Species suitability on clay unknown
#00075
The Sundgau's heavy clay soils, which become rock-hard and impenetrable when dry, are very different from the sandy or loamy soils where most candidate replacement species have been tested. There is no published guidance on which FAA-recommended species will actually succeed on Sundgau clay.
Parent issue
#00072 Plant climate-adapted species
Tags
Sustainable Development Goals
Description
The FAA program's candidate species list is drawn from regional and national recommendations developed for the Grand Est and France as a whole. But the Sundgau's defining feature is its clay soils — soils that hold water in wet periods but seal up and crack in dry ones, cutting tree roots off from any moisture that does fall. Beech historically thrived on these soils, which is why it was so dominant; the species being trialled as replacements have mostly not been tested on equivalent ground.
A 2023 study documented widespread beech dieback specifically on Sundgau soils, but no equivalent study has tracked how oak, cedar, or other proposed alternatives perform on the same ground. Foresters in Altkirch and elsewhere are planting these species on faith. If the choices turn out to be wrong, the cost is another generation of failed forest — and the time loss is measured in decades, not years.