Norway spruce (Picea abies (L.) Karst.) is economically important tree species, vulnerable to impact of different biotic (cervids, bark beetle etc.) and abiotic (wind, wet snow etc.) factors and their combinations, expected to increase in frequency and/or magnitude in future due to climate changes. The aim of the study was to characterize occurrence damages in Norway spruce stands in Latvia. Data from 635 National forest inventory sample plots were used in the analysis, thus providing the information primarily on the non-lethal damages, since the dead trees in most of the cases would be removed from the stands in sanitary cuts. Damages were reported for 11.6 ± 1.1% of spruces from total basal area of spruces in the assessed pure and mixed stands. Admixture of other tree species or soil (group of forest types) had no significant effect on the proportion of damaged spruces. Also, no statistically significant differences in dimensions were observed between damaged and undamaged trees. The major cause of damages was browsing (three quarter of damaged spruces, in contrast to only one-quarter of the rest of the trees) and the highest proportion of damaged spruces were in stands in the age group 41 – 80 years, significantly differing from that in younger (up to 20 years) stands, demonstrating both the preferences of cervids to a certain dimensions of spruce as well as accumulation of damages over time.

The aim of research was to determine peculiarities of relations between mature layer of the stand with distribution of spruce (Picea abies. Kr.) regeneration according phenology forms and growth specifics. The study examined the success of the resumption of spruce in the Leningrad region under the canopy of the parent stand. In stands with different share of spruce and in various forest-typological conditions, the features of the relationship between the maternal canopy of the stand, the distribution of the natural resumption of spruce by phenological forms and its course of growth were investigated. The account of the undergrowth was carried out by two methods: continuous reading and selective-statistical method. Regardless of the state of viability of spruce undergrowth, the increase in success of regeneration goes from a late vegetation season growth start form to an early one. Under the canopy of the maternal tree stand, young spruce of the early form has the best growth and development indices. In general, under the canopy of spruce stands, the annual height increment in spruce undergrowth, regardless of the phenological structure, the size categories and the state of viability, is greater than under the canopy of pine, pine-spruce and birch-spruce stands. The best characteristics of spruce undergrowth, regardless of phenological forms in vaccinio-myrtillo-pinetum type of forest are described. When analysing the characteristics of spruce undergrowth under the canopy of the stand, taking into account the phenological and altitudinal structure, and the state of viability, it was revealed that at the average age prevailing in the spruce undergrowth of the transitional form, the best parameters of growth have small and medium forms and growth in the early form. Analysing the characteristics of spruce undergrowth under the canopy of the stand, taking into account the phenological and height structure, as well as vitality status, it was revealed that at average age, dominating for the spruce undergrowth of transitional form, the best parameters of small and medium groups of undergrowth has early vegetation season growth start form. The best parameters of the growth have a large group of undergrowth of late vegetation season growth start form.

The objective of this study is to assess the qualitative and quantitative characteristics of pine (Pinus sylvestris) and spruce (Picea abies) stands growing on lands that were previously in agricultural use in the Leningrad region. Sample areas of mature mixed pine-and-spruce prevailing stands were studied. The taxation has revealed that the average height and diameter of the stands under study are greater than those in mixed modal stands of these species on forest lands. The analysis of the results of the study was performed by dispersion, correlation and ranking methods. To determine the competitive relationship between species, the coefficients of skewness, and kurtosis were calculated. For coniferous stands growing on former arable lands, the distribution of diameter classes for pine and spruce differ depending on the prevalence of species. The predominance of one of the coniferous species in the stands leads to an aggravation of competition, which manifests itself in positive coefficients of asymmetry. The skewness indicators and the kurtosis of tree trunks distribution clearly demonstrate the strengthening and weakening of competitive relationships in the stand. Competitive relationships between species are more balanced in stand compositions that include more than half of spruce and about 40% of pine, which results in the largest volume of stemwood. A more powerful root zone of trees in the former arable soil allows mixed stands of spruce and pine to produce a larger volume of wood than in pure stands of pine and spruce for the investigated region.

Woody plants at urban greeneries in Lithuania are injured by rust fungi of 13 genera, 28 species: Coleosporium pulsatillae, C. tussilaginis, Cronartium flaccidum, C. ribicola, Cumminsiella mirabilissima, Gymnosporangium clavariiforme, G. confusum, G. cornutum, G. sabinae, G. tremelloides, Hyalopsora aspidiotus, M. allii-fragilis, M. allii-populina, M. caprearum, M. epitea, M. laricis-populina, M. populnea, Melampsora ribesii-viminalis, M. salicis-albae, Melampsorella caryophyllacearum, Melampsoridium betulinum, M. carpini, Ochropsora ariae, Phragmidium tuberculatum, Pucciniastrum areolatum, P. symphyti, Uromyces caraganicola, U. pisi-sativi. During 2009 – 2017 Gymnosporangium sabine had the strongest damages (from 0.21 ± 0.00 to 2.43 ± 0.33 grades) on Pyrus pyreaster, the weakest damages had done G. cornutum on Sorbus intermedia and S. x thuringiaca ‘Fastigiata’ – 0 – 1 ± 0.58 grades.

Rhododendron spp. plants were surveyed for Phytophthora infection in Lithuania during 2010 – 2016. This study aims to identify Phytophthora genus pathogen which infects rhododendrons in Lithuania. Samples were taken from young sick plants with visible infection symptoms. Soil sampling was performed from the rhizosphere of sick plants. DNA from soil and plant was tested for the presence of Phytophthora genus pathogens. Data showed positive results of Phytophthora genus specific probe during real-time PCR. All tested diseased leaves and soil samples have indicated Phytophthora sp. infection during Alert-LF® Phytophthora spp. analysis. The extracted DNA concentrations were not very high for Phytophthora species identification, but in most cases, it was high enough for further researches.

Establishment of sedimentation ponds is a method to reduce the negative impact of forest management (fellings, drainage) on the quality of nearby rivers, lakes and streams. The aim of the study was to determine the efficiency of sedimentation ponds in forest drainage systems during high precipitation periods. Nine sedimentation ponds with different drainage areas were analysed. The sedimentation ponds are located in the northern part of Latvia on different types of soils and managed by the Joint Stock Company ‘Latvia’s State Forests’. In order to determine efficiency of these ponds the following parameters in water samples were measured: nitrate (NO3 -), ammonium (NH4 +), phosphate ion (PO4 3-), total nitrogen and total suspended solid concentration. The amount of precipitation was taken into account. Results show that there is a correlation between the amount of precipitation and concentrations of total suspended solids and total nitrogen. Ammonium ion concentration was the only parameter that significantly exceeded water quality standards in Latvia. Only one of the objects had high concentration of pollutants, which could be explained with the peaty soil of its drainage area. In further studies data should be collected more frequently, three or four days during one precipitation period.

Land use efficiency is based on agricultural production. Correct and effective land use could solve several problems – food production, improving the welfare and provision of social stability. The use of land and natural resources is an important issue in the development of the country; therefore, many researchers and scientists have analysed and studied the use of agricultural land and land use efficiency. Efficient land use has an impact on different types of factors, which are mutually contradictory. In the paper several authors researches are analysed, studying influencing factors of the use of agricultural land. Influenced by several factors the main problems associated with the use of agricultural land are the increase of unused agricultural land, the continued degradation of land, but the major problem of land use is the existence of a fragmented property structure. For the efficient use of agricultural land, there are several conditions that need to be met or improved to achieve effective land use. The main conclusion is that analysing the problems that are associated with the use of agricultural land is seen as interactive interaction, as the fragmented property structure is one of the reasons influencing the use of agricultural land, which leads to an increase in unused areas of agricultural land, while unused areas of agricultural land are often overgrown with shrubs while promoting degradation of land.

This paper aims to deal with the phytoremediation approach for protection of environment and preventing the streaming of contaminant flows to hydrological systems. Phytoremediation is a cost-effective environmentally friendly clean-up technology, which uses plants and microorganisms in rhizosphere for soil and groundwater treatment. Phytoremediation is enhancing degradation of organic pollutants and improving stabilization of inorganic contaminants where plants can be used to treat soil and water polluted with hydrocarbons, chlorinated substances, pesticides, metals, explosives, radionuclides as well as to reduce the excess of nutrients. Selection of species for this type of treatment processes is based on evapotranspiration potential and ability to bioaccumulate contaminants. The project entitled “Phytoremediation Park for treatment and recreation at glassworks contaminated sites” (PHYTECO) aimed at cross-sector international partnership. The challenge of project was to develop remediation strategy where negative consequences from centuries long anthropogenic influence are turned to be something positive – development of the recreation park from the glass dump. New “Knowledge in Inter Baltic Partnership Exchange for Future Regional Circular Economy Cooperation” (PECEC) project is sequential continuation.

This paper investigates the effect of intake runner design on pressure wave propagation and reflection in sparkignited internal combustion (IC) engine. These events are known to leave a noticeable influence on the overall engine performance therefore the aim of this study is to evaluate how changes in intake runner geometry affect pressure oscillations and volume flow rate. Time-dependent computational fluid dynamics (CFD) analysis was carried out to determine how these changes affect the pressure oscillations during a full engine cycle at constant crankshaft speed. Steady state CFD analysis at constant pressure differential was carried out to evaluate the effect on volume flow rate. The simulations were carried out in SolidWorks Flow Simulation environment. Honda CRF450R motorcycle engine was used to define the initial conditions and basic intake runner design. Intake air speed at port entrance cross-section was calculated based on engine parameters and operating speed. The average pressure values with respect to physical time were measured and graphed across the intake port opening cross-section. Six different intake runner designs were compared. It was concluded that the runner taper angle has influence on pressure wave-length but internal geometry (steps, curvature and taper angle) has influence on volume flow rate. It was observed that cylindrical intake runner design produced an increase in pressure wave-length but a cylindrical section of the intake runner with a stepped transition to tapered extension produced a slight increase in pressure wave amplitude.

The aim of the work is to increase the efficiency of cyclone technology by using a separator plate. Cyclone technology is used not only in the processing of various agricultural products, but also in air purification from dust. Air flow trajectories and the movement of dust particles inside the cyclone unit were simulated and analysed using Computational Fluid Dynamics (CFD) and particle study analyses. The separator plate was designed in certain sizes and placed inside the cyclone, thus increasing the efficiency of the cyclone. The angle of position of the separator plate significantly affected the obtained results. The experimental equipment was assembled together to test the simulation results. Wood ash was used to determine the efficiency of the cyclone. Studies have shown that the effect of the separator plate on increasing the efficiency of the experimental equipment is less than that shown in the simulations. Most of the experiments used ash particles that were greater than 20 μm, thus cyclone efficiency was 98.9 ± 0.05%. This confirms the compliance of CFD simulations with the physical model. More detailed research should be carried out in order to use the separator plate effectively for the filtration of very small dust particles.