| Research Abstract |
1° x 1° grid cells in the Asia region were classified using the datasets of vegetation, elevation, soil type, mean annual temperature and annual precipitation. Correspondence analysis was used for plotting the samples on three-dimensional space, followed by the cluster analysis for classifying all samples into ten categories. As a result, those ten land types in Asia could be mapped and the relationship between the land types and natural conditions such as vegetation, elevation, soil, mean annual temperature and annual precipitation were grasped. The result of correspondence analysis indicates that temperature and precipitation are the most important factors causing remarkable spatial structures, that is, the concentric circle centering Tibetian Highlands and South to North change from tropics to subpolar. This land classification is verified by using χ Square test to highly correspond to cultivation intensity and distribution of soil degradation.
Then taking a small catchment in Sichuan Province, China that had been exposed to massive deforestation and reafforestation as a case study of land degradation, further study was made. Land cover changes during the past 50 years and actual status of bio-resources utilization were analyzed to evaluate the agricultural sustainability in a small catchment area in Sichuan Province, Southern China. This study clarified massive deforestation in the 1950's was for fuel wood supply in this area. Afforestaion in the 1970's restored the forest resources quantitatively, which means the forest cover ratio became twice as large as the average in Sichuan Province. The analysis of bio-resources utilization suggested that the nitrogen input mainly consisting of chemical fertilizer remarkably exceeds the nitrogen output in the study area.
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