C5 Control of alien species
The problem of the removal of invasive alien species requires the adoption of particular prudential measures and appropriate technical approaches with respect to the specific characteristics of each species. In the case of Carpobrotus sp., the elimination of the plant’s patches must be carried out before the fruiting and the dissemination in order to avoid a further production of seeds in the soil. It seems preferable to operate at the end of the life-reproductive cycle of Calendula maritima, after seed dissemination occurred. Excluding the January-March quarter (theoretically ideal period, since no other species usually disseminates) in order to avoid eventual soil erosion after the removal of Carpobrotus cover, it is better to concentrate the eradication intervention during the autumn season, when only a few other species disseminates. Since it is planned to eradicate rather small nuclei, concentrated in semi-natural coastal areas easily accessible due to low slope, we will proceed with the manual extirpation.
All Carpobrotus species produce a considerable litter layer. This hosts large amount of seeds that guarantee the species persistence in the restored habitats and its subsequent recolonization, hence compromising the success of eradication. It is therefore recommended to remove also the litter together with plants. This should be done by using low impact equipment (e.g. rakes), carefully avoiding the removal ofthe small layer of underlying soil, which on the other hand acts as seed bank of native plants. Particular attention will be payed to the eradication of the few patches located in more steep slopes, in order to avoid mechanical erosion processes of the superficial soil, with undesirable consequences on the composition and dynamism of the native plant communities. Considering that Carpobrotus seeds retain the germination potential for at least 5 years after dispersion, and hence there is a high probability of recolonization from seed as well as stem fragments escaped from the first extirpation, it is necessary to proceed to a first manual removal followed by targeted manual eradication in the next 3 autumn seasons. Before proceeding to the extirpation of Carpobrotus, “compost areas” must be identified to be used for the storage of the removed plant material. In the easiest cases (small nuclei or single individuals) the collection will take place directly in special black bags, while a rapid transfer of individuals or larger nuclei into sealed containers will be carried out. All the material will be delivered directly to the storage areas and treated through two alternative options based on economic and technical criteria: 1) shredding or 2) covering with black plastic sheets to destroy the plants by exposure to high temperature and humidity. Once the death of Carpobrotus is ascertained, the material can be dried and then burned and / or composted. The actual areas invaded by Carpobrotus are estimated at about 4 hectares, located at Ronciglio, Tonnara di S. Giuliano and Isola Colombaia. The precise spatial location and extent of the nuclei will be mapped by sub-metric GPS device, and the resulting cartographic documents used in subsequent phases of monitoring.
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