Annette Otte

Restoration of a species-rich flood meadow by topsoil removal and diaspore transfer with plant material

Abstract In previous studies, limited dispersal was revealed to be the main obstacle to restoration of species-rich flood-meadows along the northern Upper Rhine in Germany. To overcome dispersal limitation we transferred freshly mown plant material from species-rich sources to a restoration site on a former arable field. Before plant material application, topsoil was removed to accelerate nutrient impoverishment and create favourable conditions for seedling recruitment. Topsoil removal led to a drastic reduction in organic matter and essential mineral nutrients to the level of target communities (P) or even below (N, K). At a removal depth of 30 cm content of the soil seed bank that comprised exclusively of annual arable weeds, ruderals and some common grassland species, declined by 60 – 80%, while at a removal depth of 50 cm the seed bank was almost completely eliminated. With few exceptions, all species recorded in source plant material were found established at the restoration site. However, the overall correlation between seed content in plant material and establishment success was not very high. Vegetation development at the restoration site was characterized by a rapid decline in arable weeds and ruderals, while resident grassland species and species transferred with plant material increased rapidly from the third year onwards. After four years as many as 102 species were established that could be exclusively attributed to plant material transfer, among them many rare and highly endangered plants. Establishment of species from plant material was most successful in regularly flooded plots, due to the suppression of competitors as well as the creation of favourable moisture conditions for seedling emergence. Diaspore transfer with plant material proved to be an extremely successful method in restoring species-rich grassland. However, high quality of plant material and suitable site conditions with low competition in early stages of succession seem to be essential prerequisites. Nomenclature: Wisskirchen & Haeupler (1998).

Analysing land-cover changes in relation to environmental variables in Hesse, Germany

Land-use and land-cover changes affect ecological landscape functions and processes. Hence, landscape ecologists have a central interest in a comprehensive understanding of such changes. Our study focuses on the relationships between environmental conditions and agricultural land-cover changes. We present a method to (i) characterise the major spatial-temporal processes of land-cover changes, (ii) identify the correlations between environmental attributes and land-cover changes and (iii) derive potential environmental drivers of land-cover changes in a German marginal rural landscape. The method was applied to study land-cover dynamics from 1945 to 1998 in the districts of Erda, Steinbrücken and Eibelshausen, situated in the marginal rural landscape of the Lahn-Dill Highlands, Germany. We employed land-cover data gained by the interpretation of multi-temporal aerial photographs. Various environmental variables were introduced into the analyses. We identified physical landscape attributes (elevation, slope, aspect, available water capacity and soil texture) and structural landscape dimensions (patch size, patch shape and distance between patch and nearest settlement). With the aid of GIS, K-means partitioning and canonical correspondence analysis, we investigated land-cover trajectory types, land-cover transitions at individual time intervals and their relationships to these environmental variables. Our results show that, between 1945 and 1998, land-cover changes correlated with the physical attributes of the underlying landscape. On the other hand, the structural landscape dimensions correlated with land cover only in periods of minor land-cover changes (1972–98). Greater diversity of physical landscape attributes is correlated with greater land-cover dynamics. Besides the important influence of socio-economic factors, land-cover changes in the study areas took place within the relatively stable physical constraints of the underlying landscape.

The impact of site conditions and seed dispersal on restoration success in alluvial meadows

Abstract We studied the restoration success of flood plain meadows in the northern Upper Rhine valley, where between 1988 and 1992, 35 ha of arable land was converted into grassland and subsequently managed for nature conservation. Remnant populations of typical alluvial meadow species were found in old meadows and along drainage ditches that dissect the whole area. We analysed the site conditions and phytosociological relevés in old and new meadows. Small differences in site parameters between old and new meadows contrasted with a clear floristic differentiation between the two meadow types. The vegetation of old meadows was much more differentiated along prevailing environmental gradients than the vegetation of new meadows. Despite the favourable site conditions for the re-establishment of species-rich meadows on the former arable land, restoration success was limited to the vicinity of remnant stands. In contrast to old meadows, indicator species of new grassland were still typical species of regularly disturbed ruderal and arable habitats, often capable of building up a persistent seed bank. The precise mapping of 23 target species revealed that even wind dispersal predominantly leads to re-establishment in the close circumference of parent plants. We found no indication that regular flooding, hay-making and autumnal grazing had an impact on recolonization of newly created grassland. Even under favourable conditions for the re-establishment of target species, restoration success in alluvial meadows proved to be strongly dispersal limited. We discuss the implications of our findings for future restoration management in grasslands. Nomenclature: Wisskirchen & Haeupler (1998).

Effects of litter on seedling establishment in natural and semi‐natural grasslands: a meta‐analysis

1. Plant litter is a key component in terrestrial ecosystems. It plays a major role in nutrient cycles and community organization. Land use and climate change may change the accumulation of litter in herbaceous ecosystems and affect plant community dynamics. Additionally, the transfer of seeds containing plant material (i.e. litter) is a widespread technique in grassland restoration.2. Ecosystem responses to litter represent the outcome of interactions, whose sign and strength will depend on many variables (e. g. litter amount, seed size). A previous meta-analysis (from 1999) reported that litter had an overall negative effect on seed germination and seedling establishment in different ecosystems. However, recent studies indicated that this might not be the case in grassland ecosystems.3. We used 914 data from 46 independent studies to analyse the effects of litter on seedling (i) emergence, (ii) survival and (iii) biomass, employing meta-analytical techniques. Each data set was stratified according to methodology, grassland type, irrigation conditions, litter amount and seed size.4. We found an overall neutral effect of litter presence on seedling emergence and survival and a positive effect on seedling biomass. However, whereas for field experiments the response remained neutral, it was positive for common garden studies. In glasshouse experiments, litter effects were negative for emergence and positive for biomass.5. Litter may have a positive effect on seedling recruitment in dry grasslands or under water-limited conditions, or in the presence of low to medium litter amounts ( 500 g m(-2)) will inhibit seedling recruitment. Large seeds showed a more positive response to litter presence with respect to seedling emergence and survival, but not concerning biomass.6. Synthesis. Under dry conditions (e. g. dry grasslands or dry periods) or with low to medium litter amounts, litter presence has a positive effect on seedling establishment. However, climate and land use change may promote litter accumulation and reduce seedling establishment, affecting grasslands composition and ecosystem functions.

The impact of flooding regime on the soil seed bank of flood‐meadows

. We assessed the significance of flooding for the floristic composition of seed banks in flood-meadows of the northern valley of the Upper Rhine. We compared three hydrological compartments of the alluvial plain, consisting of the regularly flooded land between the river and low summer dykes (functional flood-plain), the occasionally flooded land between summer dykes and high winter dykes (hybrid floodplain) and the land behind the winter dykes, which is now only submerged by ascending groundwater (fossil flood-plain). Due to their different flooding regime, the three compartments should differ with respect to the prevailing conditions of diaspore input. The seed density of soil samples increased with the duration of flooding in the three compartments, while species richness and the proportion of species not occurring in the vegetation was constant. The increase in seed density can be largely attributed to an increase of disturbance indicators, which are present in the above-ground vegetation and capable of forming a long-term persistent seed bank. No effects of flooding on the composition of seed banks in the three flood-plain compartments were found. The differences in seed bank composition can be largely explained by corresponding differences in above-ground vegetation and former and present-day meadow management. Seeds of species absent from above-ground vegetation can be attributed to the local species pool present in the immediate vicinity of the study plots. We discuss consequences of the results for the restoration of species-rich flood-plain meadows.

Assessing soil seed bank persistence in flood-meadows: The search for reliable traits

Abstract To assess seed bank persistence of target species in endangered flood-meadows (alliances Cnidion and Molinion), we investigated established vegetation and soil seed bank of 46 plots for 3 yr and 2 yr, respectively. As traits of seed persistence we calculated various continuous indices that refer to the frequency and abundance of species in above-ground vegetation and at different soil depths. Furthermore, we tested the significance and soundness of easily observed traits such as maximum seed density per plot and seed attributes (mass, size and shape) as predictors of soil seed bank features. In linear regression, SAI, the seed accumulation index, showed the best agreement (R2 = 0.64) with the seed longevity index that was derived from the database by Thompson et al. (1997) for a set of 115 species. The second best predictor (R2 = 0.39) of the seed longevity index was maximum seed density per plot in the lower soil layer (5–10 cm). Depth distribution indices and seed attributes showed weaker but still significant relations. The dynamic character of flood-meadows was reflected by a large proportion of species with a strong tendency to accumulate seeds in the soil relative to their importance in above-ground vegetation. Most of these species have a ruderal strategy, exploiting gaps after flood disturbances, while the dominants of flood-meadows tended to have short-lived seed banks. Compared to other grassland types, a relatively large proportion of rare and endangered target species can be expected to form long-term persistent seed banks. However, only under marginal conditions that facilitate seed survival in the soil (e.g. fallow) are these persistent seed banks likely to contribute to restoration. We conclude that easily observed traits of persistence such as seed weight, size and shape do not meet the accuracy needed in scientific and practical applications. Thus, there is a crucial demand for further seed bank studies in poorly investigated habitats and of rare species. Nomenclature: Wisskirchen & Haeupler (1998). Abbreviation: SAI = Seed accumulation index.

Genetic structure among and within peripheral and central populations of three endangered floodplain violets

Understanding the partitioning of genetic variance in peripheral and central populations may shed more light on the effects of genetic drift and gene flow on population genetic structure and, thereby, improve attempts to conserve genetic diversity. We analysed genetic structure of peripheral and central populations of three insect‐pollinated violets (Viola elatior, Viola pumila, Viola stagnina) to evaluate to what extent these patterns can be explained by gene flow and genetic drift. Amplified fragment length polymorphism was used to analyse 930 individuals of 50 populations. Consistent with theoretical predictions, peripheral populations were smaller and more isolated, differentiation was stronger, and genetic diversity and gene flow lower in peripheral populations of V. pumila and V. stagnina. In V. elatior, probably historic fragmentation effects linked to its specific habitat type were superimposed on the plant geographic (peripheral‐central) patterns, resulting in lower relative importance of gene flow in central populations. Genetic variation between regions (3–6%), among (30–37%) and within populations (60–64%) was significant. Peripheral populations lacked markers that were rare and localized in central populations. Loss of widespread markers in peripheral V. stagnina populations indicated genetic erosion. Autocorrelation within populations was statistically significant up to a distance of 10–20 m. Higher average genetic similarity in peripheral populations than in central ones indicated higher local gene flow, probably owing to management practices. Peripheral populations contributed significantly to genetic variation and contained unique markers, which made them valuable for the conservation of genetic diversity.

Ecological significance of seed germination characteristics in flood-meadow species

Summary In climate chamber and outdoor experiments we analysed germination traits of 42 vascular plant species typical of floodmeadows of the alliance Cnidion. In Central Europe such flood-meadows and their highly endangered character species are confined to large lowland river corridors with a dry and warm climate. Due to the prevailing ecological conditions, particularl y the extremely high variability in soil moisture potential, it was hypothesised that flood-meadow species exhibit specific strat egies in terms of germination phenology, temperature requirements and primary dormancy to avoid constraints on seedling recruitment imposed by flooding, drought and competition from established vegetation. Furthermore, we expected that germination characteristics could be a key for the causal understanding of range size, confinement to large river corridors, recent rarification processes, seed bank persistence and establishment success in restoration projects. PCA ordination of germination traits reflected a continuous gradient of increasing primary dormancy levels ranging from species with a high capacity for fast and almost complete germination over a wide range of temperatures to those with high and narrow temperature requirements and/or a delayed and asynchronous emergence. Many of the studied species germinated only at relatively high temperature in the year of shedding, but the primary conditional dormancy disappeared in most cases after a period of cold wet stratification. Requirements for chilling and/or high germination temperature were revealed to be the most common strategies for avoidance of harmful autumn and winter germination. The majority of the studied species tends to exploit particularly favourable regeneration niches in early spring. Surprisingly, many species with large long-term persistent soil se ed banks exhibited relatively low dormancy levels in light ; this was correlated with small seed size and a consequent higher probability of burial. We found no relationship between germination characteristics and river corridor confinement or Central European range size. However, there was a significant trend in endangered species towards higher temperature requirements and delayed, asynchronous germination. This is presumably disadvantageous under the environmental conditions of subcontinental flood-meadows.

Indicators of plant species and community diversity in grasslands

Abstract Parameters which are directly related to both land use change and biodiversity may be useful tools to indicate biodiversity in marginal landscapes. In these landscapes for about five decades abandonment of cultivation, especially in favour of extensive grassland use and succession on abandoned fields, has led to considerable changes in the landscape structure. Regions such as the Lahn-Dill Highlands (Hesse, Germany), formerly characterized by small-parcelled crop and grassland rotation, increasingly feature old grassland communities over large areas. Impacts of changes in the landscape structure on the floristic–phytocoenotic diversity have been studied in two landscape tracts of this region that today are mainly used as grassland. Reconstruction of land use dynamics based on multitemporal aerial photograph interpretations of the period from 1945 to 1997 confirm the predominance of cultivation until ca. 1960 in both areas. On the basis of phytosociological surveys in one stand abandoned 3 years before the survey and in each three grassland stands of different age classes (11–27, 28–38, 39–46 and over 46 years), the floristic–phytocoenotic diversity of these stands is characterized as follows: (i) Flora and vegetation are clearly differentiated in relation to stand age. (ii) The vegetation of the older (>38 years) stands is more comparable among one another than is the vegetation of younger stands. (iii) 19- to 33-year-old stands have the highest number of exclusive species. (iv) Old stands (>46 years) have the highest α-species richness. (v) The stands can be classified into different vegetation types in relation to age. The floristic–phytocoenotic diversity is associated with site differences of the above age classes. Older stands are more frequent at upper slopes and the pH values of their soils are lower. With a small methodological outlay, grassland stands of different age and species diversity can be differentiated by red–green–blue (RGB) colour tonal values from false-colour infrared (FCIR) aerial photographs. The results open up possibilities for the qualitative and quantitative indication of floristic–phytocoenotic diversity in grasslands on the basis of stand age, site factors and also green and blue tonal values from the respective FCIR aerial photographs. Furthermore the results indicate that it is necessary to retain old grassland stands, as well as a mosaic of extensively used grassland stands of different ages to retain plant species and community diversity in the study region.

Biodiversity at the landscape level: recent concepts and perspectives for multifunctional land use

The interest of scientists, policy makers, and the general public in the concept of ‘multifunctional’ landscapes has increased enormously in recent years. The fact that landscapes provide a large number of beneficial functions and services to human beings, which go far beyond agriand silvicultural production, is now widely accepted (Foley et al. 2005). Non-commodity outputs as well as a wide array of ecosystem functions are considered to be indispensable properties of landscapes, and decision-makers are challenged by the need to consider all relevant landscape functions in management decisions at all spatial scales and each administrative level (Pinto-Correia et al. 2006). The concept of landscape multifunctionality is obviously closely related with landscape sustainability, but emphasizes more strongly the land user’s and stakeholder’s perspective. In the European Union, the ‘multifunctionality of agriculture’ has become the key concept of the Common Agricultural Policy (CAP) (Tait 2001). Multifunctionality is promoted by the EU in response to liberalisation pressures, and is seen as a way to address social and ecological concerns such as farm abandonment and biodiversity loss through agricultural subsidy policies (Potter and Burney 2002; Hollander 2004; Potter 2006). The benefits of agriculture to rural development, regulation functions and biodiversity are currently rewarded with an increasing share of EU-agricultural subsidies being transferred towards the production of ecosystem goods and services. The resulting regional agrienvironmental schemes of the member states pursue to secure the conservation and sustainable development of the old cultural landscapes (Vos and Meekes 1999; Deuffic and Candau 2006; Holloway et al. 2006; Potter 2006). However, while the concept of ‘multifunctionality’ receives also recognition outside the EU (USA: Hollander 2004; Bills and Gross 2005, Canada: Maxey 2006; Robinson 2006, Australia: Anderson 2000; Cocklin et al. 2006), it becomes increasingly evident that there is often a gap between the claim and reality of environmental (e.g., Kleijn et al. 2001), economic (e.g., Brunstad et al. 2005) or social effects (e.g., Gafsi et al. 2006) of agricultural policies. Thus, to create effective policies for the sustainable development of multifunctional landscapes, there is a demand of society and A. Otte (&) D. Simmering Division of Landscape Ecology and Landscape Planning, Interdisciplinary Research Centre for Biosystems, Land Use, and Nutrition (IFZ), Justus-Liebig-University Giessen, Heinrich-Buff-Ring 26-32, Giessen D-35392, Germany e-mail: annette.otte@agrar.uni-giessen.de