基于模拟退火算法的林分多目标经营动态可视化模拟

[目的]基于模拟退火算法,研究一种考虑林分结构健康状况和目标平均胸径的多目标森林经营方法,同时结合单木生长方程,基于Unity3D可视化引擎实现林分经营动态可视化模拟。[方法]以湖南省攸县黄丰桥国有林场5块杉木人工纯林2012-2017年样地连年调查数据为数据源,考虑林分分布状况、竞争程度、营养空间,以平均角尺度、平均大小比、林分拥挤度3个结构参数建立空间结构函数。在此基础上,以健康林分结构和平均胸径为经营目标,以竞争指数为参考初步筛选出的间伐木组合排列的结果作为经营方案的集合,通过模拟退火算法进行最优间伐经营方案解的选择。最后,通过建立考虑Hegyi竞争指数的可变生长率的单木生长方程,以结构分析-经营-生长三者不断迭代的方式并基于Unity3D渲染引擎实现林分经营动态可视化模拟。[结果]通过对5号样地(初始林分230株,年龄16 a,平均胸径20.21 cm)以健康林分结构和30 cm林分平均胸径为经营目标进行经营动态可视化模拟,结果表明林分年龄在21、26、31 a分别进行过间伐模拟,当林分年龄31 a间伐后,林分平均胸径达到30.10 cm,林分平均角尺度为0.64,林分拥挤度为0.74,林分结构接近健康水平。[结论]本研究提出的基于模拟退火算法的林分多目标经营动态可视化模拟方法能够模拟在多目标经营需求下的林分动态,并且形象直观,可以进一步为林业科研和生产提供支持。

Dynamic Visual Simulation of Stand Multi-objective Management Based on Simulated Annealing Algorithm

[Objective]Based on simulated annealing algorithm,a multi-objective forest management method considering the health status of stand structure and average diameter of stand was studied.The individual tree growth equation was used to realize the dynamic visualization of the stand management based on the Unity3D visualization engine.[Method]Based on 2012-2017 survey data of 5 Chinese fir(Cunninghamia lanceolata)sample stands located in Huangfengqiao State-owned Forest Farm of You County,Hunan Province,considering the distribution status,competition degree and nutrient space of the stand,the spatial structure function was established by three structural parameters:average angular scale,average size ratio and forest congestion degree.On the basis of spatial structure function,taking the healthy forest structure and the average diameter as management objectives,taking the results of a combinatorial permutation of thinned trees as the set of management planning with competition index as reference,the simulated annealing algorithm was used to select the optimal thinning mangement planning.Finally,by establishing a individual trees growth equation considering the variable growth rate of Hegyi competition index,the structural analysis-management-growth method was continuously iterated and the dynamic visualization of the forest management based on Unity3D rendering engine was realized.[Result]The dynamic visualization of the management dynamics was carried out on the plot 5(initial stand of 230 trees,16-years-old,average diameter 20.21 cm)with the healthy stand structure and average diameter of 30 cm as target.The stand was simulated thinned in the 21st,26th,and 31st years.When the forest was 31 years old(after thinning),the average diameter reached 30.10 cm,the average angular scale of the forest was 0.65,and the forest congestion was 0.74,which showed a health level.[Conclusion]The dynamic visual simulation method of forest multi-objective management based on simulated annealing algorithm proposed in this paper can simulate forest dynamics and meet the multi-objective management demand.The image is intuitive,and can support research and production.