Bourtsoukidis, E., Bonn, B. & Noe, S. M. 2014: On-line field measurements of BVOC emissions from Norway spruce (Picea abies) at the hemiboreal SMEAR-Estonia site under autumn conditions. Boreal Env. Res. 19: 153–167.

We investigated biogenic volatile organic compound (BVOC) emissions from a Norway spruce (Picea abies) in a hemiboreal mixed forest in autumn. Measurements were performed at the SMEAR-Estonia forest station, using PTR-MS techniques and a dynamic branch enclosure system. Parallel to BVOC measurements, atmospheric (CO₂, CH₄, H₂O, CO) and meteorological (temperature, relative humidity, global radiation, wind speed, precipitation) parameters were monitored in the ambient atmosphere and inside the enclosure (temperature, relative humidity, ozone). Prior to the measuring period, a new inlet line consisting of 19.4 m of heated and isolated glass tube was constructed. The new inlet system allowed the on-line detection and calculation of sesquiterpene (SQT) emission rates for the first time for a hemiboreal forest site. In total, 12 atmospherically relevant BVOCs were continuously monitored during the measurement campaign and the emission rates of terpenoid species and predominant oxygenated VOCs were estimated, with monoterpenes to be emitted the most, followed by acetone, acetaldehyde and sesquiterpenes.

Chmara, R., Szmeja, J. & Banaś, K. 2014: Factors controlling the frequency and biomass of submerged vegetation in outwash lakes supplied with surface water or groundwater. Boreal Env. Res. 19: 168–180.

We analysed the frequency and biomass of submerged plants in 1490 samples taken from 10 lakes located in the same geological formation (outwash) and fed with surface water (1st lake group, n = 540 samples) or groundwater (2nd group, n = 950). In the first group, mosses were very frequent (mean ± SD = 90.0% ± 18.2%), while acidophilous vascular plants were less frequent (23.9% ± 32.5%) and their biomass was low. There was one dominant species: Sphagnum denticulatum. In the second group, calciphilous vascular plants and stoneworts were in the majority, with relatively higher frequencies (40.1% ± 25.2% and 59.7% ± 23.2%) and biomass (5.1 ± 6.5 and 13.8 ± 20.5 g DW 0.1 m^–2). In the lakes fed with surface water, water pH was the factor controlling the frequency of mosses and vascular plants. In the group of lakes supplied with groundwater, sediment conductivity and calcium governed the frequency of stoneworts. Moss biomass depended on conductivity, total phosphorus and calcium concentrations in the water, while stonewort biomass depended on sediment conductivity. For both types of water supply, submerged plant frequency and biomass in the lakes were controlled more strongly by non-nutrient than by nutrient factors.

Ge, Z. M., Kellomäki, S., Zhou, X. & Peltola, H. 2014: The role of climatic variability in controlling carbon and water budgets in a boreal Scots pine forest during ten growing seasons. Boreal Env. Res. 19: 181–194.

This study reports eddy-covariance measurements of carbon and water fluxes in a boreal Scots pine (Pinus sylvestris) forest during the 1999–2008 growing seasons. We found that gross primary productivity (GPP) was limited by low rainfall and low summer temperatures, whereas evapotranspiration (ETP) was limited by temperature and precipitation. GPP was less sensitive to increased ETP in the years with little rainfall than in the years with abundant rainfall. During low-rainfall years with long-lasting drought periods and few rainy days (2000 and 2003), GPP was reduced, whereas during the low-rainfall year (2006) with evenly distributed seasonal precipitation it remained at the same level as that during the abundant-rainfall years. Ecosystem water-use efficiency (WUE) was found to be sensitive to increased ETP and vapour-pressure deficits. However, there was no difference between abundant- and low-rainfall years in the responses of WUE to climatic and edaphic variables, most likely due to the coupled feedback of the carbon and water cycles to drought. This study suggested that combined frequency (also seasonality) of precipitation and total amount of rainfall are needed to better evaluate the feedback of carbon and water budgets in boreal forests to drought, especially under expected climate change.

Robroek, B. J. M., Wubs, E. R. J., Martí, M., Zając, K., Andersen, J. P., Andersson, A., Börjesson, G., Bragazza, L., Dise, N. B., Keuskamp, J. A., Larsson, M., Lindgren, P.-E., Mattiasson, P., Solomonsson, J., Sundberg, C., Svensson, B. H. & Verhoeven, J. T. A. 2014: Microclimatological consequences for plant and microbial composition in Sphagnum-dominated peatlands. Boreal Env. Res. 19: 195–208.

In three Scandinavian peatlands we studied to what extent plant and microbial community compositions are governed by local-scale microhabitat, with a special interest in the effect of aspect (i.e. exposition of slopes). Despite differences in solar irradiance between the south- and north-facing slopes, maximum temperature was elevated in the south-facing slopes at the most northern site only. Pore-water nutrient concentrations were not affected by aspect, yet dissolved organic carbon concentrations were higher in the south-facing microhabitats. This was likely caused by higher vascular plant biomass. Plant and microbial community composition clearly differed among sites. In all three sites, microhabitat (i.e. prevailing water-table depth) affected the plant and microbial community compositions. Aspect, however, did not affect community composition, even though microclimate significantly differed between the south- and the north-facing aspects at the northernmost site. Our results highlight the complex link between plant community composition, microbial community and environmental conditions, which deserves much more attention than currently in order to fully understand the effects of climate change on peatland ecosystem function.

Hilasvuori, E., Hari, P., Aakala, T., Pulliainen, E. & Grace, J. 2014: Changes in nitrogen content and isotopic composition in subarctic Empetrum nigrum seeds in the period 1976–2010. Boreal Env. Res. 19: 209–221.

High latitude ecosystems are believed to be sensitive to increases in the availability of nitrogen (N) which may be the result of anthropogenic emissions or may be due to climate warming which accelerates the release of N from organic matter in the soil. These changes may be detected in the changes in N pools and their isotopic composition. We studied N content (N%) and isotopic composition (δ¹⁵N‰) along an elevational gradient in a subarctic environment in northern Finland, using Empetrum nigrum (crowberry) seeds collected annually over the past 35 years. We studied whether N% or δ¹⁵N‰ shows trends that can be attributed to anthropogenic nitrogen, and investigated the effect of climate variables on the N content of seeds. Among the years, variations in N% and δ¹⁵N‰, were mainly dependent on previous summer or growing season temperatures and were in opposite directions for N% and δ¹⁵N‰. Among the sites, N% and δ¹⁵N‰ were highest at a low elevation site, and lowest at the highest elevation site. Trends in δ¹⁵N‰ over time were contrasting among the sites: at the low elevation site trend was increasing, whereas at the highest elevation site the trend was decreasing. The trend in N% over time was increasing at the low elevation site. Our results suggest that N cycling in these systems has changed in the past 35 years, but there were differences among sites.

Selected papers presented at the European Inland Fisheries and Aquaculture Advisory Commission (EIFAAC) Symposium,
Finland, October 2012

Rask, M., Vuorenmaa, J., Nyberg, K., Tammi, J., Mannio, J., Olin, M., Kortelainen, P., Raitaniemi, J. & Vesala, S. 2014: Recovery of acidified lakes in Finland and subsequent responses of perch and roach populations. Boreal Env. Res. 19: 222–234.

Finnish lake survey and Finnish fish-status survey indicated that 4900 small headwater lakes suffered from acidic deposition and 1600–3200 roach (Rutilus rutilus) and perch (Perca fluviatilis) populations were affected or extinct by the end of 1980s. Since the late 1980s, successful sulphur emission reductions in Europe have induced a chemical recovery of acidified lakes. This resulted in decreases in sulphate and labile aluminium concentrations and increases in pH and alkalinity during the 1990s. The first signs of recovery in affected perch populations were observed in the early 1990s. New strong year-classes appeared and the population structure returned to normal. Little if any recovery of the affected populations of the more acid-sensitive species, roach, was recorded. This may have been due to still critical water quality conditions for successful reproduction of sensitive roach and/or organic acid episodes in the 2000s, suppressing the recovery of buffering capacity.

Jussila, J., Makkonen, J., Vainikka, A., Kortet, R. & Kokko, H. 2014: Crayfish plague dilemma: how to be a courteous killer? Boreal Env. Res. 19: 235–244.

Aphanomyces astaci is among the most serious pathogens affecting European aquatic ecosystems. We demonstrate that both virulence of A. astaci isolates and resistance of native European crayfish stocks vary notably. Some native European crayfish stocks latently carry crayfish plague, indicating adaptation and contemporary co-evolution between host and pathogen. The earliest introduced A. astaci genotypes have adapted to novel, susceptible native European crayfishes, likely under an evolutionary pressure to maintain a necessary host population as an essential habitat. Then, highly virulent genotypes that were introduced together with their original American hosts, have more resistant host populations present in Europe. This creates a dilemma for A. astaci: whether to increase virulence to better utilize invasive American hosts or to reduce virulence to better utilize the native European hosts. All A. astaci genotypes are potent killers, but they already show lowered virulence similarly to previous examples of virulence evolution in novel pathogens.

Suuronen, P. & Bartley, D. M. 2014: Challenges in managing inland fisheries — using the ecosystem approach. Boreal Env. Res. 19: 245–255.

Inland fisheries are an important source of food and livelihood. However, the socio-economic importance of inland fisheries is often undervalued and inadequately addressed in national and international policies for development. Furthermore, while irresponsible fishing can have serious consequences, there are also many outside threats to inland fisheries. The ecosystem approach to fisheries (EAF) strives to balance a diversity of societal objectives, preserving possibilities for future generations to benefit from exploitation of aquatic ecosystems. Implementation of the approach to inland fisheries presents special challenges that arise from multiple uses of inland waters, external pressures, and difficulties in acquiring accurate information. The basic elements of an ecosystem approach include identification of relevant participants, identification of objectives of management and establishment of a monitoring system with appropriate indicators.