Suo - Mires and peat vol. 54 no. 1 | 2003

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