Influence of the invasive shrub Nicotiana glauca Graham on the plant seed bank in various locations in Taif region, western of Saudi Arabia

Invasive species have been considered as one of the most serious threats to the biodiversity of various ecosystems, particularly in arid regions. The present study aimed to assess the influence of the invasive shrub Nicotiana glauca on the biodiversity of different habitats in Taif region, Saudi Arabia as well as to determine the highest habitat with seed bank of N. glauca. Soil samples were collected from three locations (Alwaht, Ash-shafa, and Ar Ruddaf), invaded with N. glauca, and analyzed for the soil seed bank. A soil seed experiment was designed in a greenhouse, whereby emerged plant seedlings were left to grow for three months and identified as well as the species density and biodiversity were assessed under and outside the canopy of N. glauca. Also, the floristic composition, life forms, and chorotype spectra of the plant species of the seed bank were analyzed. A total of 42 species, belonging to 23 families, were recorded in the soil seed bank. Asteraceae, Poaceae, and Cyperaceae were the major families (42.9%). The life form spectra of the recorded species were dominated by Therophytes (59.5%). Chorotype spectra analysis revealed that Mediterranean, Saharo-Arabian, and Irano-Turanian were the most represented elements. The species richness and evenness were higher outside the canopy, which indicates a negative effect of the invasive shrub N. glauca on the plant biodiversity in the study area, particularly in Ar Ruddaf location. This could be attributed to the competition or allelopathic effect of N. glauca. In contrast, the density of N. glauca seeds was higher under the canopy compared to outside. The soil nutrients and moisture under the canopy were higher than outside canopy. The present study provides a deeper understanding of the most susceptible habitats or communities to the invasion by N. glauca and thereby open the challenge toward control of this noxious plant and vegetation restoration.