Maria Laura Carranza

Computing β-diversity from species-area curves

Summary A measure of β-diversity is proposed for equal-sized presence-absence vegetation sample plots. The method begins by computing the minimum variance unbiased estimator of the expected species richness E[Sn] as a function of sample size n for a set of N plots. Using a semilogarithmic relation, β-diversity is then determined from the slope of the best fitting line of the E[Sn] vs. log n plot. β-diversity is thus interpretable as the linear relation between expected species richness and log sample size. The method is illustrated using 15 square plots of 100 m2 each from a Matorral community in the Arid Chaco of central Argentina. Further, some analogies between the proposed method and Whittakers multiplicative model of β-diversity are discussed. Ein Mas fur die β-Diversitat wird vorgeschlagen, das fur “presence-absence”-Vegetationsaufnahmen auf gleichdimensionierten Probeflachen gilt. Nach der Methode wird zuerst der “minimum variance unbiased estimator” des erwarteten Artenreichtums als eine Funktion der Probengrose n fur eine Anzahl von N Flachen berechnet. Unter Verwendung der semilogarithmischen Beziehung wird die β-Diversitat uber die “best-fit”-Steigung des Graphen E[Sn] vs. log n bestimmt. Die β-Diversitat kann damit als die lineare Abhangigkeit des Artenreichtums von der logarithmierten Probengrose interpretiert werden. Die Methode wird anhand von 15 Probequadraten von jeweils 100 m2 aus der Matorall-Lebensgemeinschaft des ariden Chaco Zentralargentiniens erlautert. Zudem werden einige Analogien zwischen der vorgeschlagenen Methode und Whittakers multiplikativen Modell der β-Diversitat diskutiert.

EU habitats of interest: an insight into Atlantic and Mediterranean beach and foredunes

We compared the Atlantic and Mediterranean beach and foredune habitats of European interest, focusing on floristic, structural and ecological features. We selected two representative sites of Atlantic (The Netherlands) and Mediterranean (Italy) coastal dunes. From a georeferenced vegetation database, samples of: (a) annual vegetation on drift lines (European Union habitat type 1210), (b) embryonic shifting dunes (2110), and (c) shifting dunes along the shoreline with Ammophila arenaria (2120), were selected. Floristic representativity and comparability of plot sizes were considered. For each habitat, the frequency and the fidelity of the species, the life form frequency spectra and Ellenberg ecological indicator values were assessed. We found a consistent floristic differentiation between the Atlantic and the Mediterranean coastal dune habitats and only a small set of shared species. The Italian and the Dutch annual vegetation of drift lines (1210) register a high structural similarity that strongly declines landwards. Floristic composition, life forms and Ellenberg indicator values show higher similarities among different foredune habitats of the same site than between homologous habitats of the Mediterranean and Atlantic coasts. The results confirm the current description and distribution of the habitat of European interest annual vegetation of drift lines (1210). On the other hand, the floristic, structural and ecological differences between the Atlantic and the Mediterranean embryonic shifting dunes (2110) and shifting dunes along the shoreline with Ammophila arenaria (2120) point at an inconsistency of the existing description of those habitats of European interest and highlight the need of adding in the Directive specific types that describe them in the Mediterranean basin. We suggest the introduction of two new habitat types named “Dunes along the Mediterranean shoreline with Ammophila arenaria” (new code 2280) and “Mediterranean embryonic dunes” (new code 2290) within the existing class “Sea dunes of the Mediterranean coast” (class 22 of the Annex I Habitats Directive 92/43/CEE).

A modelling approach to infer the effects of wind farms on landscape connectivity for bats

Little is known about the potentially disrupting effects of wind farms on the habitat connectivity of flying vertebrates at the landscape scale. We developed a regional-scale model to assess the wind farm impact on bat migration and commuting routes. The model was implemented for the bat Nyctalus leisleri in a region of central Italy currently undergoing considerable wind farm development. A Species Distribution Model (SDM) for N. leisleri was generated using the MaxEnt algorithm based on 47 presence records (reduced to 19 after the autocorrelation procedure) and 10 environmental variables derived from topographic and land cover maps. We used the SDM to create a map of connectivity using the software UNICOR to identify potential commuting corridors (PCCs). The incidence of each wind farm on bat flight corridors was assessed by overlaying the existing (380) and planned (195) turbine locations onto the PCCs. The SDM was statistically robust (AUCxa0>xa00.8). Most of the corridors were concentrated in the western part of the region, which hosts the largest suitable areas for the species; most of the existing (54xa0%) and planned (72xa0%) wind farms interfered with important corridors connecting the western and the eastern parts of the region. Our results provide key information on the impact of the wind farm industry on biodiversity on a regional scale. The novel approach adopted, based on SDM and connectivity analysis, could be easily extended to other flying vertebrates and landscapes and constitutes a promising planning tool necessary for harmonizing the development of renewable energy infrastructures with issues of biodiversity conservation.

Regional-scale modelling of the cumulative impact of wind farms on bats

Wind farms are steadily growing across Europe, with potentially detrimental effects on wildlife. Indeed, cumulative impacts in addition to local effects should be considered when planning wind farm development at a regional scale, and mapping the potential risk to bats at this scale would help in the large-scale planning of wind turbines and focus field surveys on vulnerable areas. Although modelling offers a powerful approach to tackle this goal, its application has been thus far neglected. We developed a simple regional-scale analysis in an area of central Italy (Molise region) that is undergoing considerable wind farm development. We implemented species distribution models (SDMs) for two bat species vulnerable to wind farm impact, Nyctalus leisleri and Pipistrellus pipistrellus. We developed risk maps by overlaying SDMs for the two species with turbine locations, assessed the alteration of the landscape patterns of foraging habitat patches determined by the wind turbines, and identified highly vulnerable areas where wind farm construction would be particularly risky. SDMs were statistically robust (AUCxa0≥0.8 for both species) and revealed that 41xa0% of the region offers suitable foraging habitat for both species. These areas host over 50xa0% of the existing or planned wind farms, with 21xa0% of the turbines located within 150xa0m of forest edges, suggesting an increase in fatality risk. The alterations in suitable foraging patches consisted of a 7.7xa0% increase in the number of patches, a 10.7xa0% increase in the shape index, and a 8.1xa0% decrease in the mean patch area. The region’s western portion, which is most suitable to both species, requires careful consideration with regard to future wind farm planning.

Changes in composition, ecology and structure of high-mountain vegetation: a re-visitation study over 42 years

Mediterranean high-mountain ecosystems are increasingly threatened by climate change, causing biodiversity loss, habitat degradation and landscape modifications. In this work, we used phytosociological relevés to conduct a re-visitation study in order to analyze changes in floristic composition over the last 42 years in the central Apennines (Majella National Park). We observed changes in floristic composition, along with a significant increase in thermophilic and nutrient-demanding species. Such changes are likely attributable to the combined effect of higher temperatures and the increase in soil nutrients triggered by global change.

Structure, ecology and plant richness patterns in fragmented beech forests

Background: Landscape fragmentation constitutes one of the most severe causes of global biodiversity loss. Aims: We studied Fagus sylvatica forests with different levels of fragmentation to address the following question: do fragmented and non-fragmented forests present a similar floristic composition and richness, structural parameters and ecological features? Methods: Vascular plant species were randomly sampled based on a beech forest map classified into three fragmentation levels. We compared overall native and diagnostic species richness patterns of the different fragmentation levels using rarefaction curves and the ratio between diagnostic and all species curves. We also contrasted different fragmentation levels of beech forests, focusing on floristic information, structural parameters, standard ecological features and the distribution of edge and clearing species. Results: Rarefaction analysis showed two opposite trends: the diversity of diagnostic species decreased in fragmented forests as the overall diversity increased. In highly fragmented forests, we found significantly higher values for therophyte and phanerophyte frequencies, light Ellenberg indicator values and edge and clearing species diversity. Conclusions: The integration of floristic analysis, particularly of certain diagnostic groups, with structural and ecological studies is more sensitive and significant than species richness alone, and could offer useful information for forest conservation and management.

Landscape fragmentation, land-use legacy and propagule pressure promote plant invasion on coastal dunes: a patch-based approach

Coastal dunes and sand areas are reported to be among the habitats most invaded by alien species in Europe. Landscape pattern could be a significant driver in invasion processes in parallel with land-use legacy. Fragmentation of natural habitats combined with the availability of propagules from the surrounding matrix may enhance the invisibility of ecological communities. Based on multitemporal land cover maps (1954–2008) and a floristic database, we analyzed how habitat fragmentation, propagule pressure and land-use legacy have affected alien plants’ presence and richness on natural dune patches along the Lazio Coast (Central Italy). Floristic data were derived from an existing geo-database of random vegetation plots (64xa0m2). A set of landscape patch-based metrics, considered to be adequate proxies of the main processes affecting alien invasion and richness, was calculated. First, we fit a generalized linear model (GLM) with binomial errors to assess which landscape metrics are influencing patch invasion. Second, we extracted invaded patches and, with GLMs, we investigated how landscape metrics affect average alien species richness. Alien invasion and alien richness seem to be affected by different processes: although alien invasion of each patch is strongly associated with its land-use legacy, the richness of aliens is more affected by landscape fragmentation and by the propagule pressure to which patch is exposed. By integrating spatial and temporal landscape metrics with floristic data, we were able to disentangle the relations of landscape fragmentation, propagule pressure and land-use legacy with the presence and richness of alien plants. The methodological approach here adopted could be easily extended to other alien species and ecosystems, offering scientifically sound support to prevent the high economic costs derived from both the control and the eradication of aliens.

Short-term signals of climate change in Italian summit vegetation: observations at two GLORIA sites

Abstract Short-term changes occurring in high mountain vegetation were analysed using the data from two Italian sites already part of the GLobal Observation Research Initiative in Alpine environments (GLORIA – central Apennines and southwestern Alps). The study focused on a set of floristic (endemics), structural (life forms) and ecological (thermic vegetation indicator) variables. Vegetation data were collected according to the GLORIA multi-summit standardized method during the last decade. The re-visitation revealed a moderate decrease in regional endemic flora and significant variations in structural and ecological parameters. The increase in caespitose hemicryptophytes in both sites, in suffruticose chamaephytes in the central Apennines and in rosette-forming hemicryptophytes in the southwestern Alps emerged, highlighting the rapid responses of the alpine vegetation to climate warming. The increase in perennial life forms is related with the expansion of graminoids and small woody plants. These life forms seem to be most suitable to face climate warming in Italian summits. The increase in the thermic vegetation indicator exceeds the mean European summits increment, and this is due to the expansion of thermophilic species. Short-term analyses with fine spatial and temporal resolutions are still necessary to improve our understanding concerning species behaviour in high-elevation ecosystems.

Assessing the diversity pattern of cryophilous plant species in high elevation habitats

This study aimed to better document the diversity and distribution patterns of vascular cryophilous species across major habitat types in a high-elevation Mediterranean system in central Italy. The research addressed the following questions: (a) whether different habitats support similar levels of biodiversity in terms of total vascular plants richness and cryophilous species richness, and (b) how each habitat contributes to the total cryophilous species diversity. A random stratified sampling approach based on a habitat map was applied to construct rarefaction curves for overall cryophilous species richness and habitat type-specific cryophilous richness. Rarefaction curves were also constructed for all-species and exclusive species. To determine whether the targeted species represented a constant proportion of all species, the ratio between the rarefaction curves of the cryophilous species and all species was also calculated. The results highlight the importance of the different habitat types in overall and cryophilous species conservation because these different habitat types had progressively higher richness values. At the regional scale, steep slopes had the highest species diversity, the greatest exclusive species richness and a steep rarefaction curve. The diversity pattern of cryophilous taxa was not related to the general pattern of total species richness, with these species being more common in three habitat types with extreme environmental conditions: ridges, cliffs, and screes. For the establishment of successful biodiversity conservation programs, it is imperative to include species-poor habitats containing a high proportion of cryophilous species, which are considered to be threatened by climate warming.

Different bat guilds perceive their habitat in different ways: a multiscale landscape approach for variable selection in species distribution modelling

AbstractContextnUnveiling the scale at which organisms respond to habitat features is crucial to understand how they are influenced by anthropogenic environmental changes. We implemented species distribution models (SDMs) based on multiple-scale landscape pattern analysis for four bat species representative of different foraging guilds: Nyctalus leisleri, Rhinolophus hipposideros, Myotis emarginatus and Pipistrellus pipistrellus.Objectives(a) to assess the environmental factors and the influence of scale on the habitat suitability of bats; (b) to develop an objective methodology to select the best performing variables from a large variable dataset.MethodsWe performed the study in central Italy (Tuscany): 381 variables were derived from topographical and habitat maps using a moving windows analysis set at three spatial scales (1, 5 and 10xa0km) that are ecologically meaningful for bats. For each species, we ran 381 univariate models to select the variables for multivariate SDMs.ResultsAll the variables retained in the SDMs described spatial pattern indices underlining the importance of landscape structure for species distribution. Species reacted differently in terms of both scale and landscape pattern. P. pipistrellus only responded to variables at 10xa0km; N. leisleri and M. emarginatus did so at two scales (5 and 10xa0km); whereas R. hipposideros also responded to variables at 1xa0km.ConclusionsOur findings make it possible to tailor SDMs according to species-specific landscape pattern requirements at appropriate scales. Our approach, which can be easily extended to other taxa and different spatial scales, represents a significant step towards more effective land management planning.