Forest is the ecosystem which consists of different related components and fulfils important environmental, economic, and social functions. Each of these components is of particular value in public perception. In the beginning of September, 2007 social research was carried out in Latvia in order to understand the meaning and importance of forest value on the questionnaire base. This survey focuses on how people, whose everyday life is related to forest sector, perceive forest values. The forest values were divided into thirteen factors. To determine the most important forest value, the participants’ answers significance was evaluated basing upon the concordance coefficient and using descriptive statistic methods. The research revealed that despite the multifunctional use of forest the basic value is granted to timber and forest land. As well as respondents were not shown significant differences expressing their opinions when they were divided into different groups (forest owners, forest sector employees and other). Results of the survey have shown that the public in Latvia are not able to value and calculate forest environmental and social functions.

The article presents the part of PhD studies of the energy wood harvesting technologies in thinning, and its development possibilities. A possibility for energy wood procurement and use in Latvia as a good amount of not used energy, including estimation of how much wood for energy purposes could be available in Latvia is analyzed. Research has been made in two parts using forest stands cutting area in three different ages to get an average volume of energy wood per ha. First part of the research has been done in a 60 years old forest stand cutting area in the way that total chips volume is measured and then recalculated to the thinning area. The average volume from studied forest stand was 20.32 m**3 haE-1. The second part of the study shows that from 30 till 45 years old forest stands cutting area by the measuring possible removal tress, the energy wood volume could be 23.74 – 33.5 m**3 haE-1. Including the slash from this forest stands cutting area the possible volume of wood for energy purposes could be ~ 33 – 47 m**3 haE-1. The calculations also have been done to study available energy wood resources from whole forest stands thinning area. Totally the available energy wood volume in Latvian conditions is 0.85 million m3 yrE-1.

Willows (Salix sp.) and reed canary grass (Phalaris arundinecea L.) (RCG) are fast growing perennial energy crop and potential cultures for recovering of cutaway peat lands. Cut away peat land soils are characterized by high acidity (pHKCl 2-3), high NH4**+1, and lack of P and K. Wood ash could be good liming agent and resource of potassium. Waste water sewage sludge (WWSS) compost is effective fertilizer and source of phosphorus. The objective of the study was to investigate the effect of application of WWSS compost and wood ash fertilizers of different doses on ingrown of willow cuttings and RCG in potted cultures. The wood ash addition of 10 g lE-1 and 20 g lE-1 to WWSS compost mix with peat from used query in proportions 1:1 and 4:1 were tested. The length of shoots and dry mass of shoots and roots were assessed to determine the effect of fertilization on growth of crops. Chemical analyses of growing media were performed to determine the content of main nutrient elements and pHKCl changes during season. The positive effect of fertilization on growth of crops was observed - an optimum dose for willows is (10 g lE-1) equivalent to 10 tDM haE-1 wood ash with mix of WWSS compost with peat. RCG produces more biomass in growing media containing largest doses of wood ash and WWSS compost premix. The willows produced bigger amount of biomass and accumulated more nutrients from growing media than RCG.

One of the key factors affecting the formation of high-quality forest is thinning. Latvia's yearly budget of commercial thinning is not met; therefore, there are plenty of forests which are not thinned as planned and this leads to declining quality of forest stands. The timber processing industry needs significant excluded volume of timber, but forest owners are unable to maximize profits in future. Extensive logging of commercial thinning is hindered by economic factors and forestry regulations. Logging business is not satisfied with the productivity indicates and restricting forestry and environmental laws. The world's leading forest engineering firm offers a variety of forest harvester design and structural solutions. The first real use of commercial harvesters in commercial thinning in Latvia's conditions revealed several problems. The most important one is how to increase harvester productivity, while ensuring the quality of residual stands. To increase effectiveness of the logging machines and the proportion of commercial thinning, it is necessary to explore main factors affecting harvester productivity. This work aims to clarify the main pressures hampering harvester productivity and evaluate the quality of remaining trees in commercial thinning in Latvia. The main results are that during night productivity of harvester decreases by 12%, while marking trees to be cut down with fluorescent colour increases productivity of harvester at night by 15%. Productivity of harvester in thinning depends on average volume of harvested trees. These results of the work were obtained through various experiments on twelve different commercial thinning areas in Latvia.

Experimental self-binding high-density fibreboard is produced of the grey alder (Alnus incana L. Moench) steam-exploded fibres without addition of synthetic adhesives. Milled grey alder chips are processed in steam-explosion unit by saturated steam under pressure of 3.2 MPa at temperature of 235 deg C for 1 min in a 0.5 l batch reactor. The steam-exploded fibres are pressed at 160 deg C temperature under 8 MPa pressure for 10 min in three steps. Properties, such as density, swelling in thickness, water absorption, bending strength, modulus of elasticity at bending, and internal bonding strength of the studied fibreboard samples are reported. Differences between the raw milled chippings and the exploded fibres are observed by scanning electron microscope. The study is focused on modified technical options of the steam-explosion unit supplied with two containers receiving different kinds of the exploded biomass farther used to obtain the hot-pressed boards. The cascade of the receivers is explained in a presently pending patent. The self-binding high-density fibreboard samples show the following properties comparable to commercial products: density of at least 1.35 g cmE-3, moisture content of 7.2%, swelling in thickness of 8.1%, water absorption of 3.2%, bending strength of 27 N mmE-2, modulus of elasticity of 6,259 N mmE-2, and internal bonding of 0.92 N mmE-2.

Appropriate discount rate for forestry is still an issue for the forest economy. Therefore, it is significant to understand the importance of discounting, and how costs of forestry production process are valued. Forest regeneration and new stands tending costs are considered as investments; they are related to each particular stand. For that reason, the goal of this study was to compare how the value of this investment is growing at the bank deposit or 1 ha forest stand. The study examined the growth rate of two different tree species value with young forest stand establishment and tending investments depositing in the bank or the growth rate of compound interests. As discounting formula derived from a compounding formula, it would allow to find an appropriate discount rate for each timber species. High rates of compound interest cause a very rapid and unrealistic future value increase, while low rates cause slow value increase for a very long period represented by a common forest rotation; for that reason high discount rates used in forestry are not rational. Taking into account an income from intermediate cuttings, the value of timber species in comparison with the deposit significantly improves. Suitable discount rate determination in forest assessment is mainly determined by the species of wood productivity and cutting age. As it is hard to find two identical forest properties, each situation should be considered individually, taking into account and understanding the relationship between a growth rate of timber and compound interests, thus choosing an appropriate discount rate.

The forests and woods are the main resources in Latvia. It is vital to understand the amount of wood resources that is being extracted from private forests now and in future in order to be able to predict the forest sector development and growth. The study objective was to identify the key factors in the wood resource availability and assess their role in private forests. In October 2009, the study was conducted to appraise the private forest owners the operational results and find out the future plans in connection to wood resource extraction. In the study a random sampling method was applied, where in the respondent selection the State Forest Service database information was used. In the study the respondent interviewing method CATI with computerized telephone interviews was used. In the selection of affecting factors the expert's method was applied. The study showed that only 25.40% of all private forest owners claimed that there was wood resources extraction in forests, but 29.50% of all private forest owners claimed that they were planning to perform the wood resource extraction in 2010. If the timber selling prices increased by more than 10 LVL per m3 in 2010, then 38% of all respondents claimed that they would increase the wood resource extraction in forests. The study data show that 30% of all private forest owners admit that there are growing stands in the forests, but they can’t be harvested, because road infrastructure is poorly developed or there are no roads in the forests.

Wood based ash can be used as a liming material and fertilizer in forest, thus providing a solution for utilization of wood ash and formation of additional increment of trees, especially on organic soils, where lack of potassium and phosphorus is a well-known factor limiting the growth of trees. Yet, many studies have been made with adverse results mostly because of different soil types and species investigated. However, by now the best results on fertilization with wood ash have been found on drained peatlands, where some nutrient deficiencies have emerged. The aim of this study was to find out the growth response of Norway spruce on drained organic soils after spreading of potassium sulphate (K2SO4) and wood ash (WA). The experiment was carried out in three middle aged Norway spruce (Picea abies) stands on drained mineral and peat soil. Experiment consisted of three replications of each treatment in each stand including WA, K2SO4 and the control on 400 square meter sub-sample plots each. The diameter and height of trees were measured. The samples of increment cores were collected 4 years after fertilization to determine the additional volume increment, which varied from 8.5 m**3 haE-1 in WA plots and from 9.7 m**3 ha-1 to 17.2 m**3 haE-1 on K2SO4 plots. Both - the wood ash and potassium application - significantly increased the increment of Norway spruce on drained mineral and peat soil, although no significant differences were found between the treatments (p = 0.82, α = 0.05).

When the measurements of power consumed by cutting mechanism electromotor are made, the mechanical cutting power cannot be obtained, because they are different physical processes. However, determination of electricity power is relatively simpler. Therefore, both powers are determined in the study, in order to evaluate coherence between them. Computer numerical control machine was used for climb-sawing of aspen (Populus tremula L.) wood with a circular saw. Mechanical cutting power was calculated from measurements of cutting force, but the electric ones – from measurements of current and voltage. As a result, changes of both powers and of specific cutting work, on what the analytical calculation of cutting power is based, were obtained depending on length of the cutting trajectory. It is found out, that mechanical cutting power is greater than electric power, and it is useful to use for the analytical calculation, based on determination of the specific cutting work, wear coefficient of the cutter that depends not only on the duration of work of cutter, but also on feed speed and the length of the cutting trajectory.

Nowadays all engineering technologies are based on the automation, but still there are some processes that are not easy to automate. One of them is the heating process using solid fuel boilers. The paper deals with automated double-link air flow control of the combustion process. The research target was to find more effective solutions of furnace air flow regulation to improve the combustion process efficiency. The research object was a 56 kW wood briquettes water heating boiler. The results of the experiment research show a higher efficiency of the combustion process with double-link air flow PI control using motor valves.