OPTIMIZATION OF GREEN ROOF INSTALLATIONS IN THE MEDITERRANEAN CLIMATE

Le coperture a verde pensile sono impianti vegetali realizzati sui tetti degli edifici mediante l'uso di una serie di stratigrafie specifiche. \uc9 stato dimostrato che i tetti verdi forniscono benefici ecologici, economici e sociali, ma l'applicazione della tecnologia \ue8 ancora poco diffusa nelle regioni a clima arido. Le attivit\ue0 di ricerca condotte nel corso della presente tesi hanno permesso di sviluppare nuovi criteri per la realizzazione di coperture a verde pensile in area mediterranea. Per aumentare le capacit\ue0 di ritenzione idrica del substrato, mantenendo spessori limitati, \ue8 stata valutata la possibilit\ue0 di ricorrere a miscele di substrato e polimeri idrofili (SAP). I SAP hanno portato all\u2019aumento della quantit\ue0 di acqua disponibile per la vegetazione ottimizzando lo stato idrico delle piante di Salvia officinalis durante i periodi aridi, specialmente se cresciute su spessori di substrato limitati. Essendo la riduzione degli spessori di substrato uno dei principali obiettivi della ricerca sul verde pensile, sono stati valutati lo stato idrico, l\u2019evapotraspirazione e l\u2019accrescimento di specie arbustive cresciute su spessori di substrato ridotti. I dati sperimentali hanno dimostrato come in condizioni di aridit\ue0 lo stato idrico delle piante \ue8 risultato essere pi\uf9 favorevole nei sistemi caratterizzati da spessori ridotti, in quanto essi promuovono un minore accumulo di biomassa vegetale e quindi un minor consumo di acqua, se paragonati a spessori superiori. Con l'obiettivo di dimostrare l'importanza della selezione delle specie vegetali accoppiata a una appropriata scelta del substrato, due specie arbustive sono state fatte crescere in due substrati che differivano in termini di caratteristiche di ritenzione idrica. I risultati hanno evidenziato come il tipo di substrato influenzi in maniera significativa lo stato idrico della vegetazione. Per approfondire le conoscenze sull'adattamento allo stress idrico della pianta modello S. officinalis \ue8 stato condotto uno studio ecofisiologico sulla specie, anche in ambiente naturale, che ha evidenziato come le foglie risultano essere pi\uf9 vulnerabili allo stress idrico in termini di perdita di efficienza di trasporto dell'acqua se paragonate ai fusti. Si pu\uf2 quindi concludere che la tolleranza alla aridit\ue0 di S. officinalis \ue8, almeno in parte, conseguenza della segmentazione idraulica. Nelle regioni a clima mediterraneo, temperature elevate e deficit idrico impongono l\u2019utilizzo nei sistemi a verde pensile di una vegetazione con buona tolleranza all\u2019aridit\ue0 e alle temperature estreme. Il presente lavoro, sulla base di uno studio che ha coinvolto 11 specie, vuole contribuire alla ottimizzazione del processo di selezione delle piante arbustive pi\uf9 idonee. Misure dello stato idrico, test di sopravvivenza su spessori di substrato ridotti e lo studio di parametri fisiologici, hanno evidenziato come i tratti che garantiscono efficienza/sicurezza al trasporto dell'acqua risultano essere buoni indicatori del tasso di accrescimento delle piante e del consumo dell\u2019acqua, ma le alte temperature del substrato influenzano in maniera molto pi\uf9 significativa la sopravvivenza delle piante su un inverdimento pensile. La tolleranza specie-specifica dell'apparato radicale al calore, nonch\ue9 la resistenza delle foglie allo stress idrico, sono caratteristiche funzionali essenziali per garantire un'adeguata copertura del verde pensile. La tutela della biodiversit\ue0 e la formazione di habitat sono due dei benefici ecologici apportati dalle coperture a verde pensile. Nel corso della ricerca sono stati analizzati lo sviluppo e la composizione floristica di coperture a piante erbacee e succulente sviluppate su volumi di substrato ridotti. L\u2019utilizzo di una miscela di semi di specie erbacee ha permesso di ottenere una buona copertura del substrato e lo sviluppo di una comunit\ue0 con elevata biodiversit\ue0

A simplified framework for fast and reliable measurement of leaf turgor loss point

Drought tolerance shapes the distribution of plant species, and it is mainly determined by the osmotic potential at full turgor (\u3c00) and the water potential at turgor loss point (\u3a8tlp). We provide a simplified framework for \u3c00 and \u3a8tlp measurements based on osmometer determination of \u3c00 (\u3c00_osm). Specifically, we ran regression models to i) improve the predictive power of the estimation of \u3c00 from \u3c00_osm and morpho-anatomical traits; ii) obtain the most accurate model to predict \u3a8tlp on the basis of the global relationship between \u3c00 and \u3a8tlp. The inclusion of the leaf dry matter content (LDMC), an easy-to-measure trait, in the regression model improved the predictive power of the estimation of \u3c00 from \u3c00_osm. When \u3c00_osm was used as a simple predictor of \u3a8tlp, discrepancies arose in comparison with global relationship between \u3c00 and \u3a8tlp. \u3a8tlp values calculated as a function of the \u3c00 derived from \u3c00_osm and LDMC (\u3c00_fit) were consistent with the global relationship between \u3c00 and \u3a8tlp. The simplified framework provided here could encourage the inclusion of mechanistically sound drought tolerance traits in ecological studies

Make it simpler: alien species decrease functional diversity of coastal plant communities

Questions: 1) Are there differences in abundance-weighted functional trait values between native and alien species in coastal plant communities? 2) Which functional traits are associated with a higher level of invasion in these communities? 3) Do functional diversity patterns differ between native and alien species? 4) Is alien species occurrence linked to small-scale functional homogenization effects on the resident native species? Location: N-Adriatic coastal ecosystems (Marano and Grado lagoon, Friuli Venezia Giulia region, Italy) Methods: We sampled coastal vegetation within two habitats (foredunes and saltmarshes) along 9 belt transects in two sampling sites. Plant species richness and abundance were assessed in 128 plots along with a suite of plant functional traits. We tested for differences in CWMs between native and alien species within the two habitats, and a Linear Mixed Model (LMMs) provided insights on traits fostering the invasion success among alien species. To check for potential functional homogenization driven by alien species invasion, we explored functional diversity patterns of native and alien species (alpha and beta functional diversity) and the relationship between alpha functional diversity and alien cover. Results: Alien species had lower functional diversity than natives and were characterized by lower leaf construction costs coupled with lower drought resistance and higher water transport efficiency. The most abundant aliens were the ones minimizing carbon investment for leaf construction. In addition, we also found evidence for small-scale functional homogenization driven by alien invasion. Conclusions: Our results suggested that native species adopt a resource conservative strategy whereas alien species are characterized by a higher resource acquisition capacity (i.e. acquisitive strategy). Our data also confirmed that alien species are less functionally diverse than natives, Functional diversity of coastal plant communities potentially driving the community towards small-scale functional homogenization, resulting in a loss of species and a reduction in the functional space

Workgroup D. Artificial Green Floating Islands

The project aims at reducing the gap between the Eastern and Western part of the Danube River, regarding economic disparities and environmental problems. This gap can be reduced by introducing Artificial Green Floating Islands in the Danube region, with the following objectives: improvement of water quality using specific plants that purify the water to be used in agriculture, attraction of tourists to the less developed countries to make a profit, opening of new jobs for young and inexperienced people, creation for the local people of public places where they can get together and socialize. The introduction of the Artificial Green Floating Islands would also change how people and countries of the area perceive the Danube River turning it from a natural border into a centre for social interaction between different coastal states

The contribution of vascular and extra-vascular water pathways to drought-induced decline of leaf hydraulic conductance

Drought stress can impair leaf hydraulic conductance (Kleaf), but the relative contribution of changes in the efficiency of the vein xylem water pathway and in the mesophyll route outside the xylem in driving the decline of Kleaf is still debated. We report direct measurements of dehydration-induced changes in the hydraulic resistance (R=1/K) of whole leaf (Rleaf), as well as of the leaf xylem (Rx) and extra-vascular pathways (Rox) in four Angiosperm species. Rleaf, Rx, and Rox were measured using the vacuum chamber method (VCM). Rleaf values during progressive leaf dehydration were also validated with measurements performed using the rehydration kinetic method (RKM). We analysed correlations between changes in Rx or Rox and Rleaf, as well as between morpho-anatomical traits (including dehydration-induced leaf shrinkage), vulnerability to embolism, and leaf water relation parameters. Measurements revealed that the relative contribution of vascular and extra-vascular hydraulic properties in driving Kleaf decline during dehydration is species-specific. Whilst in two study species the progressive impairment of both vascular and extra-vascular pathways contributed to leaf hydraulic vulnerability, in the other two species the vascular pathway remained substantially unaltered during leaf dehydration, and Kleaf decline was apparently caused only by changes in the hydraulic properties of the extra-vascular compartment

Sampling intraspecific variability in leaf functional traits: Practical suggestions to maximize collected information

The choice of the best sampling strategy to capture mean values of functional traits for a species/population, while maintaining information about traits\u2019 variability and minimizing the sampling size and effort, is an open issue in functional trait ecology. Intraspecific variability (ITV) of functional traits strongly influences sampling size and effort. However, while adequate information is available about intraspecific variability between individuals (ITVBI) and among populations (ITVPOP), relatively few studies have analyzed intraspecific variability within individuals (ITVWI). Here, we provide an analysis of ITVWI of two foliar traits, namely specific leaf area (SLA) and osmotic potential (\u3c0), in a population of Quercus ilex L. We assessed the baseline ITVWI level of variation between the two traits and provided the minimum and optimal sampling size in order to take into account ITVWI, comparing sampling optimization outputs with those previously proposed in the literature. Different factors accounted for different amount of variance of the two traits. SLA variance was mostly spread within individuals (43.4% of the total variance), while \u3c0 variance was mainly spread between individuals (43.2%). Strategies that did not account for all the canopy strata produced mean values not representative of the sampled population. The minimum size to adequately capture the studied functional traits corresponded to 5 leaves taken randomly from 5 individuals, while the most accurate and feasible sampling size was 4 leaves taken randomly from 10 individuals. We demonstrate that the spatial structure of the canopy could significantly affect traits variability. Moreover, different strategies for different traits could be implemented during sampling surveys. We partially confirm sampling sizes previously proposed in the recent literature and encourage future analysis involving different traits

Investigating physiological effects due to artificial infections of grapevine with <i>Verticillium nonalfalfae</i>

Ailanthus altissima is among the most invasive woody species worldwide, outcompeting native trees. The fungus Verticillium nonalfalfae (VN) is promising for A. altissima biocontrol, and its effects on the host have been studied via visual assessment in a range of host species. However, little research was performed to address fungal effects on the physiological processes of non-target woody plants. We investigated the occurrence of visual and non-visually recognisable perturbations of VN infection on potted vines to evaluate the potential risks of the biocontrol pathogen on viticulture. Eighteen four-years-old Vitis vinifera (cultivar Grüner Veltliner grafted on Kober 5BB) potted plants were inoculated with VN conidial suspension of the fungus (F), while nine plants were treated with sterile water (C, control). Disease symptoms and physiological parameters were monitored throughout the experiment (seven evaluation dates), while leaf water potential, leaf mass per area (LMA) and biomass were measured at the end of the study when plant tissue was sampled for re-isolation of the fungus. In our trial, inoculations with VN induced characteristic wilting symptoms only in Ailanthus (used as side control of the inoculum), while vines remained asymptomatic, thus indicating a high degree of host specificity of VN. Limited or no impact was detected on the physiology of the non-target V. vinifera. Furthermore, the LMA and biomass measured in the two experimental groups were not different. Although fungal colonisation induced vascular discolouration in both species, the fungus could only be re-isolated from dying Ailanthus but not from vine tissue. Results suggest that V. vinifera cv Grüner Veltliner is resistant to the applied VN isolate. However, the susceptibility and physiology of additional grapevine cultivars, as well as other native woody species to VN, should be studied before promoting large-scale use of the biocontrol agent

X-ray microtomography observations of xylem embolism in stems of Laurus nobilis are consistent with hydraulic measurements of percentage loss of conductance

Drought-induced xylem embolism is a serious threat to plant survival under future climate scenarios. Hence, accurate quantification of species-specific vulnerability to xylem embolism is a key to predict the impact of climate change on vegetation. Low-cost hydraulic measurements of embolism rate have been suggested to be prone to artefacts, thus requiring validation by direct visualization of the functional status of xylem conduits using nondestructive imaging techniques, such as X-ray microtomography (microCT). We measured the percentage loss of conductance (PLC) of excised stems of Laurus nobilis (laurel) dehydrated to different xylem pressures, and compared results with direct observation of gas-filled vs water-filled conduits at a synchrotron-based microCT facility using a phase contrast imaging modality. Theoretical PLC calculated on the basis of microCT observations in stems of laurel dehydrated to different xylem pressures overall were in agreement with hydraulic measurements, revealing that this species suffers a 50% loss of xylem hydraulic conductance at xylem pressures averaging 3.5 MPa. Our data support the validity of estimates of xylem vulnerability to embolism based on classical hydraulic techniques. We discuss possible causes of discrepancies between data gathered in this study and those of recent independent reports on laurel hydraulics