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.

Considering specific role of forest in carbon cycling, the scope of the study is evaluation of assimilation of carbon dioxide in a single grey alder stand. The National statistical forest inventory demonstrates that total area of afforested farmlands is 314 thousands of ha, including 212 thousands of ha are grey alder stands. Empiric data are collected in 2011 in 15 years old grey alder stand representing Aegopodiosa site type, site index II. Dendrometric characteristic of the stand are estimated using a method of 6 sample tree plots. Average height of dominant trees is 9.6 ± 0.14 m, diameter at breast height - 6.7 ± 0.18 cm, volume of stem - 0.02002 ± 0.00673 m3, number of trees per ha – 5806 ± 560, growing stock - 116.2 ± 20.0 m3 haE-1. Density of the grey alder stem wood is 411.0 ± 2.2 kg mE-3, average relative moisture - 51.6 ± 0.13%. Dry biomass of grey alder in the evaluated stand is 73.4 tons haE-1, including stem biomass - 65.3%, branches - 11.1%, leaves - 2.3%, stump - 6.8% and roots - 14.6%. In average evaluated stands accumulated 36.9 tons haE-1 of carbon removing from atmosphere 135.5 t ha-1 of CO2. Wood density is estimated according to ISO 3131:1975 standard, moisture content – according to EN13183-1:2002 standard.