ROLE OF BIOELEMENT STORAGE ON SUBSTRATUM AS ECOLOGICAL FUNCTION IN SANDBAR LANDSCAPE

Abstract

The ecosystem conservation of river environment is the key for land management. Through cooperated research among river hydraulics, ecology and limnology more than ten years, we have accumulated a lot of fragmentary information, and the problem is how to organize them properly to apply to the ecosystem assessment.

A segment with alternate sand bars is focused on. The information about habitat of typical organisms with their life cycles and bioelement cycle (nutrients-organic matters) are concentrated on the “typical micro-landscapes” as ecological function in a river with alternate bars. These micro-landscapes are classified by frequency of inundation and surface materials as terrestrial part are formed as fluvial process during floods which occur a few times in a year, while alternate sand bars are governed by floods which occur once a few years. The results indicate an ecological function is a role of bioelement storage on substratum of respective micro-landscapes. In addition, by using aerial photos taken since 1967 with the data of cross-section surveys, GIS techniques makes a map of micro-landscapes for each sand bar and it provides the area proportion of respective micro-landscapes. For the Kizu river as an example, we have showed comparison of 10 bars at present and historical change of two typical bars from 60’s to today.