Environmental factors promoting the spread of Pennisetum setaceum
Pennisetum setaceum (Poaceae, EPPO List of Invasive Alien Plants) is a perennial grass native to the North African arid Mediterranean area (Algeria, Morocco, Tunisia) and naturalized in the EPPO region in France, Italy (including Sardinia) and Spain (including Baleares and Islas Canarias). The species is invasive in South Africa where it is declared a noxious weed. Research has therefore been undertaken to understand the factors promoting the spread of this emergent alien grass. The effects of temperature regimes, nutrient and moisture addition, and soil type on seedling growth rates and biomass allocation were investigated. The results suggest that P. setaceum seedlings do not tolerate drought (they died within 1 month without water). Additional nutrients and extra water increased seedling growth rates throughout the study period. Higher temperatures with extra moisture increased seedling growth rates and the development of belowground biomass throughout the study period. This study demonstrates the importance of available environmental resources and their interaction with habitat conditions in promoting P. setaceum growth. These findings suggest that soil moisture and nutrient availability are critical factors affecting successful establishment of P. setaceum in arid environments. Managers should aim for removal of seedlings following precipitation and in areas of nutrient enrichment, such as near rivers and at road–river crossings.