BER 13 supplement B, 2008

ISSN 1239-6095 (print), ISSN 1797-2469 (online)
© Boreal Environment Research 2008

Contents of Volume 13 supplement B

Derome, J. & Merilä, P. 2008: Preface. Boreal Env. Res. 13 (suppl. B): 1–2.
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Mustajärvi, K., Merilä, P., Derome, J., Lindroos, A.-J., Helmisaari, H.-S., Nöjd, P. & Ukonmaanaho, L. 2008: Fluxes of dissolved organic and inorganic nitrogen in relation to stand characteristics and latitude in Scots pine and Norway spruce stands in Finland. Boreal Env. Res. 13 (suppl. B): 3–21.
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Lindroos A.-J., Derome, J., Mustajärvi, K., Nöjd, P., Beuker, E. & Helmisaari, H.-S. 2008: Fluxes of dissolved organic carbon in stand throughfall and percolation water in 12 boreal coniferous stands on mineral soils in Finland. Boreal Env. Res. 13 (suppl. B): 22–34.
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Merilä, P. & Derome, J. 2008: Relationships between needle nutrient composition in Scots pine and Norway spruce stands and the respective concentrations in the organic layer and in percolation water. Boreal Env. Res. 13 (suppl. B): 35–47.
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Salemaa, M., Derome, J. & Nöjd, P. 2008: Response of boreal forest vegetation to the fertility status of the organic layer along a climatic gradient. Boreal Env. Res. 13 (suppl. B): 48–66.
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Ukonmaanaho, L., Merilä, P., Nöjd, P. & Nieminen, T. M. 2008: Litterfall production and nutrient return to the forest floor in Scots pine and Norway spruce stands in Finland. Boreal Env. Res. 13 (suppl. B): 67–91.
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Hilli, S., Stark, S. & Derome, J. 2008: Water-extractable organic compounds in different components of the litter layer of boreal coniferous forest soils along a climatic gradient. Boreal Env. Res. 13 (suppl. B): 92–106.
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Hilli, S., Stark, S. & Derome, J. 2008: Qualitative and quantitative changes in water-extractable organic compounds in the organic horizon of boreal coniferous forests. Boreal Env. Res. 13 (suppl. B): 107–119.
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Mäkipää, R., Häkkinen, M., Muukkonen, P. & Peltoniemi, M. 2008: The costs of monitoring changes in forest soil carbon stocks. Boreal Env. Res. 13 (suppl. B): 120–130.
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We monitored the fluxes of nitrogen (N) compounds in throughfall (TF) and in percolation water (PW) in Scots pine and Norway spruce stands in Finland, and explored their dependence on N bulk deposition (BD) rates and general site and stand characteristics. During 1998–2004, N fluxes in BD, TF, and PW were low and remained relatively constant. Inorganic N was retained in the ecosystem (BD > TF > PW) more effectively in spruce stands, while the fluxes of dissolved organic nitrogen (DON) correspondingly increased. The canopy retention of inorganic N was correlated with the net increase in TF DON. BD DON was relatively constant, while the TF DON and BD deposition of inorganic N increased towards the south. DON accounted for 14% of the BD N, 48% of N in TF in spruce and 31% in pine stands, and 80% of the total N in PW. Stand characteristics (e.g. stand age) affected the TF fluxes of both inorganic N and DON, while only the NH₄-N flux in PW was related to deposition rates.

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The magnitude and variation in DOC fluxes in bulk deposition (BD), stand throughfall (TF) and percolation water (PW) were determined on seven Scots pine and five Norway spruce plots in Finland during 1998–2004. Water fluxes for PW were calculated using an anion budget method. The relationships between the DOC fluxes and climatic and stand parameters were also investigated. The mean DOC flux in TF varied between 2 and 6 g C m^–2 a^–1 and between 3 and 8 g C m^–2 a^–1 on the pine and spruce plots, respectively. The output flux of DOC in PW at the 40-cm depth varied between 1 and 10 g C m^–2 a^–1 on all the plots. The DOC fluxes in TF and net TF correlated positively with the effective temperature sum and growing season length on the pine and spruce plots, i.e. the highest DOC fluxes were recorded in southern Finland and the fluxes decreased towards the north. The TF and net TF DOC fluxes correlated positively with the amount of precipitation on the pine plots, and the net TF DOC fluxes with the stem volume on the spruce plots.

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We explored how N, S, P, Ca, K, Mg, Zn and Mn concentrations in percolation water (PW) and organic layer (OL) are reflected in the respective element concentrations in Scots pine and Norway spruce current needles. For both tree species, N and Ca had the highest covariation (R_adj² ≥ 0.73) between nutrient concentrations in the OL and in the needles. Mean N, S, P, K, Zn and Mn concentrations in PW significantly explained the variation in the respective needle concentrations on the spruce plots, and of K, Zn, and Mn in PW on the pine plots. The annual variation in needle element concentrations did not account for the respective variation in PW. Our results suggest that plant metabolism regulates the nutrient concentrations in the current needles more strongly in pine than in spruce, whereas the supply of soil nutrients is more clearly reflected in the nutrient concentrations of spruce.

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Salemaa, M., Derome, J. & Nöjd, P. 2008: Response of boreal forest vegetation to the fertility status of the organic layer along a climatic gradient. Boreal Env. Res. 13 (suppl. B): 48–66.

Relationships between boreal understorey vegetation and chemical composition of the organic layer, stand productivity and climatic factors were studied on 27 coniferous monitoring plots along a S–N gradient in Finland using ordination techniques (fitting environmental vectors and surfaces to the NMDS pattern). Total N, exchangeable Ca and Mg, BS, pH and organic layer thickness formed the subset of variables with maximum correlation with plant community composition. Of the stand parameters, site index (H₁₀₀), volume and basal area correlated best with the vegetation pattern. Our results support the hypothesis that site productivity can be predicted on the basis of the occurrence of understorey plants. This was especially true in herbaceous plants, where the number of species well depicted the site index on both pine and spruce plots. We present quantitative evidence that the response curves along an extensive nitrogen gradient varied between species representing dwarf shrubs, herbs, grasses, mosses and lichens.

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The main objective of this study was to determine the importance of nutrient return in litterfall (LF) to forest nutrient cycling. Therefore, we investigated the quality and quantity of LF in relation to the above-ground tree biomass (AGT) and determined the turnover rates. The study was carried out on seven Norway spruce (Picea abies) and six Scots pine (Pinus sylvestris) plots. LF was sampled during 1996–2003, and AGT in 2005–2006. The studied nutrients were N, Ca, K, Mg, P, S, Mn, Zn, Fe. Overall, the results indicated that there are quality, quantity and spatial differences in LF and AGT compartments. In general, both concentrations and mass of LF and AGT were higher on the spruce plots; 2% of the AGT biomass returned to the forest floor as LF on the plots. Magnesium turnover rate was higher on the spruce plots. The turnover rates of other nutrients were slightly higher on the pine plots, indicating faster nutrient cycling via LF. More litter needles (kg ha^–1) ended up on the forest floor in relation to living needles on the spruce plots.

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We investigated the concentrations and stocks of water-extractable carbon (WEC), nitrogen (WEN), phenolics and sugars in the main litter types (tree, dwarf shrub, moss) in boreal forests on two site types (mesic Norway spruce and sub-xeric Scots pine forests) in the south and north boreal climatic zones. WEC, sugar, and phenolic concentrations in the dwarf shrub and tree litter were higher in the north, whereas WEC and phenolic concentrations in the moss litter were higher in the south. Trees, dwarf shrubs, and mosses contributed to a varying extent to soil WEOM in the north and south boreal forests, the trees accounting for a major part of the WEOM in the south, but the understorey dwarf shrubs in the north. WEOM stocks were not predominantly determined by the concentrations of water-extractable compounds in each litter type, but instead by the quantitative proportions of the individual litter types.

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In order to investigate the changes in soil organic matter along a natural decomposition gradient, we determined the concentrations and stocks of water-extractable carbon (WEC), water-extractable nitrogen (WEN), soluble phenolics and sugars in the litter (L), fermentation (F), and humus (H) layers on two site types (mesic Norway spruce and sub-xeric Scots pine forests) and in two climatic zones (north and south boreal). The WEC, WEN, phenolic and sugar concentrations decreased considerably from the L to the H layer, but the reduction was stronger in the north than in the south. Despite the highest concentrations in the L layer, the stocks of water-extractable organic matter (WEOM) were the highest in the H layer. Our investigation demonstrates for the first time that the organic stocks in the H layer outweigh the higher concentrations of water-extractable compounds in the L layer, thus making the H layer the most important stock for water-extractable compounds.

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Mäkipää, R., Häkkinen, M., Muukkonen, P. & Peltoniemi, M. 2008: The costs of monitoring changes in forest soil carbon stocks. Boreal Env. Res. 13 (suppl. B): 120–130.

The forest soil carbon sink is of potentially great monetary value under subsequent climate conventions, but the costs of reliable monitoring have never been analysed. Our study aimed at evaluating (1) costs and precision of varied sampling intensities at the plot level, (2) sample size, and (3) costs needed to detect a change in soil carbon at the national scale. Organic layer carbon measurements cost 520 euros per plot if 10 samples are analysed. At plot scale, the precision obtained with such sampling allows detection of a large change > 860 g C m^–2. At the national scale, two measurement rounds on a minimum of 3000 plots are needed to detect an expected change of 11 g C m^–2 yr^–1 in the organic layer of upland forest soils with a 10-year sampling interval. Measuring such a network once costs approximately 4 million euros, which is about 8% of the value of the annual CO₂ sequestration of 2.57 x 10⁶ t CO₂ of upland forest soils in Finland.

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