Delineation of Japanese soil temperature regime map

Abstract

The soil temperature regime map provides for utilitarian classification that can be superimposed on soil classification to permit more precise interpretations and assessments of land use. The objects of this study are (1) to clarify the relationship between soil temperature and meteo-geographical factors, and then (2) to delineate detailed soil temperature regime map (1 km grid) as Japanese land resources inventory. There was a parallel relationship between mean annual soil temperature (MAST) and mean annual air temperature (MAAT), but this relationship was affected to some extent by the mean annual wind speed and mean annual global irradiation in this study. Furthermore, the difference between MAST and MAAT [Diff(MAST–MAAT)] showed the highest correlation with elevation. The map of RK_Diff(MAST–MAAT) was computed using this meteo-geographical relationship with the regression-kriging approach, and then the map of MAST and the soil temperature regime map were delineated using the map of MAAT and the RK_Diff(MAST–MAAT). The root mean square error of this delineation procedure was 0.47°C. It was clear that the majority of the Japanese soils had “mesic” soil temperature regime, and Japanese agricultural land was mainly distributed at “mesic” area and followed by “thermic”, “frigid”, and “hyperthermic” area. For promoting this land resource inventory, the soil temperature regime map will be uploaded on “Soil Information Web Viewer (http://agrimesh.dc.affrc.go.jp/soil_db/)”, which is provided by the National Institute for Agro-Environmental Sciences.