ISSN 1239-6095 (print),   ISSN 1797-2469 (online)
© Boreal Environment Research 2015

Contents of Volume 20 no. 5

Jiroušek M., Tůma I., Záhora J., Holub P., Kintrová K. & Hájek M. 2015: Decomposition patterns, nutrient availability, species identities and vegetation changes in central-European summit bogs. Boreal Env. Res. 20: 571–586.
Abstract
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Vuorio K., Järvinen M., Moilanen S., Kotamäki N. & Bilaletdin Ä. 2015: Water level regulation in winter triggers fouling of fishing nets by the diatom Aulacoseira islandica in a boreal lake. Boreal Env. Res. 20: 587–602.
Abstract
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Remm L., Lõhmus A. & Rannap R. 2015: Temporary and small waterbodies in human-impacted forests: an assessment in Estonia. Boreal Env. Res. 20: 603–619.
Abstract
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Chumanová-Vávrová E., Cudlín O. & Cudlín P. 2015: Spatial and temporal patterns of ground vegetation dominants in mountain spruce forests damaged by sulphur air pollution (Giant Mountains, Czech Republic). Boreal Env. Res. 20: 620–636.
Abstract
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Pumpanen J., Kulmala L., Lindén A., Kolari P., Nikinmaa E. & Hari P. 2015: Seasonal dynamics of autotrophic respiration in boreal forest soil estimated by continuous chamber measurements. Boreal Env. Res. 20: 637–650.
Abstract
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Mäkinen H., Niva T., Koljonen M.-L., Swatdipong A. & Primmer C.R. 2015: Temporal variation in lake-run brown trout (Salmo trutta) mixed-stock fishery catches in a large Fennoscandian lake. Boreal Env. Res. 20: 651–665.
Abstract
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Jiroušek M., Tůma I., Záhora J., Holub P., Kintrová K. & Hájek M. 2015: Decomposition patterns, nutrient availability, species identities and vegetation changes in central-European summit bogs. Boreal Env. Res. 20: 571–586.

The global increase in atmospheric nitrogen deposition leads to changes in decomposition activity, which has been observed especially in nutrient-limited bog ecosystems relying on atmospheric inputs as the sole source of external nutrients. We conducted a reciprocal transplant decomposition experiment in two bogs in central Europe to test the effects of Sphagnum species (S. fallax, S. magellanicum, S. rubellum/russowii, cellulose strips as controls), material origin and the environment on Sphagnum decomposition and related nutrient release. Cellulose, but not Sphagnum biomass, decomposed more rapidly in the warmer and nitrogen-richer conditions of the suboceanic Jizera Mts. than in the subcontinental Jeseníky Mts. In the Sphagnum biomass transplants, interspecific differences in decomposition overruled the effects of both the origin of the material and the environment of the decomposition site, with S. magellanicum decomposing the slowest. Possible relationships between decomposition rates and recent changes in Sphagnum species composition in N-polluted bogs are discussed.
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Vuorio K., Järvinen M., Moilanen S., Kotamäki N. & Bilaletdin Ä. 2015: Water level regulation in winter triggers fouling of fishing nets by the diatom Aulacoseira islandica in a boreal lake. Boreal Env. Res. 20: 587–602.

Water level regulation related to hydroelectric power production and flood prevention is an important hydro-morphological pressure on many watercourses around the world. Fouling of fishing nets in autumn during the open water period and in winter under the ice is a common phenomenon in large Finnish lakes where the water level is regulated. This fouling of fishing nets can sometimes be so extensive that fishing has to be stopped. Based on the practical experiences of fishermen, the main cause for the under-ice fouling has been proposed to be the winter draw-down of water causing low water level and stronger currents in lakes, but no conclusive relationship between fouling and water level regulation has yet been demonstrated. Here we show, using long-term winter data from a boreal lake and short-term netting experiments, that fouling of fishing nets results from increased water draw-down during winter (January–March). Our results also show that fouling of fishing nets takes place only if the high water flow rates are accompanied by an intensive lowering of the water level. We also discuss the relevance of our results to other regulated lakes with ice cover.
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Remm L., Lõhmus A. & Rannap R. 2015: Temporary and small waterbodies in human-impacted forests: an assessment in Estonia. Boreal Env. Res. 20: 603–619.

Temporary freshwater bodies are important as wildlife habitats and in biomass cycling, but their quantity and characteristics in relation to forest management are poorly documented. We surveyed small waterbodies in Estonian forest landscapes, along randomly placed transects in forests and non-forested fens. The area of natural puddles and floods varied by nearly two orders of magnitude among habitat types. The main effect of drainage and clear cutting was the conversion of waterbody types: natural ones were partly replaced by ditches and wheel-rut puddles, respectively. Using the common brown frog and the moor frog as indicator species revealed that anthropogenic changes are not necessarily detrimental: the frogs preferred to breed in anthropogenic waterbodies in open areas (i.e., clear cuts). Mitigation of forestry effects on the biota of temporary waterbodies should combine restoration (allowing flooding in selected areas; restoring streams) and compensatory measures (excavating ponds; retaining wheel-rut puddles in key sites).
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Chumanová-Vávrová E., Cudlín O. & Cudlín P. 2015: Spatial and temporal patterns of ground vegetation dominants in mountain spruce forests damaged by sulphur air pollution (Giant Mountains, Czech Republic). Boreal Env. Res. 20: 620–636.

We studied ground vegetation dynamics during the decline and recovery of mountain Norway spruce forests damaged by SO2 air pollution and associated stress factors. Changes in areal extent of the ground vegetation dominants, moss layer and spruce litter and trajectories of these changes, recorded at a spatial resolution of 5 x 5 cm, were analysed in 1-m2 squares located in plots differing in dynamics of spruce canopy cover. Spruce litter patches diminished during spruce stand decline being colonised by Avenella flexuosa, Calamagrostis villosa (in canopy gaps) and Vaccinium myrtillus (under gradually defoliating tree crowns). After several years of spatially dynamic coexistence of the grasses, C. villosa began to retreat being replaced by A. flexuosa. Vaccinium myrtillus then re-entered these grass stands. In less affected spruce stands, the dominants partially retreated without competing with other ground vegetation. Moreover, the applied GIS spatio-temporal analysis revealed substantial spatial movements of the dominants over the plots.
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Pumpanen J., Kulmala L., Lindén A., Kolari P., Nikinmaa E. & Hari P. 2015: Seasonal dynamics of autotrophic respiration in boreal forest soil estimated by continuous chamber measurements. Boreal Env. Res. 20: 637–650.

Soils contain a large C pool, but temporal changes in the pool size are difficult to determine. Root and rhizosphere respiration (Ra) is a major component of soil C-balance, but it cannot be measured continuously with conventional methods. Here, we present a novel method for determining the contribution of Ra. This novel method is based on temperature fitting of soil CO2 effluxes (F0) over long and short time intervals using continuous chamber measurements. We show the contribution of seasonal changes to Ra and to total soil CO2 efflux in a Scots pine forest in southern Finland. Ra contributed about 42% of the total soil CO2 efflux. The seasonally extremely variable contribution from 17% in early April to 60% in late July followed the seasonal pattern of the GPP. The contribution of Ra was 45% of the annual total GPP (1154 g C m–2) of the forest ecosystem. The increase in Ra lagged behind the increase in GPP by 18 days, and the peak in Ra was observed about six weeks after the highest values of daily GPP were attained, which reflected the changes in the seasonal pattern in above- and below ground-allocation of assimilated C.
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Mäkinen H., Niva T., Koljonen M.-L., Swatdipong A. & Primmer C.R. 2015: Temporal variation in lake-run brown trout (Salmo trutta) mixed-stock fishery catches in a large Fennoscandian lake. Boreal Env. Res. 20: 651–665.

Understanding the relative contributions of potential source populations to fishery catches is vital for proper management of harvested fish stocks. Little is known about the temporal variation in commercially important brown trout (Salmo trutta) catch in large boreal lakes. We estimated contributions of 34 putative source populations to the brown trout catch in two lakes, Inarijärvi and adjacent Paadarjärvi (northern Finland) during 2006–2011. Genetic stock identification indicated that there is considerable temporal variation in the catch proportions in Inarijärvi and they are mainly associated with different contributions of the tributaries of the Ivalojoki and Juutuanjoki. In Paadarjärvi, catch proportions were relatively constant during the sampling period. Our study demonstrated the importance of temporal sampling when estimating catch proportions for management purposes.
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