Impact of Parthenium hysterophorus L. invasion on plant species composition and soil properties of grassland communities in Nepal

Parthenium hysterophorus (Asteraceae) is a noxious plant that is considered one of the most invasive species in the world. We studied changes in the composition of plant species and soil properties related to the invasion of P. hysterophorus in three grassland communities of central Nepal. We collected vegetation and soil data along transects that were established in densely invaded to non-invaded areas within homogenous grassland stands. We found significant differences between invaded, transitional and non-invaded plots in species composition and soil properties. There were fewer species in non-invaded than transitional and invaded plots. By P. hysterophorus invasion both native and non-native species were supported or replaced, respectively. The concentrations of soil nitrogen and organic matter were significantly higher in transitional and invaded plots than in non-invaded plots. Soil pH, phosphorus and potassium were highest in the invaded plots, lowest in the non-invaded and intermediate in the transitional plots. Due to changes in above-ground vegetation and below-ground soil nutrient contents, P. hysterophorus invasion is likely to have an overall negative effect on the functioning of the entire ecosystem. Therefore, management of noxious P. hysterophorus is necessary to prevent future problems.