Abstract
Rain-induced soil CO2 pulse, a rapid excitation in soil CO2 flux after rain, is ubiquitously observed in terrestrial ecosystems, yet the underlying mechanisms in tropical forests are still not clear. We conducted a rain simulation experiment to quantify rain-induced changes in soil CO2 flux and microbial community composition in a tropical forest. Soil CO2 flux rapidly increased by ~83% after rains, accompanied by increases in both bacterial (~51%) and fungal (~58%) Phospholipid Fatty Acids (PLFA) biomass. However, soil CO2 flux and microbial community in the plots without litters showed limited response to rains. Direct releases of CO2 from litter layer only accounted for ~19% increases in soil CO2 flux, suggesting that the leaching of dissolved organic carbon (DOC) from litter layer to the topsoil is the major cause of rain-induced soil CO2 pulse. In addition, rain-induced changes in soil CO2 flux and microbial PLFA biomass decreased with increasing rain sizes, but they were positively correlated with litter-leached DOC concentration rather than total DOC flux. Our findings reveal an important role of litter-leached DOC input in regulating rain-induced soil CO2 pulses and microbial community composition, and may have significant implications for CO2 losses from tropical forest soils under future rainfall changes.
Highlights
Our results further indicated that the rain-induced CO2 pulse was primarily attributed to the input of litter-leached dissolved organic carbon (DOC)
This was an interesting finding, and was validated by the rain-induced soil CO2 pulse (RDOC) data that was estimated as 0.75–2.50 μmol CO2 m−2 s−1 after rains (Table 1), accounting for about 77% increase in rain-induced Rtotal
The simulated rains caused about 396–722 mg m−2 DOC leaching from the litter layer into the topsoil under different rain sizes (Fig. 2b)
Summary
Our findings reveal an important role of litter-leached DOC input in regulating rain-induced soil CO2 pulses and microbial community composition, and may have significant implications for CO2 losses from tropical forest soils under future rainfall changes. Rains could directly stimulate the CO2 release from litter layer (Rlitter), or indirectly promote high CO2 pulses by delivering large amounts of dissolved organic carbon (DOC) from the litter layer to the topsoil (RDOC, the contribution of litter-leached DOC input to soil CO2 flux). Previous studies have indicated that rains increased soil CO2 flux primarily by stimulating microbial activity, enhancing soil microbial biomass, or alterations in community composition[12, 26,27,28]. How soil microbial community changes after rains in tropical forest ecosystems in southern China, and whether it will be responsible for the rain-induced soil CO2 pulses have not been well studied
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
