Does shallow substrate improve water status of plants growing on green roofs? Testing the paradox in two sub-Mediterranean shrubs

Tadeja Savi (Corresponding Author), David Boldrin, Maria Marin, Veronica Lee Love, Sergio Andri, Mauro Tretiach, Andrea Nardini

Research output: Contribution to journalArticlepeer-review

21 Citations (Scopus)


Green roofs are artificial ecosystems providing ecological, economic, and social benefits to urban areas. Recently, the interest in roof greening has increased even in Mediterranean and sub-Mediterranean areas, despite the climatic features and reduced substrate depth expose plants to extreme stress. To limit installation weight and costs, recent green roof research aims to reduce substrate depth, which apparently contrasts with the need to maximize the amount of water available to vegetation. We monitored water status, growth, and evapotranspiration of drought-adapted shrubs (Cotinus coggygria, Prunus mahaleb) growing in experimental green roof modules filled with 10 or 13 cm deep substrate. Experimental data showed that: (a) reduced substrate depth translated into less severe water stress experienced by plants; (b) shallower substrate indirectly promoted lower water consumption by vegetation as a likely consequence of reduced plant biomass; (c) both large and small rainfalls induced better recovery of water content of substrate, drainage, and water retention layers when shallow substrate was used. Evidence was provided for the possibility to install extensive green roofs vegetated with stress-tolerant shrubs in sub-Mediterranean areas using 10 cm deep substrate. Green roofs based on the combination of shallow substrate and drought-tolerant plants may be an optimal solution for solving urban ecological issues.

Original languageEnglish
Pages (from-to)292-300
Number of pages9
JournalEcological Engineering
Early online date7 Sept 2015
Publication statusPublished - Nov 2015

Bibliographical note

The present study was funded by the Fondo Europeo di Sviluppo Regionale POR FESR n. 54/2009/C. D. Boldrin and M. Marin were supported by EU and Regione Friuli Venezia Giulia (Fondo Sociale Europeo, Programma Operativo Regionale 2007-2013) in the frame of the project S.H.A.R.M. (Supporting Human Assets of Research and Mobility). Plant material was kindly provided by Regione Friuli Venezia Giulia, Servizio gestione forestale e produzione legnosa, Vivaio Pascul Tarcento. We are very grateful to G. Bacaro (Univ. Trieste) for invaluable help with statistical analysis.


  • substrate depth
  • water availability
  • drought stress
  • evapotranspiration
  • Cotinus coggygria
  • Prunus mahaleb


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