The objective of this study is to evaluate the performance of models developed by Repola (2006) to estimate the vertical changes of the basic density of Scots pine (Pinus sylvestris L.), Norway spruce (Picea abies [L.] Karst), and birch spp. (mainly Betula pendula Roth) stemwood in the forests of Latvia and to develop a model for the estimation of average knot-free stem density with bark (SD) using diameter at breast height as an independent variable. The study material comprised a total of 81 spruce, 102 pine, and 105 birch stems representing a wide range of tree growing conditions in Latvia and covering all age classes. The knot-free stemwood density (SWD) of pine and birch demonstrate strong vertical dependence along the stem, while for spruce the variation pattern was less pronounced and seemed to be nearly constant along the stem. The SWD estimated by Repola’s models was 4.3% lower for spruce, but 3.4% higher for pine and 2.2% for birch comparing to average values obtained in this study. Sigmoidal regression equations constructed in our study explained 67%, 27% and 54% of variations for predicting SD for pine, spruce and birch, respectively. Birch stemwood has a highest basic SWD – 470 kg mE-3, followed by pine – 397 kg mE-3 and spruce – 385 kg mE-3. According to our results, the birch bark turned to be denser than the birch stemwood, being vice versa for the studied coniferous species.

Yasso07 soil carbon model was used to estimate soil carbon balance in dry forest site types (6 site types in total) in Latvia and the results were compared with data from Biosoil2012 soil surveys. Litter input, chemical quality and climatic data are required to run the model. Three different scenarios were used for climate data input – steady climate, climate change + 0.025 °C annually and climate change + 0.05 °C annually. Forest mineral soil is a carbon sink for the whole modelled period - the years of 1990 – 2030. Under steady climate, the average carbon removal is 0.6 t CO2 haE-1 yrE-1, under climate change (+ 0.025 °C) scenario 0.4 t CO2 haE-1 yrE-1, but under climate change (+ 0.05 °C) scenario 0.3 t CO2 haE-1 yrE-1. CO2 removal at the beginning of the period (1990) was 0.35 – 0.38 t CO2 haE-1 yrE-1. Carbon stock modelled with Yasso07 is lower than estimated in Biosoil2012 soil surveys. Differences between modelled and Biosoil2012 results vary from 2 t C haE-1 in the poorest and 41 t CO2 haE-1 in the third poorest site type. Carbon stock modelled with Yasso07 increases from the poorest to the most fertile site type while Biosoil2012 shows an increase from the poorest to the third poorest, and a decrease from the third poorest to the most fertile site type. Underestimation and different trends between Yasso07 and measured carbon stock may be explained by inappropriate equations and models used to estimate non-woody biomass. It is necessary to improve accuracy of input data for non-woody biomass by elaborating national equations and models in order to include Yasso07 in the national GHG inventory.

Urban forests provide ecological and social functions and significantly improve esthetical value of these ecosystems. These forests also function as recreational areas for urban residents. The aim of this study was to assess the influence of understory cutting of different intensity on vegetation and coincidence with Myrtillosa forest type in Mežaparks, Riga. In total nine study sites were established: three sites adjacent to roads where regular undergrowth management is practiced, three adjacent sites to edges of the pathways, where undergrowth management is practiced only occasionally and three adjacent sites to roads where there is no management activity at all. Combined 54 sample plots were created (each sized 10 × 10 m, area 100 m2 ), where vegetation survey was done using Braun-Blanquet method. This study showed that with an increase in the intensity of undergrowth management, in general, the species richness and their coverage increases, or more specifically, the number of herbaceous and moss species increases, but the occurrence of shrub species decreases. In all study sites we observed the development of synantrophic species, especifically, the development of fructification which was indicated by the following species: Sambucus nigra L., Sambucus racemosa L., Amelanchier spicata Lam. If management intensity decreases, the proportion of competitor species decreases, but the proportion of CSR strategy type species stabilizes.

The objective of the research was to characterize the qualitative and quantitative changes in ground and tree vegetation within 10 years since the beginning of observations at Level II forest monitoring plot in Valgunde. Tree height, diameter, stem volume, radial increment, crown condition and cone yield were determined, as well as crown projective cover of each plant species was estimated. To study bioindication, the average Ellenberg’s and Düll’s indicator values for the monitoring plot were estimated. Species composition in the Level II monitoring plot in Valgunde is typical for Myrtillosa forest type – there is a distinct moss layer, in which Hylocomium splendens and Pleurozium schreberi predominate, and Vaccinium myrtillus is the most common in the herb layer. Shrub layer mainly consists of spruce seedlings, and the tree layer – of Scots pine. Changes in vegetation over 10 years are insignificant. It can be explained with no forest management activities occurring within the observation plot, such as logging or fertilization, and it may take a longer time to observe significant changes. Tree stand indicators correspond to the average in Latvia in Myrtillosa type forests, but the tree volume is higher in Valgunde monitoring plot.

European beech (Fagus sylvatica L.) timber value is high in southern Europe due to a great demand from Asia. Since the timber market is global, over a long time we can expect gradual increase in demand also in other countries, including Latvia, where climatic conditions becomes increasingly more suitable for this species due to ongoing climatic changes. In order to develop recommendation for the use of beech in our country, the aim of the study was to assess the potential financial gain from Fagus sylvatica stands in Latvia. Assortment structure, defined by topdiameter and length, as well as their prices was set based on the literature survey. Results showed higher income from older (115 years) than form younger (58 years) stands: 9108 EUR haE-1, and 7939 EUR haE-1, respectively. However, the opposite was true for the net present value (r = 3%): 1423 EUR haE-1 and 304 EUR haE-1, respectively.

The normal wood colour changes due to the biochemical reactions as well as under the fungal exposure. Some of these fungi during all the exposure time cause only a discoloration (staining fungi); others change not only colour, but also the structure of the wood in its further development (wood destructing fungi). The development of blue stain in sapwood of pine roundwood and its influencing factors were studied in the spring summer period of 2016 (April, May and June) in the districts of Nica, Jelgava and Daugavpils. 650 discs from pine log end planes were prepared in order to evaluate the influence of harvesting type, spreading type of fungi spores, placement in pile, storage duration, diameter, distance from the end plane, daily average temperatures, precipitation amount and relative humidity on blue stain of sapwood and rot development. The most important factors influencing the blue stain development on pine roundwood during the storage are the harvesting type of roundwood, spreading type of fungal spores, placement in pile, storage duration, diameter, and distance from the end plane, daily average temperature and amount of precipitation. By evaluating the daily average temperatures, it was concluded that blue stain of sapwood begins to develop when the average daily temperature reaches +5...+6 °С. But when the average daily temperatures reach +10 °С, depending on the harvesting type (chainsaw or harvester) and spreading type of the fungal spores (via air or bark beetle assistance) the first signs of blue stain may occur from 10 to 42 days of storage.

The aim of this study is to improve the practice of mechanical forest site preparation (FSP) by identifying typical characteristics of FSP, including the direction of FSP machinery, manoeuvre count depending on configuration of parcel and forest type and width of manoeuvre track; to evaluate the productivity depending on different forest growing conditions; to create schemes of technological corridors for commercial thinning; to improve scheme of FSP according to the scheme of technical corridors for commercial thinning and to evaluate changes in the count of manoeuvres and total distance travelled. In this study, we have developed methods to evaluate the quality of FSP. Methods used in this study include GIS analysis of vector data from FSP machinery tracking devices and LiDAR (Light detecting and ranging) data analysis for terrain information. Study shows that there is a significant difference in productivity when the machinery of FSP is driving in different angles to the longitudinal axis of parcel. Reduced productivity is justified by prioritizing topography of the forest floor. Slope is a decisive factor in the ground water movement and should be considered in FSP planning. Study shows that the developed method could be implemented in practice of forest management in 41% of sampled forest stands.

Surface water runoff, formed in the company areas due to changing wastewater discharge and pollution fluctuations can be treated in retention ponds. Pollutants, released into the ponds, mineralize during complex natural biochemical processes in the aquatic environment. The paper presents the long-term observation data (2004 – 2016 m.) on the purification of surface wastewater, formed in the company’s production territory, in retention ponds. The aim of this work is to identify surface wastewater purification efficiency in retention ponds. Wastewater samples were taken before and after biological treatment. The samples were investigated in the Chemical Analysis Laboratory of the Water Research Institute of Lithuania University of Agriculture. Biochemical oxygen demand (BOD7 ) was determined with titrometric method, suspended solids (SS) – with gravimetric method, having filtered the substance through a mid-thickness filter. Concentrations of oil pollutants were determined with the help of a spectrophotometric device of infrared rays IKAN-1 in the Analytical Department of Agrochemical Study Center of Lithuanian Agricultural Institute. Although the suspended solids, BOD7, and oil hydrocarbon concentrations, released into the natural environment, were below the MAC when they are collected from the company’s production areas, they are often contaminated; therefore, it is necessary to treat them. The purification efficiency of researched materials was satisfactory and reached 61, 64 and 91%.

The article presents the analysis of the current situation of the damaged land in Klaipeda County. The study found that the number of affected areas in the county – 266. Because the damaged areas consist of mineral quarries and territories occupied by dumps, the article contains the description and condition of these areas. It was found that mostly sand deposits (60) predominate in Klaipeda County, of which only 8 are used. The smallest number of the deposits – the salt deposits (2). The mainly used deposits in the county are sand and gravel deposits – 29, unused – sand deposits (52). The Klaipeda municipal waste management region comprises 7 municipalities, 39 old landfills and dumps were shut down. At present, 1 regional non-hazardous waste landfill has been arranged. In Klaipeda County, in 2015, damaged land occupied 2,391.06 hectares and amounted to 0.46 percent of the county’s area. During the period between the years 2005 and 2015 the damaged land area in Klaipeda County increased by 130.25 hectares. The analysis of the damaged land by type of ownership showed that the damaged land areas in private land increased by 75.54 hectares or 58.52 percent. In the state land, the damaged land area decreased by 442.35 hectares or 20.04 percent.

The aim of the paper is to explore the possibilities of detection and reduction of land degradation in Smarde municipality rural territory (56°57′18″ N; 23°20′17″ E). To carry out land degradation prevention measures, initially the territories of degraded land should be determined. This paper highlights the field inspection method. For territory inspection a model was used that gave the opportunity to identify degradation types with their characteristic features and possibilities to reduce the land degradation. The territory of Smarde municipality rural territory was inspected in nature and degraded territories identified. The costs of land degradation elimination depend on the type of land degradation. In territories where the land degradation reduction or elimination has been done, its control has to continue in order to stop the development of land degradation.