Abstract
Decay rates of block specimens of Japanese red pine (Pinus densiflora Sieb. et Zucc.) were determined by examining the weight loss rates for two vertical positions (above and on the surface of the forest floor) and three locations along a slope (ridge and valley). Decay-rate constants based on the single-exponential decay model ranged considerably, from 0.004 to 0.316 yr^<-1>. Decay-rate constants of on the surface was significantly larger than that of above the surface however decay-rate constants was not significantly different among locations. Decay-rate constants had linear relation to water content of block specimens. Limited contact with the ground caused the lower water content of the specimens. The depth of the litter layer contributed to the variation in the water content of the specimens placed on the ground due to the subtle concavo-convex nature of the ground surface around the specimens. The change of the characteristics of the specimens by decomposition progress would cause the variation in water content of specimens. Therefore, to quantify the spatial variation in the decay rate of coarse woody debris (CWD) in forest ecosystems, the spatial variation in water content caused by differences in the environmental conditions around the CWD, such as contact with soil and depth of the litter layer, and CWD characteristics changed through decomposition progress should be considered.
