The purpose of this study was to reveal the relationships between floristic patterns and environmental factors at the landscape scale in order to develop effective methods for conservation of plant species diversity in paddy field landscapes. We selected 9 study sites according to various characteristics of topography, condition of paddy field consolidation, and degree of urbanization in Kamiina district, Nagano Prefecture. The floristic survey was done for 10 landscape elements in each site from March to November, 2009, 2010 and 2011. Using TWINSPAN and principal component analysis (PCA), we revealed that floristic patterns were affected strongly by the topographical features (e.g., relative height, elevation and urbanization). In mountainous sites, paddy slopes were rich in grassland plants. In plain sites, roads and paddy levees were rich in alien plants, while paddies and waterways were rich in aquatic plants. The presence of soil waterway was deeply related to the diversity of aquatic plants in paddy levee. The condition of paddy field consolidation affected the diversity of grassland plants in paddy slope. These environmental factors at different spatial scales should be considered for conservation planning of plant species diversity within landscape elements that need to be preferentially preserved in paddy field landscapes.
