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Last update: May 2021

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GRAL Network (Altitudinal gradients)

GRAL Network (Altitudinal gradients)
Coordination :

Altitudinal gradients provide opportunities for the study of tree adaptation to environmental variations in highly contrasted climatic conditions.

The GRAL Network groups together experimentations on natural populations, provenance tests and reciprocal transplants along altitudinal gradients.

It includes five experimental sites (Pyrenees, Ventoux, Issole, Vésubie, Briançonnais) for four species (oak, beech, larch and silver fir). It includes three types of installations:

  • natural populations (both plots and transects) distributed along altitudinal gradients,
  • provenance tests distributed at different altitudes,
  • reciprocal transplants along altitudinal gradients (Transplants).

In-situ gradients:

  • Larch: 4 plots of 200 mature trees distributed along a gradient of about 1000 m (1350, 1700, 2000, 2300 m) with a weather station in each plot. Phenotypic (microdensitometric profiles 1967-2007) and genetic data (microsatellite markers and SNPs) are available.
  • Oak and Beech: 10 populations per species distributed along two Pyrenean valleys ranging from 100 to 1600 m in elevation. Each stand is equipped with a temperature sensor. Phenological and ecophysiological monitoring are featured.
  • Beech on the Mont Ventoux: 5 populations on the Ventoux gradient from 995 to 1485 m in elevation. Each plot has a temperature sensor. Phenotypic and genetic data are collected.
  • Fir: 15 populations spread over 3 gradients (Ventoux, Issole, Vésubie), from 995 to 1550 m in elevation. Each plot has a temperature sensor. Phenotypic and genetic data are collected.
  • Oak provenance tests: 3 common gardens composed of 10 oak populations are installed at 3 different elevations, 0, 800 and 1800m, for 1000 to 3000 trees per test site.


  • Larch: 120 clones from four different elevations(30 clones each for 1350, 1700, 2000 and 2300 m). Installations of clone comparison tests (5 ramets per clone) planted at the same four altitudes, in 2014 and 2015, near the plots where the multiplied adult trees are located.
  • Oak and Beech: 5 reciprocal transplant sites installed along the Pyrenean altitudinal gradient from 100 to 1600 m with three different populations per species.
  • Silver fir: 9 reciprocal transplant sites are located at low, medium and high elevations along 3 altitudinal gradients (Ventoux, Issole, Vésubie). At each of the sites, 57 families from continuous sampling along each altitude gradient are represented.
  • Beech: 2 reciprocal transplant sites are located at low and high elevation on the Ventoux altitudinal gradient. At each of the sites, 60 families from three populations along the gradient (low, medium and high elevations) are represented.
Services offer

Access to available data

Access to experimental sites for new measurements and observations



Operations and data access

These experimetal sites are particularly intended for the study of local adaptation and phenotypic plasticity. Access is determined according to the specific objectives and interests of each study. In all cases, access is supervised and researchers are assisted by the persons in charge of each experimental site.

Data access and cost

Costs are determined on a project-by-project basis.

Available measurements

For larch only, each clonal test plots has a mini weather station managed by Agroclim (INRAE). Other devices for monitoring environmental conditions and trees will be installed as soon as possible (probes, cameras, dendrometers).