**4.1.2 Above-ground CWD decay**

The single-exponential decay coefficient (k) is an indicator of the rate of the decay process (Swift et al., 1979). The higher the k value, the faster CWD decays. Table 3 showed that, when CWD is in early or medium decay stages (data limited to about <30 years of decay since disturbance in this study), k values associated with above-ground CWD on the harvested sites were significantly higher (*p* < 0.001) than those on the fire-killed sites. These differences were attributed to the degree of contact between CWD and ground. CWD after harvesting generally has full contact with the ground, while CWD after wildfire disturbance experiences a long period of time before fully reaching the ground (from snag to partial suspended CWD and finally to fully ground-contact CWD). Decomposition is accelerated when logs are in contact with the ground, probably as a result of higher moisture content and increased interaction with the soil fauna and microflora.


Table 3. Single-exponential decay coefficients (k) for 10-20 cm diameter above-ground coarse woody debris (CWD) of different decay classes on both harvested and fire-killed sites (Wei et al. 1997) (Note: Means with the same letter within a row are not significantly different (*p* > 0.05) from each other (t-tests); standard error of the mean is shown in parentheses; \*data on various years of wood decay was grouped into two time classes as shown in the table)
