Effects of available nitrogen on numbers of native herbaceous plants in Aomori, Japan

Many herbaceous plants are threatened with extinction due to decrease in grassland in Japan. We investigated the factors affecting herbaceous plant communities in Towada, Aomori, Japan, especially the relationship with soil chemistry. We conducted vegetation surveys at 63 locations around the fields, ski sites, roadside slopes, and took soil samples for chemical analysis. 11 native herbaceous plants were observed on average. Based on stepwise multiple regression analysis, the coverage of exotic plants and available phosphate negatively affected the number of native herbaceous plants. Available nitrogen in soil was the second most influential factor and positively affected.

Many herbaceous plants are threatened with extinction due to decrease in grassland in Japan. The communities dominated by native herbaceous plants were mostly in soils with low available phosphate in notrthern Kanto area, where Andisols have developed (Hiradate et al., 2008). Available phasphte is usually limited in Andisols due to high aluminum contents, and its increases promote invasion and luxuriance of exotic herbaceous plants. We investigated the factors affecting herbaceous plant communities in Towada, Aomori, northern part of Japan, where Andisols have developed.