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- Fakultät AuL (11)
Soil seed banks have a high potential for vegetation re-establishment in restoration projects. We studied the soil seed bank in an oxbow system of a disconnected floodplain of the Danube River in Southern Germany. The aim of the study was to analyze if floodplain target species were still present in the seed bank after more than 150 years of embankment and disconnection from fluvial dynamics. In this context we investigated seed density, seed bank species richness and species composition in four broad habitat types with and without water-level fluctuations during the time of embankment (permanent water, fluctuating water, reed bed, hardwood floodplain forest). In addition, the similarity between seed bank and above-ground vegetation in these habitat types was studied in order to predict the success of future restoration measures. In total, 124 vascular plant species were determined in the seed bank samples. More than 50 % (66 species) were target species typical for floodplain habitats and 26 of these target species were lost or very rare in the above-ground vegetation. The four habitat types differed significantly in mean seed density and mean species richness. Mean species richness and the number of target species in the seed bank as well as the mean seed density were greatest in the habitats with fluctuating water level whereas mean seed density was much lower in the parts with more or less stable conditions like permanently standing water and hardwood floodplain forest. Sørensen similarity between seed bank and above-ground vegetation was very low in habitats with more or less stable water levels and desirable floodplain target species were very rare or completely absent. Our results indicate that the soil seed bank can be an important seed reservoir for the ecological restoration of floodplain plant communities especially for habitats with unstable environmental conditions during the period of disconnection. Restoration of water level dynamics is important to maintain the seed bank of populations of floodplain target species.
Despite the high significance of the Western Siberian grain belt for crop production in Russia, its weed communities are largely unknown. In this region spring wheat is grown on fertile Chernozem soils with large field sizes but land-use intensity per area is low compared to Central Europe. By usin a randomized sampling design we studied arable weed assemblages in the northern forest-steppe zone of Tyumen region on 99 within-field sampling plots of 100 m² size. Surprisingly, with average of 9.8 ± 3.8 species 100 m-2 species richness was low when compared with low-input farming in Central Europe and did not differ between areas of different land-use intensity. Against expectations species composition was not predominantly controlled by soil characteristics and climate, most likely due to short natural gradients. Instead, management factors such as fertilization and tillage intensity seemed to be important factors. Except for two species the Tyumen weed flora consisted mainly of species that are widespread throughout the temperate zone. We found only 10 species with an origin or core area in North Asia or Eastern Europe. The species pool was generally small and with 26% the proportion of non-native spe cies (archaeophytes) was low, when compared to Central European weed communities. Given that weed communities with higher species richness are described from neighboring Bashkiria, we conclude that arable land-use intensity in Tyumen region is high enough to reduce community species richness within arable fields estimated by a randomized sampling design. Since measured soil nutrient values did not affect species richness, herbicide use is most likely the crucial management factor. Furthermore, species-richness was vitally restricted by the small species pool. The low proportion of thermophilous arable weed species that originate from the Mediterranean or Middle-Eastern area and contribute signif icantly to the Central European weed diversity indicate that climatic dispersal limitations may be re sponsible for the small number of weed species in the Tyumen flora. An additional constraint was the short history of arable farming in Western Siberia, where considerable arable land use was started only by the end of the 17th century.
Between Ekaterinburg and Nowosibirsk, in the Western Siberian grain belt, spring wheat is grown on fertileChernozem soils. Field and farm sizes are large but the land-use intensity per area is low compared to CentralEurope. Fertilizers and pesticides are applied only in low to moderate quantities and yields range between 10and 20 dt ha-1 . We studied the arable weed flora in the northern forest steppe zone of Tyumen region using arandomized sampling design. Surprisingly, the species richness was only moderate, on average 9.8 ± 3.8species per 100 m². Compared to weed communities of Bashkiria (Southern Ural) and less intensively usedarable land of Central Europe these numbers are rather low. Moreover, most of the recorded species werecosmopolitans or widely distributed throughout the temperate zone. We suggest that the land use intensitywas high enough to reduce the density of a number of weed species in a way that they were not registered byour random sampling design. The limited conservational value of the weed vegetation of large grain fields inTyumen leads to the conclusion that if intensification of land use is unavoidable, it should be directed to arableland and not to ex-arable land or ancient grassland, which is of higher conservation value.
Von 2010 bis 2014 wurden im Rahmen
des Projekts „ProSaum“ Verfahren zur
Wiederansiedlung arten- und blütenreicher Säume und Feldraine mit gebietsheimischem Wildpflanzensaatgut entwickelt. Für die standortangepassten
Saatmischungen wurden einheimische
Pflanzenarten ausgewählt, die typisch für
alte artenreiche Feldraine und mesophile
Saumgesellschaften im Raum Osnabrück
sind. Die Ergebnisse eines Blockversuchs und weiterer Versuche auf Landschaftsebene zeigen, dass es möglich
ist, artenreiche Säume und Feldraine
durch Ansaat in Kombination mit sorgfältiger Bodenbearbeitung und Entwicklungspflege wiederherzustellen. Aus den
Ergebnissen werden Empfehlungen für
die Standortauswahl, Bodenbearbeitung,
Ansaat und Pflege abgeleitet.
Following the collapse of the Soviet Union in 1991 around 45 million hectares
of arable land became abandoned across Russia. Our study focused on the recovery
potential and conservation value of grassland vegetation on ex-arable land in the Tyumen
region of the Western Siberian grain belt. We compared ex-arable grasslands of different
successional stages with ancient grasslands as reference for the final stage of succession
along a climatic gradient from the pre-taiga to the forest steppe zone. Plant community
composition and species richness of ex-arable land clearly developed towards reference
sites over time, but even after 24 years of abandonment, the grassland vegetation had not
totally recovered. The c-diversity of vascular plants was slightly higher on ex-arable land
than in ancient grasslands but the mean a-diversity was still moderately lower. A significant proportion of the vegetation of ex-arable land still consisted of ruderal and mesic
grassland species and the number and cover of meadow-steppe species was significantly
lower than in ancient grasslands. Grazing and time since abandonment positively affected
the reestablishment of target grassland species, whereas it was negatively affected by the
cover of grasses. In contrast to ex-arable land, the conservation value of arable land is only
modest. Therefore, future intensification of land use is most likely less harmful if directed
to existing arable land. Re-cultivation of ex-arable land and grassland improvement operations such as seeding of competitive grass species are major threats for the biodiversity of secondary grasslands on ex-arable land in the forest steppe zone of Western Siberia.
Restoring depleted soil organic carbon (SOC) stocks of arable land to remove carbon from the atmosphere and offset fossil fuel emissions is a promising strategy for the mitigation of climate change. In agroecosystems conservational tillage practices and the abandonment of formerly plowed fields (ex-arable land) are shown to have the highest potential to sequester SOC. Nevertheless reported sequestration rates vary and the effects of environmental site conditions remain poorly understood. Our results are based on a meta-analysis of 273 paired SOC estimates from 65 publications which included only mineral soils from the temperate zone. SOC stocks of ex-arable grasslands with an average of 14 years since abandonment were 18% larger compared to the SOC of arable land. Likewise, SOC stocks of never-plowed grassland plots were 11% larger than the SOC stocks of abandoned fields. The average sequestration rate was 0.72 t C ha− 1 yr− 1. Semi-arid and sub-humid climate as well as low initial SOC stocks positively affected proportional SOC gains suggesting that the recovery of carbon stocks is not limited by low primary production. Therefore, the northward shift of cultivation areas in the temperate zone will lead to the abandonment of soils with high SOC recovery potential. However, if native soils are opened up elsewhere to compensate for yield losses due to abandonment the surplus of SOC in ex-arable land can easily be overcompensated by cultivation losses.
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.
Wasser- und Ufervegetation
(2016)