Restoration of landscape scars in former military areas: vegetation recovery in relation to fine-scale environmental heterogeneity

In a large-scale restoration project, we studied the spontaneous vegetation development after the elimination of landscape scars in a former military training area in Hortobágy National Park, Central Hungary. After the removal of approximately 40,000 unexploded ordnances the bomb-craters have been soil-filled, leaving large unvegetated surfaces on a total area of 4,000 hectares in 2017. These research settings provided a unique opportunity to study the effects of environmental heterogeneity on vegetation recovery in a study system, where soil salt content and micro-topography are the major drivers of vegetation patterns. Due to the mixing of soil layers, there were patches with extremely high salt content on the recovering surfaces and several red-listed halophyte plant species, established from the seed bank already in the first year after restoration. We found that the diversity of plant species was the largest in the first year. We detected a significant increase in the vegetation cover and the cover of perennial species from the first year to the second. In the subsequent years the recovery of the vegetation continued but slowed down from the second to the third year. By eliminating landscape scars, the restoration project was successful in increasing the area of alkaline grasslands at the landscape scale and providing grazing lands for local farmers.