Controlling factors for the distribution of sapric peat soils extracted by GIS analysis

Abstract

This study aimed to clarify the distribution trend of sapric peat soils in Japanese agricultural fields from the view point of drainage and landform conditions using the Geographic Information System (GIS). To this end, the environmental conditions in the distribution area of organic soils were divided by combining existing GIS databases of environmental factors that consist of groundwater level, drainage condition, landform classification, and grain size of sediment. In order to evaluate the contribution of these environmental factors to the distribution trend of sapric peat soils, we applied quantification method type II to construct the discrimination model that enables the differentiation of the distribution area of sapric and non-sapric peat soils. In the case of organic soils without mineral surface cover, our discrimination model clearly suggests that sapric peat soils tend to be distributed under good drainage condition on floodplains, and with coarse sediments. This indicates that the effect of drainage conditions on peat decomposition is determined by landform condition. On the other hand, in the case of the land covered with mineral soils on the surface, sapric peat soil distribution was not well estimated. Determining the relationships between the distribution trend of sapric peat soils and the environmental factors by analyzing the existing GIS database is a new application. This was achieved by the combination of GIS and quantification method type II, which contributes to the description of the peat decomposition process from the viewpoint of geographical conditions.