In Situ CO2 Efflux from Leaf Litter Layer Showed Large Temporal Variation Induced by Rapid Wetting and Drying Cycle

We performed continuous and manual in situ measurements of CO 2 efflux from the leaf litter layer ( R LL ) and water content of the leaf litter layer (LWC) in conjunction with measurements of soil respiration ( R S ) and soil water content (SWC) in a temperate forest; our objectives were to evaluate the response of R LL to rainfall events and to assess temporal variation in its contribution to R S . We measured R LL in a treatment area from which all potential sources of CO 2 except for the leaf litter layer were removed. Capacitance sensors were used to measure LWC. R LL increased immediately after wetting of the leaf litter layer; peak R LL values were observed during or one day after rainfall events and were up to 8.6-fold larger than R LL prior to rainfall. R LL declined to pre-wetting levels within 2–4 day after rainfall events and corresponded to decreasing LWC, indicating that annual R LL is strongly influenced by precipitation. Temporal variation in the observed contribution of R LL to R S varied from nearly zero to 51%. Continuous in situ measurements of LWC and CO 2 efflux from leaf litter only, combined with measurements of R S , can provide robust data to clarify the response of R LL to rainfall events and its contribution to total R S .