Embargoed until 2022-04-20
- Doctoral Thesis
Restoration of semi-natural grasslands is a top priority in European nature conservation strategies to counteract the drastic decline of biodiversity and ecosystem functioning. Although efforts to protect these threatened habitats have steadily increased, their ongoing loss could not be halted. Mild intervention methods often failed to re-establish the targeted grassland due to unsuitable soil conditions and the dominance of non-target species. High impact restoration methods, such as topsoil removal with and without seed addition, seemed to be much more successful in re-establishing nutrient-poor and species-rich grasslands. Yet, the success of grassland restoration was mainly evaluated via vegetation surveys as the sole property in the past. Other ecosystem properties, especially belowground biotic communities and soil properties, were generally neglected even after the soil had been heavily affected by restoration. Additionally, monitoring rarely covered periods of more than the first few years after restoration, mainly due to resource limitations. Therefore, long-term evaluations of restoration success spanning several decades are lacking. This lack of long-term evaluations resulted in conflicts between nature conservation (pro) and soil protection (contra) agencies as there is a disagreement with regard to the harm topsoil removal may cause to the system. Hence, there is urgent need to examine the ecological responses of biotic and abiotic, above- and belowground properties after topsoil removal, which I did in this PhD thesis. This knowledge not only advances basic research, but should also aid decision-making processes at the political and management level concerning ecological restoration. The study area in the Canton of Zurich is one of the few regions in Central Europe where various restoration intervention methods including topsoil removal were tested during the last 30 to 40 years. I re-visited i) a large-scale experiment using three different restoration methods of increasing intervention intensities established in 1995 and ii) an assembly of sites where topsoil was removed and target plant species applied at different times between 1986 and 2015. This provided me with the great opportunity to develop novel approaches for assessing the long-term success of various restoration methods. The objectives of this PhD thesis were to 1) assess the potential of different restoration methods of increasing intervention intensities to restore biodiversity, community composition and ecosystem functioning above- and belowground (Chapter 1 – 3), 2) test the suitability of multiple abiotic and biotic properties to accurately evaluate long-term restoration success (Chapter 3), 3) estimate cost-efficiency of these abiotic and biotic properties (Chapter 3), 4) study the temporal recovery of grasslands after topsoil removal (Chapter 4) and 5) suggest how monitoring of restoration success should be modified in the future for a holistic evaluation. I found that i) high impact topsoil removal methods outmatched lower impact methods such as mowing and biomass disposal, and ii) cost-efficient above- and belowground properties were better suited to assess restoration success compared to expensive properties. Combining vegetation structure, soil carbon storage and soil water holding capacity represented the best compromise between accuracy and cost-efficiency for assessing ecosystem multifunctionality and long-term restoration success. The first five to fifteen years after restoration seemed to be most important to determine restoration success, with above- and belowground properties recovering in parallel. The integration of soil biotic and functional criteria in monitoring and evaluating restoration outcome, as outlined in this thesis, represents an important step forward to improve our understanding on the long-term ecological responses at the community and the ecosystem level. Thus, the findings gained from this PhD thesis will help to develop more efficient restoration and monitoring tools and thereby support and facilitate enhanced global efforts to restore degraded or destroyed ecosystems. Show more
External linksSearch print copy at ETH Library
ContributorsExaminer: Buchmann, Nina
Examiner: Schütz, Martin
Examiner: Risch, Anita C.
Examiner: Bardgett, Richard D.
Subjectgrassland restoration; high-intensity measures; Long-term effects; above- and belowground properties; topsoil removal
Organisational unit03648 - Buchmann, Nina / Buchmann, Nina
Related publications and datasets
Is original form of: https://doi.org/10.1111/1365-2664.13400
Is original form of: https://doi.org/10.1002/eap.2133
Is original form of: https://doi.org/10.1002/eap.2271
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