北宋中期耕地面积及其空间分布格局重建

The Reconstruction of Cropland Area and Its Spatial Distribution Pattern in the Mid-Northern Song Dynasty

以北宋暖期为研究时段,依据历史文献中有关"田亩"与"户额"的记载资料,通过对赋役、户籍、土地等制度的考证,订正了北宋中期各路耕地面积和府级人口数量;并以地面坡度、海拔高程和人口密度作为影响土地宜垦程度的主导因子,网格化重建了北宋中期境内耕地空间分布格局(60km×60km)。结果表明:(1)北宋中期境内耕地约7.2亿亩,北方占40.1%,南方占59.9%;人口数量为8720万人,北方占38.7%,南方占61.3%;境内土地垦殖率为16.6%,人均耕地面积为8.2亩。(2)垦殖率较大的地区主要分布在黄淮海平原、长江中下游平原、关中平原、两湖平原以及四川盆地等,其垦殖率基本在40%以上;而岭南、西南(除成都平原外)、东南沿海和山陕黄土高原等地区垦殖率较低,其垦殖率大多小于20%。(3)耕地分布在不同海拔高度和坡度上存在明显差异,其中低海拔(<250m)、中海拔(250～1000m)和高海拔(1000～3500m)地区的耕地分别为4.43、2.15和0.64亿亩,其相应平均垦殖率为27.5%、12.6%和7.2%;而平耕地(≤2°)、缓坡耕地(2°～6°)、坡耕地(6°～15°)和陡坡耕地(>15°)的面积分别为1.16、4.56、1.44和0.02亿亩,其平均垦殖率分别为34.6%、20.7%、8.5%和2.3%。

To simulate land cover change process and its climate effects,it is significant to construct historical land use and land cover change dataset with spatial information. According to＂Cropland Taxes＂and＂the Number of Households＂data recorded in historical documents,this paper speculates cropland area and population of each Lu（administrative region of the Northern Song Dynasty）during the mid-Northern Song Dynasty by analyzing some society factors of the Northern Song Dynasty,including land-use practices,taxation system,reclamation policies.Besides,this study selects slope,altitude and population density as the main driving factors of land use suitability degree and reconstructs the gridding spatial distribution pattern of cropland of the Northern Song Dynasty（at a 60 km×60 km resolution）. The results are shown as follows.（1）The cropland area of the whole country in the mid-and late Northern Song Dynasty is about 720 million Mu,accounted for 40.1%of the north and 59.9%of the south;the population is 87.2 million,accounting for 38.7%of the north and 61.3%of the south;the territory cropland fraction is 16.6%,and per capita cropland area is 8.2 Mu.（2）The cropland fraction of the North China Plain,the Yangtze River Plain,the Guanzhong Plain,the plains of Hunan and Hubei,and the Sichuan Basin are larger while the that of the south of Nanling Ridges,Southwest China（except the Chengdu Plain）and southeast coastal regions of China are lower.（3）In terms of altitudes,we conclude that the cropland areas of low altitude,middle altitude,high altitude are 443 million Mu,215 million Mu,and 64 million Mu respectively,and the corresponding mean cropland fraction are 27.5%,12.6%and 7.2%.（4）As for slopes,we conclude that the cropland area of flat slope, slow slope,slope,steep slope are 116 million Mu,456 million Mu,144 million Mu and 2 million Mu respectively,and the corresponding mean cropland fraction are 34.6%,20.7%, 8.5%and 2.3%.