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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.
15 δ N signals in plant and soil material integrate over a number of biogeochemical processes
related to nitrogen (N) and therefore provide information on net effects of multiple
processes on N dynamics. In general little is known in many grassland restoration projects
on soil–plant N dynamics in relation to the restoration treatments. In particular, 15 δ N signals
may be a useful tool to assess whether abiotic restoration treatments have produced the
desired result. In this study we used the range of abiotic and biotic conditions provided
by a restoration experiment to assess to whether the restoration treatments and/or plant
functional identity and legume neighborhood affected plant 15 δ N signals. The restoration
treatments consisted of hay transfer and topsoil removal, thus representing increasing
restoration effort, from no restoration measures, through biotic manipulation to major
abiotic manipulation. We measured 15 δ N and %N in six different plant species (two nonlegumes and four legumes) across the restoration treatments. We found that restoration
treatments were clearly reflected in 15 δ N of the non-legume species, with very depleted
15 δ N associated with low soil N, and our results suggest this may be linked to uptake of
ammonium (rather than nitrate). The two non-legume species differed considerably in their
15 δ N signals, which may be related to the two species forming different kinds of mycorrhizal
symbioses. Plant 15 δ N signals could clearly separate legumes from non-legumes, but our
results did not allow for an assessment of legume neighborhood effects on non-legume
15 δ N signals. We discuss our results in the light of what the 15 δ N signals may be telling
us about plant–soil N dynamics and their potential value as an indicator for N dynamics in
restoration.
The aim of this study is to assess the development of plant species diversity and species composition
over a seven-year period in two calcareous grasslands abandoned for nearly 20 years and to find out
which factors influence vegetation dynamics. In the Abava River valley, Latvia, different calcareous
grasslands were studied, one on the south-west facing slope and another on the north-east facing slope.
Vegetation analyses on permanent plots showed that dry calcareous grasslands can be resistant to deterioration for a long period of time – succession was slower than reported in many cases for Central and
Western Europe. None of the studied communities showed a decrease neither in total species number
recorded per community nor in average species richness per plot. Vascular plant species richness even
increased by 3–4 species per 1-m² plot in the grassland on the south-west facing slope. An unexpected
result of the research was that Calamagrostis epigeios did not expand in this grassland. This fact can be
explained by the influence of disturbances (drought, tree cutting) and local differences in soil parameters
and topography. In parts of the north-east exposed grassland, with deeper soils and better water availability, species diversity (Shannon index) decreased significantly in areas overgrown by Aegopodium
podagraria.
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.
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.
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.
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.
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.
Ecological restoration of an urban demolition site through introduction of native forb species
(2020)
Urban brownfields can provide habitats for endangered native plant species but may also support invasive non native species. The aim of our study was to develop and test different measures for the ecological restoration of an urban brownfield. We aimed to enhance native plant species richness by seeding two native forb seed mix tures containing 25 (HD-mixture) and 13 species (LD-mixture), respectively, without affecting spontaneously colonizing plant species of nature conservation value. Additionally, we tested the effects of species introduction and mowing on the establishment of invasive non-native plant species, woody species development, and per ennial grass dominance.
With establishment rates of 84% (HD) and 92% (LD) in the first study year and about 60% for both seed mixtures in the fourth year, species introduction was successful and led to rapid re-vegetation of the formerly bare brownfield. Although seeding did not result in increased species richness using either seed mixture, the dominance of perennial grasses was significantly reduced by the establishment of forb species from the HD mixture. Overall, we observed the spontaneous establishment of ten plant species of conservation value; seeding affected these species only temporarily, in the second year. Seeding (with either seed mixture) and mowing both resulted in reduced cover of woody species and a lower frequency of the invasive non-native Robinia pseudoa cacia.
Our study demonstrated the high nature conservation value of dry and nutrient-poor urban brownfields for spontaneously occurring threatened plant species. Further studies have to evaluate if the reduced cover of grasses and woody species through introduction of site-specific native forb species might increase these sites’ aesthetic value and broader acceptance of brownfields by urban residents.
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.
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.
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.
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.
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.