Resilience of prickly burnet to management in east Mediterranean rangelands

Abstract

Large areas of rangelands in the east Mediterranean Basin are dominated by dense cover of the unpalatable, dwarf shrub prickly burnet (Sarcopoterium spinosum (L.) Spach.). This study examined the effectiveness of various shrub control treatments (mechanical removal, chemical/2,4-D control, prescribed burning), combined with NPK fertilization, to reduce shrub cover and encourage the growth of palatable herbaceous vegetation. Chemical control was the most effective treatment, reducing prickly burnet cover to 40% of the initial level 2 years after treatment. Mechanical removal maintained shrub cover at 60% of the initial level, whereas the effect of fire was not detectable after 2 years. Annual and perennial herbaceous vegetation cover was negatively correlated with shrub cover. Fertilization had no effect on the cover of the vegetative components, but increased biomass on the herbaceous patches by 25-240%, depending on the treatment. Our results demonstrate the exceptionally high resilience of prickly burnet growing on chalk substrate to disturbance or attempted eradication, thus rendering most of the tested management options highly ineffective. Effective improvement of rangeland dominated by prickly burnet requires, most probably, a combined treatment including removal of mature shrubs, suppressing their recovery, and stimulating the competing grass component.