PREVALENCE OF ALDER FORESTS IN THE LOWER REACHES OF THE KUCHORO RIVER IN KUSHIRO MARSH

Abstract

Kushiro Mire is designated wetland under the Ramsar convention and a national park. It is the largest area of its kind in Japan, and has a valuable natural enviromnent. However, enviromnental changes have been problematic in some parts of the marsh in recent years. For example, a decrease in the groundwater level and the inflow of sediment from influent rivers have caused drying and invasion by alder forests around the marsh. Meanwhile, in some parts of the lower reaches of the Kuchoro River (a branch of the Kushiro River flowing through Kushiro Mire), alder forests have disappeared and been replaced by reed and sedge communities. This paper clarifies these changes through the interpretation of existing aerial photos, and presents the results of factor analysis based on hydrological, field survey and other data.