基于代数差分方程的亚热带天然常绿阔叶混交林立地生产力指数建模与制图

Site productivity index based on height-diameter relationship of dominant trees are the most sensitive and reliable measures of site productivity. Stand structure, climate and site conditions may influence site productivity of forest. Regardless of stand spatial structure, climate and site variables, the stand non-spatial structure variables were considered into site productivity index currently. Therefore, this study focuses on the scientific issues of how the site productivity of natural mixed uneven-aged stands responds to the changes of stand structure, climate and site conditions on natural evergreen broadleaved forest in subtropics. The objectives of this study are (1) to obtain the appropriate estimator of mixed stand dominant height being constructed different estimation methods based on whether to consider tree species. (2) to construct eight different models of site productivity index based on whether the stand structure, climate and site variables are considered using algebraic difference approach, then to compare and analyze the fitting effect of different models to get the optimal model. (3) to construct a series of site productivity grade distribution maps within different conditions including real stand, optimal and extreme stand structure, optimal and extreme climate, optimal and extreme site. It can provides a theoretical basis and reference for scientific management of natural evergreen broadleaved forest through these objectives.

立地生产力指数即林分优势直径与树高关系模型对天然异龄混交林立地生产力的估计是灵敏而可靠的。林分结构、气候和立因条件会影响林分的立地生产力，而现有的立地生产力指数只考虑了林分的非空间结构因子，未考虑林分的空间结构因子，也未考虑气候和立因条件。因此，本研究围绕“天然异龄混交林的立地生产力如何响应林分结构、气候和立地条件的变化”这一科学问题，以亚热带天然常绿阔叶混交林为研究对象，主要开展：（1）混交林优势高估计方法确定。（2）立地生产力指数建模。依据是否考虑林分结构、气候和立地因素，利用代数差分方程建立8种不同的立地生产力指数模型，比较分析不同模型的拟合效果以获得最优模型；（3）立地生产力等级分布图建立。利用（2）的最优模型和空间插值法构建现实林分状态下、最优与极端林分结构状态下、最优与极端气候状态下、最优与极端立地状态下的分布图。研究成果可为科学经营管理天然常绿阔叶混交林提供理论基础与参考。

立地生产力指数即林分优势直径与树高关系模型对天然异龄混交林立地生产力的估计是灵敏而可靠的。林分结构、气候和立因条件会影响林分的立地生产力，而现有的立地生产力指数未综合考虑林分结构、气候和立地因子。项目以亚热带天然常绿阔叶混交林为研究对象，基于3期的115个固定样地数据，开展混交林优势高确定方法、立地生产力指数模型构建以及立地生产力等级制图研究。主要结果：（1）确定了以不分树种的4株最大树对应树高的断面积加权平均值HDW为最优的优势高计算方法；（2）基于代数差分方程建立了SPI0、SPI.stand、SPI.site、SPI.climate、SPI.stand.site、SPI.stand.climate、SPI.site.climate、SPI.stand.site.climate的8种不同立地生产力指数模型，通过模型拟合与参数检验分析，以考虑林分结构和立地因子的SPI.stand.climate为最优模型，其中气候因子不显著，直径多样性指数D.SimI和D.GinI为显著的林分结构因子，坡位为显著的立地因子；（3）绘制了研究区域内的立地生产力等级（分为5等级）分布图。研究结果可为如何提高天然常绿阔叶混交林的立地生产力提供理论基础与参考，也为适地适树、补植造林等营林工作提供理论依据。

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