Seasonal effects on aboveground biomass estimation in mountainous deciduous forests using ZY-3 stereoscopic imagery

Abstract

Stereoscopic images are getting attentions in the forest remote sensing. It is essential to clarify environmental effects on detecting forest spatial structures using stereoscopic images in addition to data processing algorithms. The seasonal effects in mountainous deciduous forests is systematically explored in this study from mid-summer to late winter using 8 dates of ZY-3 stereoscopic images. This study reveals that the acquisition season is an important factor affecting the detection of forest spatial structures. In the leaf-on season, for closed forest stands, the forest canopy tops are easily to be detected; for open forest stands, the ground surface can be detected through between-canopy gaps in mid-summer, but be missed in late summer or early fall. In the leaf-off season, the stereoscopic imagery acquired in late winter or early spring was preferred for the detection of ground surfaces, while the mountain shadows limit those acquired in early and middle winter. The ratio of sunlit ground visible in stereoscopic images as the season change is the factor controlling these findings. The images with the smaller ratio are preferred for the detection of forest canopy tops, while the opposite is proper for the detection of ground surfaces. The combination of ZY-3 stereoscopic imagery acquired in mid-summer and late winter gave the best estimation accuracy of forest AGB among possible combinations.