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Silva Fennica vol. 41 no. 3 | 2007

Category : Special section

article id 472, category Special section

Raisa Mäkipää, Jari Liski, Mats Olsson, Pete Smith, Esther Thürig. (2007). Workshop on Development of Models and Forest Soil Surveys for Monitoring of Soil Carbon. Silva Fennica vol. 41 no. 3 article id 472. https://doi.org/10.14214/sf.472

Abstract | View details | Full text in PDF | Author Info

Selected Papers of the Workshop on Development of Models and Forest Soil Surveys for Monitoring of Soil Carbon.

Mäkipää, Finnish Forest Research Institute E-mail: rm@nn.fi
Liski, Finnish Environment Institute, Finland E-mail: jl@nn.fi
Olsson, Swedish University of Agricultural Sciences, Sweden E-mail: mo@nn.se
Smith, University of Aberdeen, UK E-mail: ps@nn.uk
Thürig, Swiss Federal Research Institute WSL, Switzerland E-mail: et@nn.ch

article id 290, category Special section

Mikko Peltoniemi, Esther Thürig, Stephen Ogle, Taru Palosuo, Marion Schrumpf, Thomas Wutzler, Klaus Butterbach-Bahl, Oleg Chertov, Alexander Komarov, Aleksey Mikhailov, Annemieke Gärdenäs, Charles Perry, Jari Liski, Pete Smith, Raisa Mäkipää. (2007). Models in country scale carbon accounting of forest soils. Silva Fennica vol. 41 no. 3 article id 290. https://doi.org/10.14214/sf.290

Keywords: National Forest Inventory; soil carbon; greenhouse gas inventory; decomposition; IPCC; regional and national modeling; soil model

Abstract | View details | Full text in PDF | Author Info

Countries need to assess changes in the carbon stocks of forest soils as a part of national greenhouse gas (GHG) inventories under the United Nations Framework Convention on Climate Change (UNFCCC) and the Kyoto Protocol (KP). Since measuring these changes is expensive, it is likely that many countries will use alternative methods to prepare these estimates. We reviewed seven well-known soil carbon models from the point of view of preparing country-scale soil C change estimates. We first introduced the models and explained how they incorporated the most important input variables. Second, we evaluated their applicability at regional scale considering commonly available data sources. Third, we compiled references to data that exist for evaluation of model performance in forest soils. A range of process-based soil carbon models differing in input data requirements exist, allowing some flexibility to forest soil C accounting. Simple models may be the only reasonable option to estimate soil C changes if available resources are limited. More complex models may be used as integral parts of sophisticated inventories assimilating several data sources. Currently, measurement data for model evaluation are common for agricultural soils, but less data have been collected in forest soils. Definitions of model and measured soil pools often differ, ancillary model inputs require scaling of data, and soil C measurements are uncertain. These issues complicate the preparation of model estimates and their evaluation with empirical data, at large scale. Assessment of uncertainties that accounts for the effect of model choice is important part of inventories estimating large-scale soil C changes. Joint development of models and large-scale soil measurement campaigns could reduce the inconsistencies between models and empirical data, and eventually also the uncertainties of model predictions.

Peltoniemi, Finnish Forest Research Institute, Vantaa Research Unit, P.O. Box 18, FI-01301 Vantaa, Finland E-mail: mikko.peltoniemi@metla.fi
Thürig, Swiss Federal Institute for Forest, Snow and Landscape Research (WSL), Birmensdorf, Switzerland; European Forest Institute, Joensuu, Finland E-mail: et@nn.ch
Ogle, Natural Resources Ecology Laboratory, Colorado State University, Fort Collins, USA E-mail: so@nn.us
Palosuo, European Forest Institute, Joensuu, Finland E-mail: tp@nn.fi
Schrumpf, Max-Planck-Institute for Biogeochemistry, Jena, Germany E-mail: ms@nn.de
Wutzler, Max-Planck-Institute for Biogeochemistry, Jena, Germany E-mail: tw@nn.de
Butterbach-Bahl, Institute for Meteorology and Climate Research, Forschungszentrum Karlsruhe GmbH, Garmisch-Partenkirchen, Germany E-mail: kbb@nn.de
Chertov, St. Petersburg State University, St. Petersburg-Peterhof, Russia E-mail: oc@nn.ru
Komarov, Institute of Physicochemical and Biological Problems in Soil Science of Russian Academy of Sciences, Pushchino, Russia E-mail: ak@nn.ru
Mikhailov, Institute of Physicochemical and Biological Problems in Soil Science of Russian Academy of Sciences, Pushchino, Russia E-mail: am@nn.ru
Gärdenäs, Dept. of Soil Sciences, Swedish University of Agricultural Sciences, Uppsala, Sweden E-mail: ag@nn.se
Perry, USDA Forest Service, Northern Research Station, St. Paul, MN USA E-mail: cp@nn.us
Liski, Finnish Environment Institute, Helsinki, Finland E-mail: jl@nn.fi
Smith, School of Biological Sciences, University of Aberdeen, Aberdeen, UK E-mail: ps@nn.uk
Mäkipää, Finnish Forest Research Institute, Vantaa Research Unit, P.O. Box 18, FI-01301 Vantaa, Finland E-mail: raisa.makipaa@metla.fi

article id 289, category Special section

Thomas Wutzler, Martina Mund. (2007). Modelling mean above and below ground litter production based on yield tables. Silva Fennica vol. 41 no. 3 article id 289. https://doi.org/10.14214/sf.289

Keywords: uncertainty; thinnings; soil carbon; biomass turnover; carbon accounting; harvest residues; sensitivity analysis

Abstract | View details | Full text in PDF | Author Info

Estimates of litter production are a prerequisite for modeling soil carbon stocks and its changes at regional to national scale. However, the required data on biomass removal is often available only for the recent past. In this study we used yield tables as a source of probable past forest management to drive a single tree based stand growth model. Next, simulated growth and timber volume was converted to tree compartment carbon stocks and biomass turnover. The study explicitly accounted for differences in site quality between stands. In addition we performed a Monte Carlo uncertainty and sensitivity analysis. We exemplify the approach by calculating long-term means of past litter production for 10 species by using yield tables that have been applied in Central Germany during the last century. We found that litter production resulting from harvest residues was almost as large as the one from biomass turnover. Differences in site quality caused large differences in litter production. At a given site quality, the uncertainty in soil carbon inputs were 14%, 17%, and 25% for beech, spruce, and pine stands, respectively. The sensitivity analysis showed that the most influential parameters were associated with foliage biomass and turnover. We conclude that rates of mean past litter production and their uncertainties can reliably be modeled on the basis of yield tables if the model accounts for 1) full rotation length including thinning and final harvest, 2) differences in site quality, and 3) environmental dependency of foliage biomass and foliage turnover.

Wutzler, Max Planck Institute for Biogeochemistry, Jena, Germany E-mail: tm@nn.de
Mund, Max Planck Institute for Biogeochemistry, Jena, Germany E-mail: mm@nn.de

article id 288, category Special section

Björn Berg, Per Gundersen, Cecilia Akselsson, Maj-Britt Johansson, Åke Nilsson, Lars Vesterdal. (2007). Carbon sequestration rates in Swedish forest soils – a comparison of three approaches. Silva Fennica vol. 41 no. 3 article id 288. https://doi.org/10.14214/sf.288

Keywords: carbon sequestration; stable humus; forest floor C; litter decomposition; limit value

Abstract | View details | Full text in PDF | Author Info

Carbon sequestration rates in forest soil can be estimated using the concept of calculable stable remains in decomposing litter. In a case study of Swedish forest land we estimated C-sequestration rates for the two dominant tree species in the forest floor on top of the mineral soil. Carbon sequestration rates were upscaled to the forested land of Sweden with 23 x 10⁶ ha with Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (Karst.) L.). Two different theoretical approaches, based on limit-value for litter decomposition and N-balance for vegetation and SOM gave rates of the same magnitude. For the upscaling, using these methods, 17 000 grids of 5 x 5 km were used.

The ‘limit-value approach’ gave a sequestration of 4.8 10⁶ tons of C, annually sequestered in the forest floor, with an average of 180 kg C ha^–1 yr^–1 and a range from 40 to 410 kg C ha^–1 yr^–1. The ‘N-balance approach’ gave an average value of c. 96 kg ha^–1 yr^–1 and a range from –60 to 360 kg ha^–1 yr^–1. A method based on direct measurements of changes in humus depth over 40 years, combined with C analyses gave an average rate that was not very different from the calculated rates, viz. c. 180 kg ha^–1 yr^–1 and a range from –20 to 730 kg ha^–1 yr^–1. These values agree with forest floor C sequestration rate based on e.g. sampling of chronsequences but differ from CO₂ balance measurements.

The three approaches showed different patterns over the country and regions with high and low carbon sequestration rates that were not always directly related to climate.

Berg, Dept. of Forest Ecology, University of Helsinki, Finland (present address: Dipartimento Biologia Strutturale e Funzionale, Complesso Universitario, Monte S. Angelo, Napoli, Italy E-mail: bjorn.berg@helsinki.fi
Gundersen, Forest & Landscape Denmark, University of Copenhagen, Denmark E-mail: pg@nn.dk
Akselsson, Swedish Environmental Research Institute, IVL, Gothenburg, Sweden E-mail: ca@nn.se
Johansson, Department of Forest Soils, SLU, Uppsala, Sweden E-mail: mbj@nn.se
Nilsson, Department of Forest Soils, SLU, Uppsala, Sweden E-mail: an@nn.se
Vesterdal, Forest & Landscape Denmark, University of Copenhagen, Denmark E-mail: lv@nn.dk

article id 287, category Special section

Mikko Peltoniemi, Juha Heikkinen, Raisa Mäkipää. (2007). Stratification of regional sampling by model-predicted changes of carbon stocks in forested mineral soils. Silva Fennica vol. 41 no. 3 article id 287. https://doi.org/10.14214/sf.287

Keywords: uncertainty; soil carbon; anticipated variance; forest soil; monitoring; repeated measurement; soil survey; stratified sampling

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Monitoring changes in soil C has recently received interest due to reporting under the Kyoto Protocol. Model-based approaches to estimate changes in soil C stocks exist, but they cannot fully replace repeated measurements. Measuring changes in soil C is laborious due to small expected changes and large spatial variation. Stratification of soil sampling allows the reduction of sample size without reducing precision. If there are no previous measurements, the stratification can be made with model-predictions of target variable. Our aim was to present a simulation-based stratification method, and to estimate how much stratification of inventory plots could improve the efficiency of the sampling. The effect of large uncertainties related to soil C change measurements and simulated predictions was targeted since they may considerably decrease the efficiency of stratification. According to our simulations, stratification can be useful with a feasible soil sample number if other uncertainties (simulated predictions and forecasted forest management) can be controlled. For example, the optimal (Neyman) allocation of plots to 4 strata with 10 soil samples from each plot (unpaired repeated sampling) reduced the standard error (SE) of the stratified mean by 9–34% from that of simple random sampling, depending on the assumptions of uncertainties. When the uncertainties of measurements and simulations were not accounted for in the division to strata, the decreases of SEs were 2–9 units less. Stratified sampling scheme that accounts for the uncertainties in measured material and in the correlates (simulated predictions) is recommended for the sampling design of soil C stock changes.

Peltoniemi, Finnish Forest Research Institute, Vantaa Research Unit, P.O. Box 18, FI-01301 Vantaa, Finland E-mail: mikko.peltoniemi@metla.fi
Heikkinen, Finnish Forest Research Institute, Vantaa Research Unit, P.O. Box 18, FI-01301 Vantaa, Finland E-mail: jh@nn.fi
Mäkipää, Finnish Forest Research Institute, Vantaa Research Unit, P.O. Box 18, FI-01301 Vantaa, Finland E-mail: raisa.makipaa@metla.fi

Category : Research article

article id 471, category Research article

Michael Vohland, Johannes Stoffels, Christina Hau, Gebhard Schüler. (2007). Remote sensing techniques for forest parameter assessment: multispectral classification and linear spectral mixture analysis. Silva Fennica vol. 41 no. 3 article id 471. https://doi.org/10.14214/sf.471

Keywords: Picea abies; remote sensing; stand variables; stem number; multispectral classification; Linear Spectral Mixture Analysis

Abstract | View details | Full text in PDF | Author Info

One of the most common applications of remote sensing in forestry is the production of thematic maps, depicting e.g. tree species or stand age, by means of image classification. Nevertheless, the absolute quantification of stand variables is even more essential for forest inventories. For both issues, satellite data are attractive for their large-area and up-to-date mapping capacities. This study followed two steps, and at first a supervised parametric classification was performed for a German test site based on a radiometrically corrected Landsat-5 TM scene. There, eight forest classes were identified with an overall accuracy of 87.5%. In the following, the study focused on the estimation of one key stand variable, the stem number per hectare (SN), which was carried out for a number of Norway spruce stands that had been clearly identified in the multispectral classification. For the estimation of SN, the approach of Linear Spectral Mixture Analysis (LSMA) was found to be clearly more effective than spectral indices. LSMA is based on the premise that measured reflectances can be linearly modelled from a set of so-called endmember spectra. In this study, the endmember sets were held variable to decompose pixel values to abundances of a vegetation, a background (soil, litter, bark) and a shade fraction. Forest structure determines the visible portions of these fractions, and therefore, a multiple regression using them as predictor variables provided the best SN estimates. LSMA allows a pixel-by-pixel quantification of SN for complete satellite images. This opens the view to exploit these data for an improved calibration of large-scale multi-parameter assessment strategies (e.g. statistical modelling or the kNN method for satellite data interpretation).

Vohland, University of Trier, Faculty of Geography and Geosciences, Remote Sensing Department, Trier, Germany E-mail: mv@nn.de
Stoffels, University of Trier, Faculty of Geography and Geosciences, Remote Sensing Department, Trier, Germany E-mail: js@nn.de
Hau, University of Trier, Faculty of Geography and Geosciences, Remote Sensing Department, Trier, Germany E-mail: ch@nn.de
Schüler, Research Institution for Forest Ecology and Forestry (FAWF), Department of Forest Growth and Silviculture, Trippstadt, Germany E-mail: gs@nn.de

article id 286, category Research article

Riitta Hänninen, A. Maarit I. Kallio. (2007). Economic impacts on the forest sector of increasing forest biodiversity conservation in Finland. Silva Fennica vol. 41 no. 3 article id 286. https://doi.org/10.14214/sf.286

Keywords: forest biodiversity conservation; roundwood market; forest industry production

Abstract | View details | Full text in PDF | Author Info

In the next coming years, political decisions will be made upon future actions to safeguard forest biodiversity in Southern Finland. We address the economic consequences on the Finnish forest sector of conserving additional 0.5% to 5% of the old growth forest land in Southern Finland. The impacts on supply, demand and prices of wood and forest industry production are analysed employing a partial equilibrium model of the Finnish forest sector. An increase in conservation raises wood prices and thus the production costs of the forest industry. This makes sawnwood production fall, but does not affect paper and paperboard production. The forest owners’ aggregated wood sales income is unaffected or slightly increased, because an increase in stumpage prices offsets the decrease in the harvests. If conservation increases wood imports, negative effects on forest industry become smaller whereas aggregated forest owners’ income may decline depending on the magnitude of import substitution.

Hänninen, Finnish Forest Research Institute, Unioninkatu 40 A, FI-00170 Helsinki, Finland E-mail: riitta.hanninen@metla.fi
Kallio, Finnish Forest Research Institute, Unioninkatu 40 A, FI-00170 Helsinki, Finland E-mail: maarit.kallio@metla.fi

article id 285, category Research article

Heli Peltola, Antti Kilpeläinen, Kari Sauvala, Tommi Räisänen, Veli-Pekka Ikonen. (2007). Effects of early thinning regime and tree status on the radial growth and wood density of Scots pine. Silva Fennica vol. 41 no. 3 article id 285. https://doi.org/10.14214/sf.285

Keywords: thinning response; ring width; early wood; late wood; intra-ring wood density; X-ray densitometry

Abstract | View details | Full text in PDF | Author Info

Peltola, University of Joensuu, Faculty of Forest Sciences, P.O. Box 111, FI-80101 Joensuu, Finland E-mail: heli.peltola@joensuu.fi
Kilpeläinen, University of Joensuu, Faculty of Forest Sciences, P.O. Box 111, FI-80101 Joensuu, Finland E-mail: ak@nn.fi
Sauvala, Finnish Forest Research Institute, P.O. Box 18, FI-01301 Vantaa, Finland E-mail: ks@nn.fi
Räisänen, University of Joensuu, Faculty of Forest Sciences, P.O. Box 111, FI-80101 Joensuu, Finland E-mail: tr@nn.fi
Ikonen, University of Joensuu, Faculty of Forest Sciences, P.O. Box 111, FI-80101 Joensuu, Finland E-mail: vpi@nn.fi

article id 284, category Research article

Tuomo Nurminen, Jaakko Heinonen. (2007). Characteristics and time consumption of timber trucking in Finland. Silva Fennica vol. 41 no. 3 article id 284. https://doi.org/10.14214/sf.284

Keywords: logistics; cut-to-length operations; time study; work phases; log-normal distribution

Abstract | View details | Full text in PDF | Author Info

Cost efficiency and flexibility have become increasingly important in the logistics of cut-to-length harvesting operations. At the same time, the operating conditions for long-distance transportation have become more demanding and variable. Since the number of log products has increased and the size of harvesting sites has decreased, loads of timber must increasingly be collected from several log decks, increasing the time consumption and costs of the trucking operation. The objectives of this study were to formulate time-consumption models for typical timber transportation activities in Finland and introduce a statistical procedure for examining the variation in time consumption during the trucking phases. The study used a combination of time studies and follow-up studies based on empirical data for 368 loads (a total volume of nearly 18 000 m³) collected from one wood procurement district in central Finland. The model included the following explanatory factors: driving distance, number of log decks, log product and load volume. Since transportation includes several phases and since many factors affect the work performance, significant variation in the total transportation time was observed. This makes planning and cost accounting more difficult. The models developed in this study are a promising initial tool to support route planning and optimization, and cost and profitability calculations for trucking entrepreneurs and the forest industry.

Nurminen, University of Joensuu, Faculty of Forest Sciences; Forest Agency Tuomo Nurminen, Joensuuntie 5 B 8, FI-41800 Korpilahti, Finland E-mail: tn@nn.fi
Heinonen, Finnish Forest Research Institute, Joensuu Research Unit, P.O. Box 68, FI-80101 Joensuu, Finland E-mail: jh@nn.fi

article id 283, category Research article

Ilkka Korpela, Tuukka Tuomola, Esko Välimäki. (2007). Mapping forest plots: an efficient method combining photogrammetry and field triangulation. Silva Fennica vol. 41 no. 3 article id 283. https://doi.org/10.14214/sf.283

Keywords: remote sensing; least squares adjustment; intertree positioning; spatial resection; trilateration

Abstract | View details | Full text in PDF | Author Info

Intra stand spatial information is often collected in ecological investigations, when functioning or interactions in the ecosystem are studied. Local relative accuracy is often given priority in such cases. Forest maps with accurate absolute positions in a global coordinate system are needed in remote-sensing applications for validation and calibration purposes. Establishing the absolute position is particularly difficult under a canopy as is creating undistorted coordinate systems for large plots in the forest. We present a method that can be used for the absolute mapping of point features under a canopy that is efficient for large forest plots. In this method, an undistorted network of control points is established in the forest using photogrammetric observations of treetops. These points are used for the positioning of other points, using redundant observations of interpoint distances and azimuths and a least squares adjustment. The method provides decimetre-level accuracy and only one person is required to conduct the work. An estimate of the positioning accuracy of each point is readily available in the field. We present the method, a simulation study that explores the potential of the method and results from an experiment in a mixed boreal stand in southern Finland.

Korpela, University of Helsinki, Department of Forest Resource Management, P.O. Box 27, FI-00014 University of Helsinki, Finland E-mail: ilkka.korpela@helsinki.fi
Tuomola, University of Helsinki, Department of Forest Resource Management, P.O. Box 27, FI-00014 University of Helsinki, Finland E-mail: tt@nn.fi
Välimäki, University of Helsinki, Department of Forest Resource Management, P.O. Box 27, FI-00014 University of Helsinki, Finland E-mail: ev@nn.fi

article id 282, category Research article

Annika Kangas, Lauri Mehtätalo, Matti Maltamo. (2007). Modelling percentile based basal area weighted diameter distribution. Silva Fennica vol. 41 no. 3 article id 282. https://doi.org/10.14214/sf.282

Keywords: stand structure; diameter distribution; prediction; interpolation

Abstract | View details | Full text in PDF | Author Info

In percentile method, percentiles of the diameter distribution are predicted with a system of models. The continuous empirical diameter distribution function is then obtained by interpolating between the predicted values of percentiles. In Finland, the distribution is typically modelled as a basal-area weighted distribution, which is transformed to a traditional density function for applications. In earlier studies it has been noted that when calculated from the basal-area weighted diameter distribution, the density function is decreasing in most stands, especially for Norway spruce. This behaviour is not supported by the data. In this paper, we investigate the reasons for the unsatisfactory performance and present possible solutions for the problem. Besides the predicted percentiles, the problems are due to implicit assumptions of diameter distribution in the system. The effect of these assumptions can be somewhat lessened with simple ad-hoc methods, like increasing new percentiles to the system. This approach does not, however, utilize all the available information in the estimation, namely the analytical relationships between basal area, stem number and diameter. Accounting for these, gives further possibilities for improving the results. The results show, however, that in order to achieve further improvements, it would be recommendable to make the implicit assumptions more realistic. Furthermore, height variation within stands seems to have an important contribution to the uncertainty of some forest characteristics, especially in the case of sawnwood volume.

Kangas, Department of Forest Resources Management, P.O.Box 27, FI-00014 University of Helsinki, Finland E-mail: ak@nn.fi
Mehtätalo, University of Joensuu, Faculty of Forestry, P.O. Box 111, FI-80101 Joensuu, Finland E-mail: lm@nn.fi
Maltamo, University of Joensuu, Faculty of Forestry, P.O. Box 111, FI-80101 Joensuu, Finland E-mail: mm@nn.fi

article id 281, category Research article

Florence Renou-Wilson, Edward P. Farrell. (2007). The use of foliage and soil information for managing the nutrition of Sitka and Norway spruce on cutaway peatlands. Silva Fennica vol. 41 no. 3 article id 281. https://doi.org/10.14214/sf.281

Keywords: fertilization; Picea abies; foliar analysis; long-term trend; Picea sitchensis; cutaway peatland

Abstract | View details | Full text in PDF | Author Info

This investigation focuses on the development and nutrient status of the first Sitka spruce and Norway spruce stands established on milled cutaway peatlands in Ireland in the late 1980s and early 1990s. Phosphatic fertilization at planting is critical for the establishment of trees on cutaway peatlands but may not be sufficient to see the stands close canopy. Results from this study indicate the likely demand for P and N fertilizer during the rotation of these plantations. During the ten-year-study period (1994–2004), the nutrient status of both Norway and Sitka spruce stands deteriorated with the passage of time. Twenty-seven out of the twenty-eight examined stands became P deficient before 10 years old and half of the plots were N deficient within 13 to 15 years. Sitka spruce stands became N and P deficient earlier than Norway spruce. Regardless of species, tree stands growing on Sphagnum peat entered the critical N deficiency threshold sooner and were all severely deficient by 2004 compared to 22% of the trees growing on Phragmites peat. The effects of aerial re-fertilization were also site specific and although P deficiency was cured, the trees were likely to suffer from nutrient imbalance (N and Cu especially). These results demand a change of standard fertilization practices, which should be related more specifically to peat type and species requirements. Peat type identification and foliar analysis monitoring should become standard management tools while the long-term continuous monitoring of these new forests would be very valuable throughout their first rotation.

Renou-Wilson, University College Dublin, Dublin, Ireland E-mail: frw@nn.ie
Farrell, University College Dublin, Dublin, Ireland E-mail: epf@nn.ie

article id 280, category Research article

Mika Nieminen, Mikko Moilanen, Sirpa Piirainen. (2007). Phosphorus allocation in surface soil of two drained peatland forests following wood and peat ash application – why effective adsorption on low sorptive soils? Silva Fennica vol. 41 no. 3 article id 280. https://doi.org/10.14214/sf.280

Keywords: forestry; ash fertilization; peat; aluminium; iron; phosphorus adsorption; phosphorus fractionation

Abstract | View details | Full text in PDF | Author Info

Fertilization of drained peatland forests with wood ash and different commercial phosphorus fertilizers (calcium phosphates) generally give similar stand growth responses. However, it has been shown that use of calcium phosphate fertilizers generally lead to highly increased P release to recipient water courses. On the other hand, no corresponding release has been reported after ash fertilization. Soil samples from the surface peats from a nutrient poor and a fertile drained peatland site were collected before and 1–4 years after application of five different types of ash products. The changes over time in the different chemical forms of P in the substrate were studied. The results indicated that the reason for the low liability to leaching of ash fertilizers was that significant amounts of P are adsorbed by Al and Fe during weathering of the ash fertilizers. However, further studies are needed to clarify whether the adsorption of P occurs with the Al and Fe of the ash or the native Al and Fe compounds present in soil before ash fertilization.

Nieminen, Finnish Forest Research Institute, Vantaa Research Unit, P.O. Box 18, FI-01301 Vantaa, Finland E-mail: mika.nieminen@metla.fi
Moilanen, Finnish Forest Research Institute, Vantaa Research Unit, P.O. Box 18, FI-01301 Vantaa, Finland E-mail: mm@nn.fi
Piirainen, Finnish Forest Research Institute, Vantaa Research Unit, P.O. Box 18, FI-01301 Vantaa, Finland E-mail: sp@nn.fi

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