The steppe of La Crau is defined as a priority habitat by the E.U. Twenty-three hectares of this habitat were destroyed in 2006 during the construction of an underground pipeline. As it is known from previous studies, the steppe vegetation resilience is extremely low. Mitigation thus included ecological restoration experiments in order to find ways of accelerating steppe vegetation colonization on the buried pipelines.

The aims of the study were to

1) compare steppe vegetation with vegetation resilience on the 2006 buried pipeline, for which precautions to be taken during construction were specified (e.g. remove topsoil with seed bank, stockpile it during construction, spread it on top at the end of construction) and with vegetation resilience on a pipeline constructed in 1982 for which no particular precautions were taken. To do so, vegetation was sampled and soil analysed at three sites on each of the two pipelines (2006 and 1982);

2) to test the efficiency of hay transfer to reintroduce steppe stress-tolerant species in a Mediterranean ecosystem. A factorial experiment was set up at three sites to test the effects of grazing and habitat characteristics on hay transfer.

Expected results include i) low efficiency of the measures taken during pipeline construction due to construction delays; ii) differences between the 1982 and 2006 recolonization due to differences in soil compaction; iii) relative success of hay transfer as seedlings are already germinating two months after seeding. Conclusion will be drawn from vegetation sampling which will be carried out in spring 2006.