基于无人机影像的天山云杉林伐后更新地林分密度估测研究

【目的】林分密度是影响森林生态系统结构和功能的主要因素,是森林资源调查的一项重要指标,对林木生长发育有着十分重要的影响。基于无人机影像,以实现提取不同郁闭度的林分密度,旨在为天然林保护工程实施后山区森林资源更新恢复评价提供技术支撑。【方法】以新疆农业大学实习林场伐后更新的天然林为研究对象,以天山云杉Picea schrenkiana var.tianshanica纯林为主,基于无人机影像,利用面向对象多尺度分割方法提取了低、中、高3种不同郁闭度林分的天山云杉冠幅信息,进而估算林分密度,提出了采用平均冠幅法估测高郁闭度林分冠层遮挡区域林木株数的方法。【结果】采用面向对象方法对新疆农业大学实习林场伐后更新的天山云杉树冠边缘信息提取精度较高,提取的林分密度与实测结果相近。其中低、中郁闭度林分中林分密度提取精度分别为0.9868和0.9333,高郁闭度林分中林分密度提取精度相对较低,为0.7657。【结论】总体来看,该方法用于研究区天山云杉林伐后更新地林分密度估测是可行的,采用树冠平均冠幅法能够快速准确地提取伐后更新造林地的林分密度。

Research on estimation of stand density of regenerate Picea schrenkiana var. tianshanica based on UAV images

【Objective】Forest density is the main factor affecting the structure and function of forest ecosystem. As an important index in forest resource investigation, it has a very important influence on the growth and development of forest. This study based on UAV images to extract stand densities with different canopy densities, which can provide technical support for the evaluation of forest resources renewal and restoration in mountainous areas after the implementation of natural forest protection project to a certain extent. 【Method】Taking the natural forest updated after cutting in practice forest farm of Xinjiang Agricultural University as the research object, the Picea schrenkiana var. tianshanica was the main research object. The UAV image as the data source, and the information of the canopy of the Picea Schrenkiana var. tianshanica of low, medium and high canopy density was extracted with the object-oriented multi-scale segmentation method. Then the stand density is estimated accordingly. Average crown width method is proposed to estimate the number of forest strains in the blocked area of high canopy density.【Result】The results showed that the extraction accuracy of the canopy edge information of the cutover forest in Xinjiang Agricultural University is higher with object-oriented method and the extracted stand density is similar to the measured result. The extraction accuracy of forest density in low and medium canopy density was 0.986 8 and 0.933 3 respectively, while the extraction accuracy of forest density in high canopy density was reduced to 0.765 7.【Conclusion】Overall, average crown width method can be used to extract the stand density of cutover forest. The average crown amplitude method can quickly and accurately extract the stand density of replanted land after cutting.