Suo - Mires and peat 54 (2003)

Estimates of the area of cultivated acid sulphate soils in Finland range from 50,000 ha to 336,000 ha. In these soils, sulfides are oxidized to sulphuric acid upon aeration, which is promoted by drainage. Agricultural use of these soils requires abundant liming. Acidic drainage waters impact the aquatic life negatively. Early research concentrated on the agricultural utilization of acid sulphate soils while more recently environmental aspects have been emphasized. Controlled drainage, aiming at a high water table, is considered an option for the management of acidity. Owing to evapotranspiration, however, sulfidic layers may be exposed to oxidation every summer in spite of controlled drainage. Successful submerging of sulfidic layers may require pumping of water to the field from outside sources. Abandoning the most acidic sulphate soils and stop draining them would prevent further oxidation of sulfides. This is a sensitive issue, because the farmland is private property. Moreover, it is not exactly known where the most acidic sulphate soils are located and how their abandonment would impact the quality of water in recipient rivers.

• Yli-Halla, MTT Agrifood Research Finland, Environmental research, FIN-31600 Jokioinen, Finland Sähköposti: ei.tietoa@nn.oo

Despite agreement that organic matter is an essential soil component, terminological confusion may result in inexact concepts of its role in controlling the chemical, physical and biological processes. Humus, which is synthesized primarily in humification process by microbes, is structurally very complex and resistant to degradation. It is produced from non-humus material: litter, a whole series of decomposition products, and identifiable constituents. Classifying soil organic matter into humus and non-humus materials permits the systematization of reactions involving organic matter. Microbial degradation of non-humus material releases plant nutrients and produces polysaccharides that stabilize soil aggregates, thus improving conditions for root growth. Antibiotics, vitamins and other active compounds affecting the biotic system can end up into soil as byproducts of the microbial metabolism. Only a very small portion of non-humus material is used as raw material for humus, whose importance is based on physico-chemical properties. Through its high water holding capacity, humus can physically control the mobility of compounds. Diverse functional groups participate in various types of chemical reactions (ion exchange, complex formation, dissolution, physical sorption of non-polar organic chemicals, etc). Similarly as in soil, humus acts as a buffer in water bodies. However, in contrast to soil, in waters photochemical reactions can enhance its degradation, thus leading to nutrient loadings and oxygen budget problems.

• Hartikainen, Department of Applied Chemistry and Microbiology, Box 27, 00014 University of Helsinkin, Finland Sähköposti: ei.tietoa@nn.oo

A viable understorey of Norway spruce often develops under a nurse crop on nutrientrich peatlands drained for forestry. The impact of birch nurse crop density and height equalization of the Norway spruce understorey on the height growth of spruce seedlings was studied on three sites: on a transforming herbrich spruce swamp, an abandoned peat field and a mixed peat/mineral soil field. The nurse crop was managed in 1990: 1) no thinning, 4000 stems ha-1, 2) thinning to 1000 stems ha-1. 3) thinning to 500 stems ha-1, or 4) removal of the nurse crop. In addition, the spruce seedlings over 1 m in height were removed from randomized halves of each plot. The unmanaged nurse crop reduced the growth of the understorey the most on all the sites. On the other hand, the spruce seedlings grew the best on the plots where the nurse crop had been removed. Due to height equalization the growth of the spruce understorey first slowed down, but towards the end of the study period the height growth of the equalized and non-equalized spruce understoreys were almost the same.

• Päätalo, The Finnish Forest Research Institute, Muhos Research Station, Kirkkosaarentie 7, FIN-91500 Muhos, Finland Sähköposti: ei.tietoa@nn.oo
• Hilli, Sähköposti: ei.tietoa@nn.oo
• Moilanen, Sähköposti: ei.tietoa@nn.oo
• Tillman-Sutela, Sähköposti: ei.tietoa@nn.oo

The development, structure, production and fertilisation of planted black spruce (Picea mariana (Mill.) B.S.P) and Scots pine (Pinus sylvestris L.) stands growing on a drained, originally treeless Sphagnum papillosum fen (LkKaN) in Central Finland up to the age of 30 years were studied. For black spruce the stem number was 2250 stems ha–1, dominant height was ca 7.1 m, the mean stand volume 26 m3 ha–1, the annual mean volume increment 1.5 m3 ha–1 and the total mortality based on stem number was 21%. For Scots pine the comparable characteristics were 1015 stems ha–1, 10.4 m, 45 m3 ha-1 , 3.3 m3 ha-1 and 59% respectively. Fertilisation had no apparent impact on the stand characteristics. About 63% of the planted black spruce individuals had at least one vegetatively generated layer. High number of layers seemed to have a negative effect on dominant parent tree growth. It is concluded that growth and yield of black spruce are generally not competitive in operational forestry in Finland. However, black spruce could be used as an alternative tree species in treeless areas that resist afforestation, and it might also be cultivated for decorative purposes.

• Sarkkola, Department of Forest Ecology, P. O. Box 27, Fin-00014 University of Helsinki Sähköposti: ei.tietoa@nn.oo
• Päivänen, Sähköposti: ei.tietoa@nn.oo

A natural understorey of Norway spruce often develops under birch on oligo-mesotrophic peatlands, but spruce can also be planted on these sites. The effects of fertilization and the density of the pubescent birch nurse crop on the height growth and needle nutrient status of a planted spruce understorey on an old drained herb-rich sedge pine fen was investigated in this study. The spruce transplants were planted early in the 1960’s. The nurse crop was removed, thinned to 200 stems ha-1 or left unmanaged in 1988. A number of plots were also fertilized. The height growth of the spruce transplants was measured during two periods after management, and the needle nutrient concentrations were determined before fertilization and again 10 years later. The height growth of the spruce was 40 - 60% greater after removal of the nurse crop than that under the unthinned nurse crop. Even the thinned nurse crop slowed down the growth of the understorey. However, height growth was the best on the plots on which the nurse crop was removed and the plots fertilized.

• Hilli, OSLA, Kirkkotie 1, FIN-91500 Muhos, Finland Sähköposti: ei.tietoa@nn.oo
• Päätalo, Sähköposti: ei.tietoa@nn.oo
• Moilanen, Sähköposti: ei.tietoa@nn.oo
• Piiroinen, Sähköposti: ei.tietoa@nn.oo

The effects of refertilisation and growing density on the soil and tree nutrition, root penetration and growth of Scots pine stands were studied in a cutaway peatland area with deep peat layers. The fertilisation treatments were control, N1975+PKB1985 and PK1975+PKB1996 refertilisations and those of the growing density <1 300, 1 654 and 1 954 trees ha-1. The maximum root penetration varied between 26 and 34 cm independently of the treatments. The N/P ratios in pine needles were quite high even on the refertilised plots (11.6-15.7). The duration of P fertilisation seems to be shorter (about 15 years) on cutaway peatlands with deep peat layers than on drained peatland forests. The greatest yield without natural removal (239 m3 ha-1, on an average) in 35-years-old stands was measured on plots, which had the highest growing density and had been repeatedly fertilised with PK. The results show that quite a high yield of Scots pine can be reached on cutaway peatlands. However, pine has to be fertilised with PK at the afforestation stage and at least once later if the remaining peat layer is 40-60 cm, and possibly several broadcast fertilisations are needed on peat layers deeper than 60 cm. It seems that growing tree stands on cutaway peatlands in higher densities than in conventional forestry may improve nutrient cycling in stands and hence decrease leaching of nutrients from the site.

• Aro, Finnish Forest Research Institute, Parkano Research Station, Kaironiementie 54, FIN-39700 Parkano Sähköposti: ei.tietoa@nn.oo
• Kaunisto, Sähköposti: ei.tietoa@nn.oo

This review integrates the results from several recent studies on carbon (C) accumulation in undisturbed boreal and subarctic mire ecosystems in Finland, Sweden, Russia, Canada, and USA. Generally, a large variation in the average long-term apparent rate of carbon accumulation (LORCA) has been found among mires based on the mire type, age and geographical location. The differences in LORCA between the raised bog region and the aapa mire regions were found to be significant. The updated LORCA for undrained boreal and subarctic mire regions has been estimated at 13–20 g C m–2 a–1 throughout the Holocene, which is clearly lower than previous estimates for these northern mire regions. The age of the peat column is an important predictor of C accumulation and has to be taken into account when comparing results. The results indicate a rapid mire expansion in southern Finland from ca. 10 500 to 8500 cal. year BP, from 5000 to 3000 cal. year BP and around 2000 cal. year BP. In northern Finland the extensive mire expansion occurred from ca. 10500 to 8000 cal. year BP. The recent apparent rate of C accumulation (RERCA) in boreal and subarctic mire regions over the past 100 to 200 years ranges from 30 to 120 g C m-2 a-1. The future C balance scheme of mires is also briefly discussed. Key words: carbon accumulation, bogs, fens, boreal region, subarctic region, Holocene, climate change

• Turunen, Geological Survey of Finland, Kuopio Unit, P.O. Box 1237, 70211 Kuopio, Finland Sähköposti: ei.tietoa@nn.oo

Wood production capacity on drained peatlands depends on the site type and temperature sum. Site type is closely related to the peat total nitrogen concentration. This study aims at clarifying the effect of peat nitrogen, fertilization and refertilization on the foliar nitrogen concentration of Scots pine in different temperature sum conditions (850, 950 and 1080 d.d.) on peatland sites with a wide peat nitrogen gradient (0.79- 2.80% in the 0-10 cm layer). In the coldest region, regardless of the peat total nitrogen concentrations in the 0-10 cm surface peat layer and PK- fertilization or PK-refertilization (37 and 26 years earlier respectively), the needle nitrogen concentrations were mostly below the severe deficiency limit (N = 1.2%) and also the arginine concentrations revealed a nitrogen shortage (<0.5 mg g-1). In the middle region the mean nitrogen concentrations in the needles were clearly higher and in the PK- fertilization and PK-refertilizations (32 and 22 years earlier respectively) surpassed the slight nitrogen deficiency limit (N = 1.3%). Also the arginine concentrations surpassed the deficiency limit (0.5 mg g-1 ) in both fertilization treatments although the mean arginine concentrations were near or under the deficiency limit. In the warmest region 25-26 years after the spot fertilization the mean nitrogen concentration was 1.84% and the arginine concentration was 3.04 mg g-1 revealing a surplus of nitrogen caused by phosphorus and potassium deficiencies. The PK-fertilization given 10 years later decreased the nitrogen concentration to 1.56% and the arginine concentration to 0.58 mg g-1. In the more favourable conditions the nitrogen and arginine in the needles increased when the nitrogen in the peat increased. In conclusion, tree growth in the middle and the warmest temperature sum region would respond to PK-refertilisation above a certain total peat nitrogen level but in the coldest temperature sum region tree growth would not respond to PK-refertilization in any of the studied peat total nitrogen conditions because of nitrogen deficiency.

• Pietiläinen, The Finnish Forest Research Institute, Muhos Research Station, Kirkkosaarentie 7, FIN-91500 Muhos, Finland Sähköposti: ei.tietoa@nn.oo
• Kaunisto, Sähköposti: ei.tietoa@nn.oo