Contrasting effects of extracts from invasive Reynoutria japonica on soil microbial biomass,activity, and community structure

Invasive plants may modify soil properties through the release of phenolic compounds. The effects of phenolics produced by a noxious invader, Reynoutria japonica, on soil microorganisms have rarely been studied in experimental conditions. We performed a laboratory experiment to assess the influence of extracts from R. japonica on soil microbial activity, biomass, and community structure. Two types of extracts (shoots and rhizomes) were added in four concentrations (control—no extract, low—extract diluted 100 times, medium—extract diluted ten times, and high—undiluted extract) to soil collected under native plant species. Concentrations of 12 phenolic compounds, namely catechin, chlorogenic acid, emodin, epicatechin, hyperoside, quercetin, physcion, piceatannol, polydatin, procyanidin B3, resveratrol, and resveratroloside were analyzed in the extract and soil. We measured the activity of five enzymes, namely acid and alkaline phosphatases, β-glucosidase, phenoloxidase, peroxidase, the activity of bacteria on Biolog Ecoplates, as well as the biomass of bacteria, saprotrophic fungi, arbuscular mycorrhizal fungi (AMF), and microbial community structure using phospholipid (PLFA) and neutral (NLFA) fatty acid analysis. Many microbial parameters, namely phosphatase activities, total microbial, AMF, and G?+?bacterial biomass, were reduced following the addition of extracts. This was likely related to phenolics as concentrations of these compounds in soil increased with the concentration of extract added. In contrast, saprotrophic fungi and G- bacteria were largely positively affected by extract addition. Shoot and rhizome extracts had relatively similar effects on the soil properties. The changes in soil biota caused by R. japonica invasion may have implications for restoration of invaded areas.