渭河流域全新世农业活动及其对气候变化的响应

Since there are extreme disastrous weather events triggered by the global warming that have tremendous impact on society sustainable development， it has great significance to estimate the effection of climatic change and to explore early human activities and adaptation. To select the critical area and important episode in the Holocene which integrate with modern age and contain the similar features of climate change in future and carry out agricultural activities surrogate records research, became breakthrough of revealing features and adaptation of early agricultural activities. The emergence and development of agriculture during the Holocene supplied important cases for ancestors' adaptation of climatic change successfully. The Weihe River valley has flourishing Neolithic farming culture and plenty of relics and sites. It appears different directions of archaeological culture and early agriculture development in different geographical units. All make this district to be an ideal place for realizing our scientific goals as follow: (1) to reconstruct the vegetation succession and patterns during the Holocene based on the pollen and charcoal records; (2) by comparing the high resolution sequences of climatic change, the vegetation records, the evidence of human activities, and together with the high precision AMS14C dating, the archaeological materials, and the history literatures, to promulgate the relationship between the vegetation succession and pattern with the climatic change, and early agriculture; (3) to distinguish the different impact on agricultural activities from cultural and natural factors; (4) to investigate the effect of Holocene climate variability especially abrupt climate change events impact on the Weihe River early agricultural activities, and to reveal the ancestors' adaptation strategies about the climate change. Finally scientific basis will be provided for the prediction and assessment of human adaptation under the background of climatic change in the future.

"全球变暖"可能引发的极端环境事件给社会发展带来极大的挑战，准确评估未来气候变化影响以及人类适应意义重大。从关键区域入手，选择地质历史时期的"气候相似型"时段开展早期人类活动及适应研究成为重要的突破口，而农业起源提供了先民成功适应气候环境变化的重要例证。渭河流域全新世农业文化持续而繁荣、考古遗存丰富，是早期农业活动特征及适应研究的理想地区。本课题拟选取渭河流域天水盆地、关中盆地与渭北旱塬三个不同地理单元，通过植物指标记录（种子、植硅体、花粉、炭屑等）研究，结合高精度AMS14C测年，建立全新世农业活动年代框架，揭示渭河流域不同地貌单元早期农业活动的特征、方式及发展过程，通过高分辨率气候变化记录分析，确定气候突变事件的起迄时间与特征，揭示早期农业活动对气候环境变化的适应方式与策略，为预测和评估未来气候变化背景下的人类适应提供科学依据。

近年来，在基金委的资助下，项目负责人尚雪博士带领项目组成员开展渭河流域全新世农业活动及其对气候变化的响应等方面的研究，取得了一系列成果，较好的完成了预期目标。主要成果包括：1）重建黄土高原南部、中部、北部等不同地貌单元仰韶晚期至晚商时期的农业活动特征，结果显示南部地区和中部地区早期以粟黍作物为主，晚期出现了稻、小麦等粮食作物，其中粟类作物的比重一直较高，北部表现出较为单一的粟黍农作物类型，且长期已黍类作物为主，说明黄土高原地区早期农业活动存在“南部模式”和“北部模式”，同时粟黍比与年降水量成正相关的现象，说明先民通过调整作物类型以及作物组合来适应当地的生态环境；2）对新石器时代中晚期陕西渭南白水河流域7处遗址与嵩山南麓4处遗址出土的粟、黍、水稻、大豆以及相关动物骨骼样品的C、N稳定同位素进行分析，粟、黍、水稻的δ15N值明显高于自然植被，排除干旱等提高植物δ15N值的因素，作物较高的δ15N值应当来自人工施肥，说明中原地区早在距今5500年前就开始稳定且长期的使用施肥等农田管理技术； 3）为更好地理解作物加工过程中荞麦花粉的散布过程及其对花粉雨的贡献，并为解读考古遗址中荞麦花粉的来源及意义提供帮助，我们选择在现代村落进行荞麦作物传统加工的模拟实验，收集空气花粉并统计分析。研究表明荞麦作物花粉在居民生活区的散布与人类加工行为息息相关，其中打谷和过筛的阶段花粉释放量最大。荞麦作物加工过程花粉再次散布和埋藏是文化层中农作物花粉浓度比例显著增高的重要原因之一，不仅可以指示人类种植和加工行为, 也对辨识考古遗址中农作物加工场地，评估农业活动的强度和影响等提供依据；4）本项目尝试采用压点法对现代粟粒的植硅体进行了统计取得了很理想的结果，为植硅体的科学统计提供了新思路。