农业是对气候变化最为敏感的生产部门之一，气候变化对农业生态环境、作物生长发育、作物产量、农业病虫害、农业气象灾害等多个方面产生不同程度的影响，引起农业地域格局的演化，以及农业地域结构和功能的变迁。中国北方农牧交错带生态环境脆弱，对气候变化的响应更为敏感和强烈。气候变暖在改善区域水热资源条件的同时，也加剧了区域水资源脆弱性和自然灾害胁迫性，因而对北方农牧交错带农业发展具有“双向”影响。开展气候变化背景下北方农牧交错带农业地域格局演化研究，探明气候变化下区域农业发展的响应与适应过程，揭示北方农牧交错带农业地域格局演化动力机制，分区提出适应气候变化的农业地域格局优化途径，成为现代农业地理学及农业地域系统研究的重要课题，对于提出保障农业生态与粮食安全、推动现代农业可持续发展、促进人地系统协调发展的科学对策具有重要理论价值和现实意义。

本研究以人地系统科学理论为指导，按照“要素→结构→功能”逻辑思路，围绕“理论框架构建→格局演化解析→优化路径探讨”研究主线，应用地理学“格局→过程→机制→模拟→优化”研究方法，构建了农业地域格局演化解析框架，分析了气候变化背景下北方农牧交错带农业关键要素的时空演变趋势，剖析了农业地域格局的区域分异特征、时空演化规律和格局分异的动力机制，模拟了未来多气候情景农业生产适宜布局，梳理提出了农业地域格局优化途径与策略。主要研究结论包括五个方面：

（1）阐释农业地域格局的科学内涵与研究定位，理论解析农业地域格局时空演化、响应机制与优化途径，构建农业地域格局演化的理论框架。农业地域格局是指一定地域范围内，农业系统各种自然资源要素和社会经济要素相互影响、交互耦合所形成的具有不同阶段特征的结构和功能的农业空间体系。农业地域格局演化发展是人地系统耦合发展的重要体现，其研究内容主要体现在“五观”，即系统论视角下的科学观、发展论视角下的过程观、地理学视角下的地域观、可持续理论下的协调观以及气候变化视角下的调控观。

（2）探明中国北方农牧交错带农业地域格局关键要素的时空演变过程与分异规律。1980-2019年全区平均气温和≥10℃积温均显著增加，气候倾向率分别为0.36℃/10a（P<0.01）和122.68℃﹒day/10a（P<0.01），为作物生长适宜区北扩提供了更为充足的热量资源，特别是气候变暖为作物复种指数提升和农业种植结构调整提供了巨大潜力；全区降水的剧烈波动与时空分布不均，将会增加区域农业生产脆弱性。1990-2020年全区耕地、林地和草地之间频繁转换，不同时期耕地的来源与去向结构在不同农业地域分区呈现明显的分异特征，耕地重心在山西省内沿东南方向摆动，但迁移速率持续增加。30年间北方农牧交错带粮食总产量、农业机械总动力和化肥施用量均呈增长态势，而农业从业人员数量总体呈减少趋势。

（3）解析北方农牧交错带农业地域格局演化过程及其动力机制。1990-2020年全区大部分县域农业生产要素投入结构、农业产出结构和农业经济结构均发生显著变化，化肥施用强度、人均粮食占有量、耕地生产效率和劳均农业总产值明显提升，其中“高-高”型聚集区主要分布在北方农牧交错带东北部地区。1990-2020年全区农业生产供给功能水平显著上升，生活保障功能水平小幅提升，生态保育功能水平呈先升后降的演变趋势，在空间上表现为西高东低、南高北低的梯度变化特征。各农业地域功能耦合度呈共振发展态势，协调度稳步提升，生产供给功能与生活保障功能的时空格局高度耦合，生产供给功能优势区与生态保育功能弱势区呈现高度重合。农业地域功能格局呈现出明显的时空分异特征，这是不同阶段、不同地区气候资源要素与社会经济要素耦合交互作用的结果。在气候变暖驱动下，农业生产优势区与水热资源优越区重叠度不断升高，特别是对于中高纬地区的东北平原区。另外，在多种社会经济要素交互作用下，农业地域功能格局区域差异逐渐显化。

（4）模拟未来北方农牧交错带农业生产适宜性布局。2020-2050年，SSP1-2.6情景下气候变暖趋势逐渐减缓，SSP2-4.5和SSP5-8.5情景下气候持续变暖；各情景下年降水量均有较大波动，且在SSP2-4.5情景和SSP5-8.5情景下呈显著波动增加趋势。借助土地利用模拟模型、最大熵模型、InVEST模型等，结合未来气候模式数据，模拟2050年不同气候情景下耕地分布适宜性和农业生产潜在风险，将北方农牧交错带划定为薄弱提升区、适宜生产区和核心生产区，并诊断各类型区未来农业发展目标。薄弱提升区农业发展的关键在于优化水土资源配置以提高耕地分布适宜性；适宜生产区农业发展的关键在于防范农业生产潜在风险点位增多；核心生产区农业发展的关键在于权衡农业生产与生态保护之间的关系。

（5）提出农业地域格局优化途径与科学对策。基于北方农牧交错带农业生产适宜性分区，旨在合理利用气候资源的同时，降低未来气候变化可能带来的环境胁迫性影响，科学统筹北方农牧交错带农业生产与生态协调发展，针对薄弱提升区水资源短缺、耕地质量普遍偏低等问题，提出构建节水型农业生产综合体系，助力高效节水农业发展；运用农业地理工程技术提升耕地质量，推进保护性耕作等农业地域优化途径。针对适宜生产区未来农业生产潜在风险较高和农业地域多功能水平亟待提高等问题，提出增强农业风险管理与预警，提高农业地域系统气候韧性；优化农业生产布局，推动气候智慧型农业发展等农业地域格局优化途径；针对核心生产区化肥施用强度过高和农业生产生态功能失衡等问题，提出农业生产与生态保护并重，推进农业绿色低碳循环发展；挖掘农业多种功能和乡村多元价值，推进农业全产业链发展等农业地域格局优化途径。另外，从政策、资金和人才等方面构建长效保障机制，确保优化途径的有效实施，为实现区域农业水土气生人耦合协调发展提供科学参考。

Agriculture is one of the most sensitive fields to climate change. Climate change will have different impact on agroecological environment, crop growth, crop yield, agricultural pests and diseases, agro-meteorological disasters and many other aspects, resulting in the evolution of agricultural regional pattern and the transition of agricultural regional structure and function. The farming-pastoral ecotone of Northern China with fragile ecological environment is more sensitive and intense to climate change. Climate warming not only improves regional hydrothermal conditions, but also intensifies regional water vulnerability and natural disaster stress, which has double-edged influence on agricultural development. It is of great significance to strengthen the comprehensive agricultural productivity, ensure food security and promote sustainable agricultural development in the farming-pastoral ecotone of Northern China by exploring climate change on the evolution of agricultural regional pattern and proposing targeted policies to optimize agricultural regional pattern.

Guided by human-earth system science theory, from the perspective of element-structure-function, this study focused on the progressive research main line of theoretical framework construction, pattern evolution analysis and optimization path discussion. Following geographic research paradigm of pattern, process, mechanism, simulation and opatimation, the theoretical framework of agricultural regional pattern evolution was firstly constructed, and spatio-temporal evolution and differentiation characteristics of key agricultural elements and agricultural regional patterns in the farming-pastoral ecotone of Northern China were analyzed, then the dynamic mechanism of pattern evolution was identified. This study also simulated future suitablity distribution of agricultural production under different climate scenarios and proposed targeted strateiges to optimize agricultural regional pattern. The main conclusions are as follows:

(1) Through defing the concept and research orientation of agricultural regional pattern, this study analyzed the spatio-temporal evolution, response mechanism and optimization paths of agricultural regional pattern from the theoretical level, and builded theoretical framework for the evolution of agricultural regional pattern. Agricultural regional pattern is the spatial distribution of agricultural regional structure and function on different development stages within a certain region, which is formed by the interaction and coupling of multiple natural resource elements and economical social elements in the agricultural system. The evolution and development of agricultural regional pattern is an important embodiment of human-earth system coupling, the main research contents highlight ‘five views’, namely ‘scientific view’ under the perspective of system theory, ‘process view’ under the perspective of development theory, ‘regional view’ under geography perspective, ‘coordination view’ under the perspective of sustainable theory and ‘regulation view’ under the perspective of climate change.

(2) This study firstly analyzed the spatio-temporal evolution and regional differentiation of key elements of agricultural regional pattern in the farming-pastoral ecotone of Northern China. The average annual temperature and the annual accumulated temperature above 10℃ (AAT10) significantly increased during 1980-2019, and the climate tendency rates were 0.36℃/ decade (P<0.01) and 122.68℃·day/ decade (P<0.01), respectively, which provided more sufficient thermal resource for northward expanding of crop growth suitable region. In particular, climate warming provided great potential for improving the multiple cropping index and adjusting agricultural cropping structure in the Loess Plateau. However, the precipitation fluctuation and uneven spatio-temporal distribution might increase the vulnerability of regional agricultural production. Croplands, forests and grasslands changed frequently for the period of 1990-2020, the source structure and destination structure of cultivated lands showed obvious regional differentiation characteristics during different periods in different agricultural zones. The barycenter of croplands swung back and forth along the southeast direction in Shanxi Province, but the migration rate increased continuously. During the past 30 years, the total grain output, the total agricultural machinery power and the consumption of chemical fertilizers showed an increasing trend in the farming-pastoral ecotone of Northern China, while the number of agricultural employees presented a decreasing trend.

(3) Analyzing the evolution process of agricultural regional pattern in the farming-pastoral ecotone of Northern China and revealing the dynamic mechanism of regional differentiation. Per capita share of grain, cropland production efficiency, fertilizer consumption intensity and per labor of gross agricultural output increased significantly in most counties during 1990-2020, and the High-High conunties were mainly concentrated in the northeastern region. The production supply function increased significantly, the living security function increased slightly and the ecological conservation function firstly increased and then decreased, showing a gradient evolution characterastic of "high in the west and low in the east, high in the south and low in the north". The coupling degree of each agricultural function showed a resonance development situation, and the coordination degree was improved steadily. The spatio-temporal patterns of production supply function and living security function were highly coupled, and the regions of superiority production supply function were high coincidence with the regions of weak ecological conservation function. The spatial distribution of all agricultural regional functions were influence by climate conditions, of which the production supply function had the strongest response to climate (0.186). Meanwhile, slope, effective irrigation area, total agricultural machinery power, rural population, distance from rivers and roads also affected the spatial distribution of different agricultural regional functions to different degrees.

(4) The climate warming trend gradually slowed down under SSP1-2.6 scenario, while the climate continued significantly warming under SSP2-4.5 and SSP5-8.5 scenarios for the period of 2020-2050. The annual precipitation fluctuated strongly under all scenarios, and showed an increasing trend under SSP2-4.5 and SSP5-8.5 scenarios. Based on the simulation results of cropland suitability distribution and potential agricultural production risks, the study area was divided into three agricultural production suitability zones, i.e., weak improvement zone, suitable production zone and core production zone, and the future agricultural development goal of each zone was explored. Agricultural development in core production zone needed more focus on balancing the relationship between agricultural production and ecological protection. Agricultural development in suitable production zone needed pay more attention on preventing the increase of potential agricultural production risk. Agricultural development in weak improvement zone needed more focus on optimizing water-soil resource allocation so as to improve the cropland suitability distribution.

(5) In order to realize human-earth coordination development in regional agricultural system, this study seperatley proposed optimization paths of agricultural regional patterns for weak improvement zone, suitable production zone and core production zone based on their limiting factors through agricultural development process. The optimization paths aimed to reasonably utilized climate resources and reduce the potential environmental stress cased by future climate change; meanwhile, the coordinated development of agricultural production and ecological proteciton was also taken into account. Furthermore, the guarantee mechanism, including the aspects of policies, fundings and talents, was constructed to ensure the effective implementation of multiple optimization paths.