Abstract:

Applicable accuracy of one-variable tree volume tables used in national continuous forest inventory(NFI)for long-term perspective has been worthy of attention.Based on the mensuration data of sample plots from oak(Quercus spp.)forests in 2014 Shaanxi of the 9th NFI,the test method for applicable accuracy of 4 one-variable tree volume tables was discussed.The approach is to develop 4 tree height-diameter regression models for oak forests using two sets of data,466 pairs of mean diameter and mean tree height of oak stands and 1447 pairs of diameter and tree height of average oak trees,and obtain 4 new one-variable tree volume tables,then compare with the old tables and calculate total relative errors(TRE).The results showed that the TREs of 2 old one-variable tree volume tables did not exceed ±3%,and the TREs of other 2 volume tables exceeded ±5%,and the largest one reached about -10%.Therefore,keeping the one-variable tree volume tables constant in long-term application may cause bias in volume estimation.It is recommended that one-variable tree volume tables/models need to be tested every 10 or 20 years,and the significantly biased ones should be corrected in time.

Key words: volume estimation, one-variable volume table, relative error, Quercus spp., Shannxi