In order not to decrease the significance of a forest in the environmental maintenance and its role in the national economy, Latvian Forest policy needs to ensure that the existing forest areas are not decreasing, establish forest land transformation restrictions, thus, maintaining a long lasting development of forests. The preconditions for the change of the forest land use is one of the instruments for the state policy realisation, with the help of which a long-term development of forests can be ensured. At the moment working out the land policy in Latvia on a country level is being started. The publication is in the context of setting strategic targets for forestry and human resource development planning strategy, within the framework of Latvian forest and related department national programme. Due to the reasons mentioned, the topic discussed in the article is a problem of the day, and the research in this direction has got both theoretical and practical significance. The author investigate the forest land transformation process, by analysing normative acts and political documents in the article, as well as by summarising statistical data about the relevant processes in Latvia and in the world, during last six years. The issues, related to the forest land transformation process have been covered in the article; it has been analysed whether there are cases when a necessity arises to review the existing normative regulations. The answers have been given how to eliminate identified shortcomings, contradictions or problems.

The task of this paper is to create a simulation model of wood resource flow, enabling analysis of the flow of resources to the customer. The model consists of four modelling steps - the study of the system, the creation of conceptual and logical model, as well as data analysis. The model has been developed in UML (Unified Modelling Language) diagrams and the simulation model has been created using software EXTEND Industry. For the simulation of the model the scenario has been created. Based on this scenario, extended scenarios have been developed. Model of basic simulation represents the loading of resources into the transport, transportation, discharging from the transport and the return to the loading point. Using this basic scenario, the extended scenario has been created. This scenario analyzes the flow of wood resources to the customer, taking into account two criterions restricting the flows - assortment to be processed and the distance from the loading place to the customer's location. Extended scenario allows to analyze the load of each sector, as well as to follow each unit existent in the process of simulation. There are attributes of information (type, assortment etc.) added to the unit equivalent to 1m**3 of wood resources. These attributes can provide information about the unit flow within any part of the process.

Area of grey alder stands is 190.6 thousand ha that is 6.8% of the total area of forests in Latvia with average volume 31.3 million m**3 4.9% of total yield is in the state forests, but 95.1% in the forests of other managers. Scientific literature affirms that grey alder is easy growing trees species. Its stands are quick - growing and wood has high heating capacity. Empirical data in 1 - 10 years old stands are collected from 25 m2 sample plots, 15 in each stand. Data from older (11 - 30 years) stands are obtained by 6 - trees - sample - plot method, from 180 trees in each stand. Number of trees (y) in the stands diminishes with age (x) that is characterized by regression equation y = 72534xE-1.1488. The division of the number of trees in diameter classes characterizes distribution of trees diameters in stands and trees differentiation processes within the stands. At the age of 1 - 5 years, grey alder stems were in diameter classes under 2 cm but at the age 6 - 10 years - 2 and 4 cm. In 11 - 15 years old stands 89% of all the measured trees are included in four (4 - 10 cm) diameter classes. It pointed to growing differentiation of diameters of the trees. Starting from age 16 - 20 years, 76 - 89% of the trees were of four to five diameter classes (10 - 18 cm). The average standing volume in 11 and 15 year old stands was 110 m3 haE-1 and it increased step by step to 180 m3 haE-1 in the stands of age 26 - 30 years. The basal area in the age of 15 - 30 years varied between 20 - 26 m2 haE-1. The average diameter reached 15 cm in stands of 25 -30 years.

The manufacturers of wood-based panels are interested to get easy and cheap method for determination of characteristic values of panels. The correlation between European standards EN 789 and EN 310 tests results can be used as an alternative procedure for determination of characteristic values of bending properties. The correlations between two results of bending properties determined by testing methods of European standards EN 789 and EN 310 are studied in this paper. The ratio of EN 789 test results divided with EN 310 test results (ratio of EN 789/EN 310), depending on panel thickness and glue type, was examined. Samples from 846 panels of birch (Betula sp.) plywood with thickness ranging from 6.5 to 30 mm and two glue types - phenol formaldehyde and melamine urea formaldehyde resin - were used for verification of the correlations. The results show that the panel thickness influences the ratio of EN 789/EN 310 and the highest ratio were found between 12 and 15 mm panels. When the panel thickness is increased or decreased, the ratio of EN 789/EN 310 decreases significantly. The regression equations for each thickness of plywood are presented. The difference between plywood glued with phenol formaldehyde and melamine urea formaldehyde resin glues was not found.

The study focuses on protected landscape aesthetic quality assessment where the main problem is how to associate aesthetical and ecological approaches. High ecological quality does not often correlate with high landscape aesthetic quality, and this relationship may differ depending on specific ecosystem. The landscape aesthetic quality assessment historically developed on two approaches. One of them - expert approach, which has dominated in landscape planning and management practice, and the second - perception approach, which has dominated in research. In protected landscape aesthetic quality assessment traditional approaches will be revised by ecology and green philosophy aspects. The study example regards important natural and protected areas around river Lielupe - from Jelgava city to Kalnciems. This is the landscape with high heritage, natural, biological values and it is also living, recreation place for people. Therefore, cooperation between aesthetic and ecological approaches in landscape assessment is needed. The outdoor investigations were carried out in autumn 2006. There were photographs and video materials on the first stage of investigation. In the second part aesthetic quality of views was analyzed with expert approach. There were three main groups of evaluation criteria of protected landscape aesthetic quality. These covered design and compositional outlines - features, their quality and relationship among these features. The results showed that not all criteria are suitable and effective for evaluation of protected landscape aesthetic quality because of restriction of specific ecological conditions.

Highly polluted wastewater is formed on private farms. The wastewater contains Ntotal and Ptotal concentrations up to 150 mg lE-1 and 30 mg lE-1 respectively, which is 2-3 times higher than that contained in domestic wastewater. During the biological treatment of wastewater the removal of organic pollutants (BOD5- biochemical oxygen demand, and SS - suspended solids) is about 96% and the treatment efficiency satisfies the environment protection standards. However, the removal of biogenic pollutants is only 55%, thus the residual pollution with biogenic substances exceeds the maximum allowable rate according to Ntotal and Ptotal for wastewater released into the environment. Currently, different natural and artificial powdery mineral materials (zeolite, filtralite, etc.) containing metals and carbon compounds are transported into Lithuania. Such materials could be used as Ntotal and Ptotal adsorbing filters. In respect of the filter load with pollutants, biologically pre-treated wastewater treatment efficiency of Ntotal and Ptotal was determined to be from 50 to 91% and from 49 to 90% respectively. Having filtrated to the wastewater through a filter containing 50% of zeolite and 50% of filtralite, Ntotal and Ptotal removal efficiency was fluctuating from 28 to 60% and from 23 to 70% respectively. Having made the investigations with different loads of minerals, it was determined that N removal is more efficient in the zeolite mineral filter, while P removal is more efficient in the filtralite filter. In order to reach the best results of biogenic pollution removal, both mineral mixtures should be used for the load of the filter.

The objective of the present studies has been to estimate peculiarities of nitrogen removal in constructed wetlands of different construction. In limited companies (LTD) 'Pastoge' and 'Nikola', constructed wetlands of vertical flow (VFCW) are arranged, while limited company (LTD) 'Agaras' has two-stage constructed wetlands of horizontal flow (HFCW). In all the objects the supplied wastewater is after primary treatment. Having compared the efficiency of ammonium and nitrite nitrogen removal in two types of constructed wetlands (VFCW and HFCW) it was determined that larger amounts of total nitrogen are removed in HFCW (38.1%) rather than in VFCW (24.4%). However, in VFCW smaller amounts of ammonium and nitrite nitrogen are discharged with wastewater. No significant effect of the fluctuations of ambient temperature on the removal of ammonium and nitrite nitrogen was observed in HFCW (difference in average values of cold and warm periods was 3-8%). A rather reliable relation (R2 = 0:738) was determined between ammonium nitrogen concentrations in wastewater outflow and HFCW load according to total nitrogen, however, ammonium nitrogen amounts in treated wastewater (when filter load according to total nitrogen is 0.3 to 4.6 g mE-2 dE-1) exceeded the maximum allowable concentration (MAC) and were fluctuating from 6 to 32 mg lE-1.

The objective of the present studies has been to estimate wastewater treatment efficiency of surface-flow wetlands for finishing treatment of secondary effluent. The studies have been carried out within the reconstructed wastewater treatment facilities in Babenai (Kedainiai district, Lithuania), where, after the initial wastewater treatment in the septic tanks and biological ponds, a plant filter has been set for finishing the wastewater treatment. The removal efficiency of the main pollutants in the filter like BOD5, suspended solids, total N (nitrogen), and total P (phosphorus) has become the focus of the analysis as well. Wastewater treatment efficiency analysis was done on base measurements taken in all seasons of the year within the period 2003-2006. Surface-flow wetlands are characterised by good removal efficiency of the organic pollutants. At the average load of the examined plant filter - 0.9 mg O2 lE-1 BOD5 (biochemical oxygen demand), the removal efficiency reached up to 61.2%. Low winter temperatures reduce the rate of removal for BOD and the biological reactions responsible for nitrification and denitrification. During the warm period of the year, the treatment efficiency of BOD5 was 70.8%, and during the cold one - 52.4%. However, the total N constituted up to 16.7% and 9.7% respectively. Due to the anoxic and anaerobic conditions in the filter, wastewater after the treatment on average contains 66.0% of ammonium nitrogen of the total N concentration. After a year, with the growth of plants the phosphorus removal efficiency improved and at the average load of the examined plant filter according to P 0.063 g mE-2 dE-1, on average 0.018 g mE-2 dE-1 of the total P was removed, i.e., the removal efficiency constituted 28.6%.

The paper presents the study material and analysis of the distribution of woody vegetation of regulated streams in southeast Lithuania. The studies were carried out in 110 randomly selected slope strips of regulated streams in the Neris River basin in the Baltic Highland within the period of 2005 to 2006. During the studies 32 species of woody vegetation were found, from which 14 species of trees and 18 species of bushes. In regulated streams different species of willows are most common. However their distribution on channel slopes is different. For most species of woody vegetation the conditions are most favourable in the lower and middle part of slopes. Here their density is highest (0.34 +- 0.89 and 0.73 +- 0.139 units mE-2 respectively), the frequency is 0.56 and 0.64 respectively. As it was determined, the frequency of woody vegetation on slope strips of regulated streams is na = 0:61. On the slope the lower overgrowth limit of woody vegetation is ra = 1:58 +- 0:16 m, the upper limit is rv = 4:13 +- 0:22 m. In southeast Lithuania, in discharge network of drainage systems there are more possibilities for planning of ecological means, when trees and bushes are allowed to grow on slopes.

The paper deals with statistic analysis of the relation between variables of cultural heritage and that of regional development in Latgale region. Latgale was selected as the study area - it is one of the five cultural or historical ethnographic regions of Latvia with stable original features, which are formed in the result of the specific historical processes but stands out among other regions of Latvia with the lowest indicators of development. According to the results of analysis of correlation, the number of architectural and archaeological monuments per 1000 people or their density in area have no close correlation with the major part of the parameters under examination. The analysis of regression was carried out between 'the number of architectural monuments against the area', and 'the natural logarithm from the density of population in 2005'. The ratio is expressed by the function y = 0.0339x**2 - 0.1422x + 0.1671, where y is the number of architectural monuments per square kilometre, but x - natural logarithm from the density of population (the number of people per square kilometre). The coefficient of determination for this relation is almost the same as for a functional one - 0.9499. Both for the coefficients of the equation and free member of equation have very high validity (t - empirical respectively 21.7; -11.1; 7.9).