In conditions where induction motors are frequently started, overloaded and used in high inertia applications with long starting times, supplied from frequency converter, a temperature protection system are more reliable to protect induction motor stator winding against thermal overloads. There are different types of temperature protections - thermostat, PTC thermistor, resistance temperature detector (RTD) and thermocouples, so it is important to know the properties of each type to choose an adequate protection system. Analyses of temperature sensor properties and their advantages and disadvantages show, that PTC thermistor is a cost-effective temperature protection solution, but for medium and high voltage induction motor protection RTD are commonly used. A virtual model has been represented to simulate the temperature sensor thermal time constant under different thermal conductivity and thickness of winding magnet wire insulation.

One of the most challenging issues in forest inventory based on remote sensing data is identification of tree species. Hyperspectral remote sensing data provides information which considerably facilitates tree species recognition. The objective of the research is to evaluate different hyperspectral data analysis methods to classify tree species in Latvian forest conditions. The study site is a forest in the central part of Latvia, Jelgava district (56º39’ N, 23º47’ E). The area consists of a mixed coniferous and deciduous forest. During research 598 trees were analyzed in 70 sample plots. Remote sensing data are 64 hyperspectral bands in the 400 - 970 nm spectral range. Two different classification techniques: linear discriminant analysis (LDA) and artificial neural networks (ANNs) were used. In LDA species classification was done by stepwise and using principal components of hyperspectral bands. In stepwise LDA 18 hyperspectral bands were used. LDA using principal components and ANNs used all 64 hyperspectral bands. The best results show stepwise LDA where 82.4% of the data were correctly classified. Scots pine was classified 94.8%, Norway spruce 83.5%, Silver birch 77%, European aspen 71.4% and Black alder 56.3%. Classification with ANN’s best results showed for Scots pine, Norway spruce and Silver birch – respectively 81%, 84%, 86%. With LDA using principal components Scots pine’s classification showed best results with 85.1% correctly classified trees.

The regeneration of European hornbeam (Carpinus betulus L.) has been assessed in the National Gene Reserve Forest near Lukne in the south-western part of Latvia, which is the northernmost point of hornbeam distribution in Europe. In the studied stand, six sampling plots and four transects were established to assess stand structure and the effect of irradiation parameters on stand regeneration. Successful regeneration of hornbeam was shown by its presence in all height and diameter classes. Nevertheless, in the smallest height and diameter classes, an increased abundance of other shade tolerant species (maple (Acer platanoides L.) and lime (Tilia cordata Mill.) was observed. Norway spruce (Picea abies Karst.) mainly formed a scattered second forest floor and, apparently, competed with hornbeam. Light parameters, particularly, the diffuse radiation, had a significant effect (p=0.05) on the distribution and abundance of hornbeam understory. The threshold values of irradiation parameters for hornbeam were notably higher compared to other species. The number and height of hornbeam saplings correlated tightly with the amount of available light. Nevertheless, under sufficient light conditions hornbeam showed good vitality, thus suggesting suitability of growing conditions.

In Latvia, two European ash (Fraxinus excelsior) genetic resource forests (GRF) have been designated in Skrīveri and Bērvircava. However, as the degree of damage of ash by the pathogenic fungus Hymenoscyphus fraxineus has increased, many stands have died and many do not comply anymore with minimum requirements for GRF. The aim of the present research was to evaluate and examine the quality of ash GRFs. In each forest unit, one 20×20 m plot was established, and the first (E3) and second (E2) layer projective cover of each species was determined in August 2014. All undergrowth and advance regeneration species were counted and the degree of ash damage by H. fraxineus was determined along a diagonal 25×1 m transect in each plot. In total, 101 plots were established. Quality evaluation was carried out according to the basic criteria for selection of GRF as well as based on criteria cited in other research. Their variation was established by using principal component analysis. Ash in layer E3 was better maintained in Skrīveri, but ash regeneration there was worse, as well as a higher degree of damage by H. fraxineus was observed. Ash regeneration density is significantly influenced by its cover on layers E3 and E2 as well as by tree species dominating the growth. The most valuable GRFs have been maintained in Skrīveri where 50% of units were rated of average quality and few of bad quality. In Bērvircava, 56% of forest units were of bad and very bad quality.

The emergence of human–induced edges in forested landscapes has caused major threat for the existence of habitat specialists. Woodland key habitat (WKH) concept has been created in the Baltic and Fennoscandian forests to preserve small forest parcels with a high biodiversity value in the production forests. In this study we investigated the occurrence of epiphytic lichen indicator species in black alder WKHs in Southern Latvia. In total 30 black alder WKHs with age of 84 to 129 years were chosen for analysis including stands adjacent to young, middle–aged and mature stands. Sample plots were placed at three distances from the forest edge. Our results indicate significant differences in number of species per sample plots adjacent to stands of different age. Lichen indicator species were considerably more common in habitats adjacent to mature forest stands and further (40–50 m) from the edge. From four lichen indicator species found in this study, sample plots adjacent to young stands hosted only two species. We argue that the indicator species response to human–induced edges is species specific and some of them are resistant to microclimatic changes near the edges.

The tree growth compensation followed by insect damage is important for tree survival. Insect damage by making 3 and 6 holes per each leaf, and clipping one third of a leaf were simulated for one-year old silver birch (Betula pendula Roth) seedlings once, at the beginning of the vegetation season. The height, aboveground and root biomass, root length, stem diameter and leaf area were measured for all damaged and control seedlings. The aim of the study was to examine the effects of different insect-damage simulations on silver birch growth. Our study demonstrated that leaf dry mass decreased in response to leaf perforations and clipping one third of leaf. However, at the end of the experiment, the cumulative dry mass reached the level of the control. We found no statistically significant effect on the aboveground and total biomass of damaged seedlings compared to the control. The leaf clipping decreased the leaf area and stem diameter compared both to the treatment with hole-damaged seedlings and the control. The induced birch growth response showed that tree seedlings were able to compensate their growth up to the control level after the insect damage in eight weeks.

Thinning of young forest stands is a contribution to the future of the stand development. Our study focuses on damage of the remaining trees and soil. Now it is common to see thinning of young stands with heavy forest machines, but most of these operations take place in commercial thinning. This study is focused on precommercial thinning to evaluate different mechanized thinning methods in relation to the damage done to the remaining trees and soil in deciduous tree stands. Data were collected in four stands where the average diameter of trees at breast height was 6.2 cm, the height of average trees - 9.5 m, but number of trees per hectare was more than 2900. The stands regenerate naturally. Damage was evaluated separately after harvester and forwarder operations. The study proves that forwarding makes much less damage to the remaining trees than harvesting. According to the study data, the traditional method results in the largest number of damaged trees, because operators need to cut all trees closer than 1.5 m from the target tree. Both schematic thinning methods result in significantly less damage. A statistically significant difference (p is less than 0.001) was found in a proportion of damaged remaining trees between all of the applied working methods. The smallest amount of damage is associated with complex symmetrical thinning method. The most damage appears during harvesting. The aim of this study was to compare three working methods of biofuel production in pre-commercial thinning using harvester John Deere 1070D with accumulating felling head Bracke C16.b in grey alder (Alnus incana) pure stand.

Scots pine (Pinus sylvestris L.) is the most common wood species in Latvia. It is classified as not durable, therefore additional protection against microorganisms is needed prior its use outdoors. Presently Cu-containing wood preservatives are commonly used, but the biggest drawback is the poor Cu fixation, therefore raising concerns about the impact on the environment. Three types of specimens were used to carry out the experiments – untreated, Latvian originated Scots pine; Scots pine commercially treated with preservatives that belong to a group of Cu-boron-triazole (CBA) products; and Scots pine, impregnated with micronized-Cu solution using a standard full cell process. In order to make sure that all of the specimens are equal in their components, elemental analysis was performed and content of nitrogen (1.2 – 2.5 g kgE-1), carbon (485.5 g kgE-1), oxygen (456.0 g kgE-1) and hydrogen (55.6 g kgE-1) was determined. The treated specimens were leached according to the European standard EN 84. For micronized-Cu impregnated Scots pine the total Cu content in leachates obtained by atomic absorption spectroscopy was 0.15 mg gE-1 of wood, and 0.06 mg gE-1 of absolute dry matter with CBA preservative impregnated Scots pine wood. Subsequently, according to the European standard EN 113, treated Scots pine blocks were exposed to brown-rot fungus Coniophora puteana and to white-rot fungus Trametes versicolor for 16 weeks. Mass loss for wood treated with micro-Cu was 48.4% (484 g kgE-1) and 1.5% (15 g kgE-1) respectively, but for CBA – 49.5 % (495 g kgE-1) and 1.2% (12 g kgE-1). Both samples proved to be inappropriate for outdoor use (use class 3).

Colour and colour homogeneity are of special importance for establishing the quality of wood products. In the present study the effect of thermal treatment at 140 °C and 170 °C on colour and its homogeneity was studied for aspen (Populus tremula L.), grey alder (Alnus incana Moench) and ash (Fraxinus excelsior) wood. Wood colour was monitored and evaluated by spectrophotometrical measurements of reflectance spectra and colour parameter calculations using CIELAB colour model with L* as the lightness, and a* and b* as the chromatic parameters. Wood colour changed substantially and all studied types of wood acquired quite similar colour due to the thermal treatment with greater discolouration and almost the same colour detected for treatment at 170 °C. The average colour difference within a board surface as well as among boards of one species was found to be less than 3 DEab units for all thermally treated specimens which can be regarded as hardly perceptible colour difference. However, noticeable differences in colour were detected between the surface and inner layers of thermally treated wood boards. Greater colour heterogeneity throughout the depth of a board was detected for woods treated at 140 °C.

This article deals with conception and particularity of management process and functions of non-governmental organisations (hereinafter referred to as NGO), as well as peculiarities of management functions of NGO. Empirical research results of implementation of NGO management functions in Kaunas District have been presented, the major advantages and disadvantages of implementation of NGO management functions in Kaunas District have been pointed out. With reference to the data of theoretical analysis and empirical research, the directions towards development of problematic areas of NGO management functions have been indicated and justified, highlighting the elimination of drawbacks to the implementation of management functions.