Thus, if the Birch effect carbon release is primarily from microbial materials, dry–wet cycling might reduce long-term carbon loss from soil. In contrast, if the Birch effect results from mobilizing otherwise stable old carbon pools, it would fuel microbial growth, possibly priming the loss of additional stable soil carbon.

It has long been recognized that rewetting a dry soil causes a pulse of CO2 (the Birch effect)

It is also unclear whether the flush of activity on rewetting is driven by microbial growth or by the physical/chemical processes that mobilize organic matter