农业土地系统研究及其关键科学问题

如何科学合理利用土地是实现人类可持续发展的关键。随着人类对土地利用问题愈发关注，在“土地利用/土地覆盖变化”、“全球土地计划”等国际科学研究计划的推动下，“土地系统科学”的学科体系逐步形成，农业土地系统研究成为土地系统科学的热点方向之一。本文以全球土地计划与土地系统科学为指引，旨在明晰“农业土地系统”的概念，系统梳理农业土地系统研究的技术方法、内容对象以及关键科学问题，为进一步丰富和完善土地系统科学学科体系，推动全球变化、粮食安全及农业可持续研究提供参考。研究认为：第一，多维度格局探测与分析是农业土地系统研究的重要基础：农业土地系统不仅关注耕地与其他土地利用类型之间的相互转换特征、规律和过程，而且更为关注耕地内部多熟种植制度、农作物空间格局、利用集约度、综合生产能力等结构和功能的多维变化，因此，需要依靠多学科/数据的交汇、融合等手段来揭示农业土地系统的复杂特征；第二，多模型耦合的过程与机制解析是农业土地系统研究的核心内容：在明晰农业土地系统时空格局特征的基础上，通过建立土地系统格局与其影响因素之间的关系，并将这种关系在时间维度进行扩展，进而实现农业土地系统变化过程和机制的动态表达，目前，土地变化模型的建模手段已从传统单一的地理模型或经济模型研究转向模型耦合研究，以反映农业土地系统中“人类-环境”的复杂关系；第三，多内容的综合效应评估与调控是农业土地系统研究的关键任务：农业土地系统与全球变化、粮食安全及农业可持续发展等问题密切关联，农业土地系统时空格局探测、过程机制解析的最终目的在于通过协调农业土地系统与农业资源、环境和生态的相互关系，考虑不同系统之间的权衡优化关系，追求土地利用的最佳社会、经济和生态综合效益，以建立人地和谐、可持续的农业土地利用模式。解决农业土地系统研究的这些关键科学问题，将有力促进自然科学和社会科学的融合，推动土地系统科学及相关研究领域的发展。

Key Research Priorities for Agricultural Land System Studies

Agricultural land use and its dynamics have attracted much attention from researchers due to their ecological and socio-economic implications for agricultural sustainability. Several international programs such as the Land-Use and Land-Cover Change (LUCC) and the Global Land Project (GLP) have promoted the emergence of Land System Sciences. Based on the latest progress in Land System Science, this review paper provides a definition of the Agricultural Land System (ALS) and conceptualizes a framework for the ALS studies relating to global change, food security, and sustainability studies. It is proposed that: 1) Multi-faceted patterns of ALS are the basis for subsequent analysis. It should consider not only the characteristics ALS at the land use and land cover level, e.g. the transitions between cropland and other land cover types, but also the characteristics of cropping system, crop allocation, intensification and productivity within cropland. Interdisciplinary approaches and data integration are necessary for understanding the complex characteristics of ALS. 2) Multi-model coupling through the interpretation and intercorrelation of ALS patterns and underlying drivers is an essential way to represent ALS dynamic changes, processes and its mechanisms, by which it is able to better understand the coupled human-environment interactions across different time, space and scales. 3) It is important to link the ALS with other parallel systems to understand their synergies and trade-offs, in order to build up a sustainable pathway for future agricultural land use. Those solutions for ALS studies would substantially promote the interdisciplinary integration and will contribute to the development of Land System Science and its relevant sciences.