RATE OF PEAT INCREMENT IN HUMMOCK AND LAWN COMMUNITIES ON SWEDISH MIRES DURING THE LAST 150 YEARS

We have described the relationship between depth and age of surface peat in hummock and lawn communities on eleven Swedish mires in order to estimate the rate of annual peat increment. The study comprises peat down to a depth of ca. 0.6 m and altogether 679 age determinations were made. Peat younger than 50 yr was found at highly variable depths. Consequently, the rate of annual peat increment was also highly variable. The highest maximum rate of annual peat increment was always found in hummock communities. With increasing age of peat, the range of depths in which peat of a certain age occurred, decreased. This was more obvious in hummock than in lawn communities, indicating that the compaction was more pronounced in hummock communities. Most of the compaction occurred when the peat was younger than 50 yr. The age of the surface peat was determined by the use of small specimens of Scots pine Pinus sylvestris L. on which we measured the vertical distance from the growing point to the mire surface and counted the annual rings.