Elevational variation in abundance of coarse woody debris in subalpine forests, central Japan

In recent years, coarse woody debris (CWD) of deadwood has attracted attention as a long-term carbon pool for global warming problems. Environmental factors such as temperature and precipitation vary greatly with elevation. Hence, it is expected that the carbon storage by CWD varies with elevation. However, few studies have examined the abundance of CWD along elevations. Therefore, we investigated the abundance and decay classes of CWD, aboveground biomass (AGB) and aboveground net primary production (ANPP) of living trees along an elevational gradient (1600-2800 m above sea level) in subalpine coniferous forests, central Japan. AGB, ANPP and CWD decreased with increasing elevation. AGB at 2800 m was about 10% of that at 1600 m a.s.l. On the other hand, CWD at 2800 m was only 2.2% of that at 1600 m a.s.l. Thus, the ratio of CWD to AGB was lower at higher elevations. The relative frequency of small CWD increased with elevation. In addition, smaller CWD tended to decay less. The lower ratio of CWD mass to AGB at higher elevations was probably caused by smaller CWD because small CWD rapidly disappears via the high decomposition rate due to its high ratio of surface area to volume. Therefore, this study suggests that the importance of CWD relative to AGB for carbon storage decreases with elevation in subalpine forests. Climate change may alter the balance between CWD and AGB by changing ANPP and decomposition rates along elevation gradients.