基于无人机影像探讨格氏栲天然林林窗数量分布及其影响因素

探讨格氏栲(Castanopsis kawakamii)天然林林窗数量特征及其空间分布对预测森林种群动态变化及演替具有重要意义。该文采用无人机航拍获取格氏栲天然林正射影像图并结合野外调查,通过提取林窗特征参数和计算植被覆盖率来探讨林窗空间分布及其影响因素。结果表明:(1)保护区内格氏栲天然林植被覆盖率为75.53%,部分地区出现一定面积裸露土地。(2)研究区林窗空隙率为2.40%,密度为6.50ind.·hm-2,平均林窗面积为36.86 m2。(3)研究区林窗数量随林窗面积增加呈负指数分布,以微、小和中型林窗为主,面积100 m2以上的林窗数量较少。(4)低海拔林冠层覆盖度好,中海拔地区林窗个体数和平均林窗面积较大,高海拔地区林窗密度和空隙率相对较大。林窗主要分布在缓坡和斜坡上,其平均面积、密度和林窗空隙率也明显较高。西和南方位林窗数量较多,北、西北和东南方向林窗密度和空隙率相对较大。格氏栲天然林植被覆盖率较高,以微、小和中型林窗为主,地形因子通过改变林窗面积、林窗密度和林窗空隙率特征驱动了格氏栲天然林林窗数量与空间分布格局。

Using UAV images to explore quantitative characteristics and influencing factors of forest gaps in Castanopsis kawakamii natural forest

It is of great significance to explore the quantitative characteristics of Castanopsis kawakamii natural forest gaps and its spatial distribution. It can help us to predict C. kawakamii forest population dynamics and its succession. In this paper, the orthoimage of C. kawakamii natural forest was obtained by using unmanned aerial vehicle(UAV)and field investigation. Then we extracted the characteristics factors for forest gaps and calculated the vegetation coverage to explore the forest gap spatial distribution and its influence factors. The results were as follows:(1)The vegetation coverage of the C. kawakamii natural forest was 75.53% in this reserve. However, there existed a certain area of bare land in the reserve.(2)The gap ratio and density of forest gaps were 2.40% and 6.50 ind·hm^-2.(3)The number of forest gaps had a negative exponential distribution with the increase of gap area. This forest dominated by tiny, small and medium gaps, and few gaps with area above 100 m².(4)Forest canopy coverage was good in the low elevation, and the number and average area was relative more in the middle elevation, while high elevation had higher gap density and gap ratio. Forest gaps mainly distributed on the gentle and incline slope, and their average areas, densities, and ratios were relatively high. There were many forest gaps in western and southern directions, and the gap densities and ratios were relatively large in northern, northwestern and southeastern directions. The vegetation coverage of C. kawakamii natural forest was relatively high, and dominated by tiny, small and medium area of forest gaps. Topographic factors drive the quantitative and spatial distribution of forest gaps by changing the gap area, density and ratio of C. kawakamii natural forest. The study provides a theoretical basis for the application of UAV in forest gaps.