Invasive Species Compendium

Detailed coverage of invasive species threatening livelihoods and the environment worldwide

Abstract

Differences in phenolics produced by invasive Quercus rubra and native plant communities induced changes in soil microbial properties and enzymatic activity.

Abstract

Invasive trees can alter soil properties and ecosystem functioning by producing phenolic compounds. Phenolics can influence carbon and nitrogen availability as well as enzymatic activity or act as signaling molecules. In plant-microorganism interactions, species-specific phenolics can be the source of food or toxicity. They may have antimicrobial, stimulatory or both (ambiguous) properties and thus affect soil microbial properties, enzymatic activity, and plant-soil feedbacks differently. We hypothesized that phenolic compounds with antimicrobial properties produced by invasive Quercus rubra would reduce soil microbial biomass and enzymatic activity, and alter microbial community structure. We expected these changes to be most pronounced in the soil organic horizon as they are driven by litter chemistry. We tested changes, potentially associated with the concentrations of 12 phenolic compounds in Q. rubra litter and soil, in microbial properties (respiration rate, bacterial and fungal biomass), enzymatic activity, and microbial community structure in organic and mineral soil horizons as well as in arbuscular mycorrhizal fungi (AMF) spore number and species richness in mineral soil horizon. We found that Q. rubra reduced several soil parameters, namely respiration rate, phosphatase activity, total microbial biomass, bacterial (both G + and G-) biomass, and 16:1ω5 NLFA AMF storage lipid marker as well as changed microbial community structure, which supports our hypothesis that the phenolics produced by Q. rubra have mostly toxic effect on native soil communities. However, Q. rubra did not affect arylsulfatase and urease activity, saprotrophic fungi population, and the number of AMF spores and species. The changes in soil microbial properties and enzymatic activity may be related to high amounts of ellagic acid, ferulic acid, phloridzin, and syringic acid provided with newly shed Q. rubra litter to the soil surface. Some phenolics found in soil, i.e., phloridzin and (-)-epicatechin, correlated negatively, while others, i.e., quercetin and chlorogenic acid, correlated positively with soil microbial parameters and/or enzymatic activity, which suggest either antimicrobial or stimulatory properties of these compounds. Our study demonstrated that invasive Q. rubra has multiple potential effects on soil microbial communities, which can mediate plant-soil feedbacks. Future research should address the long-term consequences of these changes for forest ecosystems and the fitness of native flora.