5. Conclusion
This study explored the direct and legacy effects of DWC on active and
relatively resistant SOC decomposition by using three soils from a
long-term experimental field as well as an incubation experiment.
Compared to the mean constant-moisture treatment (60% WHC), the strong
DWC treatment (100-20% WHC) had minor effects on SOC mineralization of
OF soil and BF soil in most of the
cycles, but stimulated SOC mineralization of BF+ soil. This result
suggests that the relatively resistant SOC is more vulnerable to DWC
than active SOC during the DWC period (0-90 d). Moreover, the DWC had a
legacy effect on SOC decomposition during the extended period (100-128
d), being positive for active SOC but negative for relatively resistant
SOC. Both MBC and DOC may contribute to this legacy effect. However,
when both direct effect and legacy effect were considered, the strong
DWC did not significantly affect the cumulative SOC decomposition of OF
and BF+ soils, but had a negative effect on that of BF soil during the
entire incubation period. Taken together, our study demonstrated that
DWC could create both direct and legacy effects on SOC decomposition,
and these effects vary with DWC intensity and SOC pools. These findings
suggest that more frequent alternating drought and rapid precipitation
in the future may have a minor or even negative effect on soil C loss.