Identification of plant ranges adapted
to water limited conditions of green
roofs : a case study from France
Olivier Damas, Plante et Cité, ([email protected])
Johanna Donvez, EPLEFPA Vert d’Azur Antibes, ([email protected])
Denis Ferrando, EPLEFPA Vert d’Azur Antibes, ([email protected])
Alain Ferre, Arexhor Pays de la Loire, ([email protected])
Philippe Marqueyssat, Tecomah, ([email protected])
Pierre Delhommeau, EPLEFPA Lyon-Dardilly-Ecully, ([email protected])
Abstract
Green roof plant range is dominated by Crassulaceae and
particularly the Sedum genius. The aim of this project is to
determine what new diversification plants are able to
tolerate extensive green roofs conditions in France. Thus an
experimental system tests plants in four different climatic
regions.
The assess focuses on plant behaviour, soil moisture, climate
and global biodiversity monitoring. Sixty three different taxa
were or are currently investigated. Many of them have
already given good results and can be used for operational
green roofs. A first rough observation of the biodiversity shows
a potential for green roofs to be one of the supports of
ecological corridors.
Keywords: plant diversification, drought tolerance, green roofs, water, growing
media
Background
Industrial Context
Surfaces of green roof are becoming more and more important in France like in
many other countries. On the one hand, almost all of the green roofs installed in
France are based on the same plants type: Sedum and Crassulaceae. This
limited range of plant options limits consequently the number of industrial actors
and prospects.
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Many plant diversification options exist in the international literature but mostly
for climates in USA, Canada, Great Britain and Germany having most of the
time shorter dry periods in summer (i.e. number of days without rainfall) than in
France (Dunett 2008, Snodgrass 2008, Lasalle 2008). Moreover, more and more
often, green roofs planted with Crassulacae in the southern third of France are
installed with irrigation.
On the other hand, local government parks services and landscaping
companies are confronted to economic, environmental and society challenges
for the creation and management of green spaces (increase of surfaces to
manage with identical or decreasing means, societal expectations and needs
for urban green spaces, environmental and ecological functions of green
spaces).
Problem
Professionals need green roofs with a greater diversification potential but also
limiting inputs (water and labour), in a word, an autonomous and ecologically
functional system. An experiment plan has been developed in four different
climatic locations in order to identify plants adapted to dry and specific
conditions of green roofs in different places in France. These plants have to be
grown with the most extensive management way possible, without any water
input, and limiting as much as possible the maintenance labour time.
Learning Objectives:
•
Is it possible to grow greenroofs anywhere in France without any watering?
•
Is it possible to grow something else than Crassulaceae plants?
•
What are the plants making that possible?
•
What is the potential of plant diversification in different part of France?
•
Characterisation of the green roof environment : fauna and flora monitoring
Approach
The experiment takes place at four different places (Fig.1). Planted plots are on
real roofs or are reconstituted on the ground:
-
Angers and Antibes since spring 2008 with 20 cm deep
Jouy-en-
growing media ;
-
Lyon and Jouy-en-Josas (Paris peri-urban suburbs) since Anger
autumn 2009, with respectively 15 cm and 10 cm deep
growing media.
World Green Roof Congress, 17-18 September, London Page 2
Lyon
Antib
Figure 1: The four experiment sites in France
The different types of climates are the followings (Fig. 2):
-
Angers: Oceanic – mild winter, cool or hot summer;
-
Antibes: Mediterranean – mild winter, hot or very hot summer, long dry
period in summer;
-
Lyon: Semi continental – very cool winter, hot summer;
-
Jouy-en-Josas: Semi ocenanic – cool winter, cool or hot summer.
120
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Annual rainfall = 702 mm
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Rainfall (mm)
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Rainfall (mm)
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Annual rainfall = 732 mm
Jouy-en-Josas 1979-2009
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Lyon 1979-2009
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Annual rainfall = 840 mm
Rainfall (mm)
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Average temperature (°C)
Antibes 1979-2009
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Rainfall (mm)
Average temperature (°C)
Angers 1979-2009
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Annual rainfall = 682 mm
Figure 2: Climate description for the different experiment sites (30 years average
values)
Analysis
Monitoring
The monitoring focuses on the plant (growth, coverage, flowering, root profile),
climate (rainfall, potential evapotranspiration, air and soil temperatures, wind
speed) and soil water availability (Watermark tensiometry sensors). The
behaviour of each taxon is assessed and compared to a weak drought
tolerance plant control (Dianthus carthusianorum) and a high drought
tolerance plant control (Sedum sediforme). No irrigation is practised, except for
first weeks after planting and if the Sedum control shows a sign of wilting.
The monitoring involves also a simple biodiversity dynamics of the flora and
fauna: colonisation from indigenous plants, from seedlings and cuts of planted
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taxa, entomo and macro fauna. Climatic conditions are assessed and
compared with the average values of the last thirty years.
For each site, eight species and the two plant controls are tested every year for
a period of two years. The size of the experiment unit is 1m². Each plant modality
is repeated 6 times the first year and 3 times the second year. Three repetitions
are rooted up after 1 year for root profile assess.
Growing media
The growing media is the same for all the experiment sites: 70% pouzzolane
3/6 mm (volcanic material), 20% blond peat, 10% black peat. The depth of
growing media varies for the different sites : 20 cm at Angers and Antibes, 15 cm
at Lyon, 10 cm at Jouy-en-Josas.
Plant material
Every taxon tested in this experiment is mentioned in the following table. The
experiment has started in 2008 and will last for several years. Then, new plants
will be tested:
Angers
2008
2009
2009
2010
2010
2011
Acaena novaezelandiae
Aethionema
grandiflorum
Alyssum montanum
Calamintha
grandiflora
Cotula hispida
Erigeron glaucus
Erodium manescavii
Gypsophila
cerastoides
Antennaria dioica
Callirhoe involucrata
Draba aizoides
Hyssopus officinalis
Oenothera speciosa
Petrorhagia saxifraga
Teucrium chamaedrys
Thymus
pseudolanuginosus
Trifolium repens
Geranium endressii
Leptinella squalida
Rubus arcticus (syn.
acaulis ou stellatus)
Linum flavum
Potentilla nepalensis
Sedum lydium
Phuopsis stylosa
Antibes
Achillea umbellata
Centaurea bella
Convolvulus sabatius
Delosperma cooperi
Iris lutescens
Myoporum parviflorum
Rosmarinus officinalis
Sedum gypsicola
Helicrysum italicum
Scabiosa cretica
Salvia chameadryoides
Antirrhinum hispanicum
Dianthus plumarius
Dorycnium hirsutum
Dorycnium pentaphyllum
Lavandula angustifolia
"Luberon"
Senecio cineraria
Helianthemum
lavandulifolium
Helichrysum stoechas
Sedum ochroleucum
Satureja montana
Thymus serpyllum
Lyon
Jouy-en-Josas
/
/
/
/
Silene schafta
Achillea umbellata
Phlox subulata
Erinus alpinus
Gypsophila repens
Duchesnea indica
Hieracium pilosella
Delosperma cooperii
Anthemis tinctoria ‘Kelwayi’
Armeria juniperifolia
Filipendula vulgaris
Potentilla nepalensis
‘MissWillmott’
Geranium cinereum ‘Purple
pillow’
Dryas octopetala
Artemisia schmidtiana
‘Nana’
Bouteloua curtipendula
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Dianthus carthusianorum
Sedum sediforme
Weak drought tolerance
control
High drought tolerance
control
Figure 3: The two plant controls (© Olivier Damas-Plante & Cité)
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Results and Business Impacts
Key Findings
Angers – July 2009 (© Olivier Damas-Plante &
Cité)
Antibes – June 2010 (© Denis Ferrando-Eplefpa
Antibes)
Jouy-en-Josas – June
Marqueyssat-Tecomah)
Lyon – May 2010 (© Pierre DelhommeauEplefpa Dardilly)
2010
(©
Philippe
Figure 4: View of the four sites in France
Climatic conditions
Climatic conditions have been usual or stronger than usual conditions in terms of
frost and drought. Thus we obtained the optimal selection conditions.
Summer drought conditions are particularly extreme at Antibes, with a very
weak total rainfall between 10th of June and 15th of September (more than 3
months): 43 mm in 2008, 16 mm in 2009.
Watering happened only once during the whole program, in August 2009 at
Antibes when the Sedum control showed a significant sign of wilting.
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Plant results
Angers
After two complete years of experiments, Acaena novae-zelandiae,
Aethionema grandiflorum, Alyssum montanum, Erigeron glaucus, Gypsophila
cerastoides, and Sedum sediforme show a high tolerance to drought. With only
one season of survey, Antennaria dioica, Hyssopus officinalis, Petrorhagia
saxifraga, Teucrium chamaedrys and Thymus pseudolanuginosus present results
very encouraging.
Callirhoe involucrate, Draba aizoides and Oenothera speciosa tolerate also well
drought conditions of the first year of experiment but this tolerance seems to be
limited. Further assess will confirm this first result or not. Calamintha grandiflora,
Cotula hispida and Erigeron glaucus, did not tolerate roof drought conditions
well and died. Erodium manescavii use is not validated because of its strong
root system presenting a potential risk for roof waterproofing systems. Dianthus
carthusianorum confirms its weak drought tolerance but survives at Angers.
Nevertheless its use is not recommended because of its high colonization
potential by spontaneous seeding.
Antibes
Four species deals well with Mediterranean drought conditions without any
irrigation: Delosperma cooperi, Iris lutescens, Sedum gypsicola and Sedum
sediforme. Many species died almost completely with just very few survivors:
Salvia chaeadryoides, Antirrhinum hispanicum, Achillea umbellata. Finally, other
species died completely: Myoporum parvifolium, Convolvulus sabatius,
Centaurea
bella,
Helicrysum
italicum,
Scabiosa
cretica,
Dianthus
carthusianorum and Dianthus plumarius.
Dianthus carthusianorum and Dianthus plumarius perform their complete
vegetative cycle before to die, maintaining and developing their population on
the experimental plot by seeds. Sedum gypsicola presents a strong power of
colonization on the "sterile" zone (inert media surrounding the plot area
composed with gravels).
Lyon and Jouy-en-Josas
The experiment began just last autumn 2009 for these two sites. No results have
been obtained yet at the writing time of this paper. Results will be available
later.
Biodiversity approach
In comparison with usual inert roofs, richer presence of entomofauna, bird
fauna, amphibias and batrachians has been observed on both sites of Angers
and Antibes.
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Business Impacts
These results open new business perspectives. The diversification potential with
innovative plant options creates new prospects for nurseries industry, and
extends the green roofs market to additional products and technical
opportunities. The knowledge capitalized on technical possibilities and
functioning enables to develop key-tools for the understanding and the
knowhow of green roofs design and maintenance.
Conclusions
This experiment program deals with a plant diversification research in extensive
green roofs. This project still in progress has already permitted to identify (i) a
wider range of plants for several climatic locations in France, (ii) new esthetical
options and plant products, (iii) an increased potential of biodiversity on green
roofs, (iv) new landscaping techniques knowledge. In addition to the current
assesses, the program evolves also towards a thinking on the proper methods to
establish plants on roofs (containers, seedbeds, micro clods, etc.) and on the
composition of growing media.
Key Lessons Learned:
•
Growing green roofs without any irrigation is possible in France, even in the
Mediterranean area
•
A wider range of plants used for roof greening in France is possible, developing
esthetical benefits of green roofs in very urbanised environments
•
The diversification potential is not the same through the country. It is much lower
in the Mediterranean area for example
•
A first and rough evaluation demonstrate that green roofs increase the
biodiversity
•
63 taxa tested or currently tested; 13 taxa validated among the 41 tested at
least one year long
References
Dunnett, N., and Kingsbury, N. (2008) Toits et murs végétaux. Ed. Editions du
Rouergue. 325 p.
Lasalle, F. (2008) Végétalisation extensive des terrasses et toitures. Ed. Le
Moniteur. 244 p.
Snodgrass, E.C., and Snodgrass, L.L. (2008) Guide des plantes de toits végétaux.
Ed. Editions du Rouergue 201 p.
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Authors’ Biographies
Olivier Damas
2008-2010: Plante & Cité, urban plant engineering
experiments (agronomy, urban soils, plant diversification)
and
2006-2007: CIRAD, Experiment program on cover crops as an
alternative for herbicide in tropical citrus orchards
2005: Biomasse Normandie, organic waste valorisation surveys
2000-2004 : Master at INH, Angers (national college on horticulture
and landscape design)
Johanna Donvez
Project leader Partnership - Villa Thuret
AgroParisTech, Master of Engineering - Forestry
Denis Ferrando
Coordinator-teacher for ITIAPE (School for engineering techniques
in
landscape creation)
Professor of biology-ecology for the French Ministry of Agriculture
Research Professor conducting experiments for the Vert d’Azur
Education
and Vocational Training Institution
PhD in Mediterranean biogeography
Alain Ferre
Technical manager of the experimental center AREXHOR Pays de
la Loire
Philippe Marqueyssat
Horticultural techniques lecturer for 30 years at TECOMAH, School
of Environment affiliated to the Paris Chamber of Commerce
Vocational training teacher for urban flowering in the local
authorities of Paris Region
Technical manager of the iris collection and the international
FRANCIRIS competition
Pierre Delhommeau
2010: Sustainable development manager - Landscape school
EPLEFPA Lyon-Dardilly-Ecully
2009: Person in charge green spaces, Switzerland
2008: Technical trainer (BTS - two year technical degree)
2005/2008: Missions at the Zoo of Lyon and urban parks
maintenance service of Lyon.
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