Invasive alien plant species have impacts on nature conservation, ecosystem services and agricultural production. To identify environmental and human-related drivers of the invasion of Solanum elaeagnifolium (Solanaceae)—one of the worst alien invasive plants worldwide—we conducted an extensive drive-by survey across the Greek territory (presence/absence data; all national major multilane highways; 12–25% of the remaining road network; driven 3–5 times during 2000–2020). These data were linked in GIS with (i) physical environmental attributes (elevation, climate, soil properties) and (ii) type and intensity of human-related activities (land uses, settlements and road type). Compared to previous records, our survey showed that the range of S. elaeagnifolium increased by 1750% during the last decades, doubling its main distribution centers and reaching higher elevations. Our study revealed that the presence of S. elaeagnifolium is associated with (i) higher maximum temperatures and precipitation in summer and low precipitation in winter, as well as with (ii) soil disturbance related to agricultural activities, settlements and road networks, thus facilitating its spread mainly at low altitudes. Our study elucidates the current invasion pattern of S. elaeagnifolium and highlights the urgent need for its widespread monitoring, at least in the noninvaded areas in Greece that have been surveyed in this study. Preventative measures and integrative initiatives should be implemented quickly, and urgently incorporated into current agricultural, road network and conservation-management regimes.
Agroforestry systems have been practiced for hundreds of years with multiple benefits both environmentally and economically in terms of productivity. Olive cultivation is widespread in the countries of the Mediterranean basin, including Greece. Agroforestry practices are common in olive groves, but little research has been conducted on the productivity of such systems, especially with medicinal–aromatic plants (MAPs) as understory crops. Natural populations of MAPs can be found in various ecosystems, while some of them are cultivated. The purpose of this research was to study the effects of fertilization and shading both on yield and chemical composition of essential oils derived from chamomile (Matricaria recutita L.) and anise (Pimpinella anisum L.), grown in olive silvoarable systems. Fertilization and shading increased the plant height of chamomile and delayed the flowering. In addition, fertilization increased the concentration of α-bisabolol oxide A and (Z)–spiroether, and reduced the α-bisabolone oxide A and hamazulen. Shade also reduced α-bisabolone oxide A and hamazulen but increased the α-bisabolol oxide B. In the case of anise, fertilization increased plant height, decreased the concentration of limonene, and increased the concentration of E-anethole. Shading reduced plant height. Intercropping of olive trees with chamomile and anise yielded essential oils rich in the substances defined by the commercial specifications.
Invasive alien plants have severe impacts on biodiversity and ecosystem services worldwide. To assess the invasion of Solanum elaeagnifolium Cav. (a major alien invasive plant; Solanaceae) in Greek protected areas (PAs), we conducted an extensive drive-by survey across the country crossing half of the Greek Natura 2000 sites. The occurrence data were then linked in GIS with (i) the boundaries of the Natura 2000 sites, (ii) the mapped habitat types in the invaded sites, and (iii) the Corine land cover, from which we calculated the ecosystem services. The results showed that approximately 24% of the investigated PAs were invaded by S. elaeagnifolium to varying degrees of extension and density of the populations. A variety of 29 different habitat types of Annex I of the Directive 92/43/EEC (including a priority habitat and seven habitat types of national importance) were found to be invaded (one in four habitat types present in Greece). In the invaded Natura 2000 sites, we recorded human activities/threats that were mostly related to agricultural activities of high intensity, while the potential in ecosystem service provision was relatively low for the category of regulating services in the invaded sites. Our study provides the first nationwide report of the distribution of S. elaeagnifolium in Natura 2000 sites of Greece, providing baseline maps and information for future monitoring. Our results highlight the need of an effective management strategy across the Natura 2000 network to effectively protect the local biodiversity, which should include management measures for invasive species, mitigating habitat fragmentation, and soil degradation, as well as the adaptation of eco-enhancing management strategies for the provision of multiple ecosystem services in agriculture.
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