The objects of research are the lime-tree forests of the Leningrad region. The studies were carried out on 2 permanent plots established by the authors in May 2013 in the Lisino forest district (Leningrad region, Russia). The goal of research was to obtain a complex characteristic of stands dominated by linden (Tilia cordata). The objective of the research included a taxation and geobotanical description on permanent plots and studies of the soil cover (morphological and agrochemical characteristics of soils). The general health status of stands on the surveyed areas was determined as satisfactory – mean score 2.5 and 2.8 (relevant health status was determined with the help of the following 6-grade scale for each tree: 1 – no signs of weakening; 2 – weakened tree; 3 – very weakened tree; 4 – partial mortality of the tree; 5 – dead-standing trees of the current year; 6 – dead-standing trees of previous years). The average mortality rate varies from 3.05% year-1 on the sample plot 2 to 5.7% year-1 on the sample plot 1. Vegetation on sample plots attributes to a nemorose-herbal series of forest types, soils – to a podzolic type with a weak development of the podzol-forming process. They were well-mediated ones by humus in the upper horizon. This fact was facilitated by the lime litter: a lime has a deep root system to take up nutritional chemicals from a greater depth, where moraine loams enriched with calcium carbonate located. Old-aged forests of this type are being in the phase of gap dynamics now. This means that they can occur for a rather long time in the same place, however, the lime-tree forests of natural origin are constantly under threat of being replaced by spruce. The results of our study have shown that low levels of soil mineral nutrients supply are sufficient for the successful linden growth.

The study represents results on remote sensing methods based evaluation of land use and land use changes in former and existing peat extraction areas in Latvia. The aim of the study is to elaborate activity data set for the National GHG inventory for the wetlands remaining wetlands for peat extraction. The study results provide sufficient data for application of the default emission factors for the peat extraction sites and flooded lands. Abandoned peat extraction fields, which are not yet afforested, flooded or rewetted, should be reported as peat extraction sites following a conservative approach in application of the emission factors. The study results can be used to report land use changes since 1990; however, linearized approach in calculation of the land use change may result in overestimation or underestimation of GHG emissions in certain periods of time. According to study results, the area of peat extraction sites is considerably bigger than currently reported in the National GHG inventory, mainly due to considerable areas of abandoned peat extraction fields. Flooded lands may be a significant source of emissions and should be introduced in the National GHG inventory to secure consistency of reporting. Methodology for calculation of GHG emissions from flooded lands should be also elaborated. It is also necessary to elaborate emission factors for fertile and no fertile peat extraction sites and continue work on separation of different soils in the inventory to increase accuracy of calculations.

Precision of the forest inventory still is one of the most important problems in the forestry nowadays. The aim of this research was to estimate the results of the combined forest inventory (CFI), using high spatial resolution aerial images in the planned areas of clear-cuts, comparing the results with the calipering and production files of harvesters. Testing of algorithms showed considerable difference in results between the CFI, forest inventory data and harvester production data. CFI results and production data had a close correlation with R2 =0.83. Comparing CFI calculated growing stock with production data, the average relative error amounted to 10.7%, which means the possibility for integration of these results into the forest inventory system. Comparing to CFI, there is a weak correlation between forest inventory and production data with R2 =0.34. The results indicate that LiDAR CFI technology can be used in the forecasting of the forest management, offering precise information about potential amount and economic value of assortments.

The aim of the research is to find out changes in productivity depending on the diameter of the tree to be cut as well as the most important factor influencing the reduction of productivity using small size forest machines in thinning in Latvia. The equipment used in the study – both the harvester and the forwarder is Vimek. The results of the research confirm the appropriateness of the exact technique in thinning if diameter of the harvested trees is 3 to 30 cm. The average productivity of the harvester achieved with a harvester head Keto Forest Eco (option 2) in Norway spruce stands with 8 cm weighted average tree reached 9.59 m**3 hE-1, in deciduous tree stands with 9 cm weighted average was 10.17 m**3 hE-1, but in Scots pine stands with 12 cm average weighted tree diameter reached 10.19 m**3 hE-1. By using the Keto Forest Eco Harvester head according to the thinning productivity figures, no significant difference among the tree species was detected. For the forest owner to predict the theoretical productivity of the harvester, it is possible to apply the equation R = K + KD * D, that is statistically significant, R2 =0.85. This equation is applicable to thinnings when the diameter of thinned trees is between 4 and 25 cm. Forwarder’s average productivity in thinned stands is 8.63 m**3 hE-1.

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.