华北平原农业物候动态对地表生物物理过程的影响机理与模拟研究

The surface characteristic is an important driver of climate change by influencing surface biophysical process. As an important surface feature of farmland ecosystem, agricultural phenology had changed significantly in the context of climate change and human intervention, and imposed great influence on surface energy and water budget and climate at regional scale and in specific period. However, there is a lack of systematic research on the key influence periods and influence mechanism of agricultural phenology dynamics on the surface biophysical process. This project keeps up the core research direction of applicant, relies on the research advantage and data accumulation of research group and institute, takes winter wheat and maize in North China Plain as research objects, using SiBcrop model driven by observation data and remote sensing data to study: (1) Phenology dynamics and phenology change scenarios in winter wheat – maize double cropping system and maize single cropping system. (2) The influence mechanism and critical influence periods of phenology dynamic on the surface biophysical process. (3) The quantitative contributions of surface energy distribution and surface albedo mechanisms to canopy temperature in the phenology change process. The results of the study is helpful to boost the understanding of the impact mechanism of agricultural phenology dynamic on surface biophysical process, to improve research of land surface process and model simulation in farmland ecosystem, and to provide decision basis and theoretical guidance for mitigation of regional climate change and security of water resource.

地表特征影响地表生物物理过程是气候变化的重要驱动力之一。作为农田生态系统的重要地表特征，农业物候在气候变化和人为活动干预下发生了显著的变化，对区域尺度、特定时期内的地表水热平衡和气候产生了重要影响。但是，农业物候动态对地表生物物理过程的关键影响期和影响机制等问题缺乏系统深入的研究。本项目延续申请者的核心研究方向，延伸农业物候的研究结果，以华北平原的冬小麦和玉米为研究对象，结合站点和遥感数据并驱动SiBcrop模拟的方法研究：(1) 冬小麦-玉米二熟制系统和玉米一熟制系统发生的物候变化及物候变化情景；(2) 物候变化对地表生物物理过程的影响机理及关键影响期；(3) 物候变化过程中地表能量分配和地表反照率机制对冠层温度的相对贡献。研究结果有助于增强农业物候动态对地表生物物理过程影响机制的理解，提升农田生态系统中陆面过程及模型模拟的研究，为缓解区域气候变化及水资源安全提供决策依据和理论指导。

农业物候在气候变化和人为活动干预下发生了显著的变化，对区域尺度、特定时期内的地表水热平衡和气候产生了重要影响。本项目以华北平原的冬小麦和玉米的物候动态为依据，分别构建不同的情景，基于校准好的SiBcrop模型展开模拟，获得的研究结果有助于增强农业物候动态对地表生物物理过程影响机制的理解。选择华北平原具有冬小麦和玉米物候期完整观测记录的10个站点开展研究，站点之间播种期和收获期的变化趋势有提前和推迟等不同趋势，气候变化和农田管理发挥了重要作用。利用通量观测数据将模型成功应用于华北平原冬小麦-玉米轮作系统，模拟的叶面积指数、潜热、显热的均方根误差是0.58 m2 m-2, 16.97 W m-2, 13.69 W m-2。冬小麦构建了早播种和晚播种等两种情景，情景之间叶面积指数和冠层温度具有显著差异的时期发生在间种期、休眠期和间获期；休眠期的冠层温度差异在0.05℃，早播种情景具有较低反照率主导的增温效应为主；生长期的冠层温度差异在0.2℃，早播种情景具有较强潜热分配比例主导的冷却效应为主；播种期气候效应的空间分布特征，北方在休眠期更加显著，南方在生长期更加明显。玉米构建了春玉米、夏玉米、潜在玉米等三种情景，模拟情景之间叶面积指数差异为±2.5 m2 m-2；冠层温度差异为±0.5℃；地表反照率和能量分配是决定情景之间冠层温度差异的决定因素，播种期推迟，以反照率升高的降温效应为主；生长期延长，以潜热分配增多的降温效应为主；推迟播种期并延长生长期具有较低的增温可能性。