How accurate is coring for measuring annual increment in Quercus mongolica, Kalopanx septemlobus, and Pinus densiflora?

Coring has been widely used to measure annual increment in temperate forest ecosystems. This method is attractive because cores can be taken in just one visit. However, the accuracy of this method has not been tested. We expected coring to be less accurate than increment bands because of the eccentricity of tree growth. We also hypothesized that accuracy would be lower in hardwoods than in softwoods. We studied 60 trees at two sites in Korea, the Gwangneung Experimental Forest and Gyebangsan, which have been monitored with increments bands since 1997.  We collected two tree cores from the south and north face of each tree, 10 cm below the growth band. Increment cores were measured to 0.01 mm under the stereomicroscopy (Leica MZ16). Annual growth from 1997 to 2007 was 3.68 mm yr^-1 for  Quercus mongolica, 3.19 mm yr^-1 for Kalopanx septemlobus, and 5.66 mm yr^-1 for Pinus densiflora. There were no significant differences in annual growth by aspect (P = 0.30). The difference between the two methods was 1.15 mm yr^-1 (29.9%) for Q. mongolica, 0.97 mm yr^-1 (30.1%) for K. septemlobus, and 1.36 mm yr^-1 (23.1%) for P. densiflora. The error rate was significantly lower in P. densiflora than two hardwood species (P = 0.05). We recommend the use of growth band to improve the accuracy of biomass and production measurement in forest ecosystems.