The genesis of geotropic curvatures in the natural habitat of Sphagnum mosses is described in detail on the basis of in situ observations. A novel method of estimation of length increment of Sphagna shoots is developed, based on their geotropic curvatures, which are the markers of physical impacts. The snow load in northern areas is an example of the most typical impact on Sphagnum cover and further geotropic response of stems. Deviation in stem growth causes the curves which may form after snowmelt or under the snow layer. First attempt to use the snow induced markers, named further as "nival geotropic curvatures", for estimation of shoot increment rate of Sphagna stems were made in the late 20th century. However, first researchers ignored other than snow cover common factors that are responsible for the formation of similar markers during the growing season. Therefore, measuring increment from these markers may result in incorrect estimation, because they could be formed neither due to the snow load nor the beginning of the growing season. Our method takes into account these shortcomings. Several Sphagnum species were involved in the research for experimental comparison of the novel method with the classical tied thread method. Experimental plots were studied during a two-year period on Karelian mires. The length increment values obtained by both methods show some differences. Shoot increment values obtained by the method of the nival geotropic curvatures markedly exceed values obtained by the classical tied thread method in all cases. The difference ranged from 7.5 to 18.6 % in 2014 and from 20.8 to 45.8 % in 2015. The results could be explained by the negative effect of the tied thread method on the growth of moss, that was described in the literature. The coefficients of variation estimated by the method of nival curvatures are reliably lower than those obtained by the tied thread method for practically all samples. In 2014, mean value of the coefficients of variation were 20.3±4.2 % for samples obtained by tied thread method and 13.0±4.7 % for samples obtained by nival geotropic curvatures method. In 2015, the coefficients of variation were estimated at 21.1±5.3 % and 8.7±2.2 %, respectively.The differences are assumed to be due to the difference in the degree of impact on the structure of Sphagnum cover. РезюмеНа основании наблюдений in situ детально описан генезис геотропических изгибов стеблей в естественной среде обитания сфагнов. Разработан новый метод определения прироста побегов сфагновых мхов, в основу которого положено использование геотропических изгибов, образующихся в результате внешних физических воздействий. Снеговая нагрузка, характерная для северных регионов -пример наиболее типичного физического воздействия, вызывающего геотропическую реакцию побегов. Отклонение растущих побегов вызывает образование изгибов после снеготаяния или под снежным покровом. Первые попытки использования вызываемых действием снега маркеров (называемых нами в дальнейшем «нивальные геотропические изгибы») на ...

Linear increment of Sphagnum majus, S. fallax, S. balticum, S. obtusum, and S. subsecundum was examined in 2001-2010. The study was carried out in the mid-taiga subzone, in Koivu-Lambasuo mire conservation area (61° 48' N and 33° 35' E), Karelia, Russia. The greatest linear increment was observed for all of the Sphagnum mosses studied during favorable vegetation periods with warm spring and warm, humid summer. The growing seasons in 2002 and 2010 showed a significant decrease in growth for S. balticum, S. fallax and S. obtusum. Such a decline is likely to result from dehydration of moss capitula. Резюме Линейный прирост Sphagnum majus, S. fallax, S. balticum, S. obtusum, S. subsecundum изучался в период 2001-2010 гг. в подзоне средней тайги на территории болотного заказника Койву-Ламбасуо (61° 48' с.ш. и 33° 35' в.д.), республика Карелия, Россия. Наибольший линейный прирост отмечен у всех исследуемых сфагновых мхов в благоприятные вегетационные периоды с теплой весной и теплым влажным летом. В вегетационные периоды 2002 и 2010 г.г. наблюдалось значительное снижение прироста S. balticum, S. fallax, S. obtusum. Вероятно, это произошло в результате обезвоживания головок мха.

No abstract

No abstract

The dynamics of valuation characteristics and formation of a herb-sphagnum spruce stand during 30 years after site drainage and a clearcut with understory and polewood retention were studied. Growing stock increment was the highest (9,3 m 3 /ha per year) in the third decade, which is typical of a bilberry spruce stand of quality class I growing on mineral soils in Karelia. Thirty years after the harvest the stand's total growing stock was fully regenerated. The shares of largeand medium-size timber increased by 30% compared to their stock before the harvest. Drainage and thinning improved the conditions for understory growth and its more intensive recruitment in the commercial stock. The number of spruce trunks increased 2,3-fold 30 years after the harvest, now being more than 1000 per ha, which is sufficiently high for a high-productivity spruce stand to form on drained land. During the first three years after thinning, die-back in spruce stands on peat soils accelerated (106 trees per 1 ha). After that, as the plants grew adapted to the new situation, die-back steadied out at the level typical of undisturbed forest. Conversion cuts in birch-spruce stands have doubled their productivity, and all of the added max current increment (8,8 m 3 /ha per year) was in the most valuable spruce component of the stand. By the end of the 30-year period the stock has fully regenerated, and rose to 205% of the pre-harvest size. Up to 53% of total stock accrual happens owing to the understory. The rate of understory recruitment is higher than the rate of die-back, proving the drained spruce and birch-spruce stands are resilient against thinning.