Elena Barni

Vegetation dynamics and arbuscular mycorrhiza in old-field successions of the western Italian Alps

Abstract The relationships between vegetational and arbuscular mycorrhizal (AM) dynamics were investigated in an old-field succession in the western Italian Alps. Vegetation and AM colonization were determined in eight sites corresponding to different stages of successional dynamics: (a) a field under cultivation; (b) fields abandoned for 1, 2 and 3 years supporting ruderal vegetation; (c) grasslands; (d) shrublands; (e) early wood communities; (f) mature woods. AM colonization was evaluated on the roots of representative plants from each community. The data thus obtained, together with those from the literature, were then used to calculate the plant community mycorrhizal index. This index provides qualitative and quantitative information concerning the relative percentage of non-mycorrhizal, AM and ectomycorrhizal plant cover in an entire plant community. The AM inoculum potential of each site was also determined using a bait approach. Farming disturbance temporarily reduced soil infectivity. Non-mycorrhizal ruderal annuals dominated after 1 year abandonment and covered 90–100 % of the surface. After 2 or 3 years, a rapid change to AM-colonized competitive and competitive-ruderal perennials was observed. The increase in AM inoculum was associated with an increase in floristic richness and equitability in the community. AM were also dominant in the shrublands and early wood communities, but gave way to ectomycorrhizal species in the mature woods. The observed AM inoculum potentials are in accordance with these findings. The results of this study further emphasize the need to take into account AM infection in plans for the renaturalization of degraded areas.

Monitoring and modeling the invasion of the fast spreading alien Senecio inaequidens DC. in an alpine region.

We modeled the distribution of the South African alien Senecio inaequidens DC. in the Aosta Valley, Western Italian Alps, using data extracted from the Regional floristic database and from an intensive field survey carried out in years 2009–2010. The aims of the work were (1) to evaluate whether the species is in the introduction, colonization, or establishment stage of invasion, (2) to detect the environmental factors that drive the invasion process, and (3) to highlight the potential range of distribution of the alien species. The modeling framework was a stepwise generalized linear model (GLM), using gridded presence/absence data and environmental predictors such as topography, climate, land use, and anthropogenic and natural disturbances. GLM were fit both with and without an additional independent variable to take into account current dispersal limitations. S. inaequidens displayed a very fast spread in the Aosta Valley in the years 1990–2010. The species was positively associated with roads and rivers, southern slopes, and negatively with elevation. However, it was found at an elevation of 1600 m, showing the ability to reach higher elevations than those observed for other invasive alien species, and confirming to be pre-adapted to mountain conditions. The difference between the species distribution models, with and without dispersal constraints, suggested that the availability of seed sources still limits the potential distribution of the species, rather than the environmental variables, and that the realized regional niche differs to a great extent from the equilibrium niche. When limitations to the seed source cease (i.e., in the establishment stage), the species will likely invade large areas that are currently characterized by pastures and grasslands with native species of high agricultural importance. The invasion of S. inaequidens should therefore be considered a serious threat, due to its potential to invade mountain regions, and in particular to colonize habitats used for grazing and forage, thus leading to a high risk for cattle and human health. We discuss the relevance of the results both concerning communication with the public and to support local eradication and control activities. The inclusion of S. inaequidens in the “black list” of the regional law for the conservation of alpine flora (L.R. 45/2009) will help to transfer the information and support invasion control, in particular at medium elevations.

From plant traits to invasion success: Impacts of the alien Fallopia japonica (Houtt.) Ronse Decraene on two native grassland species

Abstract Alien invasive plants threaten biodiversity, productivity and ecosystem functioning throughout the world. We examined the effect of Fallopia japonica on two native grassland species (Trifolium repens, Lolium perenne). We hypothesized that its negative effects on the native species are dependent on three mechanisms: (i) allelochemicals released and accumulated in soil with a history of invasion, (ii) altered soil biota and (iii) direct resource competition. We measured the response of the native species as the difference in their functional traits when grown under the three conditions. Our results demonstrate that neither allelochemicals nor soil biota from soil with history of F. japonica invasion had measurable effects on either species. Competition with the invader strongly reduced height, biomass and specific leaf area (SLA) of T. repens, while it had a lower effect on L. perenne. Furthermore, our results reveal that F. japonica took advantage of a positive plant–soil and plant–plant interaction. The results show that the prominent mechanism underpinning the invasion success of F. japonica in the grassland was the direct resource competition. This prominent role is also confirmed by the significant interactions between competition, allelochemicals and soil biota from soils with history of invasion of F. japonica on SLA of the native species.

Are Non-native Plant Species a Threat to the Alps? Insights and Perspectives

Mountain systems throughout the world are recognized as important biodiversity hot spots with rich and distinct flora, compared to the surrounding lowland regions and provide ecosystem services that are important for agriculture and forestry, for touristic, recreational and cultural activities. For these reasons the spread of invasive non-native species can be a threat to the mountains, increasing direct and indirect costs or decreasing the income of the inhabitants.