Spatial distribution patterns and their causing factors of an alien plant, Vicia villosa along the Nakdonggang River

초록

Vicia villosa Roth (Leguminosae), an alien plant escaped from cultivated populations as a rotation crop, has invaded into the native vegetation and reduced biodiversity of native plant species in South Korea. The aim of the study was to elucidate the spatial patterns and the influencing factors of the distribution of V. villosa in the riparian zone of the Nakdonggang River. We mapped the distribution area of V. villosa community and investigated the land use within the levees and adjacent river and geomorphological factors at intervals of 1.5 km along a 300 km-long riparian zone of the river. Results of Wald-Wolfowitz runs test and Durbin-Watson test on spatial pattern showed that the distribution of V. villosa communities was spatially autocorrelated and aggregated in the riparian zones along the linear longitudinal scale from downstream to upatream. Especially V. villosa was abundant in the middle stream of the river. The communities of riparian zones were spatially correlated between both sides of the channel. There was significant spatial association in that the V. villosa community was abundant in areas with the abandoned cropland in the floodplains within the levees and the cropland and the bareland in the land adjacent to the stream. Our findings reveal that V. villosa may be introduced from the cultivated cropland adjacent the river and expanded mainly to the nearby abandoned cropland in the riparian area. It is recommended to start controlling V. villosa from the center of its aggregated distribution area and to restore the abandoned cropland by facilitating natural succession for the conservation of native riparian vegetation.