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Aim Our aims were: (1) to separately evaluate the elevational patterns of β-diversity for nestedness, species richness difference and replacement, (2) to identify the drivers of β-diversity patterns by testing the effect of geographical and environmental distance (human population, temperature and land-use), and (3) to compare the response on native versus alien species to elucidate mechanisms of community assembly along elevational gradients. Location Two mountain regions ( Bergamo- Brescia and Trento) in the Italian Alps. Methods We used two floristic datasets in which species composition was sampled within two regular grids. First, we extracted species elevational range and quantified species composition nestedness along the elevational gradient. Second, we partitioned β-diversity into its species richness difference and replacement components and tested drivers using regression on distance matrix and hierarchical partitioning. All analyses were performed on natives and aliens, separately. Results For aliens, we found lack of mountain specialists (i.e. species with a distribution range restricted to high elevations), large nestedness, large species richness difference and low species replacement between low and high elevations. All findings point in the same direction: a great majority of alien species were introduced to the lowlands and only a subset of this community spread up the mountains. Both human pressures and temperature selection were important processes underpinning the observed filtering, while geographical and land-use distances were not important. Natives present contrasting patterns with large replacement along the elevation gradients indicating different mechanisms of community assembly. Main conclusions The relatively large alien species replacement in the lowlands indicated the presence of a pool of species that may potentially invade the temperate mountains in the future. Investigations of the identity of alien species occurring in the lowlands and their climatic pre-adaptation might provide tools to prevent invasions in the mountains by predicting the potential invaders and their future elevational distribution. [ABSTRACT FROM AUTHOR]

The concept of the old-growth forest is highly debated in the literature because of its implications, from close-to-nature forest management to carbon balance. Studies on old-growth forests have multiplied in the last three decades. Most of these studies have focussed on defining the structural features of old-growth forests of non-Mediterranean forest ecosystems or of specific forest types. In Italy, forest structure since Roman times has been greatly influenced by man. For this reason, the concept of old-growth forest in these ecosystems seems more controversial than at the global level. Nonetheless, in the Mediterranean region, there are persistent forest formations that present a certain level of oldgrowthness. These types of forests have been identified mostly in National Parks. The description of forest structure requires a vast amount of information about several biometric attributes. Consequently, the classification of forests as old growth is very time- and resource-consuming. This research aims to describe and test a proposed methodology to classify and determine the relative oldgrowthness of a series of forest inventory plots. Data from 77 beech forest plots located all across Italy were collected and compared with a virtual reference plot. To compare the forest plots, a set of similarity/dissimilarity indexes were tested. The results obtained show that it is possible to accurately rank the oldgrowthness of forest plots and to screen them to exclude non-old-growth forests. The method described was applied for the first time on a set of plots located in the Italian National Parks to determine a priority list of beech forests where further studies need to be conducted. [ABSTRACT FROM AUTHOR]

The partitioning of β-diversity is a recurrent practice in biogeographic and ecological studies that can provide key insights for land management, such as identification of biodiversity hot-spots. In this study, we used Baselga's metrics to measure the contribution of spatial turnover (β sim ) and nestedness-resultant dissimilarity (β nes ) to overall β-diversity (β sor ) within- and between-forest types. We analyzed a presence/absence dataset concerning 593 species of nocturnal Lepidoptera sampled within chestnut, silver fir, beech, and black pine forests of southern Italy. Ordination methods and analysis of similarities were used to assess the relative contribution of β sim and β nes to β sor , and to assess their relationships with variables linked to the experimental design and known to be determinant for insect diversity and abundance. We found that β sor was mostly due to turnover, around 98.5% in β-diversity assessment of the whole sample, and around 91% in β-diversity assessment of individual forests. Using ordination analyses based on β sim , stands were grouped according to forest type, while β nes alone was used to ordinate stands coherently with their species richness. Nevertheless, the addition of β nes to β sim produced a more ecologically coherent grouping of stands within individual forest types, and β nes alone was able to recognize patterns determined by human disturbance. In conclusion, we demonstrate that β-diversity partitioning can help to detect differences in magnitude and role of processes determining the composition of forest moth communities as in different forests the same pattern can be due to opposite processes, providing strong ecological insights into managing forest biodiversity.