Detecting forest degradation in Kochi, Japan: ground-based measurements versus satellite (Terra/ASTER) remote sensing

摘要

Forest degradation, due mainly to poor management, is of increasing concern in Japan. Major ecosystem functions, such as biodiversity, productivity, and soil and water retention, are being lost or weakened in Japan's forests, especially in Japanese cypress (Hinoki; Chamaecyparis Obtusa Sieb.) plantations. Detecting forest degradation is critical to the restoration of the ecosystem in the Kochi area, but ground-based detection methods are labour intensive and difficult to implement in mountainous areas. In this study we examined the ecological characteristics (e.g. soil water content (SWC) and leaf water content) of degraded and healthy forests, based on in situ measurements and controlled experiments, and present a new method for mapping forest degradation based on remote sensing techniques. A field survey was carried out to record the locations and conditions of the degraded Japanese cypress plantations. Empirical relationships among the degraded plantation, SWC, fuel moisture content (FMC), and vegetation indices (Vis) were investigated by field survey and control experiments. We found that the SWC of the degraded Japanese cypress plantations was lower than that of the well-managed Japanese cypress plantations. We also found that the SWC, FMC, and VI are highly correlated (R > 0 80). In addition to the ground investigation, we used the advanced spaceborne thermal emission and reflection radiometer (ASTER) data and compared a number of Vis to determine their relationships to the biophysical/biochemical attributes of vegetation canopies. Our results showed that (he ASTER thermal band was the most effective method used to detect degraded Japanese cypress plantations in the study area.