Application of high-resolution airborne data using individual tree crowns in Japanese conifer plantations

Abstract

We investigated conifer plantation management in Japan using high-resolution airborne data based on an individual tree crown (ITC) approach. This study is the first to apply this technique to Japanese forests. We found that forest resources can be measured at the level of a single tree. We also produced a tree crown map for a test site with Chamaecyparis obtusa, Pinus densiflora, Larix kaempferi, Cryptomeria japonica, other conifers, and broadleaved trees, with a classification accuracy of 78%. Forest stand polygons with tree cover types were generated from this map, a tree density map, and a crownoccupied area map. Forest information for the stand polygons was extracted automatically and compared to detailed field survey data. The error rate between our ITC estimates and the field survey data ranged from 0.3 to 30.2%, depending on tree crown size, density, and other factors. Errors were highest for high-density stands with mixed compositions and tree crown diameters of ≤5.0 m. However, the error for stands with crown diameters ≥6.2 m was 11.6% or less. Therefore, this technique is best suited to pure Japanese conifer plantations without multiple layers or high-density stands.

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

“…The average interpretation accuracies of the different forest types in the three groups were calculated as shown in Figure 3 (average value and standard deviation). In the broad-leaved forest, the accuracy in the DBH ≥10 cm layer was higher than that in the DBH ≥15 cm layer and the DBH ≥20 cm layer, indicating that with the growth of broad-leaved trees, the tree tops become difficult to identify, in contrast to coniferous forests [18]. There is no significant difference in accuracy between the three groups for mixed forest.…”

“…Tree tops were interpreted with the ITC approach using WorldView-2 imagery in PCI Geomatica v9.1 software with the ITC Suite [18,28,35]. First, preprocessing for tree top interpretations was necessary to normalize the panchromatic band based on its own range in the illumination image, which was performed twice to smooth using an averaging filter of 5 × 5 pixels (2.5 by 2.5 m) [18,28].…”

“…The ITC isolation image was produced by using the valley-following algorithm. Using the normalized panchromatic band and the non-forested mask, this method treats the spectral values as topography, with shaded and darker areas representing valleys and bright pixels delineating the tree crowns [18]. This method produces a bitmap of segments of valley and crown materials in forest areas.…”

“…Accurate forest information at the individual tree level is of high importance for the selection of target trees. Therefore, individual tree crown delineation methods have received greater attention from researchers in the forest remote sensing field [17][18][19][20].…”

“…The template-matching algorithms match a synthetic image model or template of a tree crown to radiometric values [21][22][23]. The valley-following method, developed by Gougeon [24], has been successfully used to extract tree crowns and tops of man-made coniferous forests in temperate zones by using aerial photographs [18][19][20]. Additionally, the individual tree crown (ITC) approach using the valley-following method has been successfully programmed by the Pacific Forestry Centre of the Canadian Forest Service, which made it possible to delineate tree crowns and tops on a large scale.…”