基于竞争指数的水陆交错带枫杨生长模型

Pterocarya Stenoptera Growth Model in Aquatic-Terrestrial Ecotones Based on Competitiveness Index

为进行河岸流域水陆交错带植被生长的可视化模拟研究,以漓江流域枫杨树种为模拟对象,基于改进的Hegyi简单竞争指数建立了枫杨树种的单木生长模型,通过将直径分布模型和随机算法运用于全林分,利用C#编程语言、3D Max建模工具、Virtools平台等可视化相关技术,实现了漓江流域枫杨树种在不同全氮含量土壤的生长可视化模拟。研究表明,枫杨胸径年生长量与土壤全氮含量呈显著正相关,相关系数为0.749;竞争指数模型改进前和改进后的竞争指数与胸径年增长量均呈显著负相关,相关系数分别为-0.621和-0.657;模拟过程中,拟合2块样地内枫杨径阶分布时误差率分别为6.25%和11.9%,枫杨树高与胸径模型拟合决定系数为0.703,冠幅与胸径模型拟合决定系数为0.612,枫杨胸径生长模型拟合决定系数为0.734。改进的竞争指数模型和随机算法对构建水陆交错带枫杨树种的生长模拟具有较强的适用性和较高的逼真度。该研究为漓江流域植被恢复和演替模拟提供理论依据和参考。

In recent years, the phenomenon of the landscape degradation in the river basin has been more and more serious because of over ecotourism, and the forestry visualization technology provides important reference for ecosystem restoration and landscape optimization decision, therefore, it is necessary and practically significant to research the visual simulation of vegetation growth in the river basin. This paper presented the case of pterocarya stenoptera in aquatic - terrestrial ecotones in Lijiang River, and found that total nitrogen content of soil plays a critical role during its growth after analyzing the correlation between soil sample and growth data. Based on this finding, the modified Hegyi＇ s simple competition index model with added nitrogen factors was adopted to the single tree growth model for pterocarya stenoptera stands built in Lijiang River, then diameter distribution model and random algorithm were applied to whole stand model. In the process of simulation, the information of location and diameter at breast height distribution of pterocarya stenoptera in the plot was confirmed by the trees distribution model first; the next step, the height and the crown of each pterocarya stenoptera were simulated according to the fitting relationship between tree height and diameter at breast height, crowns with diameter at breast height and the diameter at breast height of each pterocarya stenoptera were measured, and then, the growth of pterocarya stenoptera was simulated by iterative execution of the growth model using the data got before; after that two-dimensional simulation with different soil nitrogen contents was achieved by implementing C# programming language and GDI ＋ technology, and then the dot and the circle in two- dimensional simulation would be mapped into specific pterocarya stenoptera model on 3D Max; finally the three-dimensional visual simulation of the growth of pterocarya stenoptera in Virtools platform was achieved. The result showed that a significantly positively relationship existed between diameter at breast height growth and soil total nitrogen content of pterocarya stenoptera, and the correlation coefficient was 0. 749 ; a significantly negative relationship exists between competition index and diameter at breast height growth, and the correlation coefficient improved from - 0. 621 to - 0. 657 with the competition index model improved; the error rates were 6.25% and 11.9% respectively when fitting the diameter distribution of pterocarya stenoptera in the simulation and the decision coefficient of diameter at breast height growth model reached 0. 734. It＇ s found that adopting modified Hegyi＇ s simple competition index model and random algorithm had strong applicability and higher fidelity for pterocarya stenoptera growth simulation in aquatic - terrestrial ecotone. The originality of this paper is to adopte modified Hegyi＇ s simple competition index model with added nitrogen factors, with the help of Virtools platform, to lay the foundation for further development of human-computer interaction and real time walkthrough. In this article, it provides theoretical basis and reference for the vegetation restoration and succession simulation in Lijiang River watershed, and presents a feasible research idea and implementation method for the forestry visualization research by visualization simulation of pterocarya stenoptera growth in the Lijiang River watershed.