Tanskanen, H. & Venäläinen, A. 2008: The relationship between fire activity and fire weather indices at different stages of the growing season in Finland. Boreal Env. Res. 13: 285–302.

This study examines the relationship between predicted fire hazard and observed fire activity at different stages of seasonal vegetation development. The data consisted of Finnish national fire records 1996–2003, the daily values of the effective temperature sum of over 5 °C, the Finnish Fire Risk Index, and the FWI and ISI codes of the Canadian Fire Weather Index System. The highest probabilities for fire-day and multiple-fire-day occurrence were found during the final stage of the growing season, at the temperature sum value of above 900. The probability of large-fire-day was highest during the early stages of the growing season. The statistical significance of the probability models was poorest during the initial and final stages of the season.

Lappalainen, H. K., Linkosalo, T. & Venäläinen, A. 2008: Long-term trends in spring phenology in a boreal forest in central Finland. Boreal Env. Res. 13: 303–318.

We studied the onset of spring phenology and the long-term trends of 31 species at the Oulainen-Ohineva site (64°13'N, 24°53'E) in central Finland. The species studied represented a wide range including deciduous trees, shrubs, grasses, 18 species of migratory birds and six insect species. The duration of the species-specific time series varied from 4 years up to 54 years during the 1952–2005 observation period. An advancing trend (p < 0.05) in the timing of spring phenology was only found for five species (with over 15 years of observations), namely, Formica rufa group, Rana temporaria, Grus grus, Ficedula hypoleuca and Hirundinidae. In local species with more than 38 years of observations, the temperature trend turned out to be the best variable to describe the advancement of the phenological event. For birds in six cases out of ten the best factor for explaining the advancement, as well as the temperature, was the NAO index.

Turunen, J. 2008: Development of Finnish peatland area and carbon storage 1950–2000. Boreal Env. Res. 13: 319–334.

This study summarizes the present knowledge of Finnish peatland areas and carbon (C) storage in peat from 1950 to 2000. In 1950, approximately 8.8 million ha of the Finnish peatland area was still undisturbed and 1.4 million ha drained. In 2000, almost 55% (5.7 million ha) of the peatland area in Finland was drained for forestry, 38.4% (4.0 million ha) was undrained, 0.8% (85 000 ha) was in agriculture, 0.6% (60 000 ha) was under water reservoirs, 0.3% (35000 ha) was under roads and 0.6% was in peat harvesting or had been removed from the harvesting business (63 000 ha). The change in mire area is considered relatively reliable, whereas the net changes in the actual C sequestration and the actual C storage change from 1950 to 2000 involves much more uncertainty. In 2000, the total C storage of Finnish peatland ecosystems was estimated at 5960 Tg, which includes 5304 Tg as peat. Since 1950, the C sequestration of undrained and drained peatlands (peat, plant biomass) basically compensated for the anthropogenic losses. The most important forms of anthropogenic C losses have occurred from agricultural peat soils, water reservoirs, harvested peat and DOC output from forestry drained peatlands. From 1950 to 2000, the total C storage of Finnish peatlands, which includes peat and living plant biomass, was estimated to increased by 52 Tg because the intensive peatland drainage significantly increased the total C storage of vegetation. However, the actual C storage in peat decreased by about 73 Tg. The well-defined changes include the decrease of mire diversity because of forestry drainage.

Timonen, H. J., Saarikoski, S. K., Aurela, M. A., Saarnio, K. M. & Hillamo, R. E. J. 2008: Water-soluble organic carbon in urban aerosol: concentrations, size distributions and contribution to particulate matter. Boreal Env. Res. 13: 335–346.

The aim of this study was to characterize the concentrations and particle mass size distributions of water-soluble organic carbon (WSOC) in urban aerosols. The sample collection was carried out in spring 2006 at the SMEAR III station in Helsinki, Finland, by using a size-segregating method (MOUDI) and by collecting sub-micrometer fraction of aerosols on the filter. During the three-month measurement period, a major 12-day biomass burning pollution episode was observed. Concentrations of WSOC, organic carbon, monosaccharide anhydrides, inorganic ions and some organic acids (oxalic, succinic and malonic acid) were analyzed from the PM₁ samples. The measured OC and WSOC concentrations varied in ranges 0.67–15.7 µg m^–3 and 0.26–10.7 µg m^–3, respectively. The WSOC/OC concentration ratio was between 0.30 and 0.89 with an average of 0.54. Size distributions of WSOC, inorganic ions and total mass were determined from the MOUDI samples. WSOC had bimodal size distributions with a clear accumulation mode below 1 µm of particle aerodynamic diameter and minor coarse mode at sizes > 1 µm.

Vallius, M., Ruuskanen, J. & Pekkanen, J. 2008: Comparison of multivariate source apportionment of urban PM_2.5 with chemical mass closure. Boreal Env. Res. 13: 347–358.

In the lack of comparisons of different source apportionment methods, we resolved daily contributions of five source categories to PM_2.5 by applying principal component analysis and multiple linear regression to air pollution data from Helsinki, Finland. From the same data we estimated mass concentrations of four major components of PM_2.5 using a chemical mass closure model. Multiple linear regression analysis suggested that secondary and other long-range transported particles contributed 58% to total PM_2.5, on the average, while traffic and mixed local combustion sources accounted for 19%, oil combustion for 14%, crustal source for 4.9% and salt for 2.4%. Mass closure suggested average contributions of 50%, 34%, 4.5% and 1.2% from ammonium sulphate, combustion-related particles, crustal material and sea salt, respectively. The crustal source and salt were apportioned similar amounts of PM_2.5 whereas results from the two methods were less comparable for the long-range transported and secondary particles, and the combustion-related source components.

Heino, J. 2008: Influence of taxonomic resolution and data transformation on biotic matrix concordance and assemblage–environment relationships in stream macroinvertebrates. Boreal Env. Res. 13: 359–369.

I examined patterns in stream macroinvertebrate assemblage structure and assemblage–environment relationships at four taxonomic levels (i.e. species, genus, family, and order) and based on four data types (i.e. presence/absence, logarithmic, square-root, and raw abundance) in a boreal drainage basin. Tests of resemblance matrix concordance within taxonomic levels showed that not all matrices were strongly correlated. Presence/absence matrices showed poor correlations with raw abundance matrices, possibly reflecting the fact that a few dominant species were responsible for assemblage patterns in the latter. By contrast, logarithmic and square-root data generally showed strong matrix correlations, and this pattern existed at the species, genus, and family levels. Assemblage–environment relationships were rather similar between species-, genus-, and family-level data sets, given that the same key environmental variables were included in the final environmental dissimilarity matrices in BIO-ENV analysis. In conclusion, researchers should pay considerable attention to data transformations when interpreting assemblage patterns at different taxonomic levels and comparing different studies, as different data transformations may provide differing information and lead to highly differing conclusions.

Lappalainen, A., Härmä, M., Kuningas, S. & Urho, L. 2008: Reproduction of pike (Esox lucius) in reed belt shores of the SW coast of Finland, Baltic Sea: a new survey approach. Boreal Env. Res. 13: 370–380.

The coastal reproduction areas of pike in the western Gulf of Finland were surveyed during spring 2004 and 2005 using a new approach. The locations of reed belts, the most important spawning substratum, were first identified using aerial photos, and 36 sites in three archipelago zones were selected for field sampling. The occurrence of pike larvae at each 100 m long site was observed with the aid of a white plate and a scoop. The majority of pike larvae were found in a habitat formed by the previous season's flattened reeds at a water depth of 20–80 cm. The comparison between archipelago zones revealed that reed belt shores in the innermost archipelago and bay area, substantially influenced by freshwater inputs in the spring, are the key reproduction areas of pike. Pike larvae were abundant in these areas, in contrast to the intermediate and outer archipelago, where pike larvae were found only sporadically. It is likely that productive habitats in the inner archipelago serve as a source and the outer archipelago as a sink, the latter maintaining pike population with the aid of juvenile immigrants from the main reproduction areas. The results also indicate that pike can not take full advantage of the slowly increasing spatial coverage of reed belts in the intermediate and outer archipelago of the western Gulf of Finland.