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Wasser- und Ufervegetation
(2016)
Im Rahmen des durch die EU geförderten LIFE-Projekts „Lippeaue“ wurden
künstliche Binnendünen angelegt, die Standorte für an Trockenheit und Nährstoffarmut angepasste Pflanzenarten bieten können. Im Jahr 2012 wurde eine Erfolgskontrolle der Vegetationsentwicklung auf den in den Jahren 2008 und 2009 neu geschaffenen Binnendünen durchgeführt.
Die meisten der neu angelegten Dünen in der Lippeaue bei Hamm waren im Jahr 2012 durch Grünlandvegetation auf sandigen und schluffigen Böden gekennzeichnet. Die Gesamtstickstoff-, Humus- und Wassergehalte des Bodens lagen an der oberen Grenze des Bereiches, der für Magerrasenentwicklung günstig ist. Da sich keine Magerrasenbestände in der Nähe befinden, ist eine Etablierung von Magerrasen ohne die gezielte Übertragung von Mahd- oder Rechgut nicht zu erreichen. Die im LIFE-Projekt angelegten Dünen sind daher nur bedingt in einzelnen Fällen für die Magerrasenentwicklung geeignet.
Die ökologische Wertigkeit von Binnendünen ergibt sich aus ihrer Eigenschaft als vegetationsökologisch bedeutsamer Sonderstandort innerhalb des durch Feuchtigkeit geprägten ökosystemaren Wirkungsgefüges der Aue. Wo sich Weidengebüsche auf den Dünen ausbreiten, müssen die Ziele der Auwaldentwicklung durch Sukzession und der Entwicklung von Magerrasen auch durch stärkere Beweidung gegeneinander abgewogen werden.
Das Forschungsprojekt „Urbane Interventionen“ war ein Pilotprojekt im Rahmen der Nationalen Stadtentwicklungspolitik und zielte darauf ab, Impulse für eine bürgergetragene Stadtentwicklung in den Stadtteilen Haste, Dodesheide und Wüste zu setzen. Dabei wurden die StadtteilbewohnerInnen aktiv in den Prozess involviert und bekamen Möglichkeitsräume angeboten, im eigenen Umfeld aktiv zu werden. Das interdisziplinäre Projektteam der Hochschule Osnabrück arbeitete mit der Stadt Osnabrück sowie lokalen Vereinen und Organisationen zusammen.
Den Auftakt bildeten die Stadtteilwerkstätten in den Stadtteilen Haste und Wüste. Während dieser wurde für je eine Woche ein Begegnungs- und Handlungsort geschaffen. Die Stadtteilwerkstatt gab bestehenden Initiativen und Vereinen sowie interessierten StadtteilbewohnerInnen Raum und Gelegenheit, Ideen für die lebenswerte Gestaltung ihres Umfelds einzureichen. Die Vorschläge wurden öffentlich vorgestellt und gemeinsam diskutiert, um solche Ideen auszuloten, die im nächsten Jahr umgesetzt werden sollten. Dazu war es auch wichtig, engagierte Menschen zu finden, die bereit waren sich an der Umsetzung zu beteiligen.
Die vorliegende Veröffentlichung informiert über die Ziele und die Vorgehensweise des Hochschulprojekts „Urbane Interventionen“ und dokumentiert die Ideen und Ergebnisse der Stadtteilwerkstätten.
Das Forschungsprojekt „Urbane Interventionen“ war ein Pilotprojekt im Rahmen der Nationalen Stadtentwicklungspolitik und zielte darauf ab, Impulse für eine bürgergetragene Stadtentwicklung in den Stadtteilen Haste, Dodesheide und Wüste zu setzen. Dabei wurden die StadtteilbewohnerInnen aktiv in den Prozess involviert und bekamen Möglichkeitsräume angeboten, im eigenen Umfeld aktiv zu werden. Das interdisziplinäre Projektteam der Hochschule Osnabrück arbeitete mit der Stadt Osnabrück sowie lokalen Vereinen und Organisationen zusammen.
Den Auftakt bildeten zwei Stadtteilwerkstätten in den Stadtteilen Haste und Wüste. Im Stadtteil Dodesheide begannen die Aktivitäten 2016 mit einem „Stadtteilcafé“. Im Rahmen eines eintägigen Workshops sammelte das Hochschulteam gemeinsam mit den TeilnehmerInnen Ideen für eine soziale und lebenswerte Stadtteilentwicklung. Die vorliegende Dokumentation stellt die Ideen und Ergebnisse des Ideenworkshops dar und informiert über die Ziele des Hochschulprojekts „Urbane Interventionen“.
Green roofs are known to mitigate the negative effects of urban consolidation by offering diverse ecosystem functions compared to non-vegetated roofs. However, the support for native biodiversity might be improved by using native plant species. In a mesocosm experiment, we studied the suitability of three commercial green-roof growth substrates for the establishment of 27 native plant species from dry sandy grasslands of northwestern Germany over the course of four years. The substrates were mineral-based, but differed in the layering of organic matter. Total establishment rates reached 44–59% in Year 4, indicating the general suitability of the substrates. During the first weeks after seeding, with light irrigation, the vascular plant cover was greater in the similar substrates Zincolit® Plus (Z) and Zincolit® Plus-Leicht (ZL) with their compost-based organic mulch layers than in the substrate Sedumteppich (ST) with its organic matter evenly admixed with the mineral aggregates. In Years 2 and 3, however, the vascular plant cover was greater in the ST substrate, likely due to the better availability of water and nutrients from the organic matter compared to the dry surface-mulch layer variants Z and ZL. After severe drought events, the decline in plant cover was more pronounced in the ST substrate, likely representing a trade-off between lush growth and a susceptibility to drought. An indicator-species analysis revealed differences in species composition between the ST and Z/ZL substrates. Annual plant species were indicators of the ST substrate. Perennials, such as Thymus pulegioides and Achillea millefolium, were typical of the Z and ZL substrates. In addition to the general suitability of the tested standard substrates for target species establishment, the study indicated that a combination of different layers of substrate components resulted in different vegetation patterns that may have a positive effect on green-roof biodiversity.
In urban areas, open space including brownfields often became rare due to increasing urbanisation. Urban brownfields can be important for biodiversity, but especially brownfields in early successional stages seem to be refused by urban residents due to their sparse vegetation and less aesthetic appearance. The aim of this study was to revegetate a young demolition site in the city core of Osnabrück, Germany and thereby to support native plant diversity and aesthetic values. We developed two seed mixtures of native plant species and tested them in a large-scale field experiment over two growing seasons.
Both seed mixtures developed towards structurally diverse and flower-rich vegetation. Establishment rates of sown species were consistently larger than 75%. Revegetation of the predominantly bare anthropogenically transformed soil by introduced species occurred fast. Vascular plant cover and vegetation height were higher on sown plots than in controls, but did not differ between the seed mixtures. Seeding did not increase plant species richness and did not reduce the establishment of a potentially invasive non-native plant species. The cover of Red-List species from the spontaneous vegetation was significantly higher in control plots. Our results indicate that not all aims can be reached on one restoration site. It has to be discussed if it is better to invest a restoration budget for measures aiming to increase acceptance of endangered pioneer plant species from the spontaneous vegetation or to introduce more attractive and more competitive species of later successional stages.
During recent decades, many studies have shown that the successful restoration of species-rich grasslands is often seed-limited because of depleted seed banks and limited seed dispersal in modern fragmented landscapes. In Europe, commercial seed mixtures, which are widely used for restoration measures, mostly consist of species and varieties of non-local provenance. The regional biodiversity of a given landscape, however, can be preserved only when seeds or plants of local provenance are used in restoration projects. Furthermore, the transfer of suitable target species of local provenance can strongly enhance restoration success.
We review and evaluate the success of currently used near-natural methods for the introduction of target plant species (e.g. seeding of site-specific seed mixtures, transfer of fresh seed-containing hay, vacuum harvesting, transfer of turves or seed-containing soil) on restoration sites, ranging from dry and mesic meadows to floodplain grasslands and fens. Own data combined with literature findings show species establishment rates during the initial phase as well as the persistence of target species during long-term vegetation development on restoration sites.
In conclusion, our review indicates that seed limitation can be overcome successfully by most of the reviewed measures for species introduction. The establishment of species-rich grasslands is most successful when seeds, seed-containing plant material or soil are spread on bare soil of ex-arable fields after tilling or topsoil removal, or on raw soils, e.g. in mined areas. In species-poor grasslands without soil disturbance and on older ex-arable fields with dense weed vegetation, final transfer rates were the lowest. For future restoration projects, suitable measures have to be chosen carefully from case to case as they differ considerably in costs and logistic effort. Long-term prospects for restored grassland are especially good when management can be incorporated in agricultural systems.
The biennial plant Gentianella bohemica is a subendemic of the Bohemian Massif, where it occurs in seminatural grasslands. It has become rare in recent decades as a result of profound changes in land use. Using amplified fragment length polymorphisms (AFLP) fingerprint data, we investigated the genetic structure within and among populations of G. bohemica in Bavaria, the Czech Republic, and the Austrian border region. The aim of our study was (1) to analyze the genetic structure among populations and to discuss these findings in the context of present and historical patterns of connectivity and isolation of populations, (2) to analyze genetic structure among consecutive generations (cohorts of two consecutive years), and (3) to investigate relationships between intrapopulational diversity and effective population size (Ne) as well as plant traits. (1) The German populations were strongly isolated from each other (pairwise FST= 0.29–0.60) and from all other populations (FST= 0.24–0.49). We found a pattern of near panmixis among the latter (FST= 0.15–0.35) with geographical distance explaining only 8% of the genetic variance. These results were congruent with a principal coordinate analysis (PCoA) and analysis using STRUCTURE to identify genetically coherent groups. These findings are in line with the strong physical barrier and historical constraints, resulting in separation of the German populations from the others. (2) We found pronounced genetic differences between consecutive cohorts of the German populations (pairwise FST= 0.23 and 0.31), which can be explained by local population history (land use, disturbance). (3) Genetic diversity within populations (Shannon index, HSh) was significantly correlated with Ne (RS= 0.733) and reflected a loss of diversity due to several demographic bottlenecks. Overall, we found that the genetic structure in G. bohemica is strongly influenced by historical periods of high connectivity and isolation as well as by marked demographic fluctuations in declining populations.
The break-up of the Soviet Union in 1991 triggered cropland abandonment on a continental scale, which in turn ledto carbon accumulation on abandoned land across Eurasia. Previous studies have estimated carbon accumulationrates across Russia based on large-scale modelling. Studies that assess carbon sequestration on abandoned land basedon robust field sampling are rare. We investigated soil organic carbon (SOC) stocks using a randomized samplingdesign along a climatic gradient from forest steppe to Sub-Taiga in Western Siberia (Tyumen Province). In total, SOCcontents were sampled on 470 plots across different soil and land-use types. The effect of land use on changes in SOCstock was evaluated, and carbon sequestration rates were calculated for different age stages of abandoned cropland.While land-use type had an effect on carbon accumulation in the topsoil (0–5 cm), no independent land-use effectswere found for deeper SOC stocks. Topsoil carbon stocks of grasslands and forests were significantly higher thanthose of soils managed for crops and under abandoned cropland. SOC increased significantly with time sinceabandonment. The average carbon sequestration rate for soils of abandoned cropland was 0.66 Mg C ha1yr1(1–20 years old, 0–5 cm soil depth), which is at the lower end of published estimates for Russia and Siberia. Therewas a tendency towards SOC saturation on abandoned land as sequestration rates were much higher for recentlyabandoned (1–10 years old, 1.04 Mg C ha1yr1) compared to earlier abandoned crop fields (11–20 years old,0.26 Mg C ha1yr1). Our study confirms the global significance of abandoned cropland in Russia for carbonsequestration. Our findings also suggest that robust regional surveys based on a large number of samples advancemodel-based continent-wide SOC prediction.
Within the frame of the EU Common Agricultural Policy, most countries subsidise the establishment and maintenance of perennial flower strips on arable land within Agri-Environmental Schemes to provide foraging habitats and refuges for wildlife.
In a replicated field experiment, we studied the effects of different types of seed mixtures on the establishment and maintenance of perennial flower strips on fertile arable land in the federal state of Saxony-Anhalt, Germany over seven years. The seed mixtures were commonly applied within recent Common Agricultural Policy funding periods: (1) a low-diversity cultivar standard seed mixture (CULTIVAR), (2) a high-diversity cultivar and native plant mixture (MIX), and (3) a high-diversity native plant mixture (WILDFLOWER). All plots were mulched every year in March and at the beginning of August.
The low success of CULTIVAR triggered the massive encroachment of spontaneously established perennial grasses. In MIX, too, cultivars have disappeared after the first year. Both wildflower variants were successful in maintaining a high cover of sown perennial native forbs and a high ratio of established sown species, even after seven years. WILDFLOWER always tended to show better values than MIX. Furthermore, spontaneously establishing species began to spread their cover in MIX in the fifth year, with a very strongly increasing tendency, whereas in WILDFLOWER cover of spontaneously immigrating species stayed satisfyingly low.
Using native wildflowers to establish perennial wildflower strips was very effective in maintaining high species diversity within the Agri-Environmental Schemes funding period of five years and beyond. WILDFLOWER was especially successful. On the other hand, CULTIVAR failed completely. On fertile soils in regions with rather low yearly precipitation, mulching twice a year supported the maintenance of perennial wildflower strips.
Reconnection of floodplains to rivers to enhance fluvial dynamics is a favored method of floodplain restoration in Europe. It is believed that the restoration of hydrological conditions of the floodplain facilitates natural dispersal of target species, and hence the reestablishment, of typical plant communities. The aim of our study was to investigate whether floodplain target species could reach restoration sites via hydrochorous dispersal. We analyzed seed inflow from the river and seed dispersal in different sectors of a new watercourse in the Danube floodplain. Seeds were captured using 27 seed traps during three sampling periods of 3 weeks each from summer 2011 to spring 2012. After germination seedlings were identified, we detected a total of almost 39,000 seeds of 176 species, including 80 target species of riparian habitats. We found significant differences between seasons (most seeds in autumn/winter) and between stream sectors. Fewer seeds came in from the Danube (2,800 seeds) than were transported within the floodplain. Several new floodplain target species were detected, which had not been found in the aboveground vegetation or soil seed bank before the start of the restoration. Seeds of nonnative species did not disperse further than approximately 1 km. Our results indicated that hydrochorous seed dispersal from upstream habitats along the new watercourse was important for the establishment of target species and hence for the success of floodplain restoration. Technical water diversion weirs must be traversable for seeds, and small donor sectors upstream might enhance the reestablishment of target vegetation along new sectors downstream.
After foundation of the Wadden Sea National Park, grazing and artificial drainage was ceased or reduced on large areas of the salt marshes at the Schleswig-Holstein mainland coast (Northern Germany). The effect of grazing cessation versus intensive and moderate grazing on vegetation diversity was studied on small (plant species richness on plots between 0.01 and 100 m2) and large scale (vegetation type richness per hectare) over 18 to 20 years by analysing data from long-term monitoring programs. Plant species richness and vegetation type richness increased strongly over time in all management regimes, because grazing-sensitive species increased first in ungrazed marshes and later dispersed to and established in intensively grazed marshes. Dominance of the tall, late-successional grass Elymus athericus on 7% to 52% of all moderately and ungrazed (primarily high marsh) plots led to a decrease in species richness. After 18 to 20 years, species richness was highest in moderately and intensively grazed high marshes. Differences were significant only on small plots of up to 4 m2. On the large scale, vegetation type richness in the low marsh was higher without grazing, while no differences were found in the high marsh. Our results indicate that grazing effects differ between spatial scales and that different spatial scales have to be considered for monitoring and evaluation of vegetation diversity in salt marshes. To conserve vegetation diversity on all scales, a large-scale mosaic of different management regimes should be maintained.
Green roofs can mitigate negative environmental effects of urban densifcation to some extent, but they are often covered by species-poor Sedum mixtures with a low value for biodiversity. By combining a habitat template and a seedprovenance approach, we review the suitability of plant species from regionally occurring dry sandy grasslands (Koelerio-Corynophoretea) for extensive roof greening in northwestern Germany. Since 2015, we have studied the effects of species introduction on vegetation dynamics on experimental mini-roofs. Treatments included sowing seeds of regional native origin in two densities (1 g and 2 g/m2) and the transfer of raked material from an ancient dry grassland area classifed as Natura 2000 site. The applied raked material contained diaspores of 27 vascular plant species (including seven threatened species) and vegetative fragments of grasslandspecifc mosses and lichens. Since 2018, we have tested more species-rich seed mixtures in a large-scale experiment on a roof of 500 m2 with different engineered green-roof substrates and layering. In 2019, a green roof of 10,200 m2 was established in cooperation with a local enterprise to support regional native biodiversity.
In this chapter, we summarise the most important results of our studies and discuss how to support regional native biodiversity on green roofs.