Klavins, M. & Rodinov, V. 2010: Influence of large-scale atmospheric circulation on climate in Latvia. Boreal Env. Res. 15: 533–543.
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Natunen, A., Arola, A., Mielonen, T., Huttunen, J., Komppula, M. & Lehtinen, K. E. J. 2010: A multi-year comparison of PM_2.5 and AOD for the Helsinki region. Boreal Env. Res. 15: 544–552.
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Tahovská, K., Kopáček, J. & Šantrůčková, H. 2010: Nitrogen availability in Norway spruce forest floor — the effect of forest defoliation induced by bark beetle infestation. Boreal Env. Res. 15: 553–564.
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Vestgarden, L. S., Austnes, K. & Strand, L. T. 2010: Vegetation control on DOC, DON and DIN concentrations in soil water from a montane system, southern Norway. Boreal Env. Res. 15: 565–578.
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Saltikoff, E., Huuskonen, A., Hohti, H., Koistinen, J. & Järvinen, H. 2010: Quality assurance in the FMI Doppler Weather Radar Network. Boreal Env. Res. 15: 579–594.
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Lappalainen, M., Koivusalo, H., Karvonen, T. & Laurén, A. 2010: Sediment transport from a peatland forest after ditch network maintenance: a modelling approach. Boreal Env. Res. 15: 595–612.
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Klavins, M. & Rodinov, V. 2010: Influence of large-scale atmospheric circulation on climate in Latvia. Boreal Env. Res. 15: 533–543.

Analysis of the long-term trends in several meteorological parameters (air temperature, precipitation and river discharge) demonstrated significant climatic changes in Latvia. The character of the climate change had a strong seasonal pattern and largely depended on the large-scale atmospheric circulation pattern over Latvia and influence of long-term changes in air temperature (especially in winter), amounts of precipitation, ice regime of rivers and their runoff in Latvia. The climate change signals were related to increased temperature and precipitation at first during winters, and were associated with increased intensity of zonal circulation. Large-scale atmospheric-circulation processes were the most important factor influencing climate in Latvia.

Natunen, A., Arola, A., Mielonen, T., Huttunen, J., Komppula, M. & Lehtinen, K. E. J. 2010: A multi-year comparison of PM_2.5 and AOD for the Helsinki region. Boreal Env. Res. 15: 544–552.

We studied the relationship between satellite-based aerosol optical depth (AOD) and particulate matter (PM_2.5) which is aerosol mass concentration measured on the ground. PM_2.5 data originated from four sites located near each other within the Helsinki region, Finland. Depending on the site, the data covered between two and seven years. We investigated how temporal PM_2.5 averaging affects the correlation between PM_2.5 and AOD. In addition, we studied the seasonality of the correlation. The time-averaging increased the correlation coefficient as compared with one-hour PM_2.5 measurements. Regarding the monthly averages of PM_2.5 and AOD, the correlation coefficients were between 0.57 and 0.91. We also studied PM_2.5 and AOD gradients between an urban and a rural site. Monthly averages at the urban site were regularly higher than those at the rural site. However, the seasonal behaviour was similar.

Tahovská, K., Kopáček, J. & Šantrůčková, H. 2010: Nitrogen availability in Norway spruce forest floor — the effect of forest defoliation induced by bark beetle infestation. Boreal Env. Res. 15: 553–564.

The objective was to evaluate whether lower nitrogen (N) immobilization by spruce trees (Picea abies) or higher microbial N mineralization in the soil is the main mechanism changing the soil N balance after forest defoliation caused by bark beetle. We measured in situ mineral N availability using ion exchangers, net N mineralization (N_miner, ammonification and nitrification) and N content in microbial biomass (N_microb) in the forest floor of infested and control plots in an unmanaged area of The Bohemian Forest National Park. In situ N availability already increased before the defoliation culminated, which affirms the primary effect of reduced N immobilization by vegetation. N mineralization was enhanced after maximum forest defoliation (2 vs. 30 µg N g^–1 d^–1). The contribution of N_miner to in situ N availability was supported by the correlations found between in situ mineral N availability and N_miner/N_microb and N_miner/C_miner ratios. The influence of litter input with low C/N ratio on N mineralization is discussed.

Vestgarden, L. S., Austnes, K. & Strand, L. T. 2010: Vegetation control on DOC, DON and DIN concentrations in soil water from a montane system, southern Norway. Boreal Env. Res. 15: 565–578.

Soil water concentrations of dissolved organic carbon (DOC) and nitrogen (DON) may depend on vegetation composition. The objective of the present study was to quantify the concentrations of DOC, DON and dissolved inorganic N (DIN) in soil water below vegetation dominated by Calluna, Molinia or Sphagnum. In addition we investigated the difference in concentrations in water collected with macro rhizons (tension lysimeters) and plate (zero tension) lysimeters. The soil water concentrations of DOC, DON and DIN showed high variability. Concentrations of DOC and DON at the 0–10 cm depth increased in the order Sphagnum < Molinia < Calluna in summer, whereas in late autumn the DOC concentrations were at least as high in soil water below Molinia as below Calluna. The soil water concentrations of DOC and DON at the 20–30 cm depth increased in the order Calluna < Molinia < Sphagnum. The concentrations of nitrate (NO₃^–) and, to a lesser degree ammonium (NH₄⁺)_, generally increased in the following order: Sphagnum < Molinia < Calluna. Generally, vegetation was an important control on C and N release in the studied montane system.

Saltikoff, E., Huuskonen, A., Hohti, H., Koistinen, J. & Järvinen, H. 2010: Quality assurance in the FMI Doppler Weather Radar Network. Boreal Env. Res. 15: 579–594.

The Finnish Meteorological Institute designed, acquired and installed a network of 8 C-band Doppler radars during the years 1993–2005. We describe the principles used in the network design, the basic infrastructure of the network, as well as the technical properties of the radars. Data quality is improved by filtering of unwanted echoes and thresholding, and the electrical calibration of power and the antenna pointing is controlled by paired-radar analysis and solar observations. The radar data are used to serve society in a wide range of applications from aviation weather service to flood protection. High quality of end-user products is achieved by maintaining optimal measurements of individual radars, homogeneity of the entire radar network, and careful processing of the data. Volume scans consisting of 11 elevation angles have been designed to give simultaneously good quality precipitation data near the surface, secondly, good quality wind profiles based on the Doppler data, and thirdly, three-dimensional data (cloud tops and cross sections) for the requirements of aviation. Doppler-filtering, image processing and adjustment for vertical profile of reflectivity are applied to improve the data quality.

Lappalainen, M., Koivusalo, H., Karvonen, T. & Laurén, A. 2010: Sediment transport from a peatland forest after ditch network maintenance: a modelling approach. Boreal Env. Res. 15: 595–612.

The objective of this study was to describe erosion, sedimentation and transportation processes of erodible material in peatland forests after ditch network maintenance. A sediment transportation model was developed to simulate bed elevation changes in ditches and concentration of suspended solids in water. The model was suitable for simulating short-term effects (the first two years) of ditch network maintenance. The modelled spatial differences in sediment concentration were related to variation in the ditch bottom slope. The temporal variability in concentration was influenced by the water discharge rate. Other factors controlling the erosion and sedimentation in the model were the particle size of the material in bed and in suspension, the roughness height of the bed, and the Manning coefficient. Further development of the model calls for testing against comprehensive field measurements of sediment load and changes in channel dimensions.