Impact of Clethra arborea Aiton (Clethraceae) in a Special Protection Area of São Miguel Island, Azores.

Moniz, João; Silva, Luís

http://hdl.handle.net/10400.3/175

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Authors

Moniz, João

Silva, Luís

Abstract(s)

Clethra arborea Aiton (Clethraceae) is a tree endemic to Madeira Island, and a recent introduction to São Miguel Island at Tronqueira/Pico da Vara, a Special Protection Area (SPA) included in Natura 2000, habitat of the endemic bird Pyrrhula murina Godman (Aves: Fringillidae). In this work the impact of C. arborea on the native vegetation was evaluated. Microhabitats associated with C. arborea and with native trees, and areas with different degrees of infestation by C. arborea were compared for soil pH, soil conductivity, soil macronutrient availability, leaf litter production, number of seedlings and vegetation structure. There were no clear differences in soil pH, conductivity and macronutrient availability, either between micro-habitats associated with C. arborea and with native trees, or between areas with different degrees of infestation by C. arborea. Leaf litter production was significantly higher in micro-habitats associated with C. arborea and higher still in areas with high levels of infestation. The number of seedlings and the percentage of endemic seedlings differed significantly between microhabitats associated with C. arborea and those associated with endemic trees. Invasion by C. arborea modified vegetation structure, especially biovolume, which was much higher in invaded areas. By considerably decreasing the proportion of biovolume allocated to native trees, C. arborea infestations may have a negative impact on the conservation efforts at the SPA.