Allelopathic effects of aqueous extracts from uncomposted and composted Mexican devel (Ageratina Adenophora) plants on forest fungal growth and soil nitrogen and phosphorus mobilization

Abstract Mexican devil [ Ageratina adenophora (Spreng.) R.M. King & H. Rob.], a globally invasive weed with destructive effects on forests, has spread to numerous countries. To elucidate the inhibition of tree growth by A. adenophora , a study was conducted using the fungi ( Lactarius deliciosus , Ceriporia lacerat and Fomitopsis palustris ) involved in the recycling of carbon and nutrients in forests. The focus was on investigating soil nitrogen and phosphorus availability, in response to aqueous extracts from uncomposted and aerobically composted A. adenophora (EUA and ECA, respectively). The samples of CA from different sites exhibited a significant reduction in the concentration of allelochemicals 4,7-dimethyl-1-(propan-2-ylidene)-1,4,4a,8a-tetrahydronaphthalene-2,6(1H, 7H)-dione and 6-hydroxy-5-isopropyl-3,8-dimethyl-4a,5,6,7,8,8a-hexahydronaphthalen-2(1H)-one. This reduction more than 94% when compared to the concentration of these allelochemicals in CA. The EUA solutions at 5.0 and 10 mg L -1 (oven-dried plant biomass base) minimized Lactarius deliciosus and Ceriporia lacerate growth, and significantly decreased Fomitopsis palustris growth on the soil surface and within the soil. However, soil with ECA had no effect or promoting effect on the fungal growth. Compared to CK (only fungal inoculation in tested soil), the EUA solution reduced soil nitrogen and phosphorus, while ECA had the opposite effect; soil pH was increased by 0.01-0.08 under EUA treatment, while decreased by 0.5-0.41under ECA treatment. Nitrogen and phosphorus availability were positively correlated with protease and phosphatase activity ( r = 0.723-0.944), while available phosphorus was inversely correlated with pH in tested soils ( r = -(0.809-0.978)). As such, the EUA solution decreased soil nitrogen and phosphorus supplies by inhibiting the liberation of proteases, phosphatases, and protons, which may lead to poor growth or even mortality of three fungal species. The in situ aerobically composted A. adenophora residues left may directly supply fungal specie with nutrients and indirectly increase soil nutrient availability via the promotion of nitrogen and phosphorus mobilization.