Departement für Biologie, Abt. Ökologie und Evolution
Universität Freiburg (Schweiz)
Creation of grassland habitat on ex-arable land
ESCHEN René
The intensive agricultural practice in the past century has led to a loss of extensively
managed, species-rich grassland habitats in the European landscape, due to the conversion
of such habitats into arable land. Although widely practiced, the success of Agri-Environment
schemes to create species-rich grassland habitats on ex-arable land is often disappointing.
This has been attributed to a number of site factors, including limited dispersal of late-seral
species, herbivore and pathogen attack, and a lack of trophic linkages. The first two studies
in this thesis aimed to assess factors that limit the creation of species-rich grassland habitat
on ex-arable land, specifically the roles of dispersal from adjacent late-seral grasslands and
the relative importance of soil and aboveground habitat on establishment of late-seral
species. The last two studies assessed carbon addition to the soil as a management tool to
reduce soil nitrogen availability and favor the establishment of late-seral species on ex-arable
land.
The results show that limited seed dispersal, and the dominance of early-seral plant
species as a result of high soil nitrogen content can be constraining factors for the
colonization of late-seral plant species on ex-arable land. Carbon addition appears to be a
useful management tool to reduce nitrogen availability in ex-arable soil, which increases
vegetation succession through species-specific growth responses. Based on these results, it
is recommended that seeds of late-seral plant species should be sown at the start of habitat
creation to overcome dispersal limitation. The addition of carbon should be used to reduce
competition from surrounding early-seral plant species, in order to promote the establishment
of the sown late-seral species. Furthermore, it is suggested that sites with abiotic soil
conditions correlated with potentially high mycorrhizal colonization of plant roots should be
selected for habitat creation.
Jury:
Prof. Heinz Müller-Schärer (Dissertationsleiter)
Dr. Urs Schaffner, CABI Bioscience Centre Switzerland, Delémont (Externer Gutachter)
Prof. Marcel G.A. Van der Heiden, Universität NL-Amsterdam (Externer Gutachter)
Prof. Fritz Müller, Leiter Biologiedepartement, Universität Freiburg Schweiz (Jurypräsident)