Artikkelit kirjoittajalta Klaus Silfverberg

The low availability of usable phosphorus (P), as well as the scarcity of potassium (K), are often limiting tree growth on peatlands. Approximately one third of the 5.5 million ha of peatlands drained for forestry in Finland has been fertilized during the last 50 years. The aim of this study was to determine the long-term effect of PK fertilization on the nutrient status of Scots pine on different site types of drained peatlands. Changes in nutrient concentrations (N, P, K) and dry mass of current needles was used for examining the effect of fertilization. The material included 82 fertilization experimental stands comprising a total of 892 needle samples; 434 from PK-fertilized and 458 from unfertilized control stands. The needles were collected and analyzed between 1980 and 2002. Depending on the experiment, a time period of 1–35 years had elapsed between fertilization and needle sampling. More than half (54%) of the control stands had P concentration below the defi ciency limit 1.3 mg g–1, and correspondingly, 48% had K concentration below 4.0 mg g–1. Fertilization increased considerably the needle dry mass and foliar P and K concentration raised above the deficiency limits. The lower the concentrations of foliar P and K and the higher the concentration of N were in control trees, the more pronounced the effect of PK fertilization was. Compared to control, the needle P concentration was still noticeably higher on the fertilized stands after 21–35 years of the fertilization. However, K concentration had decreased and was at the same level as in the control trees. The effect of fertilization was strongest on sites which had been treeless or sparsely forested before drainage and which had severe nutrient shortages or imbalances. The response to fertilization was very similar regardless of the temperature sum of the year the needles first appeared. The results of this study show that the P status of Scots pine could be improved for over 30 years with single fertilization. On the other hand, ensuring the K status will require 1–2 refertilization treatments during the rotation period.

• Silfverberg, Finnish Forest Research Institute, Vantaa Research Unit, P.O. Box 18, FI-01301 Vantaa Sähköposti: ei.tietoa@nn.oo
• Moilanen, Sähköposti: ei.tietoa@nn.oo

Six field experiments on the use of mineral soil for amelioration of pine-dominated peatland forests were established in the 1920’s and 1930’s on drained mires in southern and central Finland. The treatments consisted of varying amounts of different textured mineral soil added on top of peatland. Soil samples were taken 52–74 years after the mineral soil application in 10 cm layers, up to 40 or 50 cm depth. The samples were analysed for pH, ash content, bulk density and nutrient concentrations. In two of the experiments, foliar samples of Scots pine were analyzed 66 and 77 years after the mineral soil application, and in one experiment, tree growth was measured for the period of 31–60 years after the application. The mineral soil had a long term effect on the physical and chemical properties of the top peat layer. Ash content and bulk density of the peat increased along with increasing application amounts, as did soil total P, K, Ca, Mg, Zn, Fe and B. The changes caused by the mineral soil were mostly restricted to the top 30 cm layer. The higher the soil fine fraction was, so was the increase in peat total P, K, Ca and Mg amounts. The addition of mineral soil increased tree growth and improved nutrient deficiencies (P, K) of Scots pine on one experiment, but decreased the B concentrations near the deficiency level.

• Hytönen, Finnish Forest Research Institute, Kannus Research Unit, P.O. Box 44, FI-69101 Kannus, Finland Sähköposti: ei.tietoa@nn.oo
• Moilanen, Sähköposti: ei.tietoa@nn.oo
• Silfverberg, Sähköposti: ei.tietoa@nn.oo

Metsäntutkimuslaitos perusti vuosina 1973–1978 ojitusaluemetsiin maanlaajuisen nk. H-kulttuurikoesarjan. H-kulttuurilla tarkoitetaan metsänuudistamis- ja kasvatustapaa, jossa puuntuotannon olosuhteet — puiden vesi- ja ravinnetalous sekä myös puunkorjuu — on optimoitu puuntuotoksen ja metsänkasvatuksen talouden maksimoimiseksi. Vuosien 1999–2003 aikana tästä koesarjasta mitattiin yhdeksän koetta. Kokeiden perustamisesta oli tällöin kulunut 24–30 vuotta. Mitatut kohteet olivat istutusmänniköitä, jotka saivat istutuksen yhteydessä laikku- tai kaistalannoituksen. Kasvupaikat vaihtelivat karuista keskiviljaviin; kohteiden ravinnetila (turpeen typpi, neulasten pääravinteet) oli varsin hyvä. Yleiset kasvutekijät (lämpösumma, viljavuus) ovat määränneet puuntuotoksen tason. Pelkän istutuslannoituksen saaneilla koealoilla runkopuun kokonaistuotos oli kokeesta riippuen 46–192 m3 ha–1. Vuonna 1994 tehtyjen jatkolannoituskäsittelyjen vaikutus vaihteli suuresti. Parhaiten kasvaneella Padasjoen mustikkaturvekankaalla tuotokset olivat 1973 1999, käsittelystä riippuen, 182–238 m3 ha–1. Kokeiden perustamisvaiheessa esitettyihin tuotostavoitteisiin (300 m3 ha–1 30 vuodessa) ei päästy missään kokeessa. Nykykäsityksen mukaan manuaaliseen puunkorjuuseen perustunut ja paljon hoitotöitä vaatinut H-kulttuuri tuottaa liian kallista puuta. Ajatukseltaan ja toteutukseltaan tämä tutkimuksellinen lähestymistapa on kuitenkin ollut kokopuukorjuu- ja energiametsäasioiden edelläkävijä. Avainsanat: intensiivinen kasvatus, kokonaistuotos, lannoitus, neulaset, turvemaa Key words: intensive cultivation, total yield, fertilisation, needles, peatland hiilen kierto, Fennoskandia, Holoseeni, Pohjois-Venäjä, palsa, ikirouta, kasvimakrofossiili, radiohiiliajoitus

• Silfverberg, Sähköposti: ei.tietoa@nn.oo
• Issakainen, Sähköposti: ei.tietoa@nn.oo
• Haikarainen, Sähköposti: ei.tietoa@nn.oo

In this study the vegetation composition of a drained mire that was partly forested and partly kept treeless was compared. The study site was a low sedge fen near the town Oulu in west central Finland. Drainage was carried out in the 1930s. A power transmission line was drawn through the fen in 1956. The area under the line was kept treeless through repeated cleanings. In summer 2004 the vegetation was inventoried on a study area half of which was on the treeless and half on the forested part. The forested and treeless parts were similar with respect to mire site type, depth of peat layer and efficiency of drainage. Therefore the effect of the tree stand on the vegetation on the forested part was obvious. The secondary succession of the vegetation had been significantly slower on the treeless part. Practically no forest moss species, but also fewer Sphagnum moss species were found on the treeless part. On the other hand, a number of sedge-like plants were found only there. With regard to species number and coverage, the largest group was dwarf shrubs, especially on the forested part.

• Silfverberg, Metsäntutkimuslaitos, Vantaan toimintayksikkö (Finnish Forest Research Institute, P.O. Box 18) PL 18, FIN- 01301 Vantaa, Finland Sähköposti: ei.tietoa@nn.oo
• Seväkivi, Sähköposti: ei.tietoa@nn.oo

Relationships between the peat nutrient concentrations and the degree of humification, the ground vegetation and the botanical composition of the peat were studied on an afforested, originally treeless mire with a wide nitrogen gradient. The afforestation was carried out in 1971 using spot sowing and spot fertilisation. A broadcast fertilisation experiment that involved six replicates with four treatments, (i) a control, (ii) PK (rock phosphate and KCl), (iii) PK+ B, Cu and (iiii) wood ash was established in 1981–82. The surface peat layers were sampled for nutrient analyses in 1995 and for peat type determinations in 1997. The ground vegetation was inventoried in 1995. In 1995, the peat total nitrogen concentration varied from 8.7 to 29.1 mg g-1 in the 0–5 cm peat layer. The total nitrogen, phosphorus and iron concentrations and the degree of humification in the peat were all positively correlated with the proportion of Carex components and with each other. The frequency of Sphagnum mosses correlated negatively but that of forest mosses positively with the peat total nitrogen concentration. Broadcast fertilisation with wood ash increased the concentrations of phosphorus, potassium, calcium, magnesium, manganese, boron, copper and zinc especially in the 0–5 cm peat layer but did not affect other peat properties or the ground vegetation.

• Hartman, Finnish Forest Research Institute, Vantaa Reseach Centre, P.O. Box 18, 01301 Vantaa Sähköposti: ei.tietoa@nn.oo
• Kaunisto, Sähköposti: ei.tietoa@nn.oo
• Silfverberg, Sähköposti: ei.tietoa@nn.oo

The nutrient concentrations of the water percolating through fertilised peat cores were investigated in a greenhouse experiment. The nutrient concentrations in the peat cores were also determined before and after the experiment. The fertiliser treatments were 500 kg ha-1 of PK peatland fertiliser, 5 000 and 25 000 kg ha-1 of birch ash, and an unfertilised control. The cores were watered on three occasions after application of the fertilisers. The percolation water collected from the fertilised cores contained significantly more nutrients than the control. The total amounts of leached nutrients were equivalent to 0.01 - 20.1 % of the nutrients in the peat cores, K clearly being leached the most. The susceptibility of the nutrients to leaching followed the order K > Mg > Ca > Mn > P. The fertiliser treatments also increased the leaching of nitrate and ammonium. The amount of leached nutrients was relatively the highest from the PK treatment, but in absolute terms the highest from the largest dose of wood ash. According to the peat analyses, the concentrations of most of the nutrients had increased only in the surface layer of the peat (0 - 5 cm). In contrast, the K concentrations had increased throughout the whole profile (0 - 20 cm). The application of large amounts of ash fertiliser should be avoided in order to minimise nutrient leaching losses. Although the fertilisers used in this experiment have been or are being replaced by new types of fertiliser, the results of this study can be used to facilitate the interpretation of the results of field experiments in which these fertilisers have been used..

• Silfverberg, Finnish Forest Research Institute, P.O. Box 18, FIN-01301 Vantaa, Finland Sähköposti: ei.tietoa@nn.oo

The profitability of wood ash-fertilizing (5-16 t ha-1) of four drained peatland Scots pine stands in central Finland was investigated. The profitability of forest drainage alone and forest drainage plus ash-fertilization was compared. After 44-56 years, the wood ash-fertilization had increased mean productivity by 3.1-12.1 m3 ha-1 a-1. Using an interest rate of 3 % and without subsidies, the net present value of the stands was 2500-20300 FIM ha-1 higher as a result of the ash-fertilization than the value given by forest drainage alone. The real internal rate of return due to ash-fertilization without subsidies was 3.7-9.3 %. The interest rate, the fertilization dose and related costs, and the stumpage prices affected profitability. The state forest improvement subsidies further increased the profitablity of ash-fertilization. Key words: forest fertilization, internal rate of return, net present value, Scots pine, stem volume, wood ash

• Lauhanen, The Finnish Forest Research Institute, Kannus Research Station, FIN-69100 Kannus, Finland Sähköposti: ei.tietoa@nn.oo
• Moilanen, Sähköposti: ei.tietoa@nn.oo
• Silfverberg, Sähköposti: ei.tietoa@nn.oo
• Takamaa, Sähköposti: ei.tietoa@nn.oo
• Issakainen, Sähköposti: ei.tietoa@nn.oo

Biosludge from a biological waste-water treatment plant was tested in a greenhouse experiment on three substrates at 7 levels (0-240 m3/ha). The growth of birch seedlings was best on nitrogen poor substrate collected from a Vaccinium vitis-idaea (VT) forest site. NPK-fertilization was superior to sludge treatments on poor peat substrate. Biosludge increased the foliar nitrogen content on all three soils. Nutritional value of coal ash was tested at 17 levels (0.4-160 t/ha) on mineral soil from an afforested field. Low application levels of coal ash (400-1600 kg/ha) increased the growth of the birch seedlings more than other applications. However, even extremely high coal ash amounts (up to 160 t/ha) were not lethal for birch seedlings. Coal ash increased foliar boron contents two to three fold and with applications higher than 20 t/ha increase was five to seven fold. Birches planted in 1978 on a coal ash landfilling area showed good survival and growth, despite toxic boron contents and visual disturbances in the leaves. Key words: Boron toxicity, fertilization, peat substrate, recycling

• Veijalainen, The Finnish Forest Research Institute, Box 18, FIN-01301 Vantaa Sähköposti: ei.tietoa@nn.oo
• Silfverberg, Sähköposti: ei.tietoa@nn.oo
• Hytönen, Sähköposti: ei.tietoa@nn.oo

The study was made in four experimental fields on drained peatland in western Finland (63-66°N). One of the experiments was laid out in 1972; the others in 1978-1979. Treatments included different kinds of wood ash and PK-fertilizer, an ash-imitating mixture and apatite+biotite. Needle analyses and growth measurements were carried out in 1983— 1986. The concentrations of Mg and Mn generally decreased after fertilization. A rise in the foliar P, foliar K and foliar weight correlated with the growth response. Best growth increment was achieved with the ash-imitating mixture and PK-fertilizer, while apatite+biotite did not increase growth. In the first years after fertilization, growth on the ash plots was weaker, but later stronger or equal to growth on PK- and ash-imitating plots. The correlation between initial tree height and post-fertilization growth was similar on the different treatments. The poor growth increment on some ash treatments was probably due to the insufficient amount of nutrients in the ashes used. Key words: Ash fertilization, Finland, growth, needle analysis, peat, Scots pine

• Silfverberg, The Finnish Forest Research Institute, P.O. Box 18, SF-0I301 Vantaa, Finland Sähköposti: ei.tietoa@nn.oo

This study included growth and needle analysis in ash-fertilized spruce and pine stands near Oulu (65 °N, 26 °E). Most of these stands, totalling 770 measured trees, were on peat and fertilized in wintertime 1980 and 1981 as practical work with 40 m3/ha. By 1985 there was a clear increment of growth, especially in spruce stands, probably due to the great amount of phosphorus (375 kg/ha) applied. Keywords: peatland forestry, tree growth, ash-fertilization, phosphorus.

• Silfverberg, Department of Peatland Forestry, The Finnish Forest Research Institu­te, Unioninkatu 40 A, 00170 Helsinki, Finland Sähköposti: ei.tietoa@nn.oo
• Issakainen, Sähköposti: ei.tietoa@nn.oo

Since 1961 an investigation has been carried out to determine the role of certain growth factors in peatland forests. The study area was a drained dwarf-shrub pine bog at Jaakkoinsuo, Central Finland (62°03'N, 24°43'E). The water table in the ditches surrounding the sample plots was maintained at four (10, 30, 50, 70 cm) levels below the peat surface. One of the series was fertilized twice with NPK. and another covered with a thick cover of straw The third was unfertilized. At a regulation level of 70 cm the volume growth increment for 1961-80 was as great on the unfertilized plot as on the one fertilized twice with NPK. This was chiefly due to the effective mobilization of the nutrient resources in the peat. At the 10 cm level, growth was weak because of poor aerobic conditions in the root zone. NPK fertilization gave the greatest increment at levels of 30 and 50 cm. The greatest increment was, however, achieved on the straw-covered plots. The reason was most probably the elimination of competing field and ground layers. The differences between the regulation levels remained quite similar throughout the study period. We can thus suppose that effective drainage may partly compensate for fertilization, if the nitrogen reserves in the peat are adequate.

• Silfverberg, Sähköposti: ei.tietoa@nn.oo