Artikkelit jotka sisältää sanan 'Acrotelm'

The carbon pool of surface layers (up to 500 years old) in 73 boreal mires was investigated in order to assess its significance in the carbon cycle. Peat columns were collected from mires of varying depth, age and degree of natural state in the aapa mire and raised bog regions and coastal mires of southern and central Finland and Russian Karelia. The quantities of carbon sequestered during recent centuries and over the entire lifetimes of the mires were determined using a total of 367 dates (186 14C AMS and 181 conventional dates) and age-depth models derived from bulk density measurements. Particular attention was paid to accumulation over the last 100 and 300 years, as these periods encompass the best estimates of the acrotelm age across the range of sites investigated. The average carbon pool of layers younger than 300 years was determined as 101 ± 8 tonnes ha-1 in the aapa mire region, 115 ± 9 tonnes ha-1 in the raised bog region and 184 ± 20 tonnes ha-1 in coastal mires. Overall, the mean carbon pool of layers younger than 300 years was calculated to be 121 ± 7 tonnes ha-1 (range 44–259 tonnes ha-1) and of layers younger than 100 years 63 ± 4 tonnes ha-1 (range 17–141 tonnes ha-1). The size and dynamics of the carbon pool represented by these surface layers depends upon the mire site type, vegetation and natural state; variations reflect differences in plant communities as well as factors that affect biomass production and decay rates. The high carbon accumulation in surface layers is temporary and mainly related to the development of the mire. The surface layers are still undergoing a rapid carbon cycle. A relatively rapid accumulation and turnover of carbon is taking place in surface layers (<300 years) in the same way as in a growing forest. Therefore, this "pre-peat" in the surface layers of mires should be distinguished as a separate class from the peat underneath. Our results indicate how important it is to understand the carbon accumulation rates of surface layers and the long-term dynamics of mire carbon accumulation in order to set the current flux estimates in perspective.

• Mäkilä, Geological Survey of Finland, P.O. Box, 96, 02151 Espoo, Finland Sähköposti: ei.tietoa@nn.oo
• Goslar, Sähköposti: ei.tietoa@nn.oo

The peat formation time scale in the acrotelm was evaluated using the rate of burial of the root collars and the tree age of buried Scots pine stems in the surface peat. The data were originally presented, but unanalysed, by A.K. Cajander (1906). During the first 30 years after the germination of pine seed the Sphagnum carpet above the root level increased its thickness without noticeable compression and decomposition. During the following 20-30 years the decomposition increased, but the growth of Sphagnum also decreased. A third phase began after 55-60 years during which the growth of Sphagnum was compensated by decomposition. Keywords: Acrotelm, peat formation, Sphagnum growth

• Lindholm, Water and Environment Research Office (Nature Conservation), Water and Environment Research Institute, P.O. Box 250, SF-0010! Helsinki, Finland Sähköposti: ei.tietoa@nn.oo