Mapping and monitoring an invasive alien plant in Tunisia: Silverleaf nightshade (Solanum elaeagnifolium) a noxious weed of agricultural areas. Sayari, N., Brundu, G., and Mekki, M. (Tunisia, Italy)

Abstract

The study was conducted during the period of June-July 2014 to update Solanum elaeagnifolium mapping in the irrigated land of Chott-Mariem (Tunisia). S. elaeagnifolium distribution was mapped with a handheld GPS. GPS point positioning took place in the centroid of each infestation. Surveys were made following roads and tracks using the full covering method. We recorded, for each plot, observation date, plot size, S. elaeagnifolium ground cover and distribution pattern within each plot and along its borders. The weed distribution maps were drawn using Quantum GIS software. Of the 105 surveyed plots 36% were infested by S. elaeagnifolium, covering 196 ha. The patchy pattern was the most common distribution type for the weed which was moderately abundant (10-50% ground cover) in 70% of the infested plots and highly abundant (> 50%) in 22% of them. On the other hand, 25 linear infestations were recorded along plot borders. They were spread over 4.8 km with an estimated continuous length of 0.5 km. Compared to 2008 survey data, the number of infested plots increased by 50% and the infested area increased by 60%. Furthermore, S. elaeagnifolium presence along plot borders increased by 3.5 times. This updated S. elaeagnifolium mapping in the irrigated land of ChottMariem reveals an ongoing invasion process in the absence of an effective control program.

Keywords

• Invasive alien plants
• mapping
• monitoring
• Solanum elaeagnifolium
• Tunisia