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.

Plywood overlaid with resin impregnated paper films is used in various decorative applications for which high stability of aesthetic qualities is of great importance. The top veneer of the plywood for these materials is perfectly protected from a direct contact with water as far as the covering film is not damaged. However, in case of film damage water can cause clearly visible defects in a relatively short period of time. To reduce these types of defects, unsophisticated and efficient way was developed. It involves filling the vessel system of the top veneer with industrial phenol-formaldehyde resin by using a hot-press. Influence of some phenol-formaldehyde resin properties on its penetration in birch veneer as well as the effect of wood moisture content were tested. The proposed top veneer pre-treatment method with phenol-formaldehyde resin reduced the average swelling zone distance from damage site by half for oven pre-dried plywood with 3% moisture content before treatment. Moreover, it was found that using plywood with moisture content of 9% the swelling zone distance was reduced by two thirds compared to untreated overlaid plywood.

In this study, antifungal properties of an organoclay additive were investigated. Two types of organoclay (red and white) were tested in Petri dishes to determine their toxicity against the brown rot fungus Coniophora puteana and the white rot fungus Trametes versicolor. Red organoclay was more efficient than the white one and, depending on the fungus, inhibited or stopped the fungal growth. Red organoclay was chosen as an additive to produce a new type of plywood product. Biological durability of this plywood product was determined according to the methods: NF B 51-295 (bending strength test) and LVS ENV 12038:2002 (mass loss test). The loss in bending strength exceeded 81% and 65% after exposure to brown and white rot fungi, respectively. The mass loss of the plywood product after the decay test was higher than 3%, which defined the material as not fully resistant against decay fungi. According to CEN/TS 15083-1:2005, the plywood product corresponded to the durability class 3 (moderately durable) to 5 (not durable) depending on the fungus.

Birch plywood has proved itself to be one of the most rational ways of wood processing. Growing demand of high performance birch plywood products requires a complex numerical analysis based on Finite Element Method (FEM), instead of using simple analytical assumptions, which prevent optimization of plywood construction (lay-up). In the research samples of birch plywood of several thicknesses, both sanded and non-sanded, with fibre direction of external veneer both in the longitudinal and transverse directions were tested. An extensometer and optical strain gauge were used for strain measurement. The FEM analysis, using commercial software SolidWorks Simulation Premium (SW), versus experimental bending and tension testing according to LVS EN 789 was carried out in this paper. The analysis of results indicates that there is a high correlation between the results of the experiments and the FEM. Particularly for in tension loaded specimens one can be tested up to the maximum ply strength (100 MPa); meanwhile, in bending up to 71MPa – the average stress in load bearing ply at the proportionality limit. Due to software restrictions, shear stresses cannot be evaluated. Future studies are considered to investigate terms for designing plywood with dynamic properties of strength and stiffness to be taken into account.

Green infrastructure (GI) is a strategically planned network of high quality natural and semi-natural areas and provides a range of ecosystem services and protects biodiversity in urban settings. It is very important to increase understanding of the role of GI from a scientific and a socio-economic perspective. The main goal was to understand and assess the ways that tourists use from experiencing urban green infrastructure in the cities they visit. An interview questionnaire survey took place among tourists of the following countries and cities: Latvia (Riga and Jelgava) and Portugal (Lisbon and Faro). The questionnaire includes perception, psychological aspects and preferences, behaviour and activities and general questions as well as biographical information about tourists. The study represents that no significant differences have been found between respondent groups in Latvia and Portugal. The results of the survey show that in future there is a need to improve the linkage between GI and social-cultural activities in cities. Therefore, studies for tourists’ perceptions, preferences and uses of GI will provide the alternative management approaches for urban planning and tourism development in future.

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.

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.

The territorial planning and the management of urban surfaces force the decrease of green spaces in urban landscapes. As the urbanization process during past decades of the last century was quite intensive not only in Europe but also in Lithuania, findings describing changes of forest cover as well as spatial structure of the forest land are requested. The aim of this study was as follows: first, to calculate and compare areas of the forest land in six major cities of Lithuania in 1950 and 2011, second, to evaluate the spatial structure of the forest land by investigated cities within the period of 1950 – 2011. Methods of descriptive statistical analysis and spatial analysis using ArcGIS and MS EXCEL software were used. The study was based on two geodatabases, representing the forest cover in 1950 and 2011. Results of this study revealed that areas of the forest land increased in all investigated cities excluding Panevėžys city. The increases of areas of the forest land were discovered to vary from 0.8% to 9.5%. The largest increase was found in Vilnius city (9.5%), the smallest – in Šiauliai city (0.8%). The decrease by 0.9% of the forest land was found just in Panevėžys city. No significant changes of the forest land spatial structure were found in largest cities of Lithuania, i.e. Vilnius city and Kaunas city. The spatial structure of forest land in other investigated cities tended to degrade.