In the study the growth and stem quality characters of geographically different Latvian Scots pine (Pinus sylvestris L.) populations were evaluated. In various regions of Latvia proportionally to the distribution of Scots pine 21 sample plot was established in 85 to 95 years old pure stands in forest type Myrtillosa growing conditions. In every sample plot 100 trees were evaluated estimating height of the tree, diameter at breast height, stem volume, length and quality of the branch-free stem section, relative branch thickness, branch angle and stem straightness. Pine populations were compared in different seed zones (Western and Eastern), as well as in various regions (Western, Central, South-eastern, North-eastern). In order to describe the geographical differences of populations with help of growth features, tree height was chosen because the relation between height and stem quality features is positive. The populations of the Eastern seed zone substantially overcome the populations of the Western seed zone both in terms of growth features, as well as in stem quality. Substantial are also differences between populations growing in various regions in terms of average height, length and quality of branch-free stem section, relative branch thickness and branch angle, but not stem straightness. Western populations present the lowest growth feature values and stem quality. The height and stem quality features of the North-eastern populations considerably exceeded the features of other regions' populations.

The productivity and quality of different origin Scots pine (Pinus sylvestris L.) progenies at the age of 43 were estimated. The investigation was carried out in 1964. The seeds from six stands growing on mineral and peaty soils in different environmental conditions were sowed. The thinning was done in 2006. The following growth and quality characters were investigated: height of the trees, diameter at breast height, stem volume, standing volume, branch free tree length, branch thickness, branch angle, stem’s straightness. The growth and quality differences of the progenies depending on the seed origin were estimated. The environmental conditions of the Zvirgzde origin place and the test locality were similar. The progeny of the Zvirgzde stand showed superiority in the growth traits (height, diameter, stem volume) as well as good stem quality and high quality of the assortment outcome in thinning. The progeny of the swamp stand (Tireli) had low values in all investigated traits. A significant influence of the environmental conditions of the seeds origin place on the growth and quality of the progeny was found out. Environmental conditions of seeds origin locality and place of forest regeneration have to be similar to avoid decrease of progeny stand’s growth and quality.

This paper discusses the usability of non-parametric knn (k-nearest neighbour) method to detect changes in forest areas from satellite images. Spot Xi images acquired 1999, main forest characteristics from field measured sample plots and data of conventional stand-wise forest inventory from the year 1988 were used to estimate the grids of following forest characteristics: mean age of main forest storey, diameter, basal area, height, volume per 1 ha, as well as the percentages of coniferous, soft and hard deciduous tree species. The differences of grids, created using stand-wise forest attributes from the 1988 inventory and estimated using the k-nearest neighbour methods were experimented to detect changes in the forest. 68.7-75.5% of areas, classified as the potential felling areas, were detected to be clear cut areas or young stands less than 15 years according to the data of stand-wise inventory of year 2003. Different settings for the methods investigated are evaluated, too.

Climatic changes are shifting the potential tree distribution limits of many tree species northwards. One of such species is Fagus sylvatica, currently represented in Latvia only by a few stands. In order to increase knowledge on its potential use in the forest management, the aim of our study was to characterize the growth of beech in a young stand in the central part of Latvia. The stand of beech and spruce, mixed in rows with an initial spacing of 2.5 x 2.5 m in Oxalidosa forest type was assessed. Survival of European beech in clear cutting was similar to that observed for the native Norway spruce (73% and 79%, respectively), but both height and diameter were notably and significantly superior for wildlings at the mean age of 15 ± 2 years, reaching on average 7.4 ± 0.30 m and 8.9 ± 0.69 cm, respectively. Increasing ring width with increasing tree age for both tree species was observed until the last four years, when large and increasing superiority of beech over spruce, coinciding with reduction of ring width of spruce, was noted. It was most likely caused by intensified competition due to very wide crowns formed by young beech trees in the plantation with wide spacing: average crown radius reached 2.4 ± 0.16 m, for few trees exceeding even 4 m.

Icing notably increases the mass of a tree crown, causing damage to the tree. So far, a very limited number of studies have assessed the icing influence on coniferous trees, none of them in Latvia. The aim of the study was to assess the influence of tree parameters and recent thinning on the proportion of damaged trees and the type of damage in Scots pine stands. The study sites were located in the eastern part of Latvia, damaged in December 2012. In total, 98 pine dominated stands of different age were selected randomly. Eight (mean) plots per stand were established; in each plot, all trees larger than 2.1 cm were measured and the type of damage assessed. The above-ground biomass from 12 randomly selected stands (57 dominant trees) of different age was weighted with and without icing. The biomass of pine with icing exceeded that without 1.5 ± 0.27 times. The mean proportion of damaged trees in pine dominated stands was 26%; the proportion of broken trees peaked in the middle-aged stands (41 – 70 years old), but the largest proportion of pooled bent and uprooted trees was found in the young (11 – 20 years old) stands. The proportion of damaged dominant trees was affected by the slenderness coefficient – a higher proportion of such trees was found among more slender trees. The results suggest that the risk of icing damage could be reduced by silvicultural measures boosting individual tree stability.

Tree roots take up a high proportion of forest biomass, and nowadays we use different methods to estimate the root biomass. Methods vary greatly due to the different studies and different excavation methods used. In the summer 2010, a study of the below-ground biomass of young Scots pine Pinus sylvestris L. stands was carried out in central Latvia. In this paper, different below-ground biomass fractions data of 10 sample trees from the abandoned agricultural land plantations were approximated by allometric functions depending on tree stem diameter at breast height 1.3 m (DBH). The main objective was to determine the average below-ground biomass and approximated below-ground biomass fractions by allometric functions depending on tree DBH of young stands of Scots pine on abandoned agricultural land. Our regressions offer good overall approximations of the data. DBH – stump, coarse root and small root and total biomass regressions were highly significant (p is less than 0.001). The most substantial part of total below-ground biomass was from stumps (45%). The smallest shares of the biomass were coarse roots 38% and small roots 16%. The largest portion (52%) of the total fine-root biomass of 12- and 14-year-old Scots pine stands was located at a depth of 0–10 cm, decreasing in deeper mineral soil layers. Total dry (DM) below-ground biomass including fine-root biomass was 19.0 ±5.2 t DM ha-E1.

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.

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.

Forest fires in Latvia occur every year. Research about vegetation and forest regeneration after forest fire is being carried out in Latvia, and sanitary conditions are being evaluated too; however, there are no large studies about the forest fire impact on radial growth dynamics of trees. The aim of the study was to analyse and compare the response reaction of a forest stand after fire in two forest site types – Hylocomiosa and Vacciniosa turf. mel. The object of the research was fire affected middle–aged managed Scots pine (Pinus sylvestris L.) stands in the aforementioned forest site types. The study compares radial growth dynamics of trees, tree mortality and forest stand sanitary conditions after fire in Hylocomiosa and Vacciniosa turf. mel. The observed fire impact on radial growth dynamics of trees was negative in both forest site types. Negative fire impact on sanitary conditions was observed, too.

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.