Reconstruction of Cropland Distribution During the Neolithic Period Based on the Archaeological Achievements in the Yarlung Zangbo River and its Two Tributaries
This study compiles and analyzes archaeological findings from the Neolithic period in the Yarlung Zangbo River and its two tributaries (Lhasa River and Nianchu River). Three scenarios of livelihood model were established, taking into account the ratio of farming and pastoralism, exclusive agriculture, agriculture with supplementary pastoralism and pastoralism with supplementary agriculture based on flotation survey reports from typical Neolithic relic sites. The population size of the region was estimated using burial analysis, and the total cropland area under each scenario was further calculated by combining per capita grain consumption. Finally, a gridded cropland distribution at a 1km×1km resolution was reconstructed for the Neolithic period by integrating archaeological site data and natural land reclamation suitability. The results showed that (1) The population of the study area during the Neolithic was approximately 550 people and the total cultivated land in the area under the three scenarios of exclusive agriculture, agriculture combined with pastoralism and pastoralism combined with agriculture is 11.14 km², 6.77 km²and 4.67 km², respectively, and the regional reclamation rate is extremely low; (2) The distribution area of cropland was scarce and accounted for only 1% of the total grids, displaying a mosaic distribution along river valleys, and mainly concentrated in the Lhasa River Basin; (3) Compared with the exclusive agriculture scenario, the total cropland area in the HYDE3.2 dataset at the same period was approximately one-third of that reconstructed, but its spatial distribution scopewas three times larger. The reconstructed result from this study not only objectively reflects the cropland pattern in the region during the Neolithic period but also effectively addresses the limitations of global datasets in this area.
人为土地覆盖变化(Anthropogenic Land Cover Change, ALCC)极大地改变了陆地景观和生态系统,是全球变化的驱动力之一[1]。而人类的土地利用活动对全球系统的影响具有累积效应,历史时期或更早时期的人类土地利用对当前生态的影响不应被忽视或低估[2,3]。土地利用/土地覆盖变化(Land Use and Land Cover Chang,LUCC)重建不仅能够反映土地覆盖的时空演变过程,而且能为全球气候、环境变化的模拟以及长期的经济发展与环境保护政策的制定提供基础数据[4,5]。
随着人口规模的增加以及技术手段的不断进步,人类活动对地表环境与地表形态的影响越来越显著。耕地是人类活动影响地表环境和地表形态的重要表现形式之一,重建长时间序列、高可靠性的耕地覆盖变化,能够为全球气候、环境变化的模拟研究提供基础数据支撑[6-8]。因此,产生了一系列全球尺度的历史LUCC数据集,包括HYDE(History database of the Global Environment,HYDE)[9]、PJ(Pongratz Julia,PJ)[10]、KK10(Kaplan and Krumhardt 2010,KK10)[11]等。但是,由于各数据集之间使用的原始资料、耕地总量估算方法、格网化分配方法等均有差异,上述数据集不仅彼此矛盾[12,13],且被众多区域重建研究结果证明其存在较大不确定性[14-16]。因此,利用区域考古、历史文献资料与发展史实的耕地重建工作是解决当前各数据集所面临问题的有效途径。
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