Evaluation von Maßnahmen zur Wiederansiedlung bultbildender Torfmoosarten auf wiedervernässten Hochmoorflächen
Year: 2024
Type: dissertation
Abstract: In view of the acute threat to raised bogs with their function as carbon reservoirs and habitats for rare animal and plant species, the restoration of such ecosystems is a high priority. However, after rewetting, most areas are not recolonised by the most important peat producers and carbon stores – the hummock-forming Sphagnum mosses. For this reason, the active reintroduction of these species by transplantation is an option. In the nature reserve “Totes Moor” in Lower Saxony transplantation was tested: In spring 2018, a total of 65 transplants of the Sphagnum species Sphagnum magellanicum, S. rubellum and S. capillifolium were planted on an area that was rewetted more than 30 years ago. The transplants were controlled in 2018, 2019 and 2021 and, as part of this study, in the winter of 2023/24. In addition to the transplants, the same area has also seen the independent re-establishment of hummock-forming Sphagnum species from surrounding areas. The aim of this study is to develop recommendations for optimised reintroduction of hummock Sphagnum mosses on degenerated raised bog areas. The focus lies on the site conditions, as these are of crucial importance for the growth of the peat mosses. Firstly, the current condition and development of the transplanted Sphagnum mosses were evaluated. The next step was to analyse the locations of the independently colonised mosses (wild finds) and compare them with the artificially selected locations of the transplants. In order to identify the wild finds, new study sites were established in the vicinity of the transplants. These were systematically searched for main peat-forming Sphagnum species. Dimensions, vitality and site conditions (location, water level and accompanying vegetation) were recorded for all transplants and wild finds. Six years after transplantation, 14 of 65 transplants, or 21.5 % were rediscovered. Despite this sharp decline, the total coverage of rediscovered transplants increased by 22% from 2021 to 2023/24. Correlating with this, the mean area size of the transplants has increased by 221 cm² to 407 cm² since 2021, while the mean height has decreased by 0.6 cm to 4.6 cm. Across all survey years, more of the transplants rediscovered in 2023/24 showed improved rather than reduced or stagnant vitality. However, the low rediscovery rate indicates that transplants in poorer condition must have died in recent years and therefore do not appear in the statistics. In the systematically searched zones, a high number (82 finds) of main peat-forming Sphagnum species were recorded. The species S. papillosum was most frequently represented with 65 finds, followed by S. magellanicum with 15 finds and S. rubellum with two finds. The site comparison showed that both transplants and wild-growing mosses grew most frequently in a lateral position to tussocks of the grass species Eriophorum vaginatum and Molinia caerulea. Sites with trees in the south were also recorded for both groups. The main difference was that the natural growth sites were also often close to ericaceous shrubs such as Calluna vulgaris and Erica tetralix, whereas such sites were not found for transplants. In contrast, sites at the top of tussocks were often chosen for transplantation, which were, regarding to the wild finds, only recorded for the resistant and drought-tolerant species S. papillosum. The identified differences between the sites correlated with the results of the accompanying vegetation: in the recording frames of the wild finds, the cover was higher for ericaceous shrubs and lower for tussock-forming grass species than in the recording frames of the transplants. At 23 cm below the capitulum, water levels of the wild finds were 10 cm lower than water levels of the transplants (13 cm below the capitulum). The analysis indicates that the establishment of hummock-forming Sphagnum mosses is influenced by a large number of complex interacting factors. The main causes for the low rediscovery rate of the transplants were identified as the persistent drought in 2018, 2020 and 2022 and subsequent heavy rainfall in 2023 in combination with unfavourable site selection. With regard to the 10 cm lower water levels of the wild finds, it can be assumed that these are related to their larger area and thus better ability to self-regulate water supply. For the reintroduction of hummock-forming Sphagnum mosses, it is recommended to use sites at the edges of tussocks, near ericaceous shrubs, with a small tree in the south and in transition areas between vascular plants and floating carpets of S. cuspidatum. With regard to the water level, locations with a high water level throughout the year and low fluctuations should be selected, taking into account the species-specific requirements of the respective Sphagnum species. The high rate of wild finds indicates that the area was not sufficiently investigated for the presence of hummock-forming Sphagnum species prior to transplantation. In order to save resources and make the most effective use of extracted donor material, it is therefore recommended that a comprehensive landscape ecology analysis with a floristic survey should be carried out in advance for subsequent reintroduction measures.
DOI: 10.15488/17966
Author: Wiedemann, Mareike
Language: English
Subfield: Ecology
Field: Environmental Science
Domain: Physical Sciences
SDG: Life on land
Open Access status: green
OpenAlex ID: W6925008720
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