No abstract

The occurrence of old-growth forests is quite limited in Mediterranean islands, which have been subject to particularly pronounced human impacts. Little is known about the carbon stocks of such peculiar ecosystems compared with different stages of secondary succession. We investigated the carbon variation in aboveground woody biomass, in litter and soil, and the nitrogen variation in litter and soil, in a 100 years long secondary succession in Mediterranean ecosystems. A vineyard, three stages of plant succession (high maquis, maquis-forest, and forest-maquis), and an old growth forest were compared. Soil samples at two soil depths (0–15 and 15–30 cm), and two litter types, relatively undecomposed and partly decomposed, were collected. Carbon stock in aboveground woody biomass increased from 6 Mg ha -1 in the vineyard to 105 Mg ha -1 in old growth forest. Along the secondary succession, soil carbon considerably increased from about 33 Mg ha -1 in the vineyard to about 69 Mg ha -1 in old growth forest. Soil nitrogen has more than doubled, ranging from 4.1 Mg ha -1 in the vineyard to 8.8 Mg ha -1 in old growth forest. Both soil parameters were found to be affected by successional stage and soil depth but not by their interaction. While the C/N ratio in the soil remained relatively constant during the succession, the C/N ratio of the litter strongly decreased, probably following the progressive increase in the holm oak contribution. While carbon content in litter decreased along the succession, nitrogen content slightly increased. Overall, carbon stock in aboveground woody biomass, litter and soil increased from about 48 Mg ha -1 in the vineyard to about 198 Mg ha -1 in old growth forest. The results of this study indicate that, even in Mediterranean environments, considerable amounts of carbon may be stored through secondary succession processes up to old growth forest.

Background and aims Carpobrotus spp. are amongst the most impactful and widespread plant invaders of\ud Mediterranean habitats. Despite the negative ecological impacts on soil and vegetation that have been documented,\ud information is still limited about the effect by Carpobrotus on soil microbial communities. We aimed\ud to assess the changes in the floristic, soil and microbial parameters following the invasion by Carpobrotus cfr.\ud acinaciformis within an insular Mediterranean ecosystem.\ud Methods Within three study areas a paired-site approach, comparing an invaded vs. a non-invaded plot, was\ud established. Within each plot biodiversity indexes, C and N soil content, pH and microbial biomass and structure\ud (bacterial and fungal) were assessed.\ud Results Invaded plots showed a decrease of α-species richness and diversity. The least represented plant species\ud in invaded plots were those related to grassland habitats. In all invaded soils, a significant increase of carbon and\ud nitrogen content and a significant decrease of pH were registered. Carpobrotus significantly increased bacterial\ud and fungal biomass and altered soil microbial structure, particularly favoring fungal growth.\ud Conclusions Carpobrotus may deeply impact edaphic properties and microbial communities and, in turn, these\ud strong modifications probably increase its invasive potential and its ability to overcome native species, by preventing their natural regeneration

Habitat monitoring in Europe is regulated by Article 17 of the Habitats Directive, which suggests the use of typical species to habitat conservation status. Yet, the Directive uses the term “typical” species but does not provide a definition, either for its use in reporting or for its use in impact assessments. To address the issue, an online workshop was organized by the Italian Society for Vegetation Science (SISV) to shed light on the diversity of perspectives regarding the different concepts of typical species, and to discuss the possible implications for habitat monitoring. To this aim, we inquired 73 people with a very different degree of expertise in the field of vegetation science by means of a tailored survey composed of six questions. We analysed the data using Pearson's Chi-squared test to verify that the answers diverged from a random distribution and checked the effect of the degree of experience of the surveyees on the results. We found that most of the surveyees agreed on the use of the phytosociological method for habitat monitoring and of the diagnostic and characteristic species to evaluate the structural and functional conservation status of habitats. With this contribution, we shed light on the meaning of “typical” species in the context of habitat monitoring.

(2015) Seasonal effects on mortality rates and resprouting of stems treated with glyphosate in the invasive tree of heaven (Ailanthus altissima (Mill.) Swingle), Arboricultural Journal, 37:3,[180][181][182][183][184][185][186][187][188][189][190][191][192][193][194][195] To link to this article: http://dx.doi.org/10.1080/03071375.2015.1112163 Tree of heaven (Ailanthus altissima) is regarded as invasive within urban and natural areas worldwide. Efficient methods to control it are significantly needed if we are to limit its well-known environmental and economic impacts. Up to now the use of herbicides has proven necessary since following mechanical damage, Ailanthus vigorously resprouts. However, the seasonal response of Ailanthus stems, treated with herbicides, has never been assessed. We compared the control efficacy recorded in autumn, winter and summer in an abandoned suburban citrus grove in Sicily, under Mediterranean-climate conditions. Glyphosate was injected within drill holes made in knee-high cut trees. Tree mortality and the resprouting ability of treated stems were significantly affected by the application timing and by diameter class of stems. Mortality was significantly lower in winter treatments within the smaller diameter class. Within the larger diameter class, only autumn treatments showed a notably higher mortality rate and a significantly lower growth of sprouts. Hence, autumn interventions are strongly recommended to effectively treat Ailanthus. Mortality was notably higher in the smaller diameter class. Our results confirm the importance of early intervention to control Ailanthus, also showing that the choice of the season is crucial to obtaining satisfactory control of its resprouting ability.