Rhizome development ofPhragmites australis in a reed community

Variations in the height, shoot density, biomasses of above- and below-ground parts and rhizome distributions ofPhragmites australis were investigated along a line-transect in a reed community at Yufutsu Mire, Hokkaido. Relationships of performance of the reed plants to soil conditions and species compositions were also examined. Three types of rhizome development were recognized in reed plants; (1) the central part of the reed community, characterized by well developed rhizomes and dense aerial shoots, (2) the intermediate part, characterized by development of rhizomes along both the peat and surface layers and very dense aerial shoots, and (3) the marginal part, characterized by development of rhizomes only along the peat layer and sparse aerial shoots. Observation showed that rhizomes in the surface layer actively produced aerial shoots, whereas rhizomes in the peat layer contributed to the spreading of their distribution range. With the growth of rhizomes, organic debris originating from dead rhizomes and roots accumulated in the mineral soil to promote organic soil formation. In dense parts of the reed stand, species composition was poor because of the shading and litter accumulation by reed plants. The effects of microtopography and water level on the establishment of reed seedlings were also considered.