Assessment of flora, plant communities, and hydrochemical conditions for adaptive management of a small artificial wetland made in a park of a cool-temperate city

In order to recreate the landscape of Ishikari Mire, an artificial wetland was made in 2000 at a city park in northern Japan. Its flora, plant communities, and hydrochemical conditions were examined in 2005 and compared with those determined in 2001 and with those of nearby intact fens. Management increased water levels by ca. 10 cm from 2002. Neutral pH, high electrical conductivity (EC), and high concentrations of nitrogen and mineral ions were the same as in 2001, but higher than in fens. The wetland was flooded by river water a few times every year. These hydrochemical conditions suit the growth of fen species. Total species increased from 73 (2001) to 105 (2005), whereas annuals and biennials decreased from 20 to 13 and naturalized exotic species from 18 to 15. Five naturalized exotic species that disappeared by 2005 were all mesophytes, and one of two newly found naturalized exotic species was a hygrophyte. Accordingly, the rapid change can be explained by the change of lifeforms in the early stage of secondary succession, and in some parts, by the disappearance of mesophytic plants as wetness increased. During the 6 years, the wetland communities changed toward that of fens because most of the migrated or imported fen species were increasing. Many other fen plants, therefore, would be able to grow in the wetland, while only four fen species had migrated. Accordingly, importation of other fen plants is essential to recreate the whole plant assemblages of mire.