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In Latvia, the effects of drought and extreme temperatures on spring barley have so far been little studied due to the availability of data and the fact that meteorological conditions are only one of the multi-influencing factors that affect the agricultural sector.Barley usually flowers before or at the same time as ear emergence. During the flowering period high ambient temperatures are critical for yield formation. If the air temperature during flowering is above 22℃ the flowers of spring barley become sterile. From 2004 - 2022, a significant and positive correlation (R = 0,57) was observed between the average maximum daily temperature from sowing to ear emergence and the number of empty flowers in the main spike. A significant negative correlation (R = 0,55) was observed between plant height and the sum of precipitation from sowing to ear emergence and spike length and the sum of precipitation from ear emergence to maturity (R = −0,54), drought also negatively affects tillering rate and number of productive stems per plant.The combination of all the above-mentioned conditions significantly impacts the yield of barley. The following and relevant findings are very important for the agricultural sector, especially in the context of climate change.

Soil waterlogging due to excess moisture resulting in hypoxic soil conditions can have detrimental effect on development of many dryland plants growing in locations with temporary water logged soils. Oxygen stress in hypoxic soils can lead to decrease root water uptake and transpiration compared to well aerated soil conditions. In turn reduction of transpiration have a positive effect on soil water budget facilitating the preservation of waterlogged state of the soil. We investigate this phenomenon in a greenhouse pot experiment using sweet corn Zea mays var. saccharate as a model species. After establishment seedlings were subject to a differentiated watering regime ranging for now watering to heavy overwatering resulting in soil waterlogging and flooding. It was observed that the elongation rate of maize seedlings decreased once soil was waterlogged. However soon after soil flooding the elongation reassumed coinciding with appearance of new adventitious roots taping the water layer above flooded soils surface. It is concluded the ability of root system adaptation to change in soil water regime determines the plant species success in sites with periodically waterlogged soils. The feedback between soil aeration status and water uptake can result in swinging between waterlogged and desiccated soil conditions, providing competitive advantages to different sets of species during dry-land and wet-land phases.

One of the most visible signs of climate change in nature are shifting growing cycles. In northern areas, mostly energy limited environments, the growing seasonality is usually defined in 3 different ways:- frost free period: time period between last spring frost and first autumn frost;- thermal growing season: in the Baltic region traditionally is defined as the number of days with mean temperatures above 5°C. - phenological growing season: the period between leaf unfolding (BBCH11) and senescence (coloring (BBCH92) or leaf fall (BBCH93)).In this study we examine recent trends in growing season length in the Baltic region according to these 3 definitions from 1991-2020. The duration of frost-free period and thermal growing season was calculated using the gridded daily temperature from the E-OBS data set version v24.0e (Cornes et al., 2018). The phenological growing season was examined using a recently published open source phenological observations data set (Kalvāne et al, 2021) and remote sensing leaf area index (LAI) obtained from Copernicus data store.Changes in the growing season vary within species, for example, for Acer platanoides, the prolongation of the growth trend is highly pronounced due to earlier flowering and later onset of autumn phases. For Populus tremula on the other hand, the changes in flowering are not as significant as the changes in the autumn phases (occurring on average later, the trend of which is positive), and the trend in the duration of the growing season is neutral. The results indicate a statistically significant trend toward pioneer species such as Alnus incana and Corylus avellana. The data regarding the end of the growing season is less conclusive. Autumn senescence in many cases does not show a significant trend.However rising temperatures contribute to the increasing length of the thermal growing season. These thermal shifts have already influenced the bird migratory patterns, for example later migration of Anser anser, as well as agricultural practices - sowing of winter cereals and soil cultivation - are taking place later in the autumn than it used to (Kalvāne and Kalvāns, 2021).This study has shown that significant seasonal changes have taken place across the Baltics landscape due to climate change.This study was carried out within the framework of the Climate change and sustainable use of natural resources institutional research grant of the University of Latvia (No. AAP2016/B041//ZD2016/AZ03) and the Latvian Council of Science, project “Spatial and temporal prediction of groundwater drought with mixed models for multilayer sedimentary basin under climate change” (No. lzp-2019/1-0165). References: Cornes, R. C., van der Schrier, G., van den Besselaar, E. J. M. and Jones, P. D.: An Ensemble Version of the E-OBS Temperature and Precipitation Data Sets, J. Geophys. Res. Atmos., 123(17), 9391–9409, doi:10.1029/2017JD028200, 2018.Kalvāne, G., Kalvāns, A., Ģērmanis, A.: Long term phenological data set of multi-taxonomic groups and agrarian activities, abiotical parameters from Northern Europa, Latvia, Earth Syst. Sci. Data, 13, 4621–4633.,https://doi.org/10.5194/essd-13-4621-2021, 2021Kalvāne, G. and Kalvāns, A.: Phenological trends of multi-taxonomic groups in Latvia, 1970-2018, Int. J. Biometeorol., 65, 895–904, doi:https://doi.org/10.1007/s00484-020-02068-8, 2021.

The ceramics of 0.95BaTiO3–0.05PbTiO3+Xwt.%CuO (X = 0.05, 0.1, 1, 3) were prepared by a solid phase reaction. The structural and morphology studies were carried out by means of X-ray diffraction te...

The paper presents the results of detailed studies of the thermal expansion of (1-x)PbNi1/3Nb2/3O3-xPbTiO3 solid solutions with x = 0-0.8. The anomalous and lattice contributions to deformation and...

Dielectric permittivity, dielectric losses and ac-conductivity of polycrystalline Bi1−xSmxFeO3 (x = 0; 0.05; 0.1; 0.15; 0.2) are measured in the frequency range 1 kHz–10 MHz and in the temperature range 25–600 °C. Anomalies have been observed at the 200 °C, 300 °C and at the Néel temperature. It has been demonstrated that doping with Sm has enhanced the dielectric properties and increased conduction in the frequency region 1 MHz) and at a certain temperature Tm, depending on the composition Bi1−xSmxFeO3, the conductivity reaches a maximum. The results are discussed with reference to the model of correlated barrier hopping., Institute of Solid State Physics, University of Latvia as the Center of Excellence has received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART²

Ba0.7Pb0.3TiO3 and Ba0.7Pb0.3TiO3+yCuO (y = 0.1 wt%, 0.5 wt%, 1 wt% and 3 wt%) samples were prepared by a solid state reaction method. High purity raw materials were used. Structural properties of the sintered pellets were studied by X-ray diffractometer X’Pert PRO (PANalytical). A single phase of perovskite structure with tetragonal phase was identified at room temperature. The surface morphology of the obtained specimens was characterized by the scanning electron microscopy (Hitachi S4700). The investigations has shown that the synthesized ceramic materials are characterized by the high density, homogeneity of microstructure and low porosity. Dielectric spectroscopy was used to study the electrical properties of the solid solution on the basis of BaTiO3 doped CuO., Institute of Solid State Physics, University of Latvia as the Center of Excellence has received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART²

Storms are the main abiotic disturbance in European forests, effects of which are expected to intensify in the future, hence the importance of forest stand stability is increasing. The predisposition of Norway spruce to wind damage appears to be enhanced by pathogens such as Heterobasidion spp., which reduce stability of individual trees. However, detailed information about the effects of the root rot on the stability of individual trees across diverse soil types is still lacking. The aim of the study was to assess the effect of root rot on the individual tree stability of Norway spruce growing on drained peat and mineral soils. In total, 77 Norway spruce trees (age 50&ndash, 80 years) growing in four stands were tested under static loading. The presence of Heterobasidion spp. had a significant negative effect on the bending moment at primary and secondary failure of the tested trees irrespectively of soil type. This suggests increased legacy effects (e.g., susceptibility to pathogens and pests due to fractured roots and altered water uptake) of storms. Damaged trees act as weak spots increasing the susceptibility of stands to wind damage, thus forming a negative feedback loop and contributing to an ongoing decline in vitality of Norway spruce stands following storms in the study region in the future. Accordingly, the results support the importance of timely identification of the decayed trees, lowering stand density and/or shortening rotation period as the measures to counteract the increasing effects of storms on Norway spruce stands.

A phenological data set collected by volunteers` observers from the Latvia Phenological Observation Network covering period 1970 to 2018 has digitized from original paper based publications in Nature Calendars and analysed. The data set includes more than 40 thousand observations, 148 phenological phases across five different taxonomic groups: insects, amphibian, birds, fungi and plants as well as agrarian activities like sowing, harvesting date and some meteorological parameters like first and late frost, snow, ice regime.The phenological changes or trends was analysed in two ways: 1. by combining data rows (station-phase-species) for one phase, such as leafing (BBCH11) for all trees and bushes; 2. by performing regression analyses for each phase and for each observation point separately.More than 80% of spring data series shows negative tendency as reported in most scientific publications on European phenology. In our data set, overall, autumn phenologies are occurring later over time or the trends are neutral.Regression analyses of phenology date versus year shows the disparities among species and among locations within a species: spring migrants’ return earlier, while staying longer in the fall with exceptions, for example the white stork in autumn leaves earlier than in the beginning of the period.The commencement of the agricultural activities in spring such as sowing date have not changed significantly. However, such activities as livestock grazing and sowing of winter cereals takes place latter in the autumn. These both appear to have affected by both technological changes and changes in meteorological parameters, for example, the trend of first autumn frost and first snow is positive – they have observed latter.We have analysed trends and cross correlation with phenology in temperature regime, heat waves, precipitation, drought indexes, evapotranspiration, and soil temperature for the last 40 years.Research is supported by the ERDF Project No. 1.1.1.2/VIAA/2/18/265 at the University of Latvia.

According to studies and surveys, Latvian society is sceptical of climate changes – it is characterised by short-term thinking. STEM teachers acknowledge that the climate issue is one of the most difficult and incomprehensible topics for students. Students' understanding of climate change issues is low because there is poor understanding of concept of the climate itself and physical processes shaping the climate system. Students do not see the consequences and responsibilities of their actions. In addition, there is little climate-related teaching materials available in Latvian language hampering incorporation climate issues in the regular school programs or informal educational activities.In collaboration with youth NGO, Latvian 4H club, Faculty of Geography and Earth Sciences at University of Latvia have developed several teaching materials, easy-to-read instructions and video demonstration in Latvian for hands on climate education activities. Low-cost and easily available materials and reagents have used for all the activities. Some of the examples: what is the difference in air temperature in a jar with and without CO2 heated by incandescent light bulb or how the water pH changes when CO2 is bubbled (blown) through it with a straw?In the “60 elements in your pocket” project, we have dismantled mobile phones and discussed what raw materials have used to build and what are the environmental consequences of extracting them and demonstrating actual mineral samples. We discuss with students what are our consumption habits, and how can everyone mitigate the effects of climate change?We strongly believe that hands-on activities have to be a crucial part in any climate-related education program. Experiments and demonstrations need to be simple, understandable, and show the complexity of climate and economic system.

The crystal structure modifications of BaTiO3 induced by cobalt doping were studied. The polycrystalline (1 − x)BaTiO3 + xCo2O3 samples, with x ≤ 10 wt.%, were prepared by high temperature sintering conventional method. According to X-ray phase and structural characterization, performed by full-profile Rietveld refinement technique, all synthesized samples showed tetragonal symmetry perovskite structure with minor amount of parasitic phases. Pure single-phase composition has been detected only in the low level of doping BaTiO3. It was indicated that substitution of Co for the Ti sites in the (1 − x)BaTiO3 + xCo2O3 series led to decrease of tetragonality (c/a) of the BaTiO3 perovskite structure. This effect almost vanished in the (1 − x)BaTiO3 + xCo2O3 samples with nominal Co content higher than ∼1 wt.%, in which precipitation of parasitic Co-containing phases CoO and Co2TiO4 has been observed. Based on the results, the solubility limit of Co in Ti sub-lattice in the (1 − x)BaTiO3 + xCo2O3 series i...

A study of the effects of ageing history on the electrical properties of lead-free ferroelectric ceramics of (K0.5Na0.5)(Nb1−xSbx)O3 + 0.5 mol% MnO2 and (K0.5Na0.5)(Nb1−xTax)O3 + 0.5 mol%MnO2 for x = 0.05 is reported. The samples after storage at a constant temperature have been subject to infra-low-frequency electric field and radiation. Differences of the photoelectric response between the two examined compounds were found and the restoration of polarisation in the aged ceramic materials by cycles of applied field is discussed.

The polycrystalline sample of BaTi0.95Ge0.05O3 was prepared by solid-phase reaction using a conventional method. The morphology of investigated sample was characterised by scanning electron microscopy (SEM). The results allowed to determining the stoichiometry of the material and evaluate their microstructure. High quality samples were investigated, the grains are well shaped without of a glassy phase. The dielectric properties of the BaTi0.95Ge0.05O3 ceramics were determined. The results were compared with these ones obtained for pure BaTiO3. The obtained data indicated that the substitution of Ge+4 ions had an influence on the values of the real (ϵ′) and imaginary (ϵ″) parts of electric permittivity.