Facilitative effect of Coriaria nepalensis on species diversity and growthof herbs on severely eroded hill slopes

In this study we examine the facilitative effect of Coriaria nepalensis Wal l. verns. at two contrasting sites, a severely eroded hill slope consisting of loose material and a stable hill with normal soil cover (forest), The f acilitative effect was measured in terms of species richness and growth of herbs associated with the nurse species. The beta-diversity was more at the open microsite than below-canopy microsite, At the eroded site, the herb d ensity was greater in the open than below the Coriaria canopy, The ameliora tive effect of Coriaria bush at the eroded site was dramatic in terms of he rb biomass, Our study shows a strong facilitative effect of Coriaria in the harsh environment of the hill slope with severely eroded surface. The facilitative effect is reflected in terms of significantly higher alpha -diversity and biomass of herbs growing below Coriaria than those growing i n the open. The facilitative effect of Coriaria, however, is not manifested at the favourable forest site. The bush showed several ameliorative effect s on the eroded site, including higher rate of soil build-up and accumulati on of nutrients and organic matter leading to an increase in soil water pot ential. The ability of Coriaria plants to nurse herbs can be used to stabil ize hill slopes, to regenerate them and to promote species diversity.