%0 Articles
%T Männyn kylvö ja luontainen taimettuminen vanhoilla ojitusalueilla – turvemaiden uudistamisen erityispiirteitä
%A Saarinen, Markku
%D 2013
%J Dissertationes Forestales
%V 2013
%N 164
%R doi:10.14214/df.164
%U http://dissertationesforestales.fi/article/1947
%X Artificial and natural seeding of Scots pine in old drainage areas – Unique features of forest regeneration on peatlands

The aim of this dissertation was to investigate site characteristics unique to nutrient-poor, forestry-drained peatlands from the standpoint of establishing the second post-drainage generation of forest. Specifically, the effects of ground vegetation succession, surface peat structure and composition, water table level, and peat water retention capacity on the regeneration success of Scots pine after articial and natural seeding were examined.

As Sphagnum moss cover declines and moss species typical of upland soils increase in abundance, seedbed receptivity of forestry-drained sites gradually becomes weaker. Thus, in order for natural regeneration to succeed in old drainage areas, some means of soil preparation is necessary, at the very least scarification. Depending on the progression of vegetation succession, a raw humus layer originating from plant litter may also have developed in the forestry-drained area. Following the disappearance of Sphagnum cover, the presence of raw humus most notably reduces seedbed receptivity in old drainage areas.

After final felling, changes in the ground layer of vegetation often occur quite slowly especially on dwarf shrub and Vaccinium vitis-idaea drained peatland site types, provided that the water table level does not rise too high. The total coverage of vegetation in scalps decreased and succession markedly slowed when the water table level corresponded to that of a well drained site. Maintenance drainage carried out concurrently with soil preparation in the regeneration area is thus an effective measure when attempting to retard the invasion of vegetation onto scalped surfaces. In mounded areas, relatively large, over 25 cm high mounds remained free of vegetation for a long time, particularly when they had been created from deeply dug, highly decomposed peat.

Due to the inherent variation in the water table level (in scalps and rotavated furrows) and sensitivity of the peat to desiccation (in mounds), forest regeneration via artificial or natural seeding is highly susceptible to weather conditions. In a growing season characterized by average rainfall and temperature, the regeneration result tends to be better in mounded than scalped regeneration areas. Such is the case particularly in years when the fluctuating water table level in a scalped regeneration area rises too high during late summer. From the seedling regeneration aspect, this problematic variation in the water level of scalps is a more probable scenario than excessive desiccation of the surface peat in mounds during an average growing season. Scalps, on the contrary, are ideal seedbeds during dry and warm growing seasons when excess drying of mounds is most likely to occur.