Dead wood offsets the reduced live wood carbon stock in forests over 50 years after a stand-replacing wind disturbance

Windthrow disturbances often produce large amounts of dead woody materials in a forest. However, post-disturbance, salvage logging greatly reduces the amount of dead woody materials, and thus, carbon stocks. Because the dead woody materials can persist as coarse woody debris (CWD) for a very long time in cool climatic areas, such as boreal and subalpine forests, salvage logging might have long-term effects on the carbon stocks of disturbed forests. In this study, we examined the effects of windthrow by a super typhoon in 1959 and subsequent salvage logging on the carbon stock of subalpine forests more than a half-century after the disturbance in central Japan. We sampled disturbed and not salvaged (unsalvaged) stands versus disturbed and salvaged stands within 10 years of the disturbance (salvaged) in addition to undisturbed stands (undisturbed). The volume of CWD was higher in the unsalvaged stands versus the other two types of forests. Specifically, the volume of classes with intermediate decay was very high, contributing to greater carbon stocks of CWD in the unsalvaged stands. Although the carbon stock of living trees was higher in the undisturbed stands compared to the disturbed stands (unsalvaged and salvaged), the total carbon stock (live + dead) of the unsalvaged stands (104 Mg C ha−1) was almost equivalent to that of the undisturbed stands (99 Mg C ha−1) and was much higher than that of the salvaged stands (72 Mg C ha−1). This study demonstrates that CWD produced by a typhoon acts as a large carbon stock for more than a half-century, potentially offsetting the loss of live woody biomass in disturbed forests.