Eva Mosner

How functional is functional? Ecological groupings in terrestrial animal ecology: towards an animal functional type approach

Understanding mechanisms to predict changes in plant and animal communities is a key challenge in ecology. The need to transfer knowledge gained from single species to a more generalized approach has led to the development of categorization systems where species’ similarities in life strategies and traits are classified into ecological groups (EGs) like functional groups/types or guilds. While approaches in plant ecology undergo a steady improvement and refinement of methodologies, progression in animal ecology is lagging behind. With this review, we aim to initiate a further development of functional classification systems in animal ecology, comparable to recent developments in plant ecology. We here (i) give an overview of terms and definitions of EGs in animal ecology, (ii) discuss existing classification systems, methods and application areas of EGs (focusing on terrestrial vertebrates), and (iii) provide a “roadmap towards an animal functional type approach” for improving the application of EGs and classifications in animal ecology. We found that an animal functional type approach requires: (i) the identification of core traits describing species’ dependency on their habitat and life history traits, (ii) an optimization of trait selection by clustering traits into hierarchies, (iii) the assessment of “soft traits” as substitute for hardly measurable traits, e.g. body size for dispersal ability, and (iv) testing of delineated groups for validation including experiments.

SOIL VS. CANOPY SEED STORAGE AND PLANT SPECIES COEXISTENCE IN SPECIES-RICH AUSTRALIAN SHRUBLANDS

The fire-prone shrublands of southwestern Australia are renowned for their high plant species diversity and prominence of canopy seed storage (serotiny). We compared species richness, abundance, and life history attributes for soil and canopy seed banks in relation to extant vegetation among four sites with different substrate conditions and high species turnover (50-80%) to identify whether this unusual community-level organization of seed storage might contribute to maintenance of high species richness. Soil seed bank (SSB) densities were low to moderate (233-1435 seeds/m2) compared with densities for other Mediterranean-type vegetation and were lowest for sites with highest canopy seed bank (CSB) species richness and lowest nutrient availability, but not richness or abundance of resprouters. Annuals were infrequent in the lowest nutrient sites, but there was no evidence that small SSB size was due to low seed inputs or a trade-off between seed production/storage and seed size in response to low nutrient availability. Sorensens similarity between SSB and extant vegetation was 26-43% but increased to 54-57% when the CSB was included, representing levels higher than reported for most other ecosystems. Resprouting species were well represented in both the SSB and CSB, and there was no evidence for lower seed production in resprouters than in non-sprouters overall. The SSB and CSB held no species in common and were characterized by markedly different seed dispersal attributes, with winged or small seeds in the CSB and seeds dispersed by ants, birds, and wind (though none with wings) in the SSB. There was no evidence of spatial differentiation in the distribution of seeds of SSB species between vegetated and open microsites that might facilitate species coexistence, but most woody non-sprouters showed aggregation at scales of 1-2 m, implying limited seed dispersal. High similarity between overall seed bank (SSB + CSB) and extant species composition, high number of resprouting species, and seed dispersal processes before (SSB) and after fire (CSB) leading to differential spatial aggregation of post-fire recruits from the two seed bank types may buffer species composition against rapid change and provide a mechanism for maintaining species coexistence at the local scale.

Vegetative reproduction capacities of floodplain willows - cutting response to competition and biomass loss

While several studies on regeneration in Salicaceae have focused on seedling recruitment, little is known about factors controlling their vegetative reproduction. In two greenhouse experiments, we studied the response of floodplain willows (Salix fragilis, S. viminalis, S. triandra) to competition with Poa trivialis, and to shoot and root removal when planted as vegetative cuttings. In the first experiment, growth performance variables were analysed in relation to full competition, shoot competition, root competition and control, taking into account two different water levels. After 9 weeks, shoots were removed and the resprouting capacity of the bare cuttings was recorded. In the second experiment, the cutting performance of the three floodplain and an additional two fen willow species (S. cinerea, S. aurita) was compared when grown in three different soil compositions and with two different water levels. After 9 weeks, shoot and root biomass was removed and the bare cuttings were replanted to test their ability to resprout. Cutting performance and secondary resprouting were negatively affected by full and shoot competition while root competition had no or weak effects. The floodplain species performed better than the fen species in all soil types and water levels. Secondary resprouting capacity was also higher in the floodplain species, which showed an additional strong positive response to the previous waterlogging treatment. The results contribute to understanding of the vegetative regeneration ecology of floodplain willows, and suggest that the use of vegetative plantings in restoration plantings could be an effective strategy for recovering floodplain forests.

Differential effects of reduced water potential on the germination of floodplain grassland species indicative of wet and dry habitats

Floodplain meadow ecosystems are characterized by high water level fluctuations and highly variable soil water potentials. Additionally, climate change scenarios indicate an increasing risk for summer drought along the northern Upper Rhine and the Middle Elbe River, Germany. While adult plants often persist even after strong changes in water availability, early life phases, such as seed germination and seedling establishment, might be more vulnerable. Therefore we tested whether reduced soil water potentials will affect the germination of meadow species and whether the response varies between (1) forbs indicative of wet and dry habitats and (2) seeds originating from sites along the rivers Elbe and Rhine. We exposed seeds of 20 floodplain meadow species with different moisture requirements from five plant families to a water potential gradient ranging from 0 to -1.5MPa. While across species germination percentage and synchrony decreased, germination time increased at reduced water potentials. Germination of the species indicative of dry habitats decreased more strongly, was slower and less synchronous at reduced water potentials than that of species indicative of wet habitats. Seeds from sites along the rivers Elbe and Rhine did not differ in their germination characteristics. We propose that species of wet sites follow an all-or-nothing-strategy with fast and synchronous germination to maximize competitive advantages, betting on a high probability of moist conditions for establishment (optimists). In contrast, species from dry sites appear to follow a bet-hedging strategy with a moisture-sensing mechanism for unsuitable conditions (pessimists), resulting in a slower and less synchronous germination.

Managing floodplain-forest restoration in European river landscapes combining ecological and flood-protection issues

Throughout Europe the demands for improved flood protection on the one hand and the requirements to maintain and enhance floodplain forests on the other are perceived as conflicting goals in river-basin management, revealing the urgent need for strategies to combine both issues. We developed an interdisciplinary approach for floodplain-forest restoration identifying sites suitable for reforestations from both an ecological and hydraulic point of view. In the ecological module, habitat-distribution models are developed providing information on ecologically suitable sites. In the hydraulic module, a two-dimensional hydrodynamic-numerical model (2D-HN model) delivers the requested hydraulic information. The output of the two models is intersected. Subsequently, in an iterative procedure, the potential of plantings without exceeding critical water levels can be identified by hydraulic evaluation using the 2D-HN-model. The approach is exemplified using two reforestation scenarios at the Elbe River, Germany, showing considerable potential for softwood forest establishment without negative hydraulic effects. The approach reported here provides a solution for a severe conflict in river-basin management that hampers the reestablishment of the strongly threatened floodplain forests in Europe. Alternative measures to enhance floodplain-forest regeneration feasible under certain preconditions are discussed in the context of the current state of European large rivers.

Effects of reduced summer precipitation on productivity and forage quality of floodplain meadows at the Elbe and the Rhine River.

Background Floodplain meadows along rivers are semi-natural habitats and depend on regular land use. When used non-intensively, they offer suitable habitats for many plant species including rare ones. Floodplains are hydrologically dynamic ecosystems with both periods of flooding and of dry conditions. In German floodplains, dry periods may increase due to reduced summer precipitation as projected by climate change scenarios. Against this background, the question arises, how the forage quantity and quality of these meadows might change in future. Methods We report results of two field trials that investigated effects of experimentally reduced summer precipitation on hay quantity and quality of floodplain meadows at the Rhine River (2011-2012) and at two Elbe tributaries (2009-2011). We measured annual yield, the amount of hay biomass, and contents of crude protein, crude fibre, energy, fructan, nitrogen, phosphorus, and potassium. Results The annual yield decreased under precipitation reduction at the Rhine River. This was due to reduced productivity in the second cut hay at the Rhine River in which, interestingly, the contents of nitrogen and crude protein increased. The first cut at the Rhine River was unaffected by the treatments. At the Elbe tributaries, the annual yield and the hay quantity and quality of both cuts were only marginally affected by the treatments. Conclusion We conclude that the yield of floodplain meadows may become less reliable in future since the annual yield decreased under precipitation reduction at the Rhine River. However, the first and agriculturally more important cut was almost unaffected by the precipitation reduction, which is probably due to sufficient soil moisture from winter/spring. As long as future water levels of the rivers will not decrease during spring, at least the use of the hay from the first cut of floodplain meadows appears reliable under climate change.

River dynamics and invasion: distribution patterns of native and invasive woody vegetation at the Río Negro, Argentina

Abstract Salicaceae are typical invaders of riparian ecosystems throughout the world and they have the potential to change much of the invaded habitats. Along Patagonian streams, riparian softwood forests composed of non-native Salicaceae are increasing in abundance, area and tree species diversity. Especially in the last decades, dense floodplain forests dominated by invasive willows and poplars and additionally Russian olive and tamarisk spread almost explosively e.g. along the Río Negro in northern Patagonia. This study focuses on the identification of ecological niches and niche overlaps of the native and invasive woody species in order to assess the impact on the native Salix humboldtiana Willd. Data on species (presence/ absence) and explanatory variables were gathered in the field using a grid-based, stratified-randomized sampling design. Different environmental variables were then related to species occurrence in different life stages (adult, juvenile, seedling) using habitat distribution models. In the final models, flood duration, the amount of gravel and the location (upper or middle river valley) were included to describe the probability of occurrence of native and invasive taxa. For all life stages, a strong niche overlap could be observed for S. humboldtiana and the invasive taxa with no remaining exclusive habitats indicating a potential threat to the native willow. The study contributes to a better understanding of Salicaceae invasion and its consequences for riparian ecosystems.

Revisiting the provenance delineation of a widespread shrub, Frangula alnus—the role of spatial, temporal and environmental patterns

Including population genetic aspects into the selection of planting material within the framework of conservation and restoration measures is of vital importance for the long-term persistence of populations. This is especially true facing climate change since genetic diversity and the spread of potentially beneficial alleles are important for the adaptability of populations. Therefore, knowledge about genetic variability within and between populations is a critical aspect when determining provenance regions. In our study, we investigated the population genetic structure of a widespread, insect-pollinated and mainly bird-dispersed shrub species, Frangula alnus, on the basis of seven microsatellites and two chloroplast DNA markers throughout Germany. The aim was to determine the spatial, temporal and ecological processes genetically structuring populations to critically revise existing provenance regions. Therefore, we conducted analyses on different spatial scales (country-wide, regional and local) using the two different marker sets in addition to environmental variables. We detected distinct patterns on all spatial scales which indicated influences of historic recolonization processes, regional differences of seed dispersal across the landscape, as well as small-scale spatial genetic structures attributable to local dispersal processes. No relation of underlying environmental gradients such as temperature or precipitation and genetic patterns was found. We conclude that different aspects of historic and more recent gene flow shape population genetic structures and that a thorough analysis on a variety of spatial, temporal and environmental scales is necessary to appropriately select planting material for conservation and restoration measures. Correspondingly, management advice regarding provenance delineations will be provided.