Using UAV technology for basic data collection of Firmiana danxiaensis H. H. Hsue & H. S. Kiu, J. S. (Malvaceae), an important, nationally protected wild plant in Zhanglao Peak, Danxiashan Mountain, South China

Abstract

The protection of rare species is an urgent task for all of mankind, however this task is challenging because it is usually difficult to determine their numbers and spatial distribution. Firmiana danxiaensis H. H. Hsue & H. S. Kiu, J. S. (Malvaceae), which is listed at the highest grade of critically endangered (CR) plants in the first volume of “The China Species Red List,” can be found at Danxiashan Mountain, one of the six World Nature Heritage sites of China Danxia, in Northern Guangdong Province, China. At present, UAV low-altitude photogrammetry technology can complete and produce orthophoto maps of 1:2000 resolution and high-precision DEM data, and has a high application value in the collection and research of rare species’ basic data. For this study, UAV technology was used especially for mapping, quantifying and monitoring plant species. F. danxiaensis is a good fit for automated identification from UAV imagery due to its leaf coloration making it stand out during the end of October. A fixed-wing UAV was used to aerially survey the Zhanglao Peak Tourist Area of Danxiashan Mountain (the aerial survey area is 4.25 km2) and the valleys and cliffs where it is difficult to conduct field surveys. 638 high-precision image data were obtained. Photoscan software was used to produce mosaic image data, an orthophoto map, and DEM data. Analyses of the targets’ locations and data visualizations were done with Arc GIS 10.5 software. 1,515 individuals of F. danxiaensis have been found in the aerial survey area. The results suggest that the red line boundary of ecological protection should be delineated in the densely distributed areas of F. danxiaensis, and scientific research plans should be formulated to protect the rare species and their natural environment so as to ensure sustainable development and utilization for human beings.