Habitat characteristics of sweet flag (Acorus calamus) and their relationships with sweet flag biomass

The habitat characteristics of Acorus calamus were investigated to obtain data and define criteria that can be applied to restoration, conservation, and management. The investigation was conducted in March, June, and September to span the growth period of A. calamus. While the importance of A. calamus decreased over time, the diversity index (H′) of A. calamus communities increased in June and then decreased in September. Water levels in A. calamus habitats were lowest in March. About two-thirds of the A. calamus communities (68.4%) were found in sandy loam. Although the optimal environmental ranges of the water and soil characteristics for A. calamus changed according to growth stage, the environmental conditions in March were important for seed germination and seedling establishment. The aboveground biomass of A. calamus was 20.4 in March, 349.3 in June, and 267.0 g/m² in September. We also clarified the environmental characteristics of the water and soil at which the aboveground biomass during the growing and senescing seasons peaked. Based on our data, we were able to propose the following guidelines for wetland creation and restoration. (1) To facilitate the seed germination and seedling establishment of A. calamus, managers should seek to achieve conditions that approximate the optimal environment in March. (2) To optimize the growth of A. calamus, the soil pH should be maintained at neutral and the permeability to air should be enhanced. (3) To extend the longevity of A. calamus leaves, the habitat should be managed so as to limit the survival of other species with overlapping niches, and the water depth should be maintained at around 24 cm. Also, the supply of nitrogen components to the soil should not be excessive.