Abstract:

Historical land-use and land-cover changes caused by human activities during the last three centuries have been regarded as one of the five key frame issues in the LUCC project. China, with a history of 5000 years, has had its population boom ever since the early Qing Dynasty (around AD1700), and unprecedented development of national agricultural reclamation had started, left China as one of areas with rapid land-use and land-cover changes. Currently, there are two global historical land use datasets, generally referred as the 'RF datasets' and 'HYDE database', but at the zonal level, these global datasets are widely doubted with coarse resolution and inevitable errors. Academics have tried to reconstruct China's historical land-use and land-cover both quantitatively and spatially, but there are remarkable differences in their results, thus bringing troubles to relevant researches. Since the quantity forms the backbone of cropland restructuring, this paper grounded itself on China's historical records and related research achievements, and reconstructed China's provincial cropland data at the modern boundaries from 1661 to 1985, using a variety of methods based on resources and population, such as factor revision, man-land relationship test, and reclamation trend examination, etc. Our results differ less from HYDE, CHCD and Zhang with an average difference rate of less than 15%. But at the provincial level, our results are closer to CHCD, with 22% of provinces' average difference rate being over 30%. But significant diversities were found in a few provinces and further researches are needed. Then we analyzed China's cropland growth process and regional change characteristics. The results show that ever since the population boom in the Qing Dynasty, China's cropland trebled from 42.4×10⁶ ha in the early Qing Dynasty to 136.9×10⁶ ha in 1985. In terms of the growth rate, the process of China's cropland rise can be identified into five periods. Significant differences existed among the provincial cropland change. At the beginning of the Qing dynasty, China's farming activities mainly existed in the Yangtze River Plain, the Huang-Huai-Hai Plain, Guanzhong Basin and Yinchuan Plain. Thereafter, reclamation activities expanded to outer agriculture areas. Since the founding of the People's Republic of China, Northeast China and Northwest China have been major sources of additional cropland. National policy, disasters, wars, and economic development, are main factors affecting cropland changes.

Key words: history, revised and calibrated system, cropland change, reclamation trends, regional differences