blight in potato, resulting in higher tuber yield; 2) The alternative cruciferous oil crops are more resistant to powdery mildew than spring rapeseed; 3) The spring rapeseed is more susceptible to Alternaria black spot disease than alternative cruciferous species; 4) The growth and development as well as the yield of winter rapeseed is dependent on the sowing time, seed rate and the sum of active temperatures during autumn growth; 5) Successful overwintering and yield potential are directly related to certain crop parameters measured in autumn. Based on the results of present thesis it was found that when cultivating winter rapeseed as a cover crop, the late blight infection emerged slightly later and there was a decrease in damaged area, but the effects on disease suppression and tuber yield were not significant. The alternative cruciferous oil crops like white mustard, ruccola/arugula and oilseed radish were not infected with powdery mildew and black spot disease, even during favourable conditions for the pathogens. Hence, these species could be used as cruciferous crops in rotations without the use of pesticides. The most suitable period for sowing winter rapeseed was in the middle of August, allowing plants to optimize their parameters for winter survival. Good indicator was the time when 7-8 true leaves had been formed, resulting in 70% survival rate and also providing higher seed yield potential.
An integrated evaluation of blue space design interventions for health and well-being
(Estonian University of Life Sciences, 2024) Mishra, Himansu Sekhar; Bell, Simon (advisor); Külvik, Mart (advisor); Institute of Agricultural and Environmental Sciences; Ward Thompson, Catharine (opponent); Gidlow, Christopher (pre-opponent)
ABSTRACT. This PhD, conducted under the BlueHealth project (Horizon 2020), enhanced public health and urban planning research by focusing on 'blue' spaces—water-based environments beneficial for well-being and healthy behaviour. Despite offering unique recreational and sensory experiences, blue spaces are often underutilised and understudied compared to 'green' spaces. The PhD stands out for its multidisciplinary approach, extensive literature review, and the development of the BlueHealth Environmental Assessment Tool (BEAT), and pre-post physical intervention- assisted approach, which assessed blue spaces for health antecedents and provided evidence for planning and design. In this research, BEAT and other tools from the BlueHealth Project were adapted to support evidence-based co-creation of urban blue space interventions. These interventions engaged various stakeholders and community members, significantly advancing methodologies in environmental assessments and pre-post evaluations. The PhD evaluated the impact of blue space interventions on user frequency, accessibility, inclusivity, diversity, and the local community’s general health and well-being. A key aspect was the implementation of 'urban acupuncture' at Teat’s Hill, Plymouth, UK, involving the community actively in the project lifecycle. The pre-post (2017-2018) place assessment and intervention strategy provided evidence for co-designing a small-scale, impactful intervention for the local community and later assessing its impact. This approach highlighted the effectiveness of small-scale interventions and the need for comprehensive evaluation techniques. The PhD introduced methodological advancements by applying tools like BEAT, BlueHealth Behaviour Assessment Tools (BBAT), and the BlueHealth Community Level Survey (BCLS). These tools demonstrated how evidence-based design of blue space interventions could surpass traditional practices, making them versatile for various urban blue space evaluation, design, and management needs. Community and stakeholder engagement was crucial, with Teat’s Hill showing the benefits of involving local residents in blue space interventions through social events. This participatory approach ensured alignment with community needs and environmental values, fostering ownership and relevance among stakeholders. Additionally, BEAT addressed gaps in current assessment tools by focusing on health and well-being within blue spaces, incorporating sensory and functional affordances. It was designed to balance comprehensiveness and practicality, facilitating pilot testing and validation across awide range of European blue space settings. This thesis argues for the importance of small-scale interventions and community involvement in achieving significant public health benefits. It underscores the complexities of environmental assessments and the need for robust, reliable tools to evaluate diverse impacts of blue spaces, presenting a toolkit for planners. This research contributed methodologically and empirically to the BlueHealth project by enhancing understanding of blue spaces and advocating for their integration into urban planning and public health strategies.
The estimation of stocked and natural European eel (Anguilla anguilla) populations in Estonian waters
(Estonian University of Life Sciences, 2024) Bernotas, Priit; Vetemaa, Markus (advisor); Nõges, Peeter (advisor); Institute of Agricultural and Environmental Sciences; Ložys, Linas (opponent)
ABSTRACT. Eels, due to their mysterious life cycle and appearance have long fascinated scientists and fishers alike. In Estonia, similarly to the rest of Europe, eel populations have faced dramatic changes over the last decades, giving researchers a tough task to find out the factors behind these changes. My thesis focused on different aspects regarding the fisheries and welfare of eel in Estonian coastal and freshwater habitats. We studied a long-time series of commercial landings, scientific surveys, restocking efforts, and environmental variables, to shed light on the dynamics of these mysterious creatures. One observation from our investigation is the decline in both commercial and recreational landings of eels along the Estonian coast since the 1970s where data was available. This trend is consistent with a broader pattern seen all across Europe. However, with the fall of the Soviet Union at the beginning of the 1990s there was a sudden growth in eel landings on the Estonian coast. This was most probably due to changes in fishing practices, improvement in registering the catches, and growth in fishing effort rather than the recovery of local eel stocks. Since 2008 the landings of small fyke nets in particular dropped sharply with the main reason aside from the declining eel population being reduced effort as well as the diminishing profitability of using such gear. As opposed to small fyke nets, the number of large fyke net licenses remained unchanged. As eels are not specially targeted by large fykes the changes in the eel landings also reflect the decline of eel biomass in the coastal areas. Restocking is a part of eel management strategies in many European countries, including Estonia. Initially aimed at preserving traditional eel fisheries, most notably in Lake Võrtsjärv, restocking programs have evolved in response to declining stocks and regulatory frameworks. Our research highlights the importance of optimizing restocking efforts, considering factors such as stocking density, water conditions, and prey availability. For example, eels released to waterbodies as glass eels, tend to fare better in lakes with lower stocking densities, mixed water column, and abundant benthic invertebrates. Inland water bodies vary in their suitability for eel restocking, with well-mixed, nutrient-rich lakes offering the most optimal conditions for growth. Environmental factors, such as the prevalence of cyanobacteria, can negatively impact restocked eel populations, highlighting the overall importance of ecosystem health concerning eel management. While there have been numerous studies on eel migration, the topic is complicated and often raises a lot of questions while providing not so many answers. Restocked eels show the ability to navigate from freshwater habitats to the sea, however, their journey can be far from straightforward. Some individuals have displayed a surprising behavior of returning to their rivers of origin, spending extended periods in freshwater before resuming their migration towards the ocean. While this behavior exposes them to additional risks from predators and fisheries, it once again confirms the complexity of eel migration strategies. By investigating the Estonian eel populations, our study affirms the need for holistic management approaches that consider the interconnectedness of ecosystems and human activities both locally and internationally. When we understand the processes that influence the dynamics of eel populations, we can work towards the recovery of these mystic and unique creatures.
Leaf structure-function relationships and responses to plant hormones in non-seed plants
(Estonian University of Life Sciences, 2024) Wuyun, Tana; Niinemets, Ülo (advisor); Institute of Agricultural and Environmental Sciences; Rinnan, Riikka (opponent)
ABSTRACT. Non-seed plants are prosperous on Earth, but until now there are many mysteries about them in plant science. In the current thesis, non-seed plants were studied under two conditions: non-stressed and stressed. When under optimum conditions, leaf structural, chemical, and photosynthetic traits of non-seed plant species were studied to reveal the life strategy they chose for living. Compared to the seed plants, these early land plants tend to adopt a more conservative strategy by investing more resources to build up a robust body structure, sacrificing their capabilities to photosynthesize. Leaf density is found to be a fundamental trait (instead of the classical structure trait leaf mass per unit area) that represents structural characteristic of a plant leaf; thus, it helps to uncover trade-offs in a spectrum of interrelationships between different plant functional traits. When under stress (simulated by applying phytohormones), certain defense pathways in non-seed plants are activated. In general, non-seed plants behave similarly to seed plants in terms of both gas exchange characteristics and volatile organic compound emissions. However, there are differences. First, only four fern species out of nine close their stomata upon abscisic acid, showing a species-specific characteristic in this plant lineage; second, upon methyl jasmonate, one of the spikemosses Selaginella martensii emits a should-be time-consuming volatile compound linalool in a faster manner compared to the seed plants. Moreover, this spikemoss utilizes an alternative signaling pathway rather than the classical jasmonate pathway in seed plants.
Modelling of large shallow lake food web based on long term monitoring data
(Estonian University of Life Sciences, 2024) Bhele, Upendra; Cremona, Fabien (advisor); Institute of Agricultural and Environmental Sciences; Lobry, Jérémy (opponent)
ABSTRACT. Climate change poses a serious threat to freshwater ecosystems. With population growth, the demand for food production increases, potentially leading to excessive use of natural resources, high nutrient loads, eutrophication, and overfishing in water bodies. Modelling the food web is a valuable solution for understanding the key processes and ecological issues in a lake ecosystem, as it avoids the need for expensive experimental studies. Ecological modelling allows the exploration of the interconnected effects of environmental conditions, nutrient loading causing eutrophication, and fishing activities on the aquatic ecosystem. The Ecopath model, along with its modules Ecosim and Ecospace (EwE), is a widely used tool for investigating the structure of aquatic food webs, encompassing both top-down and bottom-up control mechanisms from producers to predatory fish to detritivores. This doctoral thesis analyses the potential impacts of climate change and associated fluctuations in water levels on the biodiversity of Lake Võrtsjärv. The modelling process considers the biomasses of all major functional groups in the lake. Using the spatial module Ecospace within the EwE modeling suite, scenarios based on realistic water level fluctuations were examined. The models also simulated top-down and bottom-up processes based on predator-prey relationships and commercial fishing data. These models were employed to understand the process-based dynamics of phytoplankton, invertebrates, fish groups, and other key functional groups in the ecosystem. The outcome of the research shows that modelling indicated that zooplankton is not efficient in controlling the biomass of cyanobacteria, leading to detritus accumulation. Global warming and eutrophication are expected to increase cyanobacterial production and the frequency of algal blooms, especially in shallow lakes. Consequently, lakes may become more dependent on detrital organic matter in the near future. Reducing factors causing eutrophication would decrease cyanobacterial dominance, thereby improving the overall feeding capacity of zooplankton. Ecospace modelling to elucidate the effects of water level changes on functional group biomass and spatial distribution in the lake showed that prolonged water level decline could trigger a trophic shift, increasing the number of predatory groups at the expense of plankton and smaller fish. A stable water level would be more beneficial for Lake Võrtsjärv biodiversity than significant water level fluctuations. The third objective of this study was to investigate simulating biomass changes in several functional groups, whether trophic cascading was “bottom-up” or “top-down” in shallow lakes. The study simulated biomass changes in multiple functional groups. The "Keystoneness" analysis revealed that the macrozoobenthos as a lower consumer group and adult pikeperch as a top predator on the food web is equally important. Sensitivity analysis showed that changes in the biomass of phytoplankton, zooplankton, and macrozoobenthos affect the biomass of all major functional groups more than changes in the fish population. The models demonstrated that a sudden change in the food web (plankton, macroinvertebrates) due to eutrophication or climate change poses a threat to the entire functioning of the food web, as environmental tolerance limits have already been reached through maximum carrying capacity.
Evaluating ecosystem services and their impact on human well-being in the peri-urban landscape of Harku Municipality, Estonia
(Estonian University of Life Sciences, 2024) Nevzati, Fiona; Külvik, Mart (advisor); Storie, Joanna Tamar (advisor); Institute of Agricultural and Environmental Sciences; Geneletti, Davide (pre-opponent); Ogletree, Scott (opponent)
ABSTRACT. This doctoral thesis focused on the complex relationship between urbanisation and human well-being, specifically in peri-urban areas—the transitional zones between urban and rural settings. Through interdisciplinary research, it explored how these landscapes influence quality of life and provide essential ecosystem services in the Harku municipality, Estonia. The thesis underscored the significance of cultural ecosystem services (CES), encompassing the intangible benefits derived from nature. It employed innovative methods like landscape character assessment (LCA) and the CES framework to explore these concepts further. By analysing landscape patterns and anticipating future scenarios, the study provided insights for sustainable planning practices. Key findings revealed the essential role of forests in cognitive well-being, schoolyard gardens in spiritual enrichment, beaches in social cohesion, and the sea in stress relief. The study was informed by expert opinions and incorporated secondary data from a resident survey on the quality of life in the municipality. Furthermore, the thesis provided recommendations for fostering more sustainable spatial planning development in peri-urban areas, striving to strike a balance between environmental conservation and human well-being. The strategic integration of CES mapping into planning frameworks facilitates the identification of ecosystem services crucial for sustainable peri-urban development, prioritising both environmental preservation and societal welfare.
Transcriptomic and volatile organic compounds analysis of resistance mechanisms and diversity of late blight pathogen populations in the Baltic Sea region
(Estonian University of Life Sciences, 2024) Agho, Collins Aimuaenvbosa; Niinemets, Ülo (advisor); Runno-Paurson, Eve (advisor); Kaurilind, Eve (advisor); Institute of Agricultural and Environmental Sciences; Abuley, Isaac Kwesi (opponent)
ABSTRACT. This thesis addressed in part the dynamics and diversity of late blight pathogen populations in unstudied regions (Estonia islands and Pskov region of north-western Russia) by understanding changes in the spatiotemporal variation of the P. infestans population structure, the prevalent reproduction mode, genotypic and phenotypic diversity and the impact of transboundary migration and gene flow on the P. infestans population (Paper I and II). Mating type determination, metalaxyl response and SSR marker genotyping of P. infestans isolates were used in the first and second experiments. Our result suggests a predominance of sexual reproduction that may have resulted in the observed high genotypic diversity and a high proportion (> 60%) of unique genotypes in these unstudied regions. Time-dependent changes in metalaxyl response and rapid changes in the pathogen populations with the absence of shared genotypes over the years were observed. Overall, there was a lack of genetic differentiation and an absence of local adaptation allowing for the exchange of genetic materials among the P. infestans populations of the Estonian islands and mainland Pskov region P. infestans populations, and between Estonian island and mainland Pskov regions populations. Secondly, the diversity of the chemical profile (volatile organic emission/VOC) of potato cultivars with variation in late blight resistance background was examined (Paper III). The result indicates the presence of qualitative and quantitative differences among the potato cultivars, and the dominance of terpenoids in the emission blend. The composition of sesquiterpenes was cultivar-specific. Interestingly, the VOC emission blend accounted for a high proportion of variation among the cultivars, and the total terpenoid and total constitutive VOC emission scale positively with resistance. The use of VOCs holds promise as a fast innovative, non-invassive marker for the selection of resistant genotypes. Lastly, an improved understanding of the molecular mechanism underlining the high field resistance to late blight disease of a widely grown potato cultivar (Ando) in Estonia was achieved using RNA sequencing technology (Paper IV).
Sustainable approaches to oilseed rape pest control : steps towards to integrated pest management
(Estonian University of Life Sciences, 2024) Vilumets, Silva; Veromann, Eve (advisor); Institute of Agricultural and Environmental Sciences; Beckmann, Michael (opponent)
ABSTRACT. Intensive agricultural has diminished the natural and semi-natural habitats in the agricultural landscapes, negatively impacting biodiversity. To maintain a biologically diverse agricultural landscape supporting various species, diversity and heterogenity are crucial. Oilseed rape, one of the most important crops in agriculture, is an attractive food source for many arthropods. However, it faces challenges from several insect pests such as the pollen beetle and cabbage seedpod weevil. Synthetic insecticides are mainly used to control the pests but both pests have developed resistance. Therefore, finding effective environmentally friendly pest control methods is crucial. The study revealed that winter oilseed rape fields located over 500m from the previous year's field had significantly fewer pollen beetles and cabbage seedpod weevils compared to fields closer than 500m. Field-adjacent habitats had minimal impact on pest abundance, highlighting the significance of temporal and spatial separation of crop fields in mitigating pest populations. The study also explored parasitoid presence, revealing high parasitism rates in all years, even up to 90%, consistently exceeding the 32% threshold for effective natural pest control. Parasitism rates were not significantly affected by the distance from the previous year's oilseed rape fields but thrived in landscapes with diverse natural and semi-natural areas. Essential oils like Cinnamomum verum and Cuminum cyminum proved to be effective against the cabbage seedpod weevil. However, the results also showed their lethal effect on parasitoids, both adults and larvae. Moreover, monitoring for species that may benefit from the changing climate conditions, build up their populations and reach to pest status, is crucial. The study identified C. sulcicollis, previously uncommon in Estonia damaging oilseed rape plants. While not presently considered an important pest, climate-induced distribution changes may alter its status. This highlights the urgency of studying various species affecting oilseed rape, especially given the changing climate. The thesis provides an important information about the biology of both pests and their natural enemies, along with practical guidance for producers on crop rotation. It emphasizes the importance of a diverse landscape and finding alternative means of control to reduce the use of synthetic insecticides, aligning with the goals of the European Union agricultural strategy "Farm to Fork".
The effect of fertilizing and modified atmosphere storage on blueberry (Vaccinium spp) fruit quality
(Estonian University of Life Sciences, 2023) Koort, Angela; Karp, Kadri (advisor); Starast, Marge (advisor); Moor, Ulvi (advisor); Institute of Agricultural and Environmental Sciences; Martinussen, Inger (opponent)
There are few cultivated plants that grow well on acidic peat fields. However, blueberries (Vaccinium spp) are calcifuges that thrive in low pH and have lower Ca requirements compared to other temperate fruit crops. As a result, they are suitable for revegetating abandoned peatlands. The increase in production and consumption of organic food is one of the current trends, driven in part by consumers’ perception of organic food as being more sustainable and healthier than conventional. Since previous studies on blueberry cultivation in abandoned peatlands primarily focused on synthetic mineral fertilizers, it is important to study sustainable fertilizer strategies for organic blueberry cultivation. Revegetating abandoned peatlands with blueberries could also reduce the negative impacts of environmentally sensitive peatland areas. Blueberries are marketed as health promoting food, therefore maintaining fruit quality during postharvest storage is equally important to prolonging postharvest storage period. Extending the blueberry postharvest life through modified atmosphere storage and preserving their sensory and nutritional quality could be an option to add value to organically grown blueberries. However, there are very few postharvest studies concerning organically grown blueberries. The aims of the research were to find out the effect of: 1) different organic fertilizers on the plant growth, yield and biochemical parameters of fruits of half-highbush blueberry ‘Northblue’ under peatland conditions; 2) modified atmosphere packages on the external quality and the nutritional value of the fruits of organically grown lowbush blueberry and half–highbush blueberry ’Northblue’. Based on the results of fertilization experiments conducted on an abandoned peat field with half–highbush blueberry ‘Northblue’, the seaweed–based low nutrient fertilizer Biolan 4–1–2 could be recommended for organic production in peatland areas. It demonstrates more stable yield performance and has a lower impact on peat pH. Algomin fertilizer, which is based on marine algae Lithothamnium calcareum, increased the soil pH up to 5.2 and suppressed the plant growth during the juvenile growth stage. Organic fertilizers containing chicken manure resulted in comparable vegetative growth and yield as the plants receiving mineral fertilizer. The yearly variation in weather conditions was more important in determining fruit biochemical content than the type of fertilizer used. The application of seaweed–based organic fertilizer Biolan 4–1–2 resulted in similar total polyphenol content in fruits as observed in the mineral fertilizer treatment. The postharvest storage experiment with lowbush and half–highbush blueberry ‘Northblue’ demonstrated that the Xtend® modified atmosphere package prolonged the postharvest life of lowbush blueberries by 15 days and half-highbush blueberries by 9 days. The LDPE modified atmosphere package did not prolong the postharvest life of lowbush blueberries, but extended the postharvest life of ‘Northblue’ by 9 days. The CO2 content was significantly higher in Xtend® package compared to the LDPE at the end of the storage period. Both modified atmosphere packages had an effect on the taste–related properties of blueberries irrespectively of the taxa. By the end of the storage period, the SSC:TA ratio of the blueberries in the modified atmosphere decreased compared to both the initial value and the berries stored in a regular atmosphere. The content of anthocyanins significantly increased under all storage conditions, regardless of the taxa. The genetic differences were more important concerning fruit firmness, shrivelling, and decay. Both modified atmosphere packages had an impact on the firmness and the shrivelling, but the fruits of the half–highbush blueberry ‘Northblue’ were firmer and less shrivelled compared to the lowbush. Based on results, the Xtend® modified atmosphere package can be recommended for blueberry postharvest storage. However further studies are needed to find the metabolic differences of blueberry taxa and to match the respiration rates of the product with the permeation rates of the packages. Additionally, the use of biodegradable films should be considered in order to ensure sustainability.

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