Karsten Raulund-Rasmussen

Effects of thinning and soil properties on accumulation of carbon, nitrogen and phosphorus in the forest floor of Norway spruce stands

Abstract Area-based sampling was carried out to investigate the effect of thinning and soil properties on accumulation of forest floor carbon (C), nitrogen (N) and phosphorus (P) in Norway spruce (Picea abies (L.) Karst.) stands in Denmark. Four thinning intensities (unthinned, and about 83%, 67% and 50% of unthinned basal area) were investigated at three sites in Denmark: a calcareous, relatively nutrient rich soil with a sandy loam/loam texture and two soils with low to intermediate nutritional status and sandy loam and loamy sand textures, respectively. The effect of thinning on accumulated carbon and nitrogen was significant at two of the investigated sites. Accumulated phosphorus was significantly affected by thinning at one of these two sitesand at the third site. Accumulated carbon and phosphorus were negatively linearly correlated with thinning intensity. pH tended to be highest and C N and C P ratios tended to be lowest in the heaviest thinned plots. It is hypothesized that the differences in accumulation may be due to a more favourable microclimate and substrate for saprophytic organisms in the most heavily thinned plots. However, the differences between sites were greater than differences between thinning intensities. The accumulation of carbon, nitrogen and phosphorus in the forest floors was much higher at the two less fertile sites with loamy sand and sandy loam than at the relatively fertile site with sandy loam/loam. Significant differences in pH and in C N and C P ratios at the three sites indicate that the amounts of available nutrients influence the mineralization pattern. In addition, at the site with the greatest forest floor root density, competition for nutrients and moisture between mycorrhiza-infected roots and free-living saprophytic decomposers may be co-responsible for the large amounts of accumulated carbon, nitrogen and phosphorus.

Composition and reactivity of DOC in forest floor soil solutions in relation to tree species and soil type

Metal coordinating propertiesof DOC (dissolved organic carbon), and henceits influence on heavy metal release andmineral weathering, depend on the compositionand properties of DOC. Tree species producelitter with different chemical composition anddegradability, and these differences mightinfluence the composition and reactivity of DOCin soil solutions. Accordingly, analysis ofcomposition and reactivity of DOC in soilsolution samples collected by centrifugationfrom 16 forest soil O horizons from the fourtree species beech (Fagus sylvatica L.),oak (Quercus robur L.), grand fir (Abies grandis Lindl.), and Norway spruce (Picea abies (L.) Karst.) on two clayey and twosandy soils were carried out. The compositionand properties of DOC were determined bycapillary zone electrophoresis, acid-basetitration, Cu ion titration, total elementalanalysis, IR and UV spectroscopy, and metalrelease assays. Concentrations of DOC rangedfrom 20 to 163 mM with pH ranging from 4.6 to7.3. Norway spruce produced the highest DOCconcentration, and the lowest pH. Carbon inlow-molecular-weight aliphatic carboxylic acids(LACA) accounted for less than 6% of DOC withformic and acetic acids as the most abundantLACAs. The DOC was cation exchanged and protonsaturated to obtain comparable forms of DOC.Titratable carboxylic acid and phenolic groupswere in the range 51 to 82 and 20 to64 mmol·mol−1 C, respectively, with fewerphenolic groups in grand fir DOC as the onlysignificant difference. Infrared spectra offreeze-dried DOC samples suggest low contentsof aromatic C in the DOC especially from grandfir stands. Stability constants, log K of Cu-DOC complexes, determined by Cu ion titrationof DOC samples with fitting of the data to atwo-site binding model, were in the range 5.63to 6.21 for the strong binding sites and 3.58to 4.10 for the weak sites, but with nosignificant effects of tree species or site.Freeze-dried DOC samples were found to consistof 41 to 45% C, 38 to 49% O, 4.4 to 5.4% Hand 1.2 to 2.0% N and C/N ratios in the range26 to 42. Reactivity of DOC in terms of releaserates of Cd, Cu and Fe cations from a soilsample (flow cell experiments) showed nosignificant differences among DOC samples fromdifferent tree species and soil types.Apparently, only minor differences occur inchemical composition and reactivity ofequivalent concentrations of DOC in forestfloor soil solutions irrespective of origin,i.e. four tree species and two soil types. Soilsolution pH and the concentration of DOCproduced by various tree species are thecritical parameters when distinguishing amongtree species in relation to heavy metal releaseand mineral weathering.

Cadmium and copper release kinetics in relation to afforestation of cultivated soil

Afforestation of cultivated soils causes soil acidification and elevated concentrations of dissolved organic matter (DOC) in the soil solution, and hence, aggravate the risk of heavy metal leaching. The kinetics of cadmium and copper release from an unpolluted arable soil applied with forest floor soil solution was investigated in the laboratory, and the release rates correlated to pH and DOC in solution through log-log equations. The soil solution was isolated from Norway spruce (Picea abies (L.) Karst.) by centrifugation, and the solution passed a cation-exchange column to remove metal cations and to protonate the DOC. Soil samples from an arable Ap horizon were placed in completely mixed flow cells, and influent solutions with 0 to 5 mM DOC were applied. The solution pH was adjusted to achieve effluent pH values in the range 3.6 to 6.9 in the flow cells at steady-state conditions. Cadmium release rates were very low at pH . 5 and increased exponentially as pH decreased to ,5. The release rate was correlated to solution pH in a simple model: log(cadmium release rate) 52 0.21 pH 2 15.28 (R 2 5 0.48), and no significant effect of DOC was observed. The kinetics of copper release from the soil was more complicated with effects of both pH and DOC. In experiments without DOC, the release rate of copper was slightly lower at high pH than at low pH. In experiments above pH 5, the presence of 5 mM DOC in the solution increased the release rate of copper. However, the copper release was retarded by DOC in the range pH 3.8 to 5.0, which coincided with a maximum retention of DOC in the flow cells. The release rate of copper was correlated to solution pH and concentration of DOC, including an interaction of pH and DOC: log(copper release rate) 5 0.86 pH 2 1.26 logDOC 1 0.24 pH z logDOC 2 19.26 (R 2 5 0.60). If the changes in soil chemical conditions after afforestation influence the cadmium and copper release rates in a similar way as observed in the flow cell experiments, then the release rate of cadmium will increase exponentially at soil solution pH , 4.5. The inhibition of copper release by DOC observed at pH 3.8 to 5.0 indicates that copper is retained in the soil by interactions with adsorbed organic matter. Copyright

Main Findings and Future Challenges in Forest Nutritional Research and Management in the Nordic Countries

Previous research has documented that nitrogen fertilization can lead to a significant tree growth increase in large parts of Scandinavia. Nutrient management of Nordic forests is currently under debate, mainly because environmental values are believed to be unnecessarily endangered by these actions. Nutrient management including fertilization, liming, recycling of wood ash or application of alternative nutrient sources can counteract nutrient deficiencies and imbalances, and be used for compensating the nutrients removed through harvesting. For successful implementation of nutritional management measures, several questions should still be studied. These questions mainly concern diagnosis of the need for applications, nutritional sustainability and treatment effects on the forest ecosystem and the surrounding environment.

Sustainable Use of Forest Biomass for Energy

The first € price and the £ and

MONOSILICATE ADSORPTION BY FERRIHYDRITE AND GOETHITE AT PH 3–6

price are net prices, subject to local VAT. Prices indicated with * include VAT for books; the €(D) includes 7% for Germany, the €(A) includes 10% for Austria. Prices indicated with ** include VAT for electronic products; 19% for Germany, 20% for Austria. All prices exclusive of carriage charges. Prices and other details are subject to change without notice. All errors and omissions excepted. D. Röser, A. Asikainen, K. Raulund-Rasmussen, I. Stupak (Eds.) Sustainable Use of Forest Biomass for Energy

Ecological and social dimensions of ecosystem restoration in the nordic countries

The constant capacitance model and the Elovich equation were combined in the following mathematical expression enabling calculation of the amount of silicic acid adsorbed by iron oxides as a function of the Si concentration, pH, soil:solution ratio, and reaction time: Ka1 is the protolytic surface constant and Ksi is the stability constant for the Fe oxide-silicate surface complex; -logKa1 = 6.40–0.54(8-pH) and logKsi = 3.85 for ferrihydrite and goethite. Good agreement was found between calculated Si adsorption and the amount actually found to be adsorbed by synthetic ferrihydrite and goethite at different pH (3–6), Si concentration (1–600 μM), solid:solution ratio (1:300, 1:1200) and reaction time (1–480h).

Biotic homogenization can decrease landscape-scale forest multifunctionality

An international overview of the extent and type of ecological restoration can offer new perspectives for understanding, planning, and implementation. The Nordic countries, with a great range of natural conditions but historically similar social and political structures, provide an opportunity to compare restoration approaches and efforts across borders. The aim of this study was to explore variation in ecological restoration using the Nordic countries as an example. We used recent national assessments and expert evaluations of ecological restoration. Restoration efforts differed among countries: forest and peatland restoration was most common in Finland, freshwater restoration was most common in Sweden, restoration of natural heathlands and grasslands was most common in Iceland, restoration of natural and semi-cultural heathlands was most common in Norway, and restoration of cultural ecosystems, mainly abandoned agricultural land, was most common in Denmark. Ecological restoration currently does not occur on the Faroe Islands. Economic incentives influence ecological restoration and depend on laws and policies in each country. Our analyses suggest that habitat types determine the methods of ecological restoration, whereas socio-economic drivers are more important for the decisions concerning the timing and location of restoration. To improve the understanding, planning, and implementation of ecological restoration, we advocate increased cooperation and knowledge sharing across disciplines and among countries, both in the Nordic countries and internationally. An obvious advantage of such cooperation is that a wider range of experiences from different habitats and different socio-economic conditions becomes available and thus provides a more solid basis for developing practical solutions for restoration methods and policies.

The effects of tree species and site on the solubility of Cd, Cu, Ni, Pb and Zn in soils

Significance Numerous studies have demonstrated the importance of biodiversity in maintaining multiple ecosystem functions and services (multifunctionality) at local spatial scales, but it is unknown whether similar relationships are found at larger spatial scales in real-world landscapes. Here, we show, for the first time to our knowledge, that biodiversity can also be important for multifunctionality at larger spatial scales in European forest landscapes. Both high local (α-) diversity and a high turnover in species composition between locations (high β-diversity) were found to be potentially important drivers of ecosystem multifunctionality. Our study provides evidence that it is important to conserve the landscape-scale biodiversity that is being eroded by biotic homogenization if ecosystem multifunctionality is to be maintained. Many experiments have shown that local biodiversity loss impairs the ability of ecosystems to maintain multiple ecosystem functions at high levels (multifunctionality). In contrast, the role of biodiversity in driving ecosystem multifunctionality at landscape scales remains unresolved. We used a comprehensive pan-European dataset, including 16 ecosystem functions measured in 209 forest plots across six European countries, and performed simulations to investigate how local plot-scale richness of tree species (α-diversity) and their turnover between plots (β-diversity) are related to landscape-scale multifunctionality. After accounting for variation in environmental conditions, we found that relationships between α-diversity and landscape-scale multifunctionality varied from positive to negative depending on the multifunctionality metric used. In contrast, when significant, relationships between β-diversity and landscape-scale multifunctionality were always positive, because a high spatial turnover in species composition was closely related to a high spatial turnover in functions that were supported at high levels. Our findings have major implications for forest management and indicate that biotic homogenization can have previously unrecognized and negative consequences for large-scale ecosystem multifunctionality.

Fertilization of Danish Forests: A Review of Experiments

Afforestation of former agricultural land changes soil characteristics such as pH and organic matter content, which may affect heavy metal solubility in the soil. In this study the effects of different tree species on heavy metal solubility were investigated at four 34 years old adjacent stands of beech (Fagus sylvatica L.), grand fir (Abies grandis Lindl.), Norway spruce (Picea abies (L.) Karst.) and oak (Quercus robur L.) planted on former agricultural land at four different sites in Denmark. The sites differ in soil characteristics and represent two texture classes (loamy sand and sandy loam). Soil pH and soil organic matter content was measured in the 16 stands and soil solution was isolated by centrifugation from three depths at four different occasions. Dissolved organic carbon (DOC), pH in the soil solution and the soil solution concentrations (availability) of Cd, Cu, Ni, Pb and Zn were determined. Analysis of variance showed that the tree species affects soil pH and organic matter content in the topsoil, but not in the lower horizons. Norway spruce and grand fir acidify more than beech and oak, and the highest amount of accumulated soil organic matter is in the topsoil under Norway spruce. The effects of tree species on soil solution pH and DOC resemble the effect on soil pH and organic matter content. Grand fir enhances the solubility of Cd and Zn in the topsoil with the lower solubility found under beech and oak and Norway spruce enhances the solubility of Cu, Ni and Pb in the top horizons. The lowest solubility of Ni and Pb is found under beech and oak, whereas the lowest Cu concentrations in the soil solution are found under grand fir. After 34 years of afforestation no effects of tree species on the concentrations of heavy metals in the soil solution from the C-horizons were found. The tree species effect on the concentration of Cd, Cu and Ni in the soil solution depends on the soil characteristics with the higher concentrations found in sandy loam soils, whereas no effect of site on the solution concentration was found for Pb and Zn. It was not possible to find a clear correlation between the soil solution concentrations of heavy metals, pH and DOC concentration.