Winter-Time Litter Decomposition in A Subarctic Woodland

Abstract

Changes in mass and quantities of potassium, calcium, magnesium, nitrogen, and phosphorus and extractable phenolics and carbohydrates were monitored over winter in three tissue types: Picea mariana needles, Betula glandulosa leaves, and Cladina stellaris. Samples were set out in litter bags on the lichen mat on 4 September 1981 and retrieved 7 November 1981, and 1 February, 17 April, and 3 June 1982. Over-winter mass losses ranged from 13 to 29% (lichen < spruce < birch) and between 46 and 80% of this loss occurred during the first sampling period, before a permanent snow cover was established. Loss of potassium, magnesium, and phosphorus and phenolics and carbohydrates was also rapid in most tissues during the first sampling period, and over-winter losses of these constituents ranged from 4 to 97%. Nitrogen losses were small in the spruce needles, but the lichen showed an increase in nitrogen over the winter. The results show the importance of winter-time litter decomposition, particularly during the period before a snow cover is established but also under the relatively warm (0 to -3°C) conditions imposed by a thick (>100 cm) snow cover.