Sonja Migge

Bio: Sonja Migge is an academic researcher from University of Göttingen. The author has contributed to research in topics: Beech & Picea abies. The author has an hindex of 11, co-authored 12 publications receiving 1904 citations. Previous affiliations of Sonja Migge include Technische Universität Darmstadt & University of Calgary.

Non‐native invasive earthworms as agents of change in northern temperate forests

Abstract: Exotic earthworms from Europe and Asia are invading many northern forests in North America that currently lack native earthworms, providing an opportunity to assess the role of this important group of invertebrates in forest ecosystems Research on earthworm invasions has focused on changes in soil structure and carbon (C) and nitrogen (N) cycling that occur following invasion These changes include the mixing of organic and mineral soil horizons, decreases in soil C storage, and equivocal effects on N cycling Less well studied are changes in the soil foodwebs that accompany earthworm invasion Soils of north temperate forests harbor a tremendous diversity of microorganisms and invertebrates, whose distribution and abundance can be substantially altered by earthworm invasion Furthermore, invasive earthworms can affect understory plant communities, raising concerns over the loss of rare native herbs in some areas The ecological consequences of earthworm invasion are mediated through physical, geochemica

Trophic niche differentiation in soil microarthropods (Oribatida, Acari): evidence from stable isotope ratios ( 15 N/ 14 N)

Abstract: The large number of animals that coexist in soil without any clear niche differentiation has puzzled biologists for a long time. We investigated stable isotope ratios ( 15 N/ 14 N) in a diverse group of soil microarthropods, oribatid mites, to evaluate trophic niche differentiation. The natural variation of the stable isotopes 15 N/ 14 N was measured in 36 species/taxa from four beech and beech-oak forests. Signatures of d 15 N formed a gradient spanning over 12 d units suggesting that (a) different species occupy different trophic niches and (b) oribatid mites span three to four trophic levels. This study for the first time documented strong trophic niche differentiation in decomposer microarthropods. The results suggest that trophic niche differentiation within taxonomic groups significantly contributes to the high diversity of soil animal taxa. q 2004 Elsevier Ltd. All rights reserved.

Trophic niche differentiation in soil microarthropods (Oribatida, Acari): evidence from stable isotope ratios (15N/14N)

Abstract: The large number of animals that coexist in soil without any clear niche differentiation has puzzled biologists for a long time. We investigated stable isotope ratios (15N/14N) in a diverse group of soil microarthropods, oribatid mites, to evaluate trophic niche differentiation. The natural variation of the stable isotopes 15N/14N was measured in 36 species/taxa from four beech and beech-oak forests. Signatures of δ15N formed a gradient spanning over 12 δ units suggesting that (a) different species occupy different trophic niches and (b) oribatid mites span three to four trophic levels. This study for the first time documented strong trophic niche differentiation in decomposer microarthropods. The results suggest that trophic niche differentiation within taxonomic groups significantly contributes to the high diversity of soil animal taxa.

The soil fauna community in pure and mixed stands of beech and spruce of different age: trophic structure and structuring forces

Abstract: Scheu, S., Albers, D., Alphei, J., Buryn, R., Klages, U., Migge, S., Platner, C. andSalamon, J.-A. 2003. The soil fauna community in pure and mixed stands of beechand spruce of different age: trophic structure and structuring forces. – Oikos 101:225–238.This study investigates the response of the soil fauna community to replacement ofbeech by spruce or by mixed stands of beech and spruce. Stands of different age wereinvestigated in a factorial design with the factors tree species (beech and spruce) andstand age (30 and 120 years). The input of leaf/needle litter did not differ significantlybetween the study sites. By contrast, the amount of organic matter in upper soillayers (L/F, H/Ah) of spruce forests strongly exceeded that of beech forests particu-larly in mature stands. The increase in organic matter in spruce stands was notassociated by an increase in the amount of microbial biomass. Biomass of eight(bacterivorous, fungivorous and omnivorous nematodes, enchytraeids, earthworms,isopodes, mycetophilid and cecidomyiid Diptera) of the twelve microbi-detritivoroussoil animal groups studied was significantly increased in beech forests; only that ofone group (elaterid beetles) was increased in spruce forests and three groups did notrespond significantly (collembolans, oribatid mites, sciarid Diptera). This indicatesthat in the forests studied neither habitat space (amount of organic matter in L/FandH/Ah layers) nor the amount of microbial biomass controlled microbi-detritivores.Rather, the quality of litter materials and the concentration of microbial biomasstherein appeared to be most important. Herbivores and predators also were favouredby beech: the biomass of one (rhizophagous nematodes) of the three herbivorousgroups studied were significantly increased in beech stands and none in spruce stands;the biomass of four (predatory nematodes, centipedes, carabid and cantharid beetles)of the seven carnivorous groups studied were increased in beech stands, none inspruce stands. Generally, the biomass ratio between prey and predators was at aminimum in mature beech and mixed stands indicating more intense top-downcontrol in these forests. Overall, the study documents that replacement of beech byspruce strongly alters the soil food web. Mixed stands were more similar to sprucestands in respect to the biomass of soil animal groups but predator–prey interactionsappeared to be more similar in mature beech and mixed stands. Differences betweentree species usually were more pronounced in 120 compared to 30 years old standsindicating that the development of stand characteristics is slow.

Influence of Diet On the Distribtion of Nitrogen Isotopes in Animals

Abstract: The influence of diet on the distribution of nitrogen isotopes in animals was investigated by analyzing animals grown in the laboratory on diets of constant nitrogen isotopic composition. The isotopic composition of the nitrogen in an animal reflects the nitrogen isotopic composition of its diet. The δ^(15)N values of the whole bodies of animals are usually more positive than those of their diets. Different individuals of a species raised on the same diet can have significantly different δ^(15)N values. The variability of the relationship between the δ^(15)N values of animals and their diets is greater for different species raised on the same diet than for the same species raised on different diets. Different tissues of mice are also enriched in ^(15)N relative to the diet, with the difference between the δ^(15)N values of a tissue and the diet depending on both the kind of tissue and the diet involved. The δ^(15)N values of collagen and chitin, biochemical components that are often preserved in fossil animal remains, are also related to the δ^(15)N value of the diet. The dependence of the δ^(15)N values of whole animals and their tissues and biochemical components on the δ^(15)N value of diet indicates that the isotopic composition of animal nitrogen can be used to obtain information about an animal's diet if its potential food sources had different δ^(15)N values. The nitrogen isotopic method of dietary analysis probably can be used to estimate the relative use of legumes vs non-legumes or of aquatic vs terrestrial organisms as food sources for extant and fossil animals. However, the method probably will not be applicable in those modern ecosystems in which the use of chemical fertilizers has influenced the distribution of nitrogen isotopes in food sources. The isotopic method of dietary analysis was used to reconstruct changes in the diet of the human population that occupied the Tehuacan Valley of Mexico over a 7000 yr span. Variations in the δ^(15)C and δ^(15)N values of bone collagen suggest that C_4 and/or CAM plants (presumably mostly corn) and legumes (presumably mostly beans) were introduced into the diet much earlier than suggested by conventional archaeological analysis.

Biodiversity and Litter Decomposition in Terrestrial Ecosystems

Abstract: ▪ Abstract We explore empirical and theoretical evidence for the functional significance of plant-litter diversity and the extraordinary high diversity of decomposer organisms in the process of litter decomposition and the consequences for biogeochemical cycles. Potential mechanisms for the frequently observed litter-diversity effects on mass loss and nitrogen dynamics include fungi-driven nutrient transfer among litter species, inhibition or stimulation of microorganisms by specific litter compounds, and positive feedback of soil fauna due to greater habitat and food diversity. Theory predicts positive effects of microbial diversity that result from functional niche complementarity, but the few existing experiments provide conflicting results. Microbial succession with shifting enzymatic capabilities enhances decomposition, whereas antagonistic interactions among fungi that compete for similar resources slow litter decay. Soil-fauna diversity manipulations indicate that the number of trophic levels, spec...

Plant functional traits and soil carbon sequestration in contrasting biomes

Abstract: Plant functional traits control a variety of terrestrial ecosystem processes, including soil carbon storage which is a key component of the global carbon cycle. Plant traits regulate net soil carbon storage by controlling carbon assimilation, its transfer and storage in belowground biomass, and its release from soil through respiration, fire and leaching. However, our mechanistic understanding of these processes is incomplete. Here, we present a mechanistic framework, based on the plant traits that drive soil carbon inputs and outputs, for understanding how alteration of vegetation composition will affect soil carbon sequestration under global changes. First, we show direct and indirect plant trait effects on soil carbon input and output through autotrophs and heterotrophs, and through modification of abiotic conditions, which need to be considered to determine the local carbon sequestration potential. Second, we explore how the composition of key plant traits and soil biota related to carbon input, release and storage prevail in different biomes across the globe, and address the biome-specific mechanisms by which plant trait composition may impact on soil carbon sequestration. We propose that a trait-based approach will help to develop strategies to preserve and promote carbon sequestration.

The Ecological Significance of the Herbaceous Layer in Temperate Forest Ecosystems

Abstract: Despite a growing awareness that the herbaceous layer serves a special role in maintaining the structure and function of forests, this stratum remains an underappreciated aspect of forest ecosystems. In this article I review and synthesize information concerning the herb layer's structure, composition, and dynamics to emphasize its role as an integral component of forest ecosystems. Because species diversity is highest in the herb layer among all forest strata, forest biodiversity is largely a function of the herb-layer community. Competitive interactions within the herb layer can determine the initial success of plants occupying higher strata, including the regeneration of dominant overstory tree species. Furthermore, the herb layer and the overstory can become linked through parallel responses to similar environmental gradients. These relationships between strata vary both spatially and temporally. Because the herb layer responds sensitively to disturbance across broad spatial and temporal scal...

Microbial contributions to climate change through carbon cycle feedbacks.

Abstract: There is considerable interest in understanding the biological mechanisms that regulate carbon exchanges between the land and atmosphere, and how these exchanges respond to climate change. An understanding of soil microbial ecology is central to our ability to assess terrestrial carbon cycle–climate feedbacks, but the complexity of the soil microbial community and the many ways that it can be affected by climate and other global changes hampers our ability to draw firm conclusions on this topic. In this paper, we argue that to understand the potential negative and positive contributions of soil microbes to land–atmosphere carbon exchange and global warming requires explicit consideration of both direct and indirect impacts of climate change on microorganisms. Moreover, we argue that this requires consideration of complex interactions and feedbacks that occur between microbes, plants and their physical environment in the context of climate change, and the influence of other global changes which have the capacity to amplify climate-driven effects on soil microbes. Overall, we emphasize the urgent need for greater understanding of how soil microbial ecology contributes to land–atmosphere carbon exchange in the context of climate change, and identify some challenges for the future. In particular, we highlight the need for a multifactor experimental approach to understand how soil microbes and their activities respond to climate change and consequences for carbon cycle feedbacks.