Joachim Schrautzer

Consequences of abandonment for a regional fen flora and mechanisms of successional change

Until the 1960s, species-rich vegetation on minero- trophic peaty soils (fen sites) were characteristic of the alluvial plains in Schleswig-Holstein (Northwest Germany). Today, many of these habitats undergo successional changes due to abandonment. Vegetation development after abandonment can be characterized as a sequence of different successional stages and described in terms of a successional model. Successional stage I includes grazed, mown and recently abandoned sites without dominants. Stages II and III are characterized by the dominance of highly competitive herbaceous species while stage IV consists of woody vegetation. Ca. 3000 phytosociological relev6s were assigned to the respective successional stages. Mean cover values were calcu- lated for 250 species of the regional fen flora and assigned to successional categories according to their changes in cover in the successional series. According to our results 141 species decrease during succession, while 100 species were restricted to early successional stages and 85 species increased. Aban- donment of all fen sites in Schleswig-Holstein will probably lead to the regional loss of 23 species of the fen flora. To identify mechanisms underlying successional change, the successional categories were correlated with life history traits and ecological requirements of the species. Results indicate that both light competition and limitation of sexual reproduction of small-seeded species might play a major role in the decrease and extinction of species during succession. Finally, conservation strategies for endangered species in a cultural landscape are discussed.

Denitrification in drained and rewetted minerotrophic peat soils in Northern Germany (Pohnsdorfer Stauung)

This study was conducted to assess the nitrogen removal potential of a minerotrophic peatland in Northern Germany, where hydrological conditions were partly restored in the beginning of the 1990s. Actual denitrification and the effect of nitrate (NO3-) and glucose additions on denitrification rates were determined in two flooded and one drained histosols in spring and summer 1998. In the flooded soils, denitrification was insignificant, but the drained field emitted significant rates. Additions of NO3- stimulated denitrification at all sites in spring and summer, whereas glucose additions had no effect. Low NO3- concentration in floodwater was obviously limiting denitrification in the flooded soils. In the drained soil, a coupled nitrification/denitrification might explain the low, but significant denitrification rates. No spontaneous production of nitrous oxide occurred in the flooded soils, whereas at the drained site an increase in spontaneous nitrous oxide concentration was measured during incubation in the summer samples. The suggested introduction of NO3- rich water from a stream flowing through the area would apparently induce denitrification in the flooded fields. (Less)

The Eidertal pasture landscape — Mire restoration and species conservation in a river valley of Schleswig-Holstein (northwest Germany)

In the valley of the river Eider (Schleswig-Holstein, northern Germany) a conservation management project was established in 1999. A large-scale grazing system has been set up and measures to rewet the area have been implemented.

Phytomasse- und Nährstoffdynamik sowie floristische Veränderungen von Knickfuchsschwanz-Flutrasen (Ranunculo-Alopecuretum geniculati Tx. 37) unter extensiver Nutzung

Summary In Schleswig-Holstein, the change of fen vegetation on peaty soils in the last decades is characterized by the development of Calthion vegetation types into species-poor Ranunculo-Alopecuretum geniculati caused by intensive agricultural use. Within the scope of the projekt, “Ecosystem Research in the Vicinity of Bornhoeveder chain of lakes”, the seasonal dynamics of phytomass and nutrients of extensively used Ranunculo-Alopecuretum stands were observed with respect to the possibility of regeneration to species-rich wet meadows. Floristic observations revealed that throughout a period of five years with annual haymaking without fertilization, no characteristic species of wet meadows have established themselves. This indicates that the environmental conditions have not effectively changed yet. The high production of above-ground stand phytomass indicates yet a good availability of nutrients, especially of nitrogen. The dynamics of nitrogen yield in the above-ground phytomass showed that in order to achieve an efficient impoverishment of soil nutrients, it is necessary to cut the vegetation at least twice a year. Additionally, this management practice interferes positively with the structure of the plant composition. The success of restoration moreover depends on the biotic potential (recent vegetation, neighbouring vegetation, seed bank). In the investigated vegetation types the seed bank contains no characteristic species of wet meadows. Therefor apart from suitable management practices, a successful restoration of species-poor Ranunculo-Alopecuretum requires much more time.

Ecosystem Manipulation and Restoration on the Basis of Long-Term Conceptions

Ecosystems are affected by anthopogenic activities at a global level and, thus, are manipulated world-wide. This chapter addresses the impacts of apparent and non-apparent manipulations and restoration by human activities in Europe with a focus on the temperate zone. Agricultural management practices induced evident site-specific modification of natural ecosystem structures and functions whereas forests and natural grasslands and also aquatic systems are considered as being less manipulated. Ecosystems such as mires, northern wetlands and the tundra, have received attention due to their vulnerability for conserving carbon and biodiversity and for identifying the role of non-apparent manipulations on ecosystem functioning. Drastic types of ecosystem manipulation include open-cast mining activities that occur worldwide and induce perturbation of large areas across landscapes. Such harsh human impacts create the need for remediation and restoration measures for mining regions that address classical food and fodder services and also nature conservation and novel social benefits. Recultivation therefore offers the opportunity to introduce new land-use types and to study processes of initial ecosystem development that are still poorly understood.

Effects of trampling on beach plants at the Baltic Sea

In the last century, increases in human population and beach tourism have affected coastlines worldwide. Resulting pressures on beach ecological systems demand research concerning tolerance of beach plants to disturbance by humans. At three different Baltic Sea beaches, Atriplex prostrata, Honckenya peploides and Crambe maritima were planted and observed while subjected to trampling stress intensities of 0, 1 and 2 footsteps·m−2·d−1. Plant height, leaf growth, number of leaves, chlorophyll content of leaves and fitness of photosystem II were measured at monthly intervals. Survival of plants was documented until the following summer. Linear mixed effect models fit the effects of trampling intensity, time and species on growth, photosynthetic productivity and reproduction of plants. Survival was fitted using general linear mixed models for binomial data. The results indicated that the annual species A. prostrata showed an initial decrease in growth at the first trampling treatment, but no effects on seed weight due to trampling pressure. Honckenya peploides was not affected by trampling. Crambe maritima showed a reduction in growth and survival under any level of trampling pressure. Experimental trampling pressure was compared to observed trampling intensities at beaches with low visitor frequency, which was ascertained to be between 3 and 8 footsteps·m−2·d−1. Because of the greater potential of endangerment for C. maritima, we suggest that nature conservation focus on reducing human trampling on the upper beach area, e.g. by closing this area. This practice would allow tourists continued recreational access to the water as well as to the lower beach area.

General Concept of the Research Pogramme and Methodology of Investigations

The integrative biological and geoscientific examination of both the nature of physical and biotic environments which make up ecosystems, and the interactions between these sub-systems, has substantiated the conception that a thorough knowledge of the ecosystem and its unifying position between ecology and environmental science is essential for a coherent understanding of environmental issues and large-scale problems in the biosphere. Recent developments in ecosystem theory have created a challenge to the development of recipes for a sustainable management of ecosystems and regions. It is increasingly considered in the disciplines of conservation biology, in the assessment of ecosystem health, integrity and sustainability, in ecological engineering, and in ecological economics in order to solve practical environmental management problems. In all of these fields modelling plays an essential role, since models provide for opportunities to develop strong transdisciplinary ties between the ecological community and the agency management personnel. A wide variety of illustrative examples of such approaches is provided by the International Biological Programme (IBP) and, in particular, by UNESCO’s Man and the Biosphere Programme (MAB) which, together with the German concept of a comprehensive ecological surveillance system (Ellenberg et al. 1978), contributed to define the concept and structure of the Bornhoved Project. They are summarized in the first part of the present Chapter while, in a concise form, the second part provides information about the practices, procedures and instrumentation used when implementing the ecosystem research scheme in the Bornhoved Lake District.