In response to the decline of Central European spruce monocultures driven by various factors, the Demonstration Object of Reconstruction of Spruce Forests (DORS) was established in Hus & aacute;rik locality, Javorn & iacute;ky Mts., northwestern Slovakia. The area includes the Hus & aacute;rik trial site, where the applicability and efficiency of different artificial regeneration methods are studied. The trial was established on a 24-ha area cleared following the outbreak of spruce bark beetles in 2011. Its altitude is 800 m a.s.l., aspect NW, slope 30%, the soil is Ranker on the soft flysch sandstone bedrock. Our study covered 4 conifers - Norway spruce (spruce), European larch (larch), silver fir (fir), and Douglas fir (doug fir). Each species was regenerated using 4 different approaches: planting of commercial bareroot transplants (BR), planting of container transplants (CON), direct seeding (DS) and vegetative cell seeding using seed shelters (VCS). Results concerning the nine-year development of transplants and seedlings, along with the calculation of cost-efficiency, are presented. As to the species, BR and CON transplants of spruce and larch reached the best survival and height. The DS larch was the most cost-efficient method of establishment of a successfully established plantation (survival > 50%; stem height > 2/3 of the weed height; ratio of damaged individuals < 50%) with a total cost of 2 372 EURha(-1). On the contrary, the slow initial growth of fir and Douglas fir and their extensive damage resulted in the incomparably higher cost of establishment of their successfully established plantation, such as 4 980 EURha(-1) for five-years-old BR fir transplants. Our findings documented that current efforts related to the restoration of salvage-felled clearings remained difficult, especially in the case of introduction or reestablishment of coniferous tree species more vulnerable to open site conditions.

Recent climatic changes significantly affected forest ecosystems in northern Eurasia. Trees growing in Siberia are very sensitive to climate change due to strong temperature limitation of their growth. Our study covers high-latitude (northeastern Yakutia, eastern Taimyr, central Evenkia) and high-altitude (Russian Altai) zones in Eurasia, where tree-ring parameters (tree-ring width, cell-wall thickness, and maximum latewood density) mainly record summer air temperature variations. To reveal the impact of moisture changes (e.g., amount of precipitation, vapor pressure deficit, relative humidity and potential evapotranspiration) on tree growth in Siberian forest ecosystems, we evaluated delta C-13 in tree-ring cellulose over the past century. We found that at all the study sites mainly June-July precipitation and June-July evapotranspiration affect larch radial growth, while the strongest influence of vapor pressure deficit on the delta C-13 was observed in northeastern Yakutia. Further increase of vapor pressure deficit and rise of air temperature in the coming decades in Siberian regions will probably lead to drought and related forest mortality even under additional source of water due to permafrost thaw.

The boreal forest accounts for approximately 22% of the Northern Hemisphere landmass with nearly 40% of this huge biome growing on continuously frozen soils. Projected climate change leading to degradation of permafrost and increasing drought situation at high latitudes in Eurasia will seriously affect productivity of forests on permafrost. Here we present the results of an on-going research of tree radial growth in the midst of the permafrost zone in Siberia, Russia (Tura region, 64 degrees N, 100 degrees E, 140-610 m a.s.1.). Tree-ring width and density chronologies of Gmelin larch and Siberian spruce from a great variety of sites characterized by different thermo-hydrological regime of soils are analyzed. The obtained results reveal that current tree radial growth and tree-ring structure in permafrost region in Siberia are largely dependent on local site conditions and may be constrained by low air and soil temperatures as well as soil water availability. Varying climatic responses and seasonal radial growth of trees at different habitats indicate a range of possible scenarios of further development of northern larch stands. Forest fire is another important factor strongly affecting tree stand dynamics and forest ecosystem functioning in the continuous permafrost zone. Analysis of tree-ring parameters indicate that post-fire dynamics of tree-ring structure is in accordance with the changes in habitat conditions caused by removal by fire and then gradual recovery of ground vegetation resulting in an alteration in soil active layer depth. In general, the results of this multi-proxy analysis for trees growing under various conditions in the continuous permafrost zone in Siberia allow assumptions about changes in tree productivity, stand dynamics and therefore carbon uptake under projected climate change and permafrost degradation.