1,721,087 research outputs found
Adaptive photosynthetic strategies of the Mediterranean maquis species according to their origin
No full textIn consideration of their origin the adaptive strategies of the evergreen species of the Mediterranean maquis were analysed. Rosmarinus officinalis L., Erica arborea L., and Erica multiflora L. had the lowest net photosynthetic rate (PN) in the favourable period [7.8±0.6 μmol(CO2) m-2 s-1, mean value], the highest PN decrease (on an average 86 % of the maximum) but the highest recovery capacity (>70 % of the maximum) at the first rainfall in September. Cistus incanus L. and Arbutus unedo L. had the highest PN during the favourable period [15.5±5.2 μmol(CO2) m-2 s-1, mean value], 79 % decrease during drought, and a lower recovery capacity (on an average 54 %). Quercus ilex L., Phillyrea latifolia L., and Pistacia lentiscus L. had an intermediate PN in the favourable period [9.2±1.3 μmol(CO2) m-2 s-1, mean value], a lower reduction during drought (on an average 63 %), and a range from 62 % (Q. ilex and P. latifolia) to 39 % (P. lentiscus) of recovery capacity. The Mediterranean species had higher decrease in PN and stomatal conductance during drought and a higher recovery capacity than the pre-Mediterranean species. Among the pre-Mediterranean species, P. latifolia had the best adaptation to long drought periods also by its higher leaf mass per area (LMA) which lowered leaf temperature thus decreasing transpiration rate during drought. Moreover, its leaf longevity determined a more stable leaf biomass during the year. Among the Mediteranean species, R. officinalis was the best adapted species to short drought periods by its ability to rapidly recover. Nevertheless, R. officinalis had the lowest tolerance to high temperatures by its PN dropping below half its maximum value when leaf temperature was over 33.6 °C. R. officinalis may be used as a bioindicator species of global change
The contribution of hedge in decreasing pollution levels in Rome
No full textOver the past two decades the anthropogenic greenhouse gas emissions have increased contributing to emphasize the effects of global climate change. Cities account for more than 71% of the energy related to global greenhouse gases which is expected to rise up to 76% by 2030. The problem is emphasized in those urban areas where vehicular traffic poses a major impact by emitting combustion gases. It has been hypothesized that CO2 emissions from road traffic worldwide will increase by 92% between 1990 and 2020 affecting the environment, health and economy. After air pollution, noise pollution reduces the quality of the urban environment because it affects human health unfavorably, both physically and psychologically. Noise pollution in cities is generated through different sources, such as road traffic, construction and commercial activities, industries and airports. In recent years, road traffic has played a dominant role in causing environmental noise. Among urban greening, hedges are ubiquitous elements of many public, commercial and residential landscapes. The mechanism of noise attenuation in plants is due to the capacity of leaves to absorb acoustic energy by transferring the kinetic energy which vibrates air molecules in a sound field to the vibration pattern of the leaves. The aim of this research was to analyze structural traits of different hedge types: Laurus nobilis L, Nerium oleander L, Pittosporum tobira (Thunb.) Aiton, and Pyracantha coccinea M. Roem. (Fig. 1) traditionally used for green infrastructure in Rome in order to quantify their CO2 sequestration and noise attenuation capability
Plant key traits conditioning evergreen shrub species responses in Mediterranean drought stress.
No full textLeaf expansion in Rhamnus alaternus L. by leaf morphological, anatomical and physiological analysis
No full textMorphological, anatomical and physiological traits of Rhamnus alaternus during leaf expansion were analysed. Bud break occurred when mean air temperature was 14.1 ± 1.2C, and it was immediately followed by the increase of leaf area and leaf dry mass. The highest leaf expansion rates happened during the first 22 days of the process. Leaf area and leaf dry mass reached the steadystate value 46 and 62 days after bud break, respectively. Net photosynthesis increased from bud break to full leaf expansion, and total chlorophyll content had the same trend, confirmed by the correlation between the two variables. Leaf dark respiration peaked during the first 11 days of leaf expansion, then decreased and reached a steadystate value 34 days after bud break. R. alaternus completed cell division and cell enlargement of the epidermal tissue 28 days after bud break, and the ones of the mesophyll tissue at full leaf expansion. The results underline that morphological, anatomical and physiological leaf traits in R. alaternus are indicative of a less sclerophyllous species (i.e. higher specific leaf area) compared with other Mediterranean evergreen species. Moreover, the higher fraction of mesophyll volume occupied by the intercellular air spaces, and the ability to end the leaf expansion process before air temperature might be a limiting factor, makes R. alaternus closer to the mesophyte species
Variazioni spaziali della struttura della macchia mediterranea e cambiamento climatico
No full textGli ecosistemi di tipo mediterraneo sono caratterizzati da un’elevata diversità di specie, che riflette le differenti strategie adattative, in risposta ai fattori di stress. Lo scopo della presente ricerca è stato quello di analizzare la struttura ed il modello di aggregazione delle specie della Macchia mediterranea, che si sviluppa lungo il tratto di costa presente all’interno della Tenuta di Castelporziano (S – SW di Roma). Lo studio è stato condotto in aree campione (ciascuna di 100 m2). In ciascuna area sono stati considerati i seguenti parametri: altezza e volume dei cespugli, volume della corona fotosintetizzante e indice di area fogliare (LAI). A livello di specie è stata analizzata la superficie fogliare totale per ciascun individuo e per ciascuna specie, la superficie fogliare specifica (SLA, data dal rapporto fra la superficie fogliare e il peso secco), la massa fogliare specifica (LMA, data dal rapporto fra il peso secco e la superficie fogliare), l’LTD (dal rapporto fra il peso secco e il volume fogliare) e la longevità fogliare. I risultati dell’analisi strutturale hanno permesso di suddividere i cespugli in tre classi dimensionali (piccoli, medi e grandi), di cui l’86 % è formato da un minimo di due ad un massimo di 10 specie. Tra le specie costituenti C. incanus è quella più frequente ed è presente in tutte le classi dimensionali, mentre E. arborea è quella a più bassa frequenza ed è esclusiva dei cespugli grandi. A livello fogliare sono stati osservati i valori più elevati di LMA e di LTD in E. multiflora, seguita da Q. ilex, P. latifolia, P. lentiscus e R. officinalis ed i più bassi in A. unedo, C. incanus ed E. arborea. Il cambiamento climatico in atto, potrebbe determinare un aumento dello stress da aridità, variando i rapporti inter ed intraspecifici, con ripercussioni sulla presenza e densità delle specie, che potrebbero essere messe precocemente in evidenza attraverso il monitoraggio strutturale degli arbusti della macchia
Shrub discriminant traits of the Mediterranean maquis
No full textMediterranean maquis is largely distributed in the Mediterranean Basin; it is dominated by evergreen sclerophyllous and drought-tolerant semi-deciduous
species. Mediterranean maquis structure results from a mixture of different shrub species making dense aggregation. Shrub composition reflects different species adaptive strategies to cope with stress factors, in particular with high air temperature and low water availability. Nevertheless, the structure of shrub species affects the microclimate beneath and around them, and it determines a heterogeneous light environment within the shrub crown affecting leaf morphology of the co-occurring species. Thus, the species aggregation and their position in a shrub depend on their light level adaptability and size. The main objective of this study was to analyse shrub structure of the Mediterranean maquis, developing along the Latium coast near Rome. Species aggregation pattern was also considered. The following parameters were analysed: total shrub and crown height, shrub crown volume, and LAI. Species measurements included: height, total leaf area per plant, specific leaf area (SLA), leaf area mass (LMA), leaf tissue density (LTD), and leaf longevity. Microclimate either within or around shrubs was measured. The results on the whole underlined the impact of shrub size on microclimate, determining a patchiness of microclimatic variations. Shrub
volume defined three different shrub sizes: small (1.9±1.5 m3), medium (13.1±4.8 m3) and large (34.9±8.8 m3). Most of the shrubs (86%) were formed by many species (up to a maximum of ten) and the other shrubs by one species. Among the most frequent species co-occurring in shrubs formation, Cistus incanus L. had the highest frequency, occurring mainly at the outermost part of the small shrubs. On
the contrary, Erica arborea had the lowest frequency occurring mainly in the large shrubs. Moreover, considering leaf morphological traits, the results underlined a low shade tolerance of C. incanus and a high drought tolerance of Phillyrea latifolia L. and Quercus ilex, characterised by the highest LMA, LTD and leaf longevity. Thus, considering the structural and morphological trait combination, associated also to a short leaf longevity, C. incanus should not be competitive in response to air temperature increase in the Mediterranean Basin. Variations in shrub structure might be the first response to global change affecting Mediterranean maquis species composition. Because of this understanding,
Mediterranean maquis shrub structure and species co-occurrence might help to forecast the effects of new climatic conditions on the Mediterranean-type ecosystems
Carbon dioxide concentration (CO2) in Rome in relationship with traffic density: the role of parks in air amelioration quality
No full textWe analyzed the atmospheric carbon dioxide (CO2) concentration in streets of different traffic levels and urban parks of different sizes in Rome. Rome represents an example of a mega‐city, where the urbanization process has been increasing over the last years, and many new sub‐urban areas have been built by scaling down free areas surrounding the city. CO2 concentration in Rome has been significantly increasing from 1995 to date due to the increase of private means of transportation. Our results underline that CO2 concentration in streets located in the city centre has a strong diurnal trend peaking in the first hours of the morning when the traffic is the highest, then decreasing at 3:00 p.m. and increasing again at 8:00 p.m., in relation to traffic level variations. It is attested also by the correlation between the two variables. The results underline the effect of buildings delimiting the urban streets on the CO2 concentration
Daily and seasonal variation of CO2 in the city of Rome in relationship with the traffic volume
No full textMeasurements of carbon dioxide (CO2) concentration carried out in the city of Rome showed an increase from 1995 (367 +/- 29 ppm mean yearly value) to 2004 (477 +/- 30 ppm, mean yearly value). The annual trend showed a peak in winter, 18% greater than the summer one correlated to traffic density (35 +/- 4 and 29 +/- 3 cars min(-1) mean winter and summer value, respectively). The weekly trend had the lowest values (414 +/- 19 ppm) during the weekends when traffic density was 72% reduced. The daily trend had a peak in the early morning when traffic was the highest and the atmosphere was more stable. The critical zones of the city (B zones) had 3.5% CO2 concentration higher than the park (D zone) and 18% more than the control zones (E zones). An increase of air temperatures from the surrounding zones (20.0 +/- 4.1 degrees C) to the centre of the city (28.9 +/- 1.2 degrees C, mean between A and B zones) was observed
Carbon sequestration by Quercus ilex L. and Quercus pubescens Willd. and their contribution to decreasing air temperature in Rome
No full textCarbon sequestration capability by Quercus ilex L and Quercus pubescens Willd., widely distributed in the city of Rome, and their contribution to decreasing air temperature were investigated. Crown volume is the most significant (p < 0.01) variable explaining variation of air temperature below the tree crown. Q. pubescens gives a higher contribution to decreasing air temperature during the hottest months, due to its inherent larger crown volume than Q. ilex (252 ± 19 and 533 ± 52 m3, respectively for the large size). Moreover, our results show the existence of a strong urban carbon dioxide dome with a peak CO2 concentration (on an average 432 ± 37 ppm) at polluted sites, 16% greater than at control sites. Total carbon sequestration is 84 ± 12 and 111 ± 9 Kg year-1 of CO2 for the small Q. ilex and Q. pubescens tree size, respectively, and 151 ± 10 and 185 ± 7 Kg year-1 of CO2 for the large Q. ilex and Q. pubescen tree size, respectively. Q. pubescens, by its higher total photosynthetic leaf surface area (39% higher than Q. ilex) and its higher mean yearly photosynthetic rates (48% higher than Q. ilex) seems to have a greater role than Q. ilex. However, taking into account the leaf longevity (i.e. 12 ± 3 months for Q. ilex and 4 ± 2 months for Q. pubescens), the evergreen species, by its continuous photosynthetic activity, contributes to reduce CO2 throughout the year, and in particular during the winter months, when traffic volume has a pick, than Q. pubescens. © Springer Science + Business Media, Inc. 2006
Atmospheric carbon dioxide concentration variations in Rome: relationship with traffic level and urban park size
No full textCarbon dioxide (CO2) concentration variations in Rome in the period January 2009 to December 2010 was monitored. Five representative sites (T sites) in the city centre with different traffic levels and urbanistic characteristics, and four urban parks (P sites) of different sizes were selected. The regression analysis underlines the significant (p a parts per thousand currency signaEuro parts per thousand 0.05) correlation between traffic levels and CO2 concentration. Considering the daytime CO2 concentration peak among T sites, Cerchi Street and Teatro Marcello Street, located in the city centre and closed by buildings, showed the highest traffic levels (85 +/- 3 and 63 +/- 2 cars min(-1), respectively) and the highest CO2 concentration (512 +/- 11 and 488 +/- 8 ppm, respectively). With regards to the considered P sites, those extending over the largest surface areas (Villa Pamphilj Park and Villa Borghese Park, 180 and 80 ha, respectively) characterized by large tree coverage (81 ha and 60 ha, respectively) had a significant lower CO2 concentration (404 +/- 9 ppm, mean value) than those extending over a small surface area (Villa Torlonia Park and Villa Celimontana Park, 14 ha and 11 ha, respectively). More efforts should be made to further reduce CO2 concentration in the cities in order to ameliorate ecosystem services related to urban parks
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