Use of remote sensing techniques to estimate plant diversity within ecological networks: a worked example

As there is an urgent need to protect rapidly declining global diversity, it is important to identify methods to quickly estimate the diversity and heterogeneity of a region and effectively implement monitoring and conservation plans. The combination of remotely sensed and field-collected data, under the paradigm of the Spectral Variation Hypothesis (SVH), represents one of the most promising approaches to boost large scale and reliable biodiversity monitoring practices. Here, the potential of SVH to capture information on plant diversity at fine scale in an ecological network (EN) embedded in a complex landscape, has been tested using two new and promising methodological approaches, based on “biodivMapR” and “rasterdiv” R packages. The first estimates α and β spectral diversity and the latter ecosystem spectral heterogeneity expressed as Rao's Quadratic heterogeneity measure (Rao’s Q). Our aims were to investigate if spectral diversity and heterogeneity provide reliable information to assess and/or monitor over time floristic diversity maintained in an EN selected as an example and located in North-East Italy. We analyzed and compared spectral and taxonomic α and β diversities and spectral and landscape heterogeneity, based on field-based plant data collection and remotely sensed data from Sentinel-2A, using different statistical approaches. We observed a positive relationship between taxonomic and spectral diversity and also between spectral heterogeneity, landscape heterogeneity, and the amount of alien species in relation to the native ones. Our results confirmed the effectiveness of estimating and mapping α and β spectral diversity and ecosystem spectral heterogeneity using remotely sensed images. Moreover, we highlighted that spectral diversity values become more effective to identify biodiversity-rich areas, representing the most important diversity hotspots to be preserved. While the spectral heterogeneity index in anthropogenic landscapes could be a powerful method to identify those areas most at risk of biological invasion

First report of naturalization of Houttuynia cordata Thunb. 1783 (Saururaceae) in Italy

The Chameleon plant (Houttuynia cordata Thunb.-Saururaceae) was introduced across all continents from Asia for ornamental and medicinal purposes at least two centuries ago. H. cordata is deemed a strong invader thanks to its great ability for rapid vegetative propagation by means of rhizomes and stolons (and their fragments) coupled with a high resistance to herbicides. Moreover, it has been suggested that H. cordata has the potential to displace native plants in wet forests and, in general, in wetland ecosystems. In New Zealand and North America, this species has been included in the black list of invasive alien species and it is included in a special control program for monitoring and eradication. In this study we record the first established naturalized population of Houttuynia cordata in Italy. It was found in July 2019 in a riverine Salix woodland. After revisiting the location, a significant expansion of the initial population was observed in June 2020, suggesting its naturalization with great invasive potential. Criteria and procedures defined by the regional intervention priorities on alien species were applied in order to further monitor and eradicate the species, as an example of good practice for the management of alien species

Determining plant diversity within interconnected natural habitat remnants (ecological network) in an agricultural landscape: a matter of sampling design?

5siIn intensively used and human-modified landscapes, biodiversity is often confined to remnants of natural habitats. Thus, identifying ecological networks (ENs) necessary to connect these patches and maintaining high levels of biodiversity, not only for its conservation but also for the effective management of the landscape, is required. However, ENs are often defined without a clear a-priori evaluation of their biodiversity and are often never even monitored after their establishment. The objective of this study was to determine the adequate number of replicates to effectively characterize biodiversity content of natural habitats within the nodes of an EN in north-eastern Italy, based on vascular plant diversity. Plant communities within habitat types of the EN’s nodes were sampled through a hierarchical sampling design, evaluating both species richness and compositional dissimilarity. We developed an integrated method, consisting of multivariate measures of precision (MultSE), rarefaction curves and diversity partitioning approaches, which was applied to estimate the minimum number of replicates needed to characterize plant communities within the EN, evaluating also how the proposed optimization in sampling size affected the estimations of the characteristics of habitat types and nodes of the EN. We observed that reducing the total sampled replicates by 85.5% resulted sufficient to characterize plant diversity of the whole EN and by 72.5% to exhaustively distinguish plant communities among habitat types. This integrated method helped to fill the gap regarding the data collection to monitor biodiversity content within existing ENs, considering temporal and economic resources. We therefore suggest the use of this quantitative approach, based on probabilistic sampling, to conduct pilot studies in the context of ENs design and monitoring and more in general for habitat monitoring.openopenFrancesco Liccari, Maurizia Sigura, Enrico Tordoni, Francesco Boscutti, Giovanni BacaroLiccari, Francesco; Sigura, Maurizia; Tordoni, Enrico; Boscutti, Francesco; Bacaro, Giovann

Evaluation of Green Infrastructure elements in rural-urban landscapes: a case study in North-East of Italy

Green Infrastructures (GIs) are defined as strategically planned networks of natural and seminatural areas designed and managed to deliver a wide range of ecosystem services. GIs are identified as one of the priorities in EU policies (e.g., the EU Biodiversity Strategy to 2020 or the new Common Agricultural Policy strategy). This imply the develop of effective approaches for planning and mapping GIs. In this framework we present the preliminary results of a study aimed to identify and to prioritize GI elements in rural landscapes of North-East of Italy. Two are the main project achievements: i) to identify the most important areas for natural stock and for ecological connectivity and ii) to evaluate multi-functionality by mapping a set of ecosystem services. In the first phase of this project, habitat suitability, least cost path analysis, spatial graphs and connectivity indices were combined to model a composite multi-species network (flora and fauna species) as expression of ecological connectivity for biodiversity at the landscape scale. As a result, almost 2000 ha of core areas and more than 4000 ha of ecological corridors, connecting 8 Special Area of Conservation (Habitats Directive 92/43/EEC) and several regional protected areas, were mapped allowing to identify the most relevant green areas to support biodiversity both in the protected and non-protected areas. In order to evaluate biodiversity within the core areas, sampling field activities were carried out: 50 plots were collected using a stratified random sampling (based on habitats within core areas) and diversity elements evaluated. Furthermore, we observed that the probability of connectivity (PC) was affected by both the extension of the target habitats considered and the species behavior. Results provide a good approximation to identify important areas for biodiversity conservation

Invasion at the Edge: the case of Rosa rugosa (Rosaceae) in Italy

7siThe Japanese Rose (Rosa rugosa) is a perennial shrub belonging to the family Rosaceae. It was introduced in Europe from East Asia as an ornamental plant in the XIX century and it is now considered an invasive species especially in northern Europe, colonising in particular the Atlantic and Baltic coastal dune habitats and threatening local biodiversity. Nevertheless, little is known about its presence and invasion patterns in the Mediterranean area. In Italy, R. rugosa has been classified as naturalised and just a few observations have been recorded in dune habitats in the North Adriatic coast. Here, we review published data about R. rugosa in Europe and present preliminary data on the invasive pattern of R. rugosa on the North Adriatic coast. We surveyed the coastline in two locations (i.e., Brussa and Bibione, Italy) where we characterised the dimension and structure (i.e., number of ramets and stem height) of the R. rugosa populations and listed the associated floristic composition. No occurrence of R. rugosa was recorded in Bibione, probably due to the success of the restoration project carried out on that site. In contrast, several stands of R. rugosa were found in Brussa, where other alien species were also found (accounting for 15.28% of the sampled species). Given the strong invasiveness of R. rugosa, it is important to keep data on its distribution up-to-date and investigate its ecology and physiology to promote appropriate management strategies to control its spread and anticipate its future potential distribution.openopenSara Ribotta, Francesco Liccari, Lucia Muggia, Alberto Pallavicini, Francesco Bagnolini, Enrico Tordoni, Giovanni BacaroRibotta, Sara; Liccari, Francesco; Muggia, Lucia; Pallavicini, Alberto; Bagnolini, Francesco; Tordoni, Enrico; Bacaro, Giovann

Connectivity, landscape structure, and plant diversity across agricultural landscapes: novel insight into effective ecological network planning

Natural habitats in rural and urban areas are increasingly fragmented and altered by human impacts that are limiting the animal and plant dispersal process. Fragmentation and isolation can be reversed by restoring landscape connectivity through effective Ecological Network (EN) planning. However, most of the studies analyzing the influence of connectivity and landscape structure on biodiversity are focused on animals, while the understanding of their interplaying role on plant diversity remains limited. We studied the relationships between α and β diversity pattern and landscape structure and connectivity in the nodes of an EN developed in agricultural landscapes, as a part of regional landscape planning framework in Friuli Venezia Giulia region (North-East of Italy). As an innovation, the study aims at parsing the interacting effect of landscape structure, surrounding habitats and nodes, and structural connectivity on EN plant diversity at two specific scales of investigation i.e., the habitat and the node scale. The habitat was the basic ecological unit, while the node was the basic cartographical unit for the EN mapping (multi-habitat or mono-habitat nodes). A total of 443 plant species were collected across 219 sample plots, in 14 different habitats and 87 nodes of the EN. We found that high node connectivity leads to higher species richness (α-diversity) but also increases plant community similarity (i.e., low β-diversity) at both scales. The effect of landscape structure showed differing trends depending on the habitat. In general, landscape composition of semi-natural land cover (i.e., hedgerows, watercourses) showed a positive effect on species diversity as opposed to that of the configuration of anthropogenic elements on both scales. Our results provided crucial information on the landscape processes useful to improving biodiversity conservation by EN. Our findings suggest that i) improving connectivity within ENs favors α plant diversity ii) different habitats have different sensibility to landscape structure iii) semi-natural land cover around nodes improve plant diversity; iv) planning both mono-habitat and multi-habitats nodes, increases the biodiversity conserved therein; v) nodes with more compact shapes are to be preferred

Do habitats show a different invasibility pattern by alien plant species? A test on a wetland protected area

Biological invasions are deemed as the second most important global driver of biodiversity loss right behind habitat destruction and ragmentation. In this study, we aimed at testing if community invasibility, defined as the vulnerability to invasion of a community, could be associated with the characteristics of a given habitat, as described by the composition and structure of its native species. Based on a probabilistic sampling of the alien flora occurring in the temperate wetland Lake Doberd\uf2 (Friuli Venezia Giulia region, NE Italy) and using a null model-based approach, observed occurrence of Invasive Alien Species (IAS) within sampling units were randomized within habitats. While testing the degree of invasibility for each habitat within the wetland, our null hypothesis postulated that habitats are equally invaded by IAS, as IAS can spread homogeneously in the environment thanks to their plasticity in functional traits which make them able to cope with different ecological conditions. The results obtained comparing observed IAS frequencies, abundance and richness to those obtained by the null model randomizations, showed that for all habitats invasion was selective. Specifically a marked preference for habitats with an intermediate disturbance level, a high nutrients level and a medium-high light availability was observed while an avoidance was detected for habitats characterized by lower levels of nutrients and light availability or extreme conditions caused by prolonged submersion. This method allows us to provide useful information using a simple-to-run simulation, for the management of the IAS threat within Protected Areas. Moreover, the method allows us to infer important ecological characteristics leading to habitat invasion without sampling the environmental characteristic of the habitats, which is an expensive operation in terms of time and money

Invasion at the Edge: The Case of Rosa rugosa (Rosaceae) in Italy

The Japanese Rose (Rosa rugosa) is a perennial shrub belonging to the family Rosaceae. It was introduced in Europe from East Asia as an ornamental plant in the XIX century and is now considered an invasive species, especially in northern Europe, colonising the Atlantic and Baltic coastal dune habitats and threatening local biodiversity. However, little is known about its presence and invasion patterns in the Mediterranean area. In Italy, R. rugosa has been classified as naturalised and just a few observations have been recorded in dune habitats in the North Adriatic coast. Here, we review the published data on R. rugosa in Europe and present preliminary data on the invasive pattern of R. rugosa on the Italian North Adriatic coast. We surveyed the coastline in two locations (i.e., Brussa and Bibione, Italy) where we characterised the dimension and structure (i.e., number of ramets and stem height) of the R. rugosa populations and listed the associated floristic composition. No occurrence of R. rugosa was recorded in Bibione, probably due to the success of the restoration project carried out on that site. In contrast, several stands of R. rugosa were found in Brussa, where many other alien species were also found (accounting for 15.28% of the sampled species). Given the strong invasiveness of R. rugosa, it is important to keep data on its distribution up-to-date and investigate its ecology and physiology to promote appropriate management strategies to control its spread and anticipate its future potential distribution

Notulae to the Italian alien vascular flora: 10

In this contribution, new data concerning the distribution of vascular flora alien to Italy are presented. It includes new records, confirmations, exclusions, and status changes for Italy or for Italian administrative regions. Nomenclatural and distribution updates published elsewhere are provided as Suppl. material 1

Notulae to the Italian alien vascular flora: 10

In this contribution, new data concerning the distribution of vascular flora alien to Italy are presented. It includes new records, confirmations, exclusions, and status changes for Italy or for Italian administrative regions. Nomenclatural and distribution updates published elsewhere are provided as Suppl. material 1