Biochemical effects of Centaurea maculosa on soil nutrient cycles and plant communities

Abstract

The Biochemical Effects o f Centaurea maculosa on soil nutrient cycles and plant communitiesThe success o f some invasive plants may be due to biochemcials that are novel to the invaded ecosystems.This is because plants, herbivores, and soil microbes native to invaded communities may lack a coevolutionary-based response to biochemical traits o f the invader.In addition, these biochemicals may also alter abiotic components o f soil nutrient cycles.I measured the effects o f Centaurea maculosa and the root exudate, ()-catechin, on the soil nitrogen and phosphorus cycles and plant communities.Most importantly, I also compared the strength o f many o f these effects in the invaded range to those in the native range.M y research provides evidence that C. maculosa has strong, biochemical effects on soil nutrient cycling, at least partially due to exudation o f the polyphenol, ()-catechin.Nitrification in soils from part o f the invaded range o f C. maculosa (Montana) was strongly reduced by both C. maculosa and application o f ()-catechin.In contrast, there were very weak effects on nitrification in soils from part o f the native range o f C. maculosa (Romania).A different study found that C. maculosa also has strong effects on the soil phosphorus cycle.In a greenhouse experiment and field study, I found that Centaurea maculosa was more phosphorus efficient than many native species, even when phosphorus was highly limiting.However, in the field study, soil phosphate was higher in areas dominated by C. maculosa than in areas where the invasive had been removed.I suggest that elevated soil phosphate and the resulting phosphorus-efficiency o f C. maculosa are due to the exudation o f ()-catechin, a strong chelator for the metals that bind phosphorus in many o f the soils invaded by C. maculosa.Finally, in a series o f studies repeated over two years, I found that when tested in situ, ()-catechin had strong allelopathic effects on the growth o f several plant species in Montana, but very weak effects on species in Romania.Thus, C. maculosa appears to alter not just the aboveground plant community, but also fundamental ecosystem properties.These effects may persist long after the removal o f the invasive species.Furthermore, biogeographic comparisons suggest that coevolution plays an important role in both plant community interactions and plant-soil interactions.