Fast-growing hybrid aspen clones are recommended for establishment of plantation on abandoned agriculture land in Northern Europe. In this study we assessed the productivity, quality and assortment structure of hybrid aspen clones at final felling. Data were collected during the hybrid aspen clonal experiment conducted in the central part of Latvia. Large variation in the productivity level between different clones was affected by growth and survival. From the compared 5 most and least productive clones, based on the yield m**3 haE-1, the faster growing clones have about 17% better survival rate at age 10. Also, the mean annual increment (MAI) differed notably and significantly (p is less than 0.05, α = 0.05) between hybrid aspen clones at the age of 18 years ranging from 7 to 34 m**3 haE-1 yearE-1. Theoretical assortment structure of hybrid aspen at the age of 18 years was the following: 43 ± 4.86% of small dimension saw logs (SDS logs), 21 ± 4.86% high quality saw logs (HQS logs), 18 ± 4.33% pulpwood, 4 ± 0.77% firewood and 13 ± 0.08% of logging residues (tops). The outcome of HQS logs on average is more than 30% from the 5 best clones and further increase can be predicted with age. Stem volume (H2 = 0.32), height (H2 = 0.47) and quality parameters (stem straightness - H2 = 0.73, branch angle - H2 = 0.60) had a high heritability and large differences between clones, indicating notable possibilities to improve the productivity of plantations via selection of the best-growing genetic material.

Economic importance of Silver birch in Latvia has been increasing in last decade, triggering scientific research, dedicated to improvement of this species, including tree breeding. Bulk of progeny trials will reach the evaluation time in next few years; therefore, decisions for further tree breeding activities have to be made. The aim of our study is to evaluate profitability of silver birch breeding, based on current situation in the year 2010 and circumstances in Latvia and assess the factors that might notably influence the result. Analysis considers all available breeding material and links between tree breeding, seed orchards and end product – forest stand, regenerated with improved plants in order to evaluate profitability of different alternatives based on differential approach. Results reveal that differential benefits from forest regeneration with selected birch material in comparison to natural regeneration, in areas with highest site indexes (Ia-II) with 3% interest rate and at least part of the stands managed in order to maximize yield of large diameter trees at age of final felling, are positive. The highest profitability can be reached if selection of best individuals is done based on clonal testing, genetic gain is maximized and combined with proper silvicultural praxis and annual planting area (utilization of seeds from selected trees) are maximized.

It is essential to have information on the tree biomass due to the fact that it is an important ecosystem pool for reporting changes in carbon stocks of forests and increased attempts to diversify the energy sources. In Latvia, comparatively few studies have focused on this topic so far. Our study was conducted on two 36 - 38 years old Norway spruce plantations. Detailed stem analysis of 39 trees was performed, and biomass of the above-ground tree components was determined. We analyzed tree and clone-level biomass distribution, biomass relations with tree dimensions and dependence on the genetic factors. The mean total biomass (kg d.w.) of all analyzed sample trees was 131.4 ± 10.58 kg, the mean biomass of stem 85.9 ± 6.98 kg, the mean biomass of dead branches 8.3 ± 0.82 kg, the mean biomass of living branches 23.5 ± 2.34 kg and the mean biomass of needles 13.7 ± 1.22 kg. On average, 66.1% of biomass was allocated to the stem, 6.4% to the dead branches, 17.4% to the living branches and 10.1% to the needles. The biomass of the analyzed trees positively correlated with all tested tree parameters - DBH, tree height, stem volume. Typically, with increasing tree parameters total biomass and stem biomass increased rapidly but branch and needle biomass increased slowly. Significant differences of tree dimensions were detected between the clones, and the differences in total biomass and stem biomass were clearly correlated with the differences in tree dimensions over clones. No significant impact of the clone was found specifically on the tree biomass or its distribution.

Oregano (Origanum vulgare L.) is one of the most popular spice and medicinal plants of untraditional horticulture in Latvia. Wild populations of this plant are too few. That is why it is necessary to cultivate oregano for keeping the biodiversity of Latvian nature. It is important to use local oregano genetic resources in agrocenosis as well as to get as rich and qualitative yield as possible. The aim of this research was to explore the parameters of oregano inflorescence in Latvia and to recommend the most productive clones for cultivation. In summer 2011, a total of 45 oregano clones from an ex situ collection of spice and medicinal plants of the Laboratory of Cultivated Plants and Apilogy (Jelgava, Strazdu Street 1) were analysed. Such inflorescence parameters as length and width were explored. The average length of inflorescence of all clones was 17.99 cm, and the average width was 5.74 cm. The results showed that the clone No 26 had the largest width of inflorescence (9.6 cm), but the clone No. 2 had the largest length of inflorescence (31.1 cm). Using oregano Draft Descriptor List, the inflorescence was characterized as short, medium or long. The variability between clones was significant (p is less than 0.05), but between samples of each clone - non-significant (p is greater than 0.05). It is recommended to grow oregano clones No. 2, 5 and 26 in agrocenosis as the most productive.