Comparison among Four Ground-Survey Methods as a Continuous Forest Inventory System for Forest Management

The objective of this study was to compare the accuracy of four ground-survey methods, which are: the point sampling method (PS), the line sampling method (LS), the circular plot method (CP), and the concentric circular plot method (CCP), as a continuous forest inventory system for forest management. This work was conducted by using the data of a sugi (Cryptomeria japonica D. Don) stand 43 years old, on the Shiragadake Experimental Forest in Kagoshima, Japan. For PS and LS the basal area factor 2 was used. For the LS, the line length was 11m, and the stems of both sides of the line were selected. For CP, the radius was 7 m, corresponding to 0.015 ha; for CCP, radii were 6 and 11m, corresponding to 0.011 and 0.038 ha respectively. Sampling intensity was 30 samples, and the systematic sampling process was applied 10 times with each method. For the number of stems per ha and the mean diameter, CP presented the least sampling error, followed by CCP; for basal area and volume per ha, PS showed the least sampling error, followed by CCP. The differences in sampling errors among these methods, however, can be considered non-significant. Therefore, the best method should not be selected only on the basis of the sampling errors.