China’s Cropland Data Reconstruction In The Recent 300 Years-based On The Resource And Population Revise

Since the beginning of the human civilization, the global environment has been changed significantly, especially after the industrial resolution, when the world population started to explode. 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, as a country with a glorious history of five thousand years, has its population boom ever since the prime Qing Dynasty (around AD 1700), when the emperor Yong Zheng started to levy tax on the basis of cropland instead of population. Meanwhile, the unprecedented development of national agricultural reclamation had started, caused dramatic land use and land cover change, leaved China as one out of a great multitude of active land-use and land-cover changes areas. Therefore, it is essential to reconstruct the cropland structure of China in the past 300 years. Currently, there are two global historical land use datasets, generally referred as the "RF datasets" and "HYDE database", but at the national level, these global datasets are widely doubted with coarse resolution and inevitable errors. International and domestic 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 bring troubles to relevant researches based on them.Since the quantity forms the backbone of cropland restructure, this paper grounded itself on China’s historical records and related research achievements, and reconstructed China’s provincial cropland data under the modern boundaries from 1661 to 2003, using a variety of methods based on resources and population, such as factor revising, man-land relationship test, reclamation trend examination, etc. Then we analyzed China’s cropland growth process, regional change characters as well as the alternation of grain production pattern and came up with the following conclusions:Firstly, ever since the population boom in the Qing Dynasty, China’s cropland had trebled from 43×106 hm2 in the early Qing Dynasty to 128×106 hm2 in 2003. According to the growth rate, the process of China’s cropland rise can be divided into 5 periods, namely, rapidly growth phase in the early and middle Qing Dynasty, slow growth phase in the late Qing Dynasty, wave phase during the period of Republic of China, Vigorous growth phase in the early years of the PRC and cropland loss phase after liberation. It turned out that human factors, such as national policy, disasters and wars, and economic development, are main reasons for cropland changes.Secondly, China’s cropland was increasing in the past 300 years as a whole, but significant differences existed among the provincial cropland change. According to the cropland average value and average growth rate, there would be six variation regions, that is, scarce resource zone with low growth rate, appropriate resource zone with low growth rate, abundant resource zone with low growth rate, scarce resource zone with high growth rate, appropriate resource zone with high growth rate and abundant resource zone with high growth rate. The first three comprises China’s traditional agriculture area and most of the newly cropland comes from the last three, which are the northeast region, the Inner Mongolia region and the northwest inland area.Thirdly, compared to SAGE and Zhou, who had evidently overweighed China’s historical cropland, our results differs less from HYDE, CHCD and Zhang with an average difference rate fewer than 15%. But at the provincial level, significant diversities appeared between our results and SAGE as well as HYDE, with 94% and 61% provinces respectively whose difference rate is above 30%. Comparatively, our results are close to CHCD because of the same data source, with 22% provinces’ average difference rate more than 30%. However, some provinces, such as Gansu, Ningxia and Shan’xi, and further researches are needed.Fourthly, grain yield had increased 1.7 ×1011 kg from early 18th century to the beginning of 21th century, mainly due to the improvement of per unit yield. Hunan, Hubei, Jiangsu, Anhui, Sichuan, Shandong, Henan and Hebei remained as major grain producing provinces in the past 300 years, while Zhejiang and Jiangxi were out. In fact, grain transportation and marketing was considerably flourishing and followed the basic rule that grain flows from less-developed areas to the advanced southeast coastal areas of China. Meanwhile, overseas grain importation was also exists.