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As one of the most abundant tree species in the hemiboreal zone, birch is important from both commercial and biodiversity perspectives. While old-growth deciduous stands are important for biodiversity conservation with an emphasis on deadwood availability, the role that deadwood in these stands plays in carbon sequestration remains unclear. We studied mature (71–110 years old) and old-growth (121–150 years old) birch stands on fertile mineral soils. The marginal mean deadwood volume was 43.5 ± 6.4 m3 ha−1 in all mature stands, 51.3 ± 7.1 m3 ha−1 in recently unmanaged mature stands, and 54.4 ± 4.4 m3 ha−1 in old-growth stands; the marginal mean deadwood carbon pool for each stand type was 5.4 ± 0.8 t·ha−1, 6.3 ± 0.9 t·ha−1, and 7.9 ± 0.6 t·ha−1, respectively. Deadwood volume was not related to stand productivity in terms of stand basal area, stand height, or stand age. The difference between mature and old-growth stands remained non-significant (p < 0.05). A high volume of deadwood was almost continuously present throughout the landscape in assessed unmanaged sites; moreover, 88% of sample plots in old-growth stands and 63% of sample plots in mature stands had a deadwood volume higher than 20 m3·ha−1. Old-growth stands had a slightly greater volume of large deadwood than unmanaged mature stands; in both, almost half of the deadwood was more than 30 cm in diameter and approximately one-fifth had a diameter greater than 40 cm. Both groups of stands had similar proportions of coniferous and deciduous deadwood and lying and standing deadwood. Old-growth stands had a higher volume of recently and weakly decayed wood, indicating increased dieback during recent years.

Zeps, M., Senhofa, S., Zadina, M., Neimane, U., Jansons, A. 2017. Stem damages caused by heart rot and large poplar borer on hybrid and European aspen. -Forestry Studies | Metsanduslikud Uurimused 66, 21-26. ISSN 1406-9954. Journal homepage: http://mi.emu.ee/forestry.studies Abstract. Solid wood production of hybrid aspen requires relative longer rotation periods, thus increasing risk of wood damages by pests and diseases. We compared damages by heart rot and poplar borer of 48 years old hybrid (Populus tremuloides Michx. × P. tremula L.) and European aspen in a progeny trial located in Eastern part of Latvia. Trees were harvested and rot patches and galleries were recorded and measured at a stump level. The number of galleries had positive relation on number of patches and total area of rot. The susceptibility of the rot and poplar borer was similar for both hybrid and European aspen. Yet, some differences among families were detected. No effect of pathogens damage was observed on the tree growth. Larger trees had smaller proportion and incidence of rot and galleries per unit of area as well as wider outer rot-free wood layer.

Highlights• Hybrid poplar and hybrid aspen were sensitive to temperature in summer and dormant periods, but none of the tested factors were strictly limiting.• Hybrid poplar was sensitive to a higher number of climatic factors than hybrid aspen.• Temperature showed a negative correlation with tree-ring width. AbstractFast-growing hybrids of Populus L. have an increasing importance as a source of renewable energy and as industrial wood. Nevertheless, the long-term sensitivity of Populus hybrids to weather conditions and hence to possible climatic hazards in Northern Europe have been insufficiently studied, likely due to the limited age of the trees (short rotation). In this study, the climatic sensitivity of ca. 65-year-old hybrid poplars (Populus balsamifera L. × P. laurifolia Ledeb.), growing at two sites in the western part of Latvia, and ca. 55-year-old hybrid aspens (Populus tremuloides Michx. × P. tremula L.), growing in the eastern part of Latvia, have been studied using classical dendrochronological techniques. The high-frequency variation of tree-ring width (TRW) of hybrid poplar from both sites was similar, but it differed from hybrid aspen due to the diverse parental species and geographic location of the stands. Nevertheless, some common tendencies in TRW were observed for both hybrids. Climatic factors influencing TRW were generally similar for both hybrids, but their composition differed. The strength of climate-TRW relationships was similar, but the hybrid poplar was affected by a higher number of climatic factors. Hybrid poplar was sensitive to factors related to water deficit in late summer in the previous and current years. Hybrid aspen was sensitive to conditions in the year of formation of tree-ring. Both hybrids also displayed a reaction to temperature during the dormant period. The observed climate-growth relationships suggest that increasing temperatures might burden the radial growth of the studied hybrids of Populus.

Cracks expose wood to fungal infections that significantly affects wood quality, while rapid wound occlusion decreases probability of infections. Assessment of scars was done at four grade scale in three adjacent hybrid aspen trials at the age of 8-10 years in central part of Latvia three years after bark crack occurrence. Occluded wounds were found for 95% of damaged trees, regardless of tree age. Among trees that had cracks wider than 1 cm, 42% had uniformly healed bark, but 7% still had open wounds. Wound development was significantly affected by crack width and length (both p < 0.001), but had no clear relation with tree DBH (diameter at breast height) and relative DBH increment (both p > 0.05). At clonal mean level, scar grade was significantly affected by grade of crack three years earlier and clone (both p < 0.001), but mean DBH of clone had no relation (p > 0.05) to proportion of trees evaluated by any of the scar grades. The results suggest that three years after the bark crack formation most of them had successfully occluded and selection of clones with better diameter growth has no influence on development of cracks.

Highlights • Beech saplings growing in the central part of Latvia had ca. 80% survival during the recent three decades. • The dimensions of saplings varied greatly likely due to canopy conditions. • Some beech self-regeneration was observed. • Mainly saplings had narrow crowns. • The distribution of sapling dimensions had the reverse-J shape, suggesting successful development of beech.

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Post-disturbance salvage logging mitigates economic loss after windthrow, and the value of salvaged timber is strongly linked to its quality and dimensions. We studied the occurrence of wind-induced damage of aspen in the hemiboreal forests of Latvia based on data from the National Forest Inventory and additional measurements. Individual tree data from three re-measurement periods were linked to follow a tree condition (live, broken, uprooted) and to link tree characteristics to a respective snag. Three linear models were developed to assess factors affecting the snapping height. An assortment outcome was calculated for undamaged and salvaged trees using the bucking algorithm, and timber value was calculated at three price levels. Wind-induced damage occurred for 3.4–3.6% of aspen trees, and among these, 45.8–46.6% were broken. The mean height of the broken trees was 27.3 ± 0.9 m, and it was significantly higher (both p < 0.01) compared to the height of undamaged and uprooted trees. The tested models indicated tree height as the main explanatory variable for relative snapping height, with higher trees having a lower point of the stem breakage. The other significant factor was the forest type group, indicating that trees growing on dry mineral soils had lower relative snapping height than trees growing on drained mineral soils. Stem breakage significantly (p < 0.001) reduced the volume of assortments, as compared to the volume of undamaged trees. Relative volume loss of sawlogs showed a logarithmic trend with a steep increase up to snapping height of 6 m, and it correlated tightly (r = 0.83, p < 0.001) with relative value loss of the total stem. Timber value loss had a strong, positive relation to tree diameter at breast height and fluctuated by 0.4% among different price levels. The mean volume reduction was 37.7% for sawlogs, 11.0% for pallet blocks, and 8.9% for technological wood.