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In June 2016, pursuit of the innovative greening of tramway track beds

In the context of its biodiversity programme and actions carried out under its "Dijon c’est ma nature ! J’agis pour la biodiversité" programme , the Dijon City and Urban Community, via its Science Gardens and Parks Department, together with the INRA/Agrosup/uBourgogne/CNRS Joint Research Unit for Agroecology, has since 2014 been conducting an innovative experiment on new ways to green its tramway tracks instead of using conventional grass.

. © INRA
Updated on 09/08/2016
Published on 06/08/2016

The first phase of the experiment started in the spring of 2014 with trials that notably focused on the mycorrhizal association of plant cover.  Indeed, a symbiotic combination of plants with mycorrhizal fungi multiplies tenfold the volume of soil explored by the roots of plants, facilitates their access to water, optimises the absorption of nutrients and helps to improve resistance to diseases.

A further experiment at a larger scale was started in June 2016:

The overall objective is to minimise the environmental impact  of maintaining grassed tracks (frequency of mowing, optimisation of water resources through a significant reduction in watering, etc.) and to thus favour urban biodiversity (linked to the ecological corridors of the urban green system).

The area will be seeded with a mixture containing varying proportions of "Microclover".  Why choose this plant?  Apart from its aesthetic qualities, it is valuable for pollinating insects.  It also ensures nitrogen "self-nutrition": clover fixes atmospheric nitrogen and returns it to a green space through its roots, thus improving soil quality in the confined areas of tram track beds.  And why a "micro" variety?  Its extremely small leaves should enable the plant to complete its life cycle without exceeding the maximum height of vegetation that will permit satisfactory running of the trams.  In addition, its roots are well suited to the shallow soil depth between tram tracks.

In practice, the experiment will focus on how these plants evolve in a specific area (approximately 800m2), when compared with other areas that are managed conventionally.  On this experimental portion of the track, watering and mowing will be very limited.  The follow-up protocol will enable the "microscopic" monitoring of growth rate, rooting depth, and the association with soil-borne beneficial fungi  etc.

Implementation of the 2016 experiment:

This experimental, scientific and technical work can only be carried out at night when the trams are no longer running.  After an initial phase when the current vegetation was removed during the night from the experimental area, seeding will take place in early June, performed by scientific and technical teams from the INRA/Agrosup/uBourgogne/CNRS Joint Research Unit for Agroecology, the Science Gardens and the city's Parks Department.

The project will be monitored for two to three years in order to obtain the initial results.  With 15 km of tram track currently under grass, 140,000 m2, the challenge of these experiments is not only ecological but also economic.

Scientific contact(s):