Detecting Forest Degradation in Kochi, Japan: Combining In Situ Field Measurements with Remote Sensing Techniques

摘要

This paper describes a method for mapping forest degradation based on in situ field measurements and remote sensing techniques. Firstly, field survey was carried out to confirm the locations and conditions of the devastated hinoki plantation (Chamaecyparis Obtusa Sieb.). Secondly, several relationships between the devastated hinoki plantation and soil water content (SWC), SWC and fuel moisture content (FMC), and FMC and vegetation index (VI) were investigated by field survey and control experiments. Results showed that SWC of devastated hinoki plantation is lower than well managed hinoki plantation. It is also seen that there are significant correlations between SWC and FMC (R=0.80), and FMC and VI (R=0.86), respectively. Thirdly, several vegetation indexes (Ratio Water Index: RWI, Water Index: WI, Normalized Difference Water Index: NDWI, Photochemical Reflectance Index: PRI, and Normalized Difference Vegetation Index: NDVI) were tested, and our results showed that RWI had the most significant correlation with FMC (R=0.86) of hinoki plantation. RWI was estimated from ASTER data, with the threshold set by using field survey data. Finally, we mapped the degraded forest based on the RWI.