Biodiversity is defined as the variety of life on earth, comprising genetic diversity, species diversity and ecosystem diversity. It is crucial for human life since it is the foundation of functioning ecosystems, which provide necessary ecosystem services. In the past centuries, human activities have altered the world’s ecosystems and led to massive losses in biodiversity. To counteract the ongoing decrease in biological diversity therefore is a key issue in conservation. The reintroduction of native plant species is a common and useful practice in restoration and approaches range from reintroduction of plant populations to the creation of whole plant communities.
Chapter One addresses the research question of this thesis and introduces the sci-entific context. The importance of biodiversity and its ongoing loss is described. Fur-ther, plant species reintroduction as an effective procedure to increase biodiversity on population and community level is presented with respect to the impact on genetic variation within restored populations and among natural and restored populations of herbaceous target species.
Chapter Two focuses on the genetic diversity within and the genetic differentiation among populations of the rare and endemic plant species Cochlearia bavarica. Am-plified Fragment Length Polymorphisms (AFLP) were used to analyze the genetic variation of 32 remnant populations of the species. With respect to conservation management, recommendations are presented to increase the success of future population reintroduction and reinforcement.
In Chapter Three the restoration of species-rich grassland communities by the transfer of green hay and threshed plant material was investigated. Species diversity and composition on restoration sites compared to their corresponding source sites was analyzed. Further genetic variation within and among populations on source and restoration sites of the common grassland species Knautia arvensis and Plantago lanceolata was examined using AFLPs. The study revealed no significant differences among source sites and their corresponding restoration sites, neither in species di-versity and composition nor in genetic variation within populations of the two plant species. Only marginal differences in genetic variation among populations on source sites and their corresponding restoration sites could be found. The transfer of local plant material is highly suited to preserve species composition of species-rich grass-lands and the natural genetic pattern of typical grassland plant species on a small geographical scale.
Chapter Four and Five focus on the restoration of species-rich grassland communi-ties by sowing commercially produced regional seed mixtures. Even though this is a common approach in restoration ecology today, there are only few long-term studies investigating if local seed mixtures can actually be applied successfully to restore species-rich grassland communities. Further, it is often questioned whether commer-cially produced seed material is viable enough to establish vital populations and how the sowing may affect genetic variation of neighboring natural populations. Hence, the outcome of a large-scale grassland restoration project which started about 15 years ago in south-eastern Germany provides more information about the impact of this restoration measure on species diversity and genetic variation of plant species and populations on restored sites.
The success of applying local seed mixtures to restore species-rich grasslands was analyzed within Chapter Four. Local seed mixtures can be used successfully to re-store species-rich grassland communities in practice: of all species that were present in the local seed mixtures 62 % were contained in the current and on average cov-ered up two thirds of the total vegetation cover. Moreover, restoration can be im-proved by using specific seed densities and species that are ecologically more suita-ble to restored sites.
In Chapter Five deal with the impact of the restoration management on genetic vari-ation within and among restored and natural populations of typical grassland species. Genetic variation of three common plant species (K. arvensis, Silene vulgaris and P. lanceolata) was analyzed with AFLPs. The study revealed that using commercially produced seed mixtures in restoration caused no decease in genetic diversity within restored populations of common grassland species but did not match exactly the lo-cal genetic pattern of the study species. However, commercially produced seed ma-terial reflects the genetic potential of an entire seed transfer zone and provides seeds for the reestablishment of genetically viable populations.
Finally, in Chapter Six the results of the four main chapters are reviewed in the con-text of nature conservation. Benefits and disadvantages of species (re)introductions are discussed. Recommendations are given to enhance the success of species reintroduction in restoration projects
