Increased soil moisture aggravated the competitive effects of the invasive tree Rhus typhina on the native tree Cotinus coggygria

AbstractBackground:Invasive exotic species have caused significant problems, and the effects of extreme precipitation and drought, which might occur more frequently under the global climate change scenarios, on interspecific relationship between invasive and native species remain unclear.Results:We conducted a greenhouse experiment with three soil water levels (30%–40%, 50%–60%, and 70%–80% of field capacity) and two cultivation treatments (monoculture pots, one seedling of either species and mixture pots, one seedling of each species) to investigate soil water content effects on the relationship between invasiveRhus typhinaand nativeCotinus coggygria.Rhus typhinahad lower height but bigger crown area thanC. coggygriain the monoculture treatment.Rhus typhinahad higher height, bigger crown area and total biomass thanC. coggygriain the mixture treatment. Drought decreased the growth parameters, total chlorophyll concentration, and leaf biomass, but did not change gas exchange and other biomass parameters inR. typhina. The growth parameters, leaf area index, biomass parameters, total chlorophyll concentration, and net photosynthetic rate ofC. coggygriadecreased under drought conditions. The log response ratio (lnRR), calculated as ln (total biomass of a target plant grown in monoculture / total biomass of a target plant grown in mixed culture), ofR. typhinawas lower than that ofC. coggygria. The lnRR ofR. typhinaandC. coggygriadecreased and increased with increase in soil water content, respectively.Conclusions:Rhus typhinahas greater capacity to relatively stable growth to the drought condition thanC. coggygriaand has strong competition advantages in the mixture withC. coggygria, especially in the drought condition. Our study will help understand the causes of invasiveness and wide distribution ofR. typhinaunder various moisture conditions and predict its expansion under climate change scenarios.