Restoring Populations of the Endangered Plant Scorzonera humilis : Influence of Site Conditions, Seed Source, and Plant Stage

Changes in land‐use have resulted in the decline of many formerly common plants of nutrient‐poor grasslands in Europe. Recently, extensification schemes have been applied at sites in order to restore former habitat conditions. However, the establishment of rare and endangered plants is often severely limited by the lack of propagules both in the seed bank and in the surrounding landscape. For such species deliberate introductions may be necessary to overcome these limitations. In a 7‐year study, we assessed the importance of gaps created by sod cutting, of plant stage, and of plant origin for the restoration of populations of Scorzonera humilis , a threatened long‐lived plant of nutrient‐poor, wet grasslands. The effect of gaps on seedling emergence and survival varied strongly among the 12 sites. Gaps increased survival at nutrient‐rich, but reduced it at nutrient‐poor sites. Remarkably, young plants grown for only 5 weeks in the laboratory and transplanted into the same sites had much higher survival than seedlings from seeds sown and there were no differences in survival between nutrient‐rich and nutrient‐poor sites. The field performance of the plants from the various populations of origin varied depending on the site into which they were transplanted, indicating genotype by environment interactions and genetic differentiation among populations, but there was no home‐site advantage. While sowing only succeeded in producing adult plants in five sites, transplanting succeeded at 10 sites. Our results suggest that transplanting young plants could be a much more effective and faster way to establish new populations than sowing seeds.