Mediterranean coastal dune vegetation: Are disturbance and stress the key selective forces that drive the psammophilous succession?

Plant communities of coastal dunes are distributed along a characteristic sea-inland gradient. Generally, there is a shift from annual and short height species with small leaves in initial successional stages to perennial tall shrubs with tough leaves in later phases. Assessing the community-weighted mean (CWM) trait values is used in plant ecology to describe ecosystem properties especially during succession. In particular, CSR (Competitive, Stress-tolerant, and Ruderal strategy) classification allows us to explore community functional shifts in terms of disturbance, stress and competition selective forces. To explore the functional basis of the psammophilous succession, we asked the following questions: (1) Can we circumscribe different functional types among plant species of Mediterranean coastal dunes? (2) How do CWM trait values vary along the environmental sea-inland gradient? (3) What is the relative importance of competition, stress and disturbance in the processes of plant community assembling? (4) Can we postulate that along primary successions there is generally a shift from ruderality to stress-tolerance? An explorative analysis of functional groups was performed by Non-Metric Multidimensional Scaling (NMDS) analysing nine morpho-functional traits measured for 45 taxa from 880 dune plots localised in Tuscany (central Italy, Europe). NMDS ordination showed a scattered distribution of psammophytes that could not be delimited in sharp plant functional types. The first NMDS axis has been interpreted as a leaf economics axis because it was correlated to leaf area (LA) and leaf dry matter content (LDMC), while the second one was a plant size axis because of its correlation with canopy height. Along the sea-inland gradient, pioneer plant communities of upper beach were dominated by ruderals (with the lowest values of LDMC and specific leaf area - SLA), well-adapted to the harsh environmental conditions of coastal dunes. More distantly from the sea, where ecological conditions were less extreme, late-successional communities of backdunes were characterised by the prevalence of stress-tolerants. This study suggested that psammophytes have evolved not a single but multiple adaptive strategies showing a high degree of functional diversity and complexity. Moreover, CSR classification supported the hypothesis of a functional shift from R-strategists in early successional stages to S-strategists in late-successional communities along a primary succession

Study of functional and physiological response of co-occurring shrub species to the Mediterranean climate

The Mediterranean basin is characterised by increasingly dry summers and the study of the adaptive traits developed by plants living in this stressful environment is of great interest, also in relation to climate projections for this area. Cistus monspeliensis, Myrtus communis and Phillyrea angustifolia are three co-occurring shrubs typical of the Mediterranean maquis. Their functional and physiological parameters were studied in spring, summer and autumn in order to highlight adjustments of these traits and to test eventual different adaptive strategies. Soil and leaf chemical characteristics were determined in the different seasons. Leaf area, specific leaf area, leaf dry matter content, succulence index, pigment contents hydric status and main markers of oxidative stress and antioxidant response were detected. The stressful summer season induced disturbance in hydric balance, decrease in succulence index and chlorophyll content and high contents of hydrogen peroxide. Thanks to higher enzymatic activities and total glutathione content, in the two evergreen species M. communis and P. angustifolia oxidative damage remained at levels equal to or lower than the other seasons. Only in the semideciduous C. monspeliensis both functional and biochemical traits showed a higher stress condition in summer. The higher stability of functional traits in the two evergreen species may be explained by the sclerophyllous nature of their leaves. Four environmental variables – Tmax, Tmin, soil conductivity and organic matter – mostly influenced NMDS segregation of these species

Checklist della flora vascolare psammofila della Toscana

Checklist of the psammophilous vascular flora of Tuscany. An updated list of the psammophilous vascular flora occurring in coastal areas of Tuscany is presented. The list is based on bibliographic analysis and field studies effected ad hoc in the year 2012-2013. 704 specific and infraspecific taxa are reported (641 native). They belong to 383 genera and 90 families. Most represented families are Poaceae (13%), Asteraceae (12%), Fabaceae (10%), Caryophyllaceae (5%), Apiaceae (4%). 63 units are naturalized exotic species (about 9% of the flora). Aloe arborescens is a casual exotic newly recorded for Tuscany. The Italian endemics are 6, of which three are exclusive of sandy Tuscan coasts (Centaurea aplolepa Moretti subsp. subciliata (DC.) Arcang., Limonium etruscum Arrigoni & Rizzotto, Solidago litoralis Savi). Only 11 taxa were recorded in all or almost all the study areas: Ammophila arenaria (L.) Link subsp. arundinacea H.Lindb, Cakile maritima Scop. subsp. maritima, Calystegia soldanella (L.) Roem. & Schult., Echinophora spinosa L., Eryngium maritimum L., Kali tragus (L.) Scop. s.l., Lagurus ovatus L. subsp. ovatus, Medicago marina L., Pancratium maritimum L., Sporobolus virginicus Kunth

Marine litter and psammophytes: a case study in the Migliarino-San Rossore-Massaciuccoli Regional Park coastal sand dunes

Coastal sand dunes are one of the most impacted ecosystems in the world (1). They host various habitats of Community interest under the Habitats Directive 92/43/EEC but are profoundly affected by pollution and waste management, even within protected areas. The factors that define the amount, type and distribution of beach litter are complex and relate more to human intervention and natural variables. This work aims to analyse the composition, abundance and distribution of marine litter within a protected area in two different chronological windows, i.e. before and after the bathing season. We also attempted to verify whether the presence of waste could alter the coverage of the psammophilous vegetation. The protected area examined in this project is the Migliarino-San Rossore-Massaciuccoli Regional Park (Tuscany, Italy), where we selected three dune sites stretching along the coastline with a North/South gradient: Lecciona (2 Km2), Bufalina (1 Km2) and Calambrone (1 Km2), respectively. We adopted a stratified random sampling design, using permanent multiscale squared-plots of 16 m2, with two nested plots placed at a fixed corner of 4 m2 and 1 m2, respectively. Each site was divided into same-area strata with a spatially optimised algorithm. Inside each layer two points were randomly selected, corresponding to the field plots; overall, a total of 22 plots were sampled. Sampling took place in two sessions, one in May and the other one in November. The data collected were the total percentage coverage of litter and the individual coverage of each type of litter for each plot. Classification of marine litter followed the directives of the "Master List of Categories of Litter Items", a list drawn up by the Joint Research Centre (JRC) of the European Commission based on several classification protocols (2). At the same time, we censused the plant species in each plot and measured their total percentage coverage at each investigated spatial scale. We compiled a litter × plot matrix with the percentage of coverage of each type of waste found in the plots at the three spatial scales and in the two periods. The PERMANOVA analysis of the matrix with 4 factors (month, site, layer and plot area) highlighted that the interaction term month × site explained significantly (P< 0.001) the variance in the composition of waste at the plot level. NMDS analysis (non-metric multidimensional scaling) showed that the categories most significantly related to the variability between plots were the following: "plastic fragments less than 2.5 cm (G78)" and "plastic fragments between 2.5 and 50 cm (G79)". These two types of litter showed contrasting patterns over time: G78 increased from June to November, G79 decreased in the same period. Multivariate analyses were carried out using the software PRIMER v.7 (3) and PERMANOVA+ (4). The diachronic study of the relationship between area and the number of litter categories, carried out using the Arrhenius power law equation (5), showed that in Lecciona and Bufalina there was in November a greater growth in types of litter as the area increased in respect to the first sampling period, while in Calambrone there were no differences. According to Pearson correlation test, temporal turnover of litter categories, quantified partitioning β-diversity following (6), and the total percentage coverage of vegetation resulted inversely correlated (cor = - 0.44, P = 0.038). In conclusion, artificial polymer materials were found to be the dominant waste type (85%) at the three study sites examined, two of which were characterised by an increase in waste after the bathing season. In the third site, however, probably due to regular manual cleaning actions, no differences were found. Where vegetation is more abundant, the total number of litter categories tends to be more stable across the seasons, suggesting that psammophytes are a relevant biotic component to be considered in the analysis of spatio-temporal dynamics of coastal litter. 1) Ciccarelli D., 2014. Environ. Manag. 54, 194–204 2) Galgani F., Hanke G., Werner S., et al. (2013) JRC Scientific and Policy reports 3) Clarke K., Warwick R. (2001). Change in marine communities: an approach to statistical analysis and interpretation Ed. 2. PRIMER-E, Plymouth 4) Anderson M.J., Gorley R.N., Clarke R.K. (2008). PERMANOVA+ for PRIMER: Guide to software and statistical methods. PRIMER-E, Plymouth 5) Arrhenius O. (1921) J Ecol, 9, 95-99 6) Baselga A. (2010). Glob Ecol Biogeogr, 19, 134-14

Mediterranean sea cliff plants: morphological and physiological responses to environmental conditions

Aims The plants of Mediterranean sea cliff ecosystems are resistant to several environmental challenges. In the present study, six species typical of the coastal rocky cliffs have been analysed in order to evaluate their diverse morphological and physiological responses to their environment across the seasons, and to examine the strategy of the ecological group to which each species belongs. Since these species are widespread across the Mediterranean region, our aim was also to highlight their ecophysiological features in habitats where the direct influence of the sea is stronger. Methods The selected species are characteristic of the sea cliffs of Elba island (Tyrrhenian sea, Italy): the halophyte Crithmum maritimum, the semideciduous Helichrysum italicum and Lavandula stoechas, and the sclerophylls Myrtus communis, Quercus ilex and Rhamnus alaternus. Four morphological traits - canopy height, leaf area, specific leaf area and leaf dry matter content - and two physiological traits - leaf water potential (LWP) and photosynthetic efficiency (PE), measured before the dawn and at midday were analysed. Water potential was measured by a pressure chamber and photosynthetic efficiency was determined by the analysis of chlorophyll fluorescence. Plant performance was also evaluated by calculating chronic (PIchr) and dynamic photoinhibition (PIdyn). Important findings Crithmum maritimum showed high resistance to the recurrent dry periods, because of the high water storage capacity of its leaves and its PE declined markedly only in July, under the harshest climatic conditions. Semideciduous taxa utilise primarily an avoidance strategy, which aims at reducing the overall leaf surface, while sclerophylls mostly show a tolerance strategy towards the prevailing stressors, as demonstrated by LWP and PE, that are lower in the sclerophylls than in the semideciduous taxa during summer, due to osmoregulation and photoinhibition, respectively. Furthermore, variability of physiological parameters was higher in the sclerophylls than in the semideciduous taxa, because the former had to withstand wider oscillations of their LWP and PE. The sclerophyllous taxa underwent a slight loss of PE also in winter, likely owing to the combined action of low temperature and high irradiance. In Mediterranean sea cliff ecosystems, the stressful combination of high irradiance, high temperatures and low rainfall typical of the summer season may have been intensified by the shallow soil which displays a poor water storage capacity. On the other hand, winter stress, caused by high solar radiation and low temperatures, does not seem to seriously affect the performance of the studied species

La ripresa della vegetazione mediterranea dopo il passaggio degli incendi: il caso di studio del Monte Castellare (PI) - Toscana nord-occidentale

In Mediterranean ecosystems, wildfires are a key factor that affects vegetation and landscapes. In particular, recurrent wildfires are dramatically dangerous because they can compromise ecosystem resilience. In this view, the present work aimed to study the effects of fire events on the Mediterranean vegetation of Castellare Mount (Pisa). Castellare Mount seemed an interesting study place since two wildfires occurred in 2008 and 2009. The study area was divided into three sites: one site interested by the wildfire event occurred in 2009, another site interested by the wildfire event occurred in 2008, and a control site. Seven dominant plant species (Arbutus unedo L., Daphne gnidium L., Erica arborea L., Myrtus communis L., Phillyrea angustifolia L., Pinus pinaster Aiton and Quercus x morisii Borzì) were selected in each study site. For each species an index of flammability (IF) was calculated, following a non-destructive protocol that took into account seven functional traits related to leaves, twigs, canopy branching, standing litter, and volatile oils production. Moreover, a global flammability index was calculated for each study site. Results showed that all the plant species had quite high values of flammability, which could be explained by their adaptations to fire. In fact, all the taxa examined were active pyrophytes, whose regeneration are stimulated by fire events. However, vegetation survey highlighted a slower process of plant community recovery in the first year after the wildfire event than those observed in the subsequent years. In conclusion, recurrent wildfires are confirmed extremely dangerous because they compromise the recovery of Mediterranean vegetation

Plant adaptation to extreme environments: The example of Cistus salviifolius of an active geothermal alteration field

Cistus salviifolius is able to colonise one of the most extreme active geothermal alteration fields in terms of both soil acidity and hot temperatures. The analyses of morphofunctional and physiological characters, investigated in leaves of plants growing around fumaroles (G leaves) and in leaves developed by the same plants after transfer into growth chamber under controlled conditions (C leaves) evidenced the main adaptive traits developed by this pioneer plant in a stressful environment. These traits involved leaf shape and thickness, mesophyll compactness, stomatal and trichome densities, chloroplast size. Changes of functional and physiological traits concerned dry matter content, peroxide and lipid peroxidation, leaf area, relative water and pigment contents. A higher reducing power and antioxidant enzymatic activity were typical of G leaves. Though the high levels of stress parameters, G leaves showed stress-induced specific morphogenic and physiological responses putatively involved in their surviving in active geothermal habitats

Anthemis maritima L. in different coastal habitats: A tool to explore plant plasticity

Anthemis maritima, a plant which has the ability to colonise different stressful coastal environments, sand dunes and rocky cliff ecosystems, exhibits a high degree of leaf trait plasticity. The key parameters are the regulation of stomatal density and size, the succulence index and the specific antioxidant response. With the aim to explore plant plasticity, we analysed various morphological and physiological traits of the leaves of A. maritima populations dwelling in three different coastal areas of Italy. The highest values of stomatal density, leaf thickness, and succulence index were found in plants living in a sub-arid climate, on rocky cliffs, with the highest soil pH and salinity. Although this population exhibited the highest content of oxygen reactive species (hydrogen peroxide), it also revealed to have the lowest value of lipid peroxidation, an indicator of oxidative stress. Ascorbate was the main protective molecule in this population, while phenols appeared to carry out this role in plants living on soils with the lowest salinity and highest annual rainfall

Mapping of Yucca gloriosa invasion along Mediterranean coastal dunes using unmanned aerial vehicles (UAVs)

Invasive Alien Plants (IAPs) are defined as those species whose introduction and/or spread outside their natural distribution can threaten the biological diversity of an ecosystem. They represent a severe threat to biodiversity and can severely alter the performance of crucial ecosystems such as coastal dunes. Coastal dunes are composed of specialized fauna and flora, converting them into strategic ecosystems due to their unique ecological functions. Coastal dunes are one of the most invaded European environments, with a total flora composed of up to 7% of IAPs. One of these IAPs is Yucca gloriosa L. (Asparagaceae), a homoploid hybrid native plant from the United States of America introduced to Europe for ornamental purposes. For Italy, Y. gloriosa is a typical invasive species related to fixed dunes dominated by Juniperus sp. pl. (with which it competes). Concerning biological invasions, maybe the most effective management strategy is early detection and mapping. In that sense, this work explores and tests the potential of unmanned aerial vehicles (UAVs) for detecting, mapping, and managing the Y. gloriosa invasion along the Mediterranean coastal dunes of a protected area located in Tuscany (Italy). In detail, this work focuses on four aspects: i) determine the suitability of RGB images to map Y. gloriosa, ii) identify the best time of data acquisition, iii) detect changes affecting the occurrence and cover of Y. gloriosa, and iv) propose a set of management actions to preserve a coastal dune ecosystem subjected to plant invasion. The UAV images allowed the generation of ultra-high spatial resolution maps to assess the Y. gloriosa invasion and distribution along the surveyed sandy dunes. The morphological characteristics of this plant – especially at the foliar level – make the invasion of Y. gloriosa particularly suitable for being evaluated and managed using UAV mapping, especially in coastal dunes vegetation that can be a mosaic of different plant communities hard to identify when airborne or satellite images are used. According to the obtained results, the spring season is the perfect time to collect data because light conditions are ideal, with minimal shading effects. Also, due to the peculiar morphology of Y. gloriosa leaves, the timing of data collection seems not crucial for mapping this IAP on coastal dune habitats. Despite the massive eradication action funded by a LIFE project during the period 2005-2009, Y. gloriosa is still present in the protected area and affects the priority habitat of juniper. This might be linked to the fact that Y. gloriosa is a perennial rhizomatous shrub capable of switching its photosynthesis from the C3 to CAM pathway and, therefore, withstand the harsh environmental conditions of dune ecosystems. The early detection using UAVs is the first line of defense against IAPs colonization over any ecosystem. From a conservation and management point of view, this work suggests the development of annual biomonitoring of Y. gloriosa to check its distribution over time and control its spread where it becomes particularly invasive. In this case, one possible strategy will be to keep the IAP in isolated nuclei of plants that are easier to remove with mechanical methods. In a broader view, the study area and the Mediterranean coast must include the ban on introducing non-native species as a strategy, adopting a short-term non-native Management Plan as urgent action

Hypoxia sustains glioblastoma radioresistance through ERKs/DNA-PKcs/HIF-1α functional interplay

The molecular mechanisms by which glioblastoma multiforme (GBM) refracts and becomes resistant to radiotherapy treatment remains largely unknown. This radioresistance is partly due to the presence of hypoxic regions, which are frequently found in GBM tumors. We investigated the radiosensitizing effects of MEK/ERK inhibition on GBM cell lines under hypoxic conditions. Four human GBM cell lines, T98G, U87MG, U138MG and U251MG were treated with the MEK/ERK inhibitor U0126, the HIF-1α inhibitor FM19G11 or γ-irradiation either alone or in combination under hypoxic conditions. Immunoblot analysis of specific proteins was performed in order to define their anti‑oncogenic or radiosensitizing roles in the different experimental conditions. MEK/ERK inhibition by U0126 reverted the transformed phenotype and significantly enhanced the radiosensitivity of T98G, U87MG, U138MG cells but not of the U251MG cell line under hypoxic conditions. U0126 and ERK silencing by siRNA reduced the levels of DNA protein kinase catalytic subunit (DNA-PKcs), Ku70 and K80 proteins and clearly reduced HIF-1α activity and protein expression. Furthermore, DNA-PKcs siRNA-mediated silencing counteracted HIF-1α activity and downregulated protein expression suggesting that ERKs, DNA-PKcs and HIF-1α cooperate in radioprotection of GBM cells. Of note, HIF-1α inhibition under hypoxic conditions drastically radiosensitized all cell lines used. MEK/ERK signal transduction pathway, through the sustained expression of DNA-PKcs, positively regulates HIF-1α protein expression and activity, preserving GBM radioresistance in hypoxic condition