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The open-cast lignite mine “Hambach” (NW-Germany) and the accompanying land reclamation replace a large ancient forest. Reclamation of an 1000 ha large overburden dump started 25 years ago and is still in progress. Reclamation methods comprise combinations of different topsoil dumping techniques and reclamation measures such as seeding or afforestation. In accordance with the spatial heterogeneity hypothesis, we hypothesize that beetle assemblages from sites where the topsoil was left structured are more diverse than those from sites with levelled topsoil, and that richly structured mid-successional sites harbour more heterogeneous assemblages than afforested sites. We tested the influence of environmental variables on assemblage characteristics of pitfall-trapped beetles from 17 sites on the overburden dump. The results are based on 35,588 individuals from 339 species. Species assemblages differed significantly between almost all sites. Habitat age did not affect assemblage characteristics, while species richness was significantly influenced by surface structure. Sites that were not levelled and that additionally included pits that slope down for several meters exhibited the highest species richness. Abundance of beetles increased in parallel to the canopy cover, whereas assemblage heterogeneity (MVDISP) decreased. Successional and grassland sites usually exhibited higher diversity (Fisher's α) than afforested sites, but diversity was not significantly predicted by a single environmental factor. Instead, diversity increased along with increasing MVDISP-values. Afforestations speed up the successional process and some euryecious forest species are already well established, but stenecious forest specialists have not yet been found.

Summary 1. In long-term laboratory studies, the influence of different food materials on parameters of population dynamics was compared in the sympatric woodlice, Porcellio scaber and Oniscus asellus, as a measure of interspecific differences in the utilization of food. 2. Freshly fallen leaf litter of different tree species had been acidified and microbially inoculated prior to the experiments. By analysing the influence of pH level, density and activity of litter-colonizing microbiota and several physico-chemical characteristics of the leaf litter, we obtained information on those factors that determine food quality. 3. The studied species responded similarly to different leaf litter species in that both P. scaber and O. asellus performed better on litter with low C:N ratio. Overall, both isopod species reproduced more successfully on litter with higher pH levels, containing half the levels of tannins and other phenolics. 4. Interspecific differences were obvious with respect to the significance of litter-colonizing microbiota, and the dependence of juveniles on particular food parameters. While the performance of adult P. scaber was influenced by both litter-colonizing microbiota and physico-chemical characteristics of the leaf litter, adult O. asellus were influenced by leaf litter characteristics, but not by litter-colonizing microbiota. Juvenile mortality was affected by the tested food parameters in O. asellus, but not in P. scaber. Growth rates of juveniles of both species were influenced by physico-chemical characteristics of the leaf litter. Additionally, leaf litter microbiota had a significant influence on growth rates in juvenile P. scaber, but not in juvenile O. asellus. 5 Reasons for, and consequences of, similarities and differences between the observed sympatric species, and intraspecific differences between ontogenetic stages, are important aspects of soil ecology and may help explain the sympatric coexistence of two species belonging to the same guild of saprophagous soil animals.

Base cation depletion due to soil acidification is a major environmental problem which can disrupt proper ecosystem functioning. We investigated nine mesic broad-leaved forests growing on Devonian sediments of the Rhenish Shield (Germany) and investigated the effect of coarse woody debris (CWD). The forests grow on soils originating from different parent material (graywacke, slates, dolostone) with upper soil pH-values ranging from 3.0 to 7.0. We analyzed soil chemistry, soil microbial parameters and the density of litter-dwelling detritivores (snails, slugs, woodlice and millipedes) to assess the influence of both acidification and CWD. The forests were classified according to their (Ca + Mg + K)/Al molar ratios into groups with ratios of either 2+ and Mg 2+ availability and an improved (Ca + Mg + K)/Al molar ratio. The presence of CWD also enhanced soil microbial biomass, the density of detritivores and species richness of snails, slugs and millipedes. Consequently, coarse woody debris influences nutrient fluxes and decreases the acidification-related risk of tree damage.

Many forest ecosystems have been extensively degraded by acidifying pollutants over the last decades. There is also widespread concern about population decline of a number of songbirds due to acidification-driven calcium limitation. We hypothesize that the carrying capacity of forests decreases with reduced soil calcium content. We analyzed songbird assemblage/habitat relationships by territory mapping at 30 sites in a total of five managed beech forests. The sites harbored 38 songbird species. A canonical correspondence analysis showed that soil acidification, represented by soil calcium content, had a significant influence on the species assemblages of the 14 most frequent songbirds. The vertical complexity of the canopy additionally influenced the assemblages. Multiple regressions revealed that the density of the territories of song thrush (Turdus philomelos) and nuthatch (Sitta europaea) were positively correlated to calcium content. Blackbirds (Turdus merula) seemed to compensate for the negative effect of acidification by selecting breeding sites close to forest edges to forage in less acidified agricultural habitats. In contrast, the territorial density of robin (Erithacus rubecula), chaffinch (Phylloscopus collybita) and coal tit (Parus ater) increased with increasing soil acidification. Contrary to our hypothesis, the overall carrying capacity of songbird was not reduced in forests with acidified soils. However, the nesting success of song thrush and blackbird, as determined by the number of fledglings, was higher in the forest with the highest calcium content when compared to the forest with the lowest calcium content. We conclude that some species are severely affected by acidification, whereas others seem to have evolved successful strategies to meet their calcium demand even in acidified habitats.

The highly invasive giant knotweed (Reynoutria spp.) often displaces nettle (Urtica dioica) dominated stands in European floodplains. Urtica-dominated stands differ from the monospecific Reynoutria stands in plant species richness and stand structure. We thus hypothesize that Reynoutria invasion profoundly alters ecosystem structure and function, with negative effects cascading up through the food chain. We performed a paired sampling design in six sites belonging to two different locations and studied effects on the soil and the litter-dwelling fauna. Reynoutria stands differed in habitat structure and were characterized by decreased soil pH and potassium depletion. The faunal analysis is based on model groups of herbivore generalists (Gastropoda), detritivores (Isopoda and Diplopoda), and predators (Opiliones). The gastropod assemblages from Reynoutria stands were severely impoverished subsets of those from Urtica stands with reduced densities, species richness and diversity. In general, snails were more sensitive to Reynoutria invasion than slugs such as the invasive Arion 'lusitanicus’. Among detritivores, the abundance of the Isopoda decreased, whereas Diplopoda were not affected by Reynoutria invasion. Yet, the relative abundance of detritivores was significantly higher within the Reynoutria stands. Abundance, species richness and diversity of the predatory Opiliones were higher in the relatively sparse Reynoutria stands. We conclude that ecosystem changes associated with Reynoutria invasion are characterized by shifts from a plant-based to a detritus-based food chain and that Reynoutria invasion primarily enhances predators that profit from the simplified vegetation structure.

Summary 1In laboratory microcosms, we investigated the influence of diversity of both leaf litter and detritivores on decomposition processes. Either woodlice or earthworms, or a combination of woodlice and earthworms, fed on leaf litter of either oak or alder, or oak and alder for 8 weeks. Mass loss of leaf litter, soil microbial respiration and soil nutrient concentrations were determined every 2 weeks. 2For four out of seven decomposition parameters, the joint effects of woodlice and earthworms were stronger than the sum of single-species effects when they had fed on alder litter. When feeding on oak litter, however, woodlice and earthworms together revealed lower decomposition rates than predicted from their single effects. Joint effects of detritivores on decomposition of mixed litter were always lower than predicted from the sum of their effects. 3In mixed-litter assays, we obtained intermediate values of decomposition parameters, indicating that doubling the species richness of leaf litter from one to two species did not promote decomposition processes. Effects of mixing litter were, thus, mostly additive; essentially only when earthworms fed on mixed litter we observed, mostly positive, non-additive effects of diverse litter. 4Our findings provide evidence for a potential effect on ecosystem functioning through joint action of detritivores even at low species diversity, while litter diversity seems to be less significant. On high-quality litter, isopods and earthworms are not functionally redundant but act synergistically on litter decomposition. The effects of detritivore diversity on ecosystem processes, however, are context-specific and depend on the quality and diversity of the available food sources, and on species-specific characteristics of the detritivores.

Herbivorous beetles were sampled in central Slovakia and in the Tatra Mountains of northern Slovakia from seven different Salix species which are partly characterized by smooth leaves containing phenolic glycosides and partly by hairy leaves containing tannins. The collection included about 8000 individuals representing 129 species. Of the 129 species, 77 species are able to use the willows as hosts; the remaining 52 ‘tourist’ species comprise less than 3% of the collected individuals. The data on species richness and abundance did not generally support the ‘feeding specialization’ hypothesis. The proportion of specialized (= monophagous and oligophagous) beetles feeding on willows of both morphological and biochemical groups was in the same range. Host plants of the two groups could support high diversity and high evenness values, even when leaf characteristics and plant chemicals largely influenced species assemblage. The region in which the willow trees grow had a considerable impact on host plant use. Generalist beetle species predominated in central Slovakia. By contrast, in the Tatra Mountains, specialist feeders which are able to use phenolic glycosides to their advantage were predominant. The number of species and the total density of individuals collected from willows containing phenolic glycosides (S. fragilis and S. purpurea) did not usually vary between the two regions. In contrast, fewer species and individuals were found in the Tatra Mountains when they settled on willow species containing tannins (S. caprea and S. cinerea). Also, the phylogenetic status of host plants affected species assemblages. In central Slovakia willow species of the subgenus Vetrix (S. purpurea, S. caprea and S. cinerea) generally showed a higher beetle diversity (Hs) than species of the subgenus Salix (S. fragilis, S. alba and S. triandra), although both subgenera comprise species of both morphological and biochemical groups. Furthermore, when the analysis was restricted to beetles of central Slovakia, which should be most adapted to their host plants (i.e. catkin feeders and phyllophages in the adult and larval stage), the phylogenetic status was found to be more important than any single leaf character measured.

Reclaimed lignite open-cast mine areas in the Rhineland are covered by a mixture of loess and sand deposits containing organic material that originates from the upper quartary soil which has been taken from the front of the mining path. Consequently, the soil fauna that has established itself on the reclaimed open-cast mine areas may result from the primary succession and also from species that are carried to the dumping mines and are able to survive the dumping process. The reclaimed landscape consists of a regular structural pattern of crests and troughs. The troughs provide appropriate habitats for establishing a rich and diverse fauna with higher densities of almost all animal groups investigated, with enhanced microbial activity and higher values of available macronutrients. In terms of plant growth, the physical and chemical conditions found in the troughs exceeded the conditions found on the crests. From laboratory studies we made the following conclusions: (1) environmental conditions in the troughs were improved not only by erosion, but additionally by the soil fauna that directly enhanced microbial activity and indirectly increased the availability of macronutrients; (2) soil animals improved soil quality by increasing the pH-values, increasing the ammonium–nitrogen content and decreasing the content of aluminium ions; and (3) a multiple-species system is able to improve soil quality more effectively than a single-species system.

In microcosm experiments Porcellio scaber increased litter disappearance of oak and alder litter. Alder litter disappeared at more than twice the rate of oak litter. Soil texture did not influence the disappearance of oak litter; however, disappearance of alder litter was enhanced on silt rather than on sand. P. scaber enhanced microbial communities (i.e. microbial respiration and microbial biomass) on both silt and sand when feeding on either alder or oak. Overall, microbial respiration increased 10-fold when isopods fed on oak litter on sand and 20-fold when isopods fed on alder litter on sand. On silt, the initially high microbial respiration remained constant when isopods fed on oak and doubled when they fed on alder litter. In all treatments without P. scaber there was a decrease in microbial respiration over the 12-week experimental period. The availability of macronutrients (Corg, Ntot, P, K, Mg, Ca) in the topsoil was increased when P. scaber fed on alder litter but less pronounced when P. scaber fed on oak litter. Using sand as a substrate, there was an apparent increase only for Corg, Mg and Ca; on silt, increases in Corg, Ntot and P were measured. Under field conditions the contribution of P. scaber to nutrient fluxes will be higher on sand than on silt.

Field studies on microbial populations and their activity in soil and litter layers of different sites revealed statistically significant correlations with climatic factors, soil characteristics and the number of terrestrial isopods (Isopoda: Oniscidea). The number of captured Porcellio scaber was negatively correlated with the density of soil microbiota, but positively correlated with both respiration and cellulolytic activity of litter-colonizing microorganisms. By contrast, the number of Oniscus asellus was positively correlated with soil microbial density and respiration, and cellulolytic and respiratory activity of the litter. These interspecific differences were unexpected between species that frequently occur sympatrically, and, thus, probably have similar ecological requirements. Hence, the results suggested species-specific interactions of these species with soil and litter-colonizing microbiota. However, further field studies are required to prove this.

Population parameters (mortality of females, reproductive success, longevity of juveniles) of the common woodlouse, Porcellio scaber (Isopoda, Oniscidea), were examined with respect to the influence of varying leaf litter attributes: pH level, microbial cellulase activity, microbial dehydrogenase activity, protein content, nitrogen content, water content, tannin content, total phenol content and toughness of the leaves. These attributes were combined by using Principal Component Analysis. We obtained three Principal Components (PC) that were defined as “acidification,”“microorganisms” and “tree species.” The PCs explained 85% of the variance of leaf litter attributes. The PC “acidification” mainly influenced the mortality of females (P

We compared Quercus petraea monocultures with adjacent mixed oak-hazel (Corylus avellana) stands at gentle (14°) and steep (25°) slopes of the Ahr-Eifel. The influence of hazel on forest floor mass, soil nutrients, microbial properties and on the abundance of Lumbricidae was studied. Litter mass was greater in mixed stands than in oak monocultures, resulting in a thicker Ah-horizon. Additionally, the PO43-, Ca2+- and Mg2+-contents were higher and the Al3+-content lower in the upper soil of mixed stands. In contrast, the contents of organic carbon , total nitrogen and the C/N ratio did not differ between the two soils. Basal respiration, specific microbial activity (qCO2) and carbon mineralisation (Cmin) were higher in mixed stands than in oak monocultures. Lumbricidae showed low densities in three of the stands studied (15-21 ind./m2) and were almost absent at the oak monoculture on the steep terrain (2 ind./m2)., Le noisetier améliore la qualité du sol des peuplements de chênes de basse montagne en Allemagne. Nous avons comparé des monocultures de type Quercus petraea avec des cultures adjacentes mixtes composées de chênes et de noisetiers (Corylus avellana) situées sur des pentes (14°/25°) différentes. L'influence du noisetier sur la masse de litière, les substances nutritives du sol, les propriétés microbiennes et l'abondance de Lumbricidae at été étudiée. Cette étude a montré que la masse de litière est plus élevée dans les cultures mixtes que dans les monocultures de chênes ; il en résulte un épaississement de l'horizon Ah. En outre, les teneurs en PO43- -P, Ca2+ - et Mg2+ - sont plus élevées et les teneurs en Al3+ -plus faibles dans les couches supérieures des sols de cultures mixtes. Par contre, la teneur en carbone organique, en azote total ainsi que la relation C/N ne diffèrent pas. La respiration de base, l'activité microbienne spécifique (qCO2) et la minéralisation carbonique (Cmin) sont plus élevées dans les cultures mixtes que dans les monocultures de chênes. Les Lumbricidae présentent des densités faibles dans trois des cultures étudiées (15-21 ind./m2), tandis qu'ils sont pratiquement absents dans les monocultures de chênes en terrain escarpé (2 ind./m2).