Restoration of Threatened Arable Weed Communities in Abandoned Mountainous Crop Fields

Arable fields maintaining species-rich weed communities have almost disappeared from European mountain areas due to their abandonment or replacement by extensive grazing systems during the last decades. The restoration of arable weed communities have become an important issue in these habitats which have a large potential to contain rare and threatened (red-list) species. In a site in the Swiss Alps, formerly managed for crop production, we investigated in experimental plowed plots the 1-year effects of fertilizing, sowing a mixture of arable weed species and sowing a crop species (triticale) on the natural regeneration (species richness and cover) of arable weed and non-weed species. The high number of newly appeared arable weed species, of which four were red-list species, indicated that propagule availability was still important after about 50 years of arable field abandonment. Plowed plots which did not receive any treatment and those with fertilization alone favored the regeneration of both wild weed and non-weed species. The crop species limited, but did not inhibit, the recovery success of weed and non-weed species and this negative effect tended to be higher under fertilization. Sowing of arable weed seeds decreased the natural regeneration of both weeds and non-weeds in the absence of triticale. Our results show that plowing is a promising method to successfully restore the weed community in abandoned arable mountain areas. Moreover, the sowing of weed species in combination with a crop species might produce sustainable food and restore and maintain the diversity of threatened arable weeds at the same time.