The impact of invasive Hyptis suaveolens on the floristic composition of the periurban ecosystems of Chandigarh, northwestern India

- Species number and diversity decline in the areas massively invaded by Hyptis suaveolens.
- Loss of species may pose socio-economic implications for the local people.
- Hyptis-invaded sites have high proportion of exotic species.
- High biomass and vigorous growth of H. suaveolens pose strong impact on the associated species.
- H. suaveolens invasion alters soil pH, conductivity, organic carbon and organic matter.

We investigated the impact of invasive Hyptis suaveolens on the natural vegetation and soil of the periurban ecosystems of Chandigarh (Northwestern India), in terms of declines in species number, importance value index (IVI), richness, diversity, evenness, and changes in soil pH, conductivity and organic matter. The number of species declined by 46-52% in the areas massively invaded by H. suaveolens. The richness, diversity, dominance and evenness of species were severely reduced in the invaded areas compared to uninvaded areas. The reasons for this strong impact may be attributed to the vigorous growth of the weed in the invaded areas. Invaded areas were characterized by high cover of the exotic species. Several economically important species like Justicia adhatoda, Anisomeles indica, Carissa carandas, Dioscorea deltoidea, Murraya koenigii and Paspalidium flavidum were conspicuously absent in the invaded areas, though present in the uninvaded areas. Absence of these species in the areas invaded by H. suaveolens may pose socio-economic problems for the local people. Further, alterations were also noticed in the pH, conductivity, organic carbon and organic matter of the soil of invaded areas. Based on these observations, it was concluded that invasion of H. suaveolens has a marked influence on the vegetation of periurban ecosystems, and causes depletion of several economically important species. The present study calls for an immediate action for the management of this noxious alien weed.