Site conditions interact with litter quality to affect home-field advantage and rhizosphere effect of litter decomposition in a subtropical wetland ecosystem.

The home-field advantage (HFA) hypothesis predicts that plant litter would decompose more quickly beneath its own plant species in the soil than beneath other plant species. Theoretically, HFA can be induced by the rhizosphere of growing plants, due to so-called rhizosphere effect (RE). Despite growing evidence for the site condition-dependence of both effects, few work has be conducted to explore how site climate, vegetation type and soil properties interact to affect RE and HFA, and especially limited in situ representation from subtropical wetland systems. In a field experiment, we reciprocally incubated three root litter species (Rumex dentatus L., Carex thunbergii Steud., and Polygonum cripolitanum Hance) along a hydroperiod gradient in a subtropical wetland, which differed mainly with respect to vegetation and soil microclimate, with and without growing plants. The occurrence and magnitude of HFA and RE were mainly determined by litter quality and were stage-specific. Collectively, we detected significant HFA with chemically-recalcitrant litter from C. thunbergii and P. cripolitanum, but only at the first stage of decomposition. The presence of growing plants generally reduced litter decomposition, but the magnitude of the response was species-specific, with the positive effects detected only for root litters from C. thunbergii at the first stage of decomposition. In addition, we did not find a significant relationship between HFA and RE, indicating that plant species that produce litters exhibiting HFA may not accelerate litter decomposition via RE at same time. Structural equation models (SEM) revealed that site microclimate factors were conducive with soil properties in regulating C dynamics. Overall, soil microclimate in this wetland ecosystem was likely important in driving C cycling, either directly by changing environmental conditions, litter quality, and plant trait spectra, or indirectly by interrupting the interactions between litter and decomposers.