Effect of the exotic invasive plant Solidago gigantea on soil phosphorus status

Invasions by exotic plant species can modify biogeochemical cycles and soil properties. We tested whether invasion by early goldenrod (Solidago gigantea, Asteraceae) modifies soil phosphorus pools at three sites in Belgium. Aboveground phytomass and soil samples (0-10 cm) were collected in early goldenrod patches and in adjacent, uninvaded, grassland vegetation. Soil P fractions varied between the three sites in line with corresponding differences in organic matter, carbonate and clay contents. In addition to site-specific impacts, plots invaded by goldenrods generally had higher concentrations of labile P [i.e. resin-extractable inorganic P (Pi) and bicarbonate-extractable Pi and organic P]. Soil CO2 release and alkaline and acid phosphomonoesterase activities were also higher in invaded plots, suggesting that the increase in labile Pi was due to enhanced mineralization. Phosphorus uptake by vegetation was 1.7-2.1 times higher in invaded plots, mostly due to the higher annual yield of S. gigantea. Altogether, the results indicate that S. gigantea enhances P turnover rates in invaded ecosystems.