COLONIZATION AND MORPHOLOGICAL CHANGES OF A SEDGE RESTRICTING REGENERATION AFTER WIND DAMAGE IN A NATURAL FOREST

Abstract

Many old trees were blown down by typhoons in 1959 and 1961 in a natural coniferous forest
deep in the mountains of Kiso District, Central Japan, and dense dwarf bamboo subsequently delayed the
growth of tree seedlings. Forest engineers have tried to suppress dwarf bamboo to promote the regeneration
of arboreal vegetation. However, after suppression of dwarf bamboo, an unknown grass unexpectedly
colonized the area and replaced them. Afterward, almost no tree seedlings could be observed in the newly
formed community, which seemed to worsen the extent of regeneration. It has been identified that the grass
as Carex oxyandra, a native sedge species indigenous to Kiso District. Commonly, Carex oxyandra grows as
short as about 10 cm like lawn grass, but it seems to have exceedingly enlarged the size in the community.
Thus, investigation on the morphological variation of this sedge in Miure Experimental Forest within the
Kiso National Forest was carried out. Leaf blade length, basal tiller length, and number of leaves per tiller
were measured in upper and lower stands on three slopes in 2009. Results revealed that leaf blade length and
basal tiller length in lower stands were approximately twice as large as those in upper stands on each slope,
whereas the number of leaves per tiller was almost the same (8.8-9.4 leaves). Consequently, tussocks of this
sedge became large in lower stands on a slope, which made the community overcrowded and damp,
restricting tree regeneration.