AI 中文总结
研究开发基于网络建模框架，通过连续时间隔室网络模型表征农业食品氮系统稳态配置及相变，用法国数据参数化并应用于多案例，揭示不同配置及性能指标变化，提供氮系统配置映射与相变分析方法。
AI 中文摘要
农业食品转型通常使用优化模型或情景方法进行评估，这些方法只能返回单一可行配置，提供系统性能估计，但关于可行氮循环配置的信息有限。本研究开发了基于网络的建模框架，以表征农业食品氮系统的替代稳态配置，并识别这些配置之间的相变。我们制定了一个连续时间隔室网络模型，其中生产、分配、回收和损失表示为质量守恒流。在稳态条件下分析系统，通过粗粒化程序识别主导回收循环并得出描述系统配置的综合指标。该模型使用法国参考数据进行参数化，并应用于涵盖施肥、畜牧业和饮食模式的案例研究。分析确定了氮网络的不同稳态配置，由主导回收结构的相变分隔，这些转变对应于系统性能指标的变化。对于法国参考系统，基于农田的饲料供应能力约为每公顷农田8.7人（取决于约束条件），而严格的饮食自主性需要约1970万公顷的农业用地。在不改变饮食或氮源的情况下减少合成肥料会导致更高的土地需求或对外部投入的更大依赖。该框架提供了一种方法，用于绘制可行的氮系统配置，并分析在替代参数和约束下农业食品氮网络中的相变。
英文摘要
Agro-food transitions are commonly assessed using optimization models or scenario approaches that return a single feasible configuration. These approaches provide estimates of system performance but limited information on feasible nitrogen cycling configurations. In this study, we develop a network-based modelling framework to characterize alternative steady-state configurations of agro-food nitrogen systems and identify phase transitions between these configurations. We formulate a continuous-time compartmental network model in which production, allocation, recycling, and losses are represented as mass-conserving flows. The system is analyzed under steady-state conditions. A coarse-graining procedure identifies dominant recycling cycles and derives aggregate indicators describing system configuration. The model is parameterized using French reference data and applied to case studies covering fertilization, livestock, and dietary patterns. The analysis identifies distinct steady-state configurations of the nitrogen network, separated by phase transitions in dominant recycling structures. These transitions correspond to changes in system performance indicators. For the French reference system, cropland-based feeding capacity is about 8.7 people per hectare of cropland (depending on constraints), while strict dietary autonomy requires about 19.7 million hectares of agricultural land. Reducing synthetic fertilization without changes in diet or nitrogen sourcing leads to higher land requirements or greater dependence on external inputs. The framework provides a method for mapping feasible nitrogen system configurations and analyzing phase transitions in agro-food nitrogen networks under alternative parameters and constraints.
Comments27 pages, 8 figures
