Interpretation of forest resources at the individual tree level at Purple Mountain, Nanjing City, China, using WorldView-2 imagery by combining GPS, RS, and GIS technologies

摘要

This study measured forest resources at the individual tree level using high-resolution images by combining GPS, RS, and GIS technologies. The images were acquired by a WorldView-2 satellite with a resolution of 0.5 m in the panchromatic band and 2.0 m in the multispectral bands. Field data of 90 plots were used to verify the interpreted accuracy. The tops of trees in three groups, namely ≥ 10 cm, ≥ 15 cm, and ≥ 20 cm DBH, were extracted by the Individual Tree Crown (ITC) approach using niters with moving windows of 3×3 pixels, 5×5 pixels, and 7×7 pixels, respectively. In the study area, there were 1,203,970 trees of DBH over 10 cm, and the interpreted accuracy was 73.68 ± 15.14% averaged over the 90 plots. The numbers of the trees that were ≥ 15 cm and ≥ 20 cm DBH were 727,887 and 548,919, with an average accuracy of 68.74 ± 17.21% and 71.92 ± 18.03%, respectively. In addition, a tree count of different species indicated that the forest of Purple Mountain is mainly dominated by Quercus acutissima, Liquidambar formosana, and Pinus massonicma.