Ability of Three Temperate Grasses to Compete with \u3cem\u3ePhalaris arundinacea\u3c/em\u3e L.

Weeds with rhizomes have become an ever-increasing problem in the grasslands of Hokkaido in northern Japan. Many meadows in the Tenpoku region, located in the northernmost part of Hokkaido, have been invaded by Phalaris arundinacea L., a grass with aggressive colonising ability known as the primary and most difficult to control weed in the Tenpoku region. However, dairy farmers in the grasslands of the Tenpoku region most commonly cultivate Phleum pratense L., in spite of its low competitive ability. The Tenpoku region frequently experiences years of low rainfall or drought, but P. pratense has low tolerance to drought (Okamoto et al., 2012; Okamoto and Furudate, 2010). Lolium perenne L. and Dactylis glomerata L. are also cultivated in the Tenpoku region, where they are used as rough forages; however, they are much less commonly cultivated than P. pratense. These species are thought to possess not only higher competitive ability than other grasses, but also higher drought tolerance than P. pratense, and thus may be more suitable for cultivation in some parts of the Tenpoku region. Therefore, we suggest that farmers choose a grass species suitable for their land. To further develop this concept, it is necessary to elucidate the differences among the abilities of these species to compete with invading P. arundinacea. Therefore, the objective of this study was to evaluate and compare the competitive ability of these temperate grass species (L. perenne, D. glomerata, and P. pratense) with those of P. arundinacea