基于GM(1,1)的天然次生林空间结构预测

【目的】系统地分析已有天然次生林林分空间结构数据,通过灰色模型预测天然次生林林分空间结构各指标未来的发展趋势,对天然林经营具有十分重要的意义。【方法】以湖南大围山自然保护区典型次生林为研究对象,依据结构化森林经营理论,选取了混交度、竞争指数、角尺度、空间密度指数、开阔比数、大小比数、林分综合均质性指数作为天然次生林林分空间结构合理性评价与预测的量化指标,构建了基于GM(1,1)的天然次生林林分空间结构灰色预测模型。模型将2008年林分空间结构各指标的平均值作为初始值,并在研究区设置了面积为20 m×20 m的5个研究样地(M1,M2,M3,M4,M5),利用保护区2008-2018年典型样地林分空间信息,预测了研究区调研样地2019年-2021年林分空间结构各指标未来的变化趋势。【结果】利用精度检验机制对该模型的精确度进行了有效性检验,检验结果表明,所有指标预测合格概率P合=71.43%,良好的概率P良好=22.86%,优的概率P优=5.71%,表明该预测模型符合精度检验要求。【结论】样地未来3 a各指标整体变化尺度不大,林分空间结构基本稳定。从各指标在2008-2018年时空上的变化规律来看,各样地林分平均竞争指数、平均大小比数及平均空间密度指数是影响林分均质性指数的关键指标。

Prediction of stand spatial structure of natural secondary forest based on GM(1,1)

【Objective】Systematic analysis of spatial structure data of natural secondary forest stands.Predicting the future development trend of the spatial structure of natural secondary forest stands by grey model is of great significance to the management of natural forests.【Method】This paper divides the typical secondary forest in Daweishan nature reserve in Hunan province into objects.According to the theory of structured forest management,the mixed degree,competition index,angular scale,spatial density index,open ratio,size ratio,and stand comprehensive homogeneity index were selected as indicators for the rationality evaluation of spatial structure of natural secondary forest stands.Grey prediction model of spatial structure of natural secondary forest stands based on GM(1,1)was constructed.The model takes the average value of each indicator of the spatial structure of the stand in 2008 as the initial value,and sets up 5 research plots(M1,M2,M3,M4,M5)with an area of 20 m×20 m in the study area.Using the spatial information of the typical plot forests in the protected areas from 2008 to 2018,the future trends of the spatial structure of the forests in the research area of the study area from 2019 to 2121 are predicted.【Results】The study used the accuracy test mechanism to test the accuracy of the model.The test results showed that the pass probability was 71.43%,the good probability is 22.86%,and the good probability is 5.71%,indicating that the prediction model meets the accuracy test requirements.【Conclusion】In the next three years,the overall change scale of each index is not large,and the spatial structure of the stand is basically stable.From the temporal and spatial variation of each index in from 2008 to 2018,the average competition index,the average size ratio and the average spatial density index are the key indicators affecting the homogeneity index of stand.