基于树木生长过程的长白落叶松树冠模型

Crown structure is characterized by the number, size, and location of primary branches, which relates to stem growth, wood quality attributes and key physiological processes such as effective light capture and photosynthesis. It is important to quantify crown traits for effective use of intensive silvicultural practices to improve tree growth in forest plantations. Branch development is great importance both for quantity and quality of timber produced from plantations. The size and vitality status (live or dead) of branches along the stem and the natural branch shedding habits of the species influence the development and persistence of knots and knot-related defects. Minimising or eliminating knots is essential for the production of high quality timber. Therefore, the control of crown development will play an important role in the production of logs with the desired properties..Crown shape and size influence production efficiency, as a measure of tree vigour for use in forest growth models. This information is used to estimate crown cover, crown volume, the fractal dimension of the crown and the distribution of foliage and interception of solar radiation. Unfortunately, the effects of silvicultural practices and stand ages on stem growth and wood properties are not as well known and are generally not included or are oversimplified in simulation systems. Thus, an integral part of the simulation systems should be the link between growth and yield models..The study aims to quantitate the crown structure of various stages of stand development through analysis of the spatial distribution of live and dead branches within the crown. Investigate whether, and under what conditions, a similar modified profile theory could also be applicable to the Larix olgensis. Defining such conditions to describe the crown dynamics and predict the development of stem structure in Larix olgensis. The primary objective is to provide insight into the size, angle, and vertical distribution of branches on Larix olgensis at various stages of stand development. The secondary objective is to develop a crown profile model from compare a system-of-equations approach. The specific aims are to develop models for predicting branch diameter and branch angle profiles along the stem and for predicting branch growth and mortality in different positions in the crown. Both a linear and nonlinear, generalized hierarchical mixed effects equation would be developed. The crown models would be developed to be applicable in growth simulators based on individual-tree growth models. The development of these branch-level prediction models will help to understand growth response at the tree-level and allow assessment of potential wood product quality in this region, which should promote more effective and efficient silvicultural practices.

树冠结构影响树干生长、木材结构及光合作用，反映了林木的生长活力，长白落叶松是东北主要用材树种之一，其树冠结构的研究对人工林的集约经营、定向培育有重要意义。树木生长过程分析是研究树木生长动态分析的经典方法，数学模型是构建树木生长模型的基础，树冠模型是定量研究树冠结构的发展趋势。以长白落叶松人工林为研究对象，在分析已有的调查资料基础上，通过动态监测树冠形成过程，测定树木和枝条生长过程数据，重新构建枝条生长动态和树冠形状的变化过程。分析不同年龄、不同密度等对枝条生长的影响，定量模拟枝条生长规律；分析树冠形成的作用机理，构建树冠冠幅、树冠率及树冠体积等具有林学意义的模型；采用线性和非线性模拟方法研究枝条大小、数量、分布模型，确定最佳方法；与树木生长与收获模型相结合，模拟基于树木生长过程为基础的树冠形状动态模型，探讨长白落叶松林树冠大小、形状与树干生长之间的作用机理。

树冠结构影响树干生长、木材结构及光合作用，反映了林木的生长活力，长白落叶松是东北主要用材树种之一，其树冠结构的研究对人工林的集约经营、定向培育有重要意义。本研究以东北小兴安岭地区的长白落叶松为研究对象，通过样地调查、树冠调查和树干解析数据采集，利用多种统计学模型、机器学习算法以及三维可视化技术对树冠形态估测模型、枝条的空间分布和预测模型、树冠形态对竞争和径向生长的响应、树冠的可视化模拟进行了研究。结果表明，Logistic模型形式能较好地拟合长白落叶松枝下高和冠幅生长，向枝下高模型中加入优势木高、大于对象木的断面积以及相对植距，向冠幅模型中加入单木断面积、胸径与平方平均胸径比值以及高径比，将样地作为随机效应构建非线性混合效应模型能充分考虑数据的嵌套性同时有效改进模型预测精度。随机森林和投票回归算法预测精度比传统的统计学方法更好。将Hegyi竞争指数分解到东、西、南和北四个方向结合联立方程组构建冠幅相容性模型和广义加性模型能考虑冠幅以及各方向冠径的相关性。枝条数量和一级枝条最大枝长在树冠中的垂直分布呈先增后减的趋势，一级枝条平均基径随冠层下降逐渐变大，一级枝条平均着枝角随冠层下降而增大，一级枝条水平空间分布的均匀分布检验表明不同方位区间的最大树冠半径之间可能存在明显差异。以Gompertz方程和Logistic方程分别作为基础式，将龄组作为第一水平、单木作为第二水平的改进模型能较好地描述胸径与着枝深度对枝条基径和枝长的影响。不同林龄样地中林木的树冠变异系数的平均值均大于20%，树冠的偏冠方向均匀分布，树冠偏冠对于树冠以下的树干径向生长具有一定的影响。利用L-studio和OpenGL基于单木三维模型，利用样地数据库的位置信息，基于构建的生长预测模型，对长白落叶松人工林的生长预测基本达到了预期的效果。定量分析树冠形态与竞争的关系、深入分析树冠结构与树木生长的关系，使其形成能最有效利用光能的树冠结构，以提高森林生产力、提升木材产量与质量，为人工林集约栽培和经营决策提供科学依据，具有重要的研究意义。