Wiederansiedlung gefährdeter Arten der Pfeifengraswiesen in Luxemburg.

Today, wet meadows and their typical flora are in sharp decline. In Luxembourg, these include characteristic species of Molinion meadows such as Oenanthe peucedanifolia, Scorzonera humilis, Stachys officinalis, Succisa pratensis and Serratula tinctoria. To support such species, the nature conservation syndicate SICONA has practiced propagation and in situ plantation since 2012. The aim of this study was to assess the long-term success of such reintroduction measures. We examined the establishment of the five target species four to nine years after reintroduction. Three questions were addressed: (1) how successful was the reintroduction, (2) how did vegetative and generative traits - as key indicators of vitality and fitness - differ between newly established and extant populations, and (3) what influence did site conditions have on establishment success? For this purpose, survival, reproduction, and establishment rates were determined on six reintroduction plots per species. Vitality and fitness in newly established (introduction sites) and sites with natural populations (reference sites) were compared using phenometric and reproductive traits. Ellenberg indicator values determined from vegetation surveys were applied to characterize site conditions. For three target species, Stachys officinalis, Succisa pratensis, and Oenanthe peucedanifolia, the newly planted populations showed successful establishment and reproduction, underlined by establishment rates between 327 and 763%. In Serratula tinctoria, one quarter of planted individuals survived, while little regeneration occurred. For these four target species and in 60% of all 30 reintroduction plots population size increased. Only for Scorzonera humilis establishment was less successful, averaging 7.5%. Whilst, for all five species, most of the newly planted individuals reached a vitality similar to that of extant populations, their reproductive fitness usually ranged lower. Comparison of Ellenberg indicator values illustrated that habitat conditions for the target species at most of the restoration sites well matched with conditions at the reference sites. In some introduction sites, indicator values suggest higher base and nitrogen supply and a lower water availability than on the long existing sites. Weaker development of the target species in such sites proves the great importance of suitable site conditions for restoration success. Nursery propagation and on-site plantation were demonstrably a well-suited method to strengthen declining populations of threatened Molinion meadow species and it seems likely that newly established populations can remain viable in the long term. Nevertheless, not all target species showed successful establishment. Serratula tinctoria barely managed to reproduce and for Scorzonera humilis both survival and reproduction rates were very low. Species-specific factors such as insufficient genetic exchange or over-aging of donor populations are discussed as potential causes. In addition, reintroduction can also be constrained by practice-related factors such as the shortage of sites suitable for stenoecious species and the lack of suitable sites for re-wetting. This study also demonstrates the importance of monitoring the long-term success of in situ conservation measures, which has received insufficient attention in restoration practice so far. [ABSTRACT FROM AUTHOR]