River corridor plants in North-western Germany are threatened by small population size and short-term environmental events (original) (raw)
Related papers
2014
River corridor plants in Central Europe account for an above-average proportion of endangered species. The main objective of this study was to examine the effects of habitat fragmentation and abiotic conditions on the survival and changes in population size of four endangered, long-lived river corridor plant species (Euphorbia palustris, Pseudolysimachion longifolium, Sanguisorba officinalis, and Senecio paludosus) over the course of at least ten years. We sampled altogether 138 populations in the Weser and Elbe river systems in Northwestern Germany. Overall, 33% of the populations went extinct during the study period. Extinction rates and changes in population size were related to initial population sizes, but not to population isolation and only marginally so to habitat quality. Large populations (> 100 individuals) had a much higher probability to survive or increase in size (to > 1000 individuals) than smaller populations. There was no general decline in population size in surviving populations, and extinction rates and changes in population size were independent of time. We therefore conclude that the high extinction rates in small populations are best explained by sudden short-term environmental events, such as changes in land use, rather than by long-term negative effects of, for example, genetic deterioration. A projection matrix for the next 117 years, however, predicted that 85% of the surveyed populations will have gone extinct. Since any establishment of new populations in the study area is unlikely owing to the lack of potential habitats and dispersal limitation, river corridor plants will probably continue to decline. Apart from preventing further habitat deterioration it will be crucial to maintain or establish an appropriate management, and to avoid sudden and adverse changes in land use.
Stromtalpflanzen im nordwestlichen Deutschland sind durch kleine Populationsgrößen gefährdet
2014
River corridor plants in Central Europe account for an above-average proportion of endangered species. The main objective of this study was to examine the effects of habitat fragmentation and abiotic conditions on the survival and changes in population size of four endangered, long-lived river corridor plant species (Euphorbia palustris, Pseudolysimachion longifolium, Sanguisorba officinalis, and Senecio paludosus) over the course of at least ten years. We sampled altogether 138 populations in the Weser and Elbe river systems in Northwestern Germany. Overall, 33% of the populations went extinct during the study period. Extinction rates and changes in population size were related to initial population sizes, but not to population isolation and only marginally so to habitat quality. Large populations (> 100 individuals) had a much higher probability to survive or increase in size (to > 1000 individuals) than smaller populations. There was no general decline in population size in...
Hydrobiologia, 2013
This resampling study in 338 semi-permanent plots analyses changes in river macrophyte diversity in 70 water courses (small streams to medium-sized rivers) from four regions of the northwest German lowlands during the last six decades. The total macrophyte species pool decreased between the 1950s and 2010/2011 by 28% (from 51 to 37 species), mean plot-level species richness by 19% (from 4.7 to 3.8 species per relevé) and the number of red-listed species by 40% (from 30 to 18 species). Species loss was associated with marked change in species traits: species with presumably higher mechanical stress tolerance (indicated by low specific leaf area and short leaf longevity) are more abundant today. Nearly, half of the species present in the 1950s had either disappeared or been replaced by other species in the recent relevés. The dramatic impoverishment is likely a consequence of continued nutrient input that drove oligo-and mesotraphent species to extinction, and of restructuring and maintenance works in the water courses that reduced stagnant and undisturbed river habitats, where stress-intolerant species can persist. Efficient measures to reduce the nutrient load and to re-naturalise stream and river beds are urgently needed to halt and reverse the loss of macrophyte diversity.
Habitat loss of floodplain meadows in north Germany since the 1950s
Biodiversity and Conservation, 2011
Floodplain meadows are severely threatened by land use change and intensification in Central Europe. This study investigates quantitative and qualitative changes in the vegetation of wet and species-rich mesic meadows in the floodplains of north Germany since the 1950s, considering their spatial extent, fragmentation, and replacement by other land use types. Historical high-resolution vegetation maps were compared with recent vegetation surveys in seven study regions (six unprotected areas, one protected reference area) in former West and East Germany. The unprotected sites showed alarming losses in wet and species-rich mesic meadows in the past 50 years ([80%). Wet meadows were substituted by species-poor, intensively managed grasslands (26-60% of the former area), arable fields (0-47%) or set-asides (2-33%). Species-rich mesic meadows were transformed to arable fields (42-72%) or species-poor, intensively managed meadows (14-72%). Decreases in effective mesh size and patch size indicated increasing fragmentation of wet meadows, whilst changes in landscape structure were less consistent in mesic meadows. Only slight changes in the protected floodplain study area indicate that landscape change is mostly caused by local effects such as fertilisation and drainage, but not by general trends such as atmospheric N deposition or climate warming. Despite the contrasting political systems in West and East Germany with different agroeconomic frames, all unprotected study areas showed similar losses and increasing fragmentation of floodplain meadows, which may negatively influence the natural dynamics of, and the gene flow between, meadow plant populations. We conclude that floodplain meadows in north Germany urgently call for high-priority conservation measures.
Biological Conservation, 1998
Since the early 19th century, particularly in the Alps, stream corridors have been affected by two major disturbances: diking/ channelization which cut off large areas of floodplain and the infilling of bypass channels which has raised the level of alluvial deposits by siltation. While these engineering works have favoured farming, some areas remained uncultivated. These are: (1) wellsilted basins which became waterlogged after the water table was raised (sedimentation within the diked channel), (2) well-silted basins used to produce firewood, and (3) unsilted or insufficiently silted basins which still show evidence of landforms characterizing the ancient braided pattern. Anthropogenically provoked disturbances such as flooding/silting followed by agricultural practices such as clearing, mowing and grazing are responsible for the establishment of relatively young fens (< 150 years old) exhibiting a higher plant diversity than unsilted areas. A comparison was made between sites in the Isrre valley and similar but more ancient habitats in the Rhrne valley. This showed the role of flooding/silting operations in promoting a rapid reinstatement of biological richness in alluvial wetlands. However, it was evident that the more newly created sites were generally much poorer in species than the older sites. Conservation biologists interested in preserving species and plant communities in stream corridors of the Aips therefore need to incorporate a dynamic perspective of biological systems that includes the overriding impact of prior land-use and historical river management. It is suggested that old flooding techniques can be used again in order to preserve or enhance present biodiversity.
Alpine Botany, 2022
The dwarf bulrush (Typha minima Hoppe) is a perennial aquatic plant that has been rapidly disappearing in Northern Europe following flood control methods (dikes, dams, embankments). Floods, by erasing and creating new banks, maintain a metapopulation system (extinction/recolonization of populations). The largest and most diverse populations are located in France. In order to identify the size of the metapopulations, we studied clonality, genetic diversity and genetic structure of an extensive sample of the French populations using AFLP markers. Clonality was high (on average, each genotype was found in three copies) but variable across sites: some genotypes had a high number of copies (> 20) and were distributed over several river catchments while 239 genotypes were unique. Genetic diversity was high but did not accumulate downstream indicating both up-and downstream long distance gene flow through pollen and seeds. Genetic diversity is structured in three major clusters. One (cluster N) is restricted to sites north of 44°4N. The other two (clusters S and E), coexist in river catchments or even in the same site. However, the highest Fst were found between cluster E and clusters N or S, indicating a recolonization from different refugia, one possibly located east of the Alps (cluster E) and one or two on the Western side. Therefore conservation actions should take into account these three major conservation units (CU) in France. These CU cover large areas. It is thus important to maintain a natural river dynamics with frequent extinction/recolonization events over whole drainage basins.
This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues. Other uses, including reproduction and distribution, or selling or licensing copies, or posting to personal, institutional or third party websites are prohibited. In most cases authors are permitted to post their version of the article (e.g. in Word or Tex form) to their personal website or institutional repository. Authors requiring further information regarding Elsevier's archiving and manuscript policies are encouraged to visit: http://www.elsevier.com/copyright a b s t r a c t The identification of optimal management strategies for a given species is a major challenge of species conservation. It becomes especially challenging when the environmental conditions are expected to change in the future, and the optimal management applied today may differ from the management that is optimal under the changed conditions (e.g. due to climate change). This study evaluates prospect of a rare plant species endemic to semi-natural grasslands in central Eur-ope, Gentianella praecox subsp. bohemica. The number of populations of this species has declined rapidly in the last 60 years; currently, a conservation action plan has been established in the Czech Republic, where most populations of this species occur. This study uses periodic matrix models to compare different management regimes under different scenarios of climate change and to identify the optimal management in each case. Without management, populations of the species are not able to survive. Flowering individuals can occur for a long time after the cessation of management, but the extinction of the population is inevitable within several decades. Without management, even very large populations (1000 flowering individuals) will go extinct in less than 50 years. Total extinction (including seed bank) will follow several years after observation of the last flowering plant. The most suitable management is mowing and disturbance (by harrowing), which is also the best method for restoration of threatened populations. Mowing is less suitable , but it is fully sufficient for large prospering populations. When managed, even small populations (10–15 flowering individuals) are able to survive. When management is applied, future climate change may have a relatively small impact on the probability of survival of the species. Climate change will, however , increase the extinction probability of very small populations.
Conservation Biology, 2006
Conservation currently relies largely on hindsight because demographic studies identify population decline after the event. Nevertheless, the degree of aggregation within a population is an "instantaneous" characteristic with the potential to identify populations presently at greatest risk of genetic impoverishment (via Allee effects and in-breeding depression) and local decline. We sought to determine the relative extinction risk for sympatric orchid species throughout Monte Barro natural park (Lecco, Italy), based on an index of dispersion ( I ) calculated from the size and location of subpopulations (recorded with GPS and mapped with GIS). Three population dispersion types were identified: (1) highly aggregated and locally abundant (large subpopulations restricted to particular sites; e.g., Gymnadenia conopsea [L.] R.Br.; I = 54.5); (2) widespread and moderately aggregated (opportunistic throughout the elevational range of the mountain; e.g., Listera ovata [L.] R.Br.; I = 18.9); and (3) weakly aggregated and locally rare (small, highly diffuse subpopulations; e.g., endemic Ophrys benacensis [Reisigl] O. & E. Danesch & Ehrend.; I = 4.4)