Network-based analysis reveals differences in plant assembly between the native and the invaded ranges.

Associated with the introduction of exotic species in a new area, interactions with other native species within the recipient community occur, reshaping the original community and resulting in a unique assemblage. Yet, the differences in community assemblage between native and invaded ranges remain unclear. Mediterranean grasslands provide an excellent scenario to study community assembly following transcontinental naturalisation of plant species. Here we compared the community resemblance of plant communities in Mediterranean grasslands from both the native (Spain) and invaded (Chile) ranges. We used a novel approach based on network analysis applied to co-occurrence analysis in plant communities, allowing us to study the coexistence of native and alien species in central Chile. This useful methodology is presented as a step forward in invasion ecology studies and conservation strategies. We found that community structure differed between the native and the invaded range, with naturalised species displaying more significant interactions and playing a key role within the invaded community. In addition, alien species displayed positive interactions among them within the communities in the invaded range. Alien species acting like keystones within the Chilean grassland communities might exacerbate the threat posed by biological invasions for the native biodiversity assets. We suggest controlling the spread of the alien species identified as keystones and developing early detection strategies in surrounding areas as management guidelines.

Phytosociology of Atractylis cancellata and Micromeria microphylla communities in southern Italy with insights on the xerothermic steno-Mediterranean grasslands high-rank syntaxa

In the present paper a phytosociological study on the dry grassland communities identified in the western sector of the Murgia Plateau (Murgia delle Gravine) and in the Lucanian badlands territory is presented. Forty vegetation releves were carried out using the Braun-Blanquet phytosociological approach. Two new associations characterized by a therophytic dominance, namely Lysimachio foeminae-Atractylidetum cancellatae and Campanulo erini-Micromerietum microphyllae, are described and discussed from a syntaxonomic and biogeographic viewpoint. In addition, new phytosociological data concerning the Petrosedum ochroleucum communities developed on limestone outcrops, the perennial Hyparrhenia hirta steppe-like grasslands of the low-altitude areas of the Murgia hills and the small-size Brachypodium distachyum therophytic communities are presented.

Impacts of sheep versus cattle livestock systems on birds of Mediterranean grasslands

Mediterranean pastures are experiencing strong changes in management, involving shifts from sheep to cattle-based livestock systems. The impacts of such shifts on biodiversity are still poorly understood. Here, we sought to contrast the grazing regime, vegetation structure, bird species richness and abundance, between sheep and cattle grazed parcels, to understand the mechanisms through which management decisions impact farmland birds. During spring 2019, we characterized livestock management, bird populations and sward structure in 23 cattle and 27 sheep grazed parcels. We used a Structural Equation Model to infer the direct and indirect effects of sheep and cattle grazing on birds. Although no effects were found on overall species richness, there were species-specific responses to sheep and cattle grazed systems. Grazing pressure (variable integrating stocking rate and the number of days in the parcel) had negative impacts on the prevalence/abundance of Zitting Cisticola, Corn Bunting and Little Bustard, either directly or indirectly, through the effects of grazing pressure on vegetation height. Animal density and vegetation cover had direct positive effects in Galerida spp. and Common Quail, respectively. Zitting Cisticola and Little Bustard also showed a direct response to livestock type. Our study emphasizes the importance of grazing pressure as a driver of negative impacts for bird populations in Mediterranean grasslands. Since the ongoing transition from sheep to cattle-based systems involves increases in stocking rate, and therefore potentially higher grazing pressure, we propose a policy change to cap the maximum allowed grazing pressure. At the landscape scale, a mix of sheep and cattle grazed fields would be beneficial for maintaining bird diversity.

The Vegetation–Climate System Complexity through Recurrence Analysis

Multiple studies revealed that pasture grasslands are a time-varying complex ecological system. Climate variables regulate vegetation growing, being precipitation and temperature the most critical driver factors. This work aims to assess the response of two different Vegetation Indices (VIs) to the temporal dynamics of temperature and precipitation in a semiarid area. Two Mediterranean grasslands zones situated in the center of Spain were selected to accomplish this goal. Correlations and cross-correlations between VI and each climatic variable were computed. Different lagged responses of each VIs series were detected, varying in zones, the year’s season, and the climatic variable. Recurrence Plots (RPs) and Cross Recurrence Plots (CRPs) analyses were applied to characterise and quantify the system’s complexity showed in the cross-correlation analysis. RPs pointed out that short-term predictability and high dimensionality of VIs series, as well as precipitation, characterised this dynamic. Meanwhile, temperature showed a more regular pattern and lower dimensionality. CRPs revealed that precipitation was a critical variable to distinguish between zones due to their complex pattern and influence on the soil’s water balance that the VI reflects. Overall, we prove RP and CRP’s potential as adequate tools for analysing vegetation dynamics characterised by complexity.

First Report of the European Vegetation Classification Committee (EVCC)

The European Vegetation Classification Committee (EVCC) was established in 2017 by the European Vegetation Survey to maintain and update a standard phytosociological classification of European vegetation. Vegetation scientists can send proposals for modification of specific parts of the EuroVegChecklist, which is used as a baseline. The proposals are accepted or rejected based on recommendations issued by a specialist group and after voting by EVCC members. Here we report the results of the first voting, which took place from 4 June to 4 July 2020. EVCC members voted on the recommendations issued for three proposals of change concerning spring and dune vegetation, and mediterranean grasslands. As a result, EVCC accepted to modify the classes Ammophiletea and Helichryso-Crucianelletea, but rejected to include the alliance Philonotidion seriatae and the class Charybdido pancratii-Asphodeletea ramosi. These rejections are not final, and similar proposals can be submitted again with new data supporting the proposed changes. Abbreviations: EVCC = European Vegetation Classification Committee; SG = Specialist Group.