Soil Acidity Parameters and Defoliation Degree in Six Norway Spruce Stands in Finland

Soil acidity parameters (pH, basesaturation, exchangeable Al) in the organic and mineralsoil layers and in soil water (pH, dissolved organiccarbon, total Al, Al³⁺ and molar Ca/Al ratios) insix Norway spruce stands in different parts of Finlandwere compared. An attempt was also made to relate thedegree of defoliation in the tree stand to N and Sdeposition and soil parameters. No relationship was foundbetween soil acidity parameters and defoliation in thesix stands. Defoliation was positively correlated withstand age and the C/N ratio of the organic layer, andnegatively with the cation exchange capacity. The plotlocated on a so-called sulphate soil on the west coast ofFinland had very low soil pH values, and extremely highAl and SO₄ ^2- concentrations and molar Ca/Alratios of well below 1.0 in soil water. Despite the highnatural acidity in the soil on this plot, defoliation inthe spruce stand was the lowest (mean 8.6%) of all sixplots. The results of this study indicate that soilacidity is not a major factor affecting stand conditionin these spruce stands, and that the variation in soilacidity parameters is closely related to climatic factorsand natural soil formation processes.     

Long-term changes in acidity and DOC in throughfall and soil water in Finnish forests

The main objective of this study was to examine if any detectable trends in dissolved organic carbon (DOC), sulphate (SO₄-S) concentrations and acid neutralizing capacity (ANC) in throughfall (TF) and soil water (SW) could be found during 1990–2010 and to relate them to recent changes in decreased acid deposition. The study was conducted in seven boreal coniferous forest sites: four of which are managed and three unmanaged forests sites. Generally, temporal trend showed a significant decrease in SO₄-S concentrations in bulk precipitation (BP), TF and SW. At some of the sites, there was an increasing tendency in BP and TF in the DOC concentrations. This feature coincides with decreasing SO₄-S concentration, indicating that SO₄-S may be an important driver of DOC release from the canopy. However, a slightly increased temperature, larger senescing needle mass and consequently increased decaying activity in the canopy may partly explain the increasing trend in DOC. In SW, no consistent DOC trend was seen. At some sites, the decreased base cation concentrations mostly account for the decrease in the ANC values in SW and TF.     

Spatially valid data of atmospheric deposition of heavy metals and nitrogen derived by moss surveys for pollution risk assessments of ecosystems

For analysing element input into ecosystems and associated risks due to atmospheric deposition, element concentrations in moss provide complementary and time-integrated data at high spatial resolution every 5 years since 1990. The paper reviews (1) minimum sample sizes needed for reliable, statistical estimation of mean values at four different spatial scales (European and national level as well as landscape-specific level covering Europe and single countries); (2) trends of heavy metal (HM) and nitrogen (N) concentrations in moss in Europe (1990–2010); (3) correlations between concentrations of HM in moss and soil specimens collected across Norway (1990–2010); and (4) canopy drip-induced site-specific variation of N concentration in moss sampled in seven European countries (1990–2013). While the minimum sample sizes on the European and national level were achieved without exception, for some ecological land classes and elements, the coverage with sampling sites should be improved. The decline in emission and subsequent atmospheric deposition of HM across Europe has resulted in decreasing HM concentrations in moss between 1990 and 2010. In contrast, hardly any changes were observed for N in moss between 2005, when N was included into the survey for the first time, and 2010. In Norway, both, the moss and the soil survey data sets, were correlated, indicating a decrease of HM concentrations in moss and soil. At the site level, the average N deposition inside of forests was almost three times higher than the average N deposition outside of forests.