Urban and peri-urban forests in the metropolitan area of Rome: Ecophysiological response of Quercus ilex L. in two green infrastructures in an ecosystem services perspective

https://doi.org/10.1016/j.ufug.2015.10.013Get rights and content

Highlights

  • Benefits provided by GIs in Mediterranean cities are impaired by stressful conditions.

  • Plant ecophysiology provides key functional parameters for ESs quantification.

  • Urban and periurban Forests contribute differently to regulating services.

  • Urban green management could substantially increase benefits from GIs.

Abstract

Green infrastructures (GI), such as urban forests, deliver ecosystem services (ESs) and benefits. Among ESs the amelioration of urban air quality through the removal of air pollutants deserves large attention owing to the positive impact on human well-being. Experimental data, as detailed descriptions of functional parameters, are needed for reliable quantification of ESs. The present study was carried out in the metropolitan area of Rome, considering an urban and a periurban forest. Both forests are dominated by Quercus ilex L., which has been chosen as target species for its wide natural distribution in the Mediterranean Basin, as well as for its widespread use in urban contexts. The two studied sites were characterized by different environmental stressor and forest management practices, resulting in different trends of leaf gas exchanges, photosystems functionality and plant water status. During spring, gas exchanges were lower in the urban than in the periurban forest, due to higher air temperature and vapor pressure deficit in the latter site. During summer, instead, in the periurban area the functionality of Q. ilex was affected by drought, which did not occur in the urban forest due to higher summer rainfalls as well as periodic irrigations. The water use efficiency was basically lower in the urban park, as well as the photosystems functionality. Differences in the intensity of the main phenological phases were also highlighted. Our results point out that the two GIs fulfill a complementary role in the ESs provision in the metropolitan area of Rome, in relation to the ozone removal and the resulting air quality improvement and climate regulation.

Introduction

Although hubs for development and human activities, urban areas threaten the environment and the ecosystem features in both urban and periurban areas (Elmqvist et al., 2013). The urban expansion has a consistent footprint, and it is a driver of land use and environmental changes (Churkina, 2008). Human settlements are a major cause for the extensive transformation and alteration of land covers, biogeochemical cycles, air quality and climate (Pataki et al., 2011, Janković and Hebbert, 2012). Several studies have reported that, owing to the higher connectivity among systems (Peters et al., 2008), environmental changes at local and regional scale may have a greater effect on vegetation than global change (Grimm et al., 2008a, Grimm et al., 2008b). The urban environment can be represented as an example of these phenomena. The change in surface energy balance, emission of greenhouse-gas, high concentration of gaseous pollutants and particulate matter (PM), are the main drivers for the local alteration of rainfall patterns (Cerveny and Balling, 1998) and promotion of the urban heat island (Hidalgo et al., 2008). These peculiarities of urban areas may enhance the stress pressure on the vegetation functionality in the form of abiotic and biotic factors (Dale and Frank, 2014), or specifically as water stress (Ugolini et al., 2015). Urban pollution is becoming a large concern for human health and thus lately the urban green is being appreciated for its ability to abate pollutants (Manes et al., 2012, Nowak et al., 2013), but also for regulating the urban microclimate (Sung, 2013). The concept of green infrastructure (GI) was introduced to deal with the high complexity and dynamism of urban areas. GI can be outlined as a network of natural and semi-natural areas (Tzoulas et al., 2007), where combinations of different functions (ecological, social and economics) are conserved and coexist, at different spatial scales, from urban centers to peri-urban areas. A functional understanding of vegetation responses to urbanization would promote the planning of multifunctional GI in order to enhance and better manage their capacity to provide the desired Ecosystem services (ESs). GI can give different contribution to the same ESs because of differences in functional vegetation types and different typology of green spaces as corridor (i.e. tree line or street trees), patch (i.e. grass field, isolated trees), matrix (i.e. urban and peri-urban forest) (Gill et al., 2007). Moreover the quality and quantity of the ESs provided by vegetation depend on the urban setting in which the GIs are located (i.e. built-up vicinity and non-urban counterparts, Janković and Hebbert, 2012). Describing the GI properties (structure, processes and ecophysiological functioning) is the first essential step to reach a reliable ESs estimation (Bastian et al., 2012). In the quantification of regulating services, the mass and energy exchange between vegetation and atmosphere has a pivotal role (Calfapietra et al., 2013), since pollutant removal or climate mitigation are underpinned by how these functions change during the season and along a small spatial scale (Escobedo et al., 2011). In Mediterranean urban areas, where stress factors related to the urban environment overlap with already existing limiting factors (summer drought, high irradiance and temperature), seasonal trend of gas exchange can have great relevance in order to seek synthetic functional index that could be useful to adjust the general models used to ESs estimation (i-Tree, CITYgreen) for a Mediterranean urban areas. In this perspective vegetation phenology can supply useful information for modeling purpose, being strictly related to air temperature and moisture availability. Moreover, phenological survey allows for the identification of urban heat island and how vegetative active phases, that have an influence on ESs provisioning, can change in response to urban environment versus natural forested areas (Jochner and Menzel, 2015). The potentiality of urban forests for mitigating the impact of urban sprawl have been accounted in minimum part for European cities (Roy et al., 2012). Among the available literature only few works considered cities located in the Mediterranean area (Manes et al., 2012, Manes et al., 2014, Soares et al., 2011, Morani et al., 2014, Baró et al., 2015; Silli et al., 2015), and a lack of information about how stressful conditions might impair urban trees and forest benefits in these climatic area is still missing (Roy et al., 2012). Quercus ilex L. (Holm oak) is largely distributed in natural ecosystems and it also is commonly used for urban green in Mediterranean. Although this species is notably resistant to summer drought and oxidative stresses in general (Baquedano and Castillo, 2006, Fusaro et al., 2014), the urban environment might represent a challenging environment for a species with a conservative use of resources such as Q. ilex (Valladares et al., 2000). Actually, the urban environment itself affects tree vitality (Ugolini et al., 2012, Savi et al., 2015). In this study we have compared the seasonal variation of key functional parameters between urban and periurban evergreen broadleaved forest, with the aim to quantify how the environmental differences and stress factors, that typify the two GI, affect the functionality of Q. ilex and consequently its capacity to provide ecosystem services such as the amelioration of air quality. We quantified (a) the magnitude of the seasonal variation of gas exchanges and photosystems functionality in each GI; (b) the environmental factors that act as major drivers of the GI functionality in the urban and periurban area. We tested the hypothesis that the periurban green infrastructure had higher functionality than the forest in the urban area, which has to cope with harsher environmental conditions, namely urban heat island and pollutants coming from different sources. The obtained results can give a contribution to implement the procedures currently used to quantify the Ecosystem Services provided by green infrastructures, and accordingly direct their management to best practices in a Mediterranean metropolitan area.

Section snippets

Studied sites

The studied sites were located inside an urban park in the northern part of Rome (Villa Ada), placed in the city centre and surrounded by an intense road traffic area, and in a periurban area (Presidential Estate of Castelporziano), located 25 km SW from the centre of Rome and just 1.5 km from the Tyrrhenian coast.

Villa Ada urban park (VA, urban forest), with an extension of 160 ha, is one of the largest urban parks in the Rome city center (Alessio et al., 2002). Artificial pastures, water bodies

Environmental condition

The analysis of the environmental parameters highlights that the differences between the two sites in terms of temperature, relative humidity and precipitation are more pronounced in 2013 than in 2014 (Fig. 1). In particular, in the urban area the temperature during the summer period rises up to 30 °C, whereas in CP the highest value of mean daily air temperature was around 26 °C. The relative humidity in the urban site decreases gradually during spring, reaching the lowest value of 40% in June

Discussion

In order to provide a reliable estimation of Ecosystem Services supply, a local scale analysis, as the one performed here in the metropolitan area of Rome, would be necessary, since the microclimatic variability and the spatial heterogeneity of the urban surface types are known to influence the energy balance of urban green, and thus the exchanges between vegetation and atmosphere. In particular, knowing the seasonal trend of gas exchange in urban and periurban vegetation, could a have great

Conclusions

Urban and Periurban Forests can contribute differently to the provision of those Ecosystem Services deriving from the exchanges between vegetation and atmosphere. Since the functional performance between the two green infrastructure changes during the seasons, it is necessary to pay attention in applying species generalized models to urban environment. In addition, the functions by which relationships between functional traits and regulating services are expressed could greatly change owing to

Acknowledgments

This research has been supported by the following grants: MIUR, Rome, Project PRIN 2010-2011 “TreeCity” (Prot. no. 20109E8F95); Ministero della Salute, Centro Nazionale per la Prevenzione ed il Controllo delle Malattie—CCM, Project: “VIIAS”; Program for Environmental Monitoring of the Castelporziano Presidential Estate, Accademia Nazionale delle Scienze detta dei XL (2010 and 2012 Grants); Sapienza Ateneo Research Project 2013 (Prot. No. C26A13E7JB). We thank the Scientific Commission of

References (62)

  • F.J. Escobedo et al.

    Urban forests and pollution mitigation: analyzing ecosystem services and disservices

    Environ. Pollut.

    (2011)
  • S. Fares et al.

    Simultaneous measurements of above and below canopy ozone fluxes help partitioning ozone deposition between its various sinks in a Mediterranean Oak Forest

    Agric. For. Meteorol.

    (2014)
  • S. Jochner et al.

    Urban phenological studies—past, present, future

    Environ. Pollut.

    (2015)
  • F. Manes et al.

    Estimates of potential ozone stomatal uptake in mature trees of Quercus ilex in a Mediterranean climate

    Environ. Exp. Bot.

    (2007)
  • A. Morani et al.

    Comparing i-Tree modeled ozone deposition with field measurements in a periurban Mediterranean forest

    Environ. Pollut.

    (2014)
  • D.J. Nowak et al.

    Modeled PM 2.5 removal by trees in ten US cities and associated health effects

    Environ. Pollut.

    (2013)
  • A.P. O’Grady et al.

    Constraints on transpiration of Eucalyptus globulus in southern Tasmania, Australia

    Agric. For. Meteorol.

    (2008)
  • S. Roy et al.

    A systematic quantitative review of urban tree benefits, costs, and assessment methods across cities in different climatic zones

    Urban For. Urban Greening

    (2012)
  • A.L. Soares et al.

    Benefits and costs of street trees in Lisbon, Portugal

    Urban For. Urban Greening

    (2011)
  • C.Y. Sung

    Mitigating surface urban heat island by a tree protection policy: a case study of The Woodland, Texas, USA

    Urban For. Urban Greening

    (2013)
  • K. Tzoulas et al.

    Promoting ecosystem and human health in urban areas using green infrastructure: a literature review

    Landscape Urban Plann.

    (2007)
  • F. Ugolini et al.

    Leaf gas exchanges and photosystem efficiency of the holm oak in urban green areas of Florence, Italy

    Urban For. Urban Greening

    (2012)
  • A.F. Armstrong et al.

    On the developmental dependence of leaf respiration: responses to short-and long-term changes in growth temperature

    Am. J. Bot.

    (2006)
  • O.K. Atkin et al.

    The crucial role of plant mitochondria in orchestrating drought tolerance

    Ann. Bot.

    (2009)
  • O.K. Atkin et al.

    Response of plant respiration to changes in temperature: mechanisms and consequences of variations in Q10 values and acclimation

  • F.J. Baquedano et al.

    Comparative ecophysiological effects of drought on seedlings of the Mediterranean water-saver Pinus halepensis and water-spenders Quercus coccifera and Quercus ilex

    Trees

    (2006)
  • C. Blasi et al.

    Carta del fitoclima dell’area romana (1:100.000)

    Inf. Bot. Ital.

    (2001)
  • C. Calfapietra et al.

    Removal of ozone by urban and peri-urban forests: evidence from laboratory, field, and modeling approaches

    J. Environ. Qual.

    (2015)
  • R.S. Cerveny et al.

    Weekly cycles of air pollutants, precipitation and tropical cyclones in the coastal NW Atlantic region

    Nature

    (1998)
  • A.G. Dale et al.

    The effects of urban warming on herbivore abundance and street tree condition

    PLoS One

    (2014)
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