Relative Performance of Woody Vegetation in Response to Facilitation by Coriaria nepalensis in Central Himalaya, India

A comparative study of four Coriaria nepalensis (hereafter Coriaria) dominated sites has been conducted to evaluate the facilitation effects on tree and shrub characteristics and soil nutrients. A gradient of Coriaria abundance (level 1-4) has been established and the sites have been arranged in order of increasing abundance of Coriaria. In this study, compared to the lowest abundance level, the tree species richness increased by 43% and the shrub species richness increased by 25% at the highest abundance level of Coriaria, indicating that the effects of Coriaria have been consistent and strongly positive on the species richness. The tree and the shrub density have also been increased along with increasing abundance of Coriaria while the tree and the shrub basal area have been decreased. The population structure and the regeneration status have suggested that regeneration of tree species has been facilitated by Coriaria in low abundance sites and inhibited in high abundance sites. These findings suggest that changes in soil characteristics that occur after the Coriaria colonization facilitate growth and regeneration of the associated woody vegetation. However, with increasing abundance of Coriaria, there is a shift from facilitation to inhibition, thus the changes in dominance of species and species composition of the vegetation.