The objective of this study was to examine the effectiveness of using the Japanese National Forest Inventory (NFI) data in modeling site productivity. We investigated the relationship between the site index of sugi (Cryptomeria japonica) planted forests derived from the NFI data and climatic and topographic factors. The study area was the main island of Kyushu located in the south-west part of Japan. We estimated the site index with the guide curve method using the data set of dominant tree height and stand age of sugi planted stands derived from the NFI data. Solar radiation index, hydrological upslope contributing area, and vertical exposure index were used as topographic factors. Annual mean temperature and annual precipitation were used as climatic factors. Correlation analysis did not detect any significant relationship between estimated site index and topographic and climatic factors. Possible scenarios that may have contributed to the lack of significant correlation, which was contrary to the findings of previous studies, are discussed.
2015 FORMATH Research Group