Simulation and analysis of ecosystem vulnerability with cascading spread caused by dust migration based on object function GeoPetri net

摘要

To describe the cascading spread problem of ecosystem vulnerability with continuous disturbance, we propose a novel model based on object function GeoPetri net (OFGPNM). The model makes ecological environment Petri net fully reflect in ecological environment system in a graphical manner. On this basis, we design four dynamic indicators (i.e., vulnerability, adaptability, state of cascade spread, state probability) for each sub-ecosystem and two global indicators (i.e., scale of cascade spread and scale rate) for entire ecosystem. Taking Shenfu coal field in Shaanxi Province of China as case study, we simulate the impact of accumulative vulnerability and dynamic evolution of three states over time. The results showed that depending on different states of the subsystem, the factors used to maintain the balance of system's original state are also different. The results showed that cyclic structure of Petri net based on the fluidity of a river made the ecosystem more vulnerable than acyclic structure. The results also showed that the emission rate of mine dust Q(o), the tolerance parameter a and the resilience parameter y had great effect on achieving the optimal state of ecosystem. Q(o) played an important role in slowing occurrence time of cascade spread. The rational investments by government in ecological construction and pollution management are the key to balancing economic expenditure with ecological benefits. The obtained results were quite convincing to prove the novel contribution of this research to the field of vulnerability with cascading spread analysis which might continue to be the reference for restoration and reconstruction of the environment.