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Physiological constraints from harsh environmental conditions, such as from calcium limitation on acidic soils, is expected not only to affect species richness, but also species abundance distributions. Also, the effects of amendments by calcium addition (soil liming) on these assemblage characteristics are poorly understood. Because of their sensitivity towards calcium availability, we use snails as model organisms and integrate field surveys and literature data. Temperate forest snail data supported a rule-of-thumb calibration with pH measurements in water being one unit higher than in KCl buffer. The resulting large data set suggests stepwise changes in snail richness that occur at transitions in soil buffer systems, especially at pH 3.2. Species abundance distributions follow the logseries model in most soil buffer systems, except for the iron buffer range (pH ≤3.2) where they swap to the geometric model. Our findings thus suggest several smaller soil pH thresholds for snail assemblages associated with shifts between soil buffer systems, and a tipping point at the threshold to pH ≤3.2. Liming with ground carbonate rocks is a technique to temporarily increase soil pH and calcium availability in forest soils, but its effects on snail assemblages produced inconsistent results that did not meet expectations from the ameliorated soil pH and might warrant a re-evaluation of liming applications.

We studied the leaf litter-dwelling fauna of managed deciduous forests and primeval reference sites in Western and Central Europe and addressed the questions if the higher overall species richness close to downed coarse woody debris (CWD) is related to intra-specific or inter-specific aggregation, if the aggregation pattern changes with the amount of CWD on the forest floor, and how much CWD is needed for different taxa. The analysis is based on shelled Gastropoda, Diplopoda/Isopoda, Chilopoda and Coleoptera. Among-sample heterogeneity was lower close to CWD than distant from CWD. This was most pronounced in Diplopoda/Isopoda and Gastropoda. Diplopoda/Isopoda are comparatively mobile and assemblages were already quite homogenous close to CWD at levels above 5 m3 downed deadwood ha−1. Gastropoda have a low mobility, and more than 20 m3 downed deadwood ha−1 is needed for assemblage homogeneity. We further focused on the Gastropoda as sensitive indicators. Enhanced densities and species richness close to CWD were not a simple function of leaf litter weight, thus effects of densities on heterogeneity are not solely driven by leaf litter accumulation close to CWD. In contrast to euryecious litter-dwellers such as the Punctidae, stenecious slow active dispersers such as the Clausiliidae clearly require more than 20 m3 CWD ha−1 for an even distribution. Specialists depending on CWD even seem to have gone extinct in some managed forests. For conserving the litter-dwelling fauna, we propose a target of at least 20 m3 downed CWD ha−1 in already managed forests and rigorous restrictions for deadwood removal from still (almost) pristine systems.

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.

Giant knotweeds (Reynoutria spp.) are highly productive and aggressive invaders in riparian wetlands of Europe and North America. We sampled ground-dwelling beetles by pitfall traps from six sites comparing monotypic Reynoutria stands with the invaded native Urtica-dominated stands. Three sites were located in a semi-natural softwood forest and three sites were on a ruderal embankment. The analyses are based on a total of 13,244 individuals from 218 species. Location and site significantly influenced beetle assemblages. Moreover, there were pronounced differences between vegetation stands. The monotypic Reynoutria stands exhibited lower beetle abundance, species richness and rarefaction diversity irrespective of location. However, the negative effect on species richness, abundance and assemblage similarities were stronger on the transformed ruderal embankment than in the semi-natural softwood forest. Reynoutria invasion seems to influence microclimatic conditions. We found a higher abundance of silvicolous and a lower abundance of xerophilous ground beetles in the Reyountria stands than in the Urtica-dominated stands. Feeding guilds reacted differently to Reynoutria invasion that reduced the abundance of predators and herbivores but enhanced that of detritivores. Detritivores assumingly profit from the perennial presence of the large quantities of Reynoutria litter. We conclude that highly productive invaders pauperise the arthropod fauna and alter link strengths in trophic cascades shifting primary producer-based food webs to detritus-based food webs.

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.

We studied the snail fauna of four primeval forests of Central Slovakia and focused on the influence of forest type and coarse woody debris (CWD) on species assemblages. We found a total of 3281 individuals from 39 species. Species assemblages differed between the forests. In SW-facing oak forests, CWD enhanced the proportion of forest species such as the wood-grazing Cochlodina laminata and decreased the proportion of euryecious species like the litter-dwelling Punctum pygmaeum. In NE-facing beech forests, hygrophilous species such as Carychium tridentatum dominated the assemblages. This litter-dwelling snail was especially abundant close to CWD. The NE-facing beech forests harbored more species and individuals than the SW-facing oak forests did. CWD enhanced snail abundance, species richness and biodiversity, irrespective of forest type. We found positive correlations for

We investigated the distribution pattern of centipedes (Chilopoda) in four primeval forests of the western Carpathians, central Slovakia. The forests are located in two different mountain ranges (Kremnicke vrchy and Pol’ana Mountains), which are exposed on either the southern (Boky, Rohy) or northern slopes (Pol’ana, Badin). In these forests, the influence of coarse woody debris (CWD) on centipede distribution was studied, by distinguishing sampling sites on the forest floor, close to CWD (c-CWD) and distant from CWD (d-CWD). In total, we collected 2,706 individuals from 20 species of centipedes. Average species richness and number of individuals per forest ranged from 8 to 12 species/m2 and from 244 to 486 individuals/m2. The oak forests on south facing slopes harboured several species, which did not occur in the more northern exposed fir-beech forests. Number of species as well as individuals, however, varied more within than between individual forests. Increase of species number and density was mainly caused by CWD and was more pronounced on the southern slopes (P

We collected 1605 isopod individuals (eight species) and 671 diplopod individuals (17 species) in four primeval forests of the Western Carpathians, Central Slovakia, by leaf litter extraction. The forests are of different temperate deciduous forest types varying in tree species, aspect, elevation and soil characteristics. The oak forests, established on southwest oriented slopes at an elevation of 280–600 m, were characterized by Hyloniscus riparius , Porcellium conspersum , Enantiulus nanus and Ophioiulus pilosus . The beech forests, established on northeast oriented slopes at an elevation of 700–1100 m, were characterised by Ligidium hypnorum , Trachysphaera costata and Polyzonium germanicum . A remarkable increase of the total number of species and individuals occurred in both forest types adjacent to coarse woody debris (CWD). Woodlice density close to CWD was between 200 and 630 individuals m −2 (35–130 individuals m −2 distant from CWD); millipede density close to CWD ranged from 60 to 230 individuals m −2 (15–75 individuals m −2 distant from CWD). Species richness of both taxa close to CWD varied from 13 to 16 species m −2 (7–12 species m −2 distant from CWD). Thus, CWD has a significant influence on saprophages. However, structural components such as CWD and the amount of leaf litter did not significantly alter species assemblages. Species at sites distant from CWD were a subset of species at sites close to CWD. According to a canonical correspondence analysis (CCA), ‘forest type’ and ‘elevation within a slope’, as well as chemistry of the upper soil layer, i.e. ‘acidification’ and ‘nutrition’, strongly influenced species assemblages.

In many afforested reclamation sites as well as in commercial forests naturally settled shrubs or trees (“non-target species”; NTS) are cut down to improve the growth of the target trees (TT). In afforested oak plantations ( Quercus robur ) of the Rhineland (Germany) the NTS broom ( Cytisus scoparius ) and birch ( Betula pendula ) can occur in high densities during the first decades of succession. Hazel ( Corylus avellana ) is a common shrub in the understory of commercial oak forests ( Quercus petraea ). We studied the influence of these NTS on selected physical, chemical and biotic soil properties in cultures of oak (TT). Soil samples taken under single oak trees were compared with samples taken under broom and birch at afforested reclamation sites of different age (2, 9, 13 years) and with samples taken under hazel in an 80-year-old oak forest. At initial stages of succession (2 years) all of the investigated soil properties indicated a higher soil quality under broom than under oak. However, the advantage of broom was less evident in a later stage of succession (9 years). Birch (13 years) and hazel (80 years) only improved soil chemical properties. The soil pH and the content of Mg 2+ were significantly higher under birch, the contents of Ca 2+ , Mg 2+ and PO 4 3− were significantly higher under hazel than under oak ( p =0.05). The results demonstrate that the selected NTS improve soil quality in afforested and commercial oak forests. This effect is pronounced under the influence of broom at initial stages of soil development.

We studied the soil properties of 18-year-old plantations beneath the crowns of the native sessile oak ( Quercus petraea ) and of the introduced red oak ( Quercus rubra ) growing on reclaimed lignite open-cast mines. The soil properties of both plantations, which are growing on either highly fertile (loess deposits, silty loam) or on low fertile (mixture of loess and sand deposits, clayed sand) soil, were measured and compared with values taken from 2-year-old Quercus robur plantations. In plantations of Q. petraea we generally found higher values of total carbon (C org ) and total nitrogen (N tot ) in the upper soil, although the amount of organic matter in the O-horizon did not significantly differ. Soils of Q. petraea plantations also exhibited higher values for microbial and faunal life. For example, microbial activity, the respiratory quotient ( q CO 2 ) and C-mineralization were about twice as high as for the Q. rubra plantations. Collembola and mites (Oribatei), both belonging to the soil mesofauna, reached higher densities in the Q. petraea plantations. When growing on highly fertile soils, the amount of soil nutrients (K + , Ca 2+ , Mg 2+ , and PO 4 3− P) did not differ between the two plantations. However, when oak trees grew on the less-fertile soil, the amount of soil nutrients was significantly lower beneath red oak. The amount of soil nutrients beneath red oak was even lower than beneath 2-year-old Q. robur plantations; the soil properties of which are almost at the beginning stage of succession. The results suggest that nutrient depletion beneath red oak when compared to sessile oak is caused both by increased immobilization into woody biomass, and by increased recalcitrance of organic matter.

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.

We studied Coleoptera emerging from deadwood in a broadleaved forest that has been managed with nature-oriented forestry since 1990 and in which an accumulation of 10 m3 deadwood/ha has been achieved. We sampled a total of 11 m3 of deadwood from oak and beech trees and yielded 32,477 individuals pertaining to 342 species. The number of species emerging from oak deadwood was significantly higher than that from beech. Significantly more species emerged from deadwood with medium size (15–21 cm) diameter than from smaller (5–7 cm) or larger (40–60 cm) diameters. The stage of decay did not influence the number of species during the first 6 years of decomposition. Species richness strongly increased with the amount of deadwood sampled. Species–area regressions yielded z-values of 0.81 for oak and 0.87 for beech deadwood. The beetle assemblage was characterized by a low number of xylophagous species and a high number of mobile zoophagous species. However, two-thirds of the individuals sampled pertained to nine species of Scolytidae. This is why Shannon–Wiener diversity (H) and evenness-indices (E) greatly decreased with increasing number of scolytids. The species and individuals yielded from the sun-exposed deadwood outnumbered those from shaded areas. Namely the scolytid Taphrorychus bicolor reached remarkably high densities in the sun-exposed beech deadwood (>800 individuals/m2). In contrast, oak deadwood never harboured such high numbers of scolytids. Felling of moribund trees had decreased the number of scolytids but it had also considerably reduced the number of rare and endangered species.

In a 2-year study we investigated soil macro-arthropods (Opilionida, Araneida, Pseudoscorpionida, Isopoda, Diplopoda, Chilopoda, Coleoptera) in a forest where forestry management is nature oriented and includes the accumulation of about 10 m 3 deadwood per ha. We focused on soil arthropod density close to (c-CWD) or distant from coarse woody debris (d-CWD) in different locations of the forest stand (interior location versus edge zone) and in different seasons (summer versus winter). We found twice as many individuals of almost all taxa at c-CWD sites compared to d-CWD sites. The influence of CWD on most taxa of soil arthropods was more pronounced in the edge zone than in the interior location. In the edge zone c-CWD sites yielded significantly higher numbers of all taxa in both seasons. In the interior location seasonal effects occurred. For example, Pseudoscorpionida and Coleoptera-Larvae preferred c-CWD sites only in summer, whereas Araneida preferred c-CWD sites only in winter. A three-way ANOVA, regarding site, location and season as the main factors, emphasised the dominant influence of CWD on the density of all taxa. Consequently, CWD is an important structural component that serves as a habitat for many saprophagous species and thus locally improves the nutritional situation of a forest stand. CWD also may reduce the pest species problem because it harbours many zoophagous soil macro-arthropods as well. # 2004 Elsevier B.V. All rights reserved.

Different explanations have been proposed for why terrestrial isopods prefer, and gain from, feeding on microbially inoculated food materials. In the present study, no-choice feeding experiments are used to test three contrasting, but not mutually exclusive, hypotheses. (1) The digestion and nutritional utilization of microbial cells enhance the nutritive value of leaf litter; (2) extracellular digestive enzymes of microbial origin promote digestion of leaf litter; (3) leaf litter-colonizing microbiota serve as indicators for easily digestible leaf litter of high nutritive value. Predictions derived from these hypotheses are compared with the results of a study with experimentally manipulated leaf litter, serving as food sources for the common woodlouse Porcellio scaber. Leaf litter-colonizing microbiota increased consumption of leaf litter by isopods and contributed somewhat to biomass gain of isopods, but not to the assimilation of ingested food. Thus, the present results coincide with predictions derived from hypothesis (3) suggesting that leaf litter-colonizing microbiota stimulate consumption by indicating high food quality. Their positive effects on assimilation and growth, however, are context-specific, being stronger in case of high-quality food than in case of low-quality food.

Cold-season beetles, Catops nigricans Spence, Choleva agilis Illiger and Choleva elongata Payk., i.e. beetles which start to lay eggs in autumn, which are active during the winter in the adult stage and develop from the egg stage to the adult stage mainly during the winter months, were collected from various locations in north-western Europe and reared in the laboratory at varying temperatures and photoperiods.Reproduction of all species started in autumn and continued during the winter months. Highest reproductive and survival rates occurred at low temperatures and within a small thermal window ranging from 5° to 10°C: The fitness of individuals decreased at higher and lower temperatures. The lower thermal threshold for all developmental stages was in the range from -5°C to +2°C. The metabolisms of the species were independent of temperature in both dormant and non-dormant stages and were elevated in the low temperature range in comparison to other species which show a temperature-dependent reaction pattern.Optimal dates for reproduction were determined by the duration of an obligatory adult summer diapause. In C. nigricans, which favours the litter layer of deciduous forests, this duration was fine-tuned by exogenic factors, such as photoperiod and temperature. In contrast, the soil-inhabiting species Ch. elongata showed a homeostatic response pattern, independent of temperature and photoperiod. Heritability (h2) of the duration of diapause was approximately 0.26 in C. nigricans, less pronounced in Ch. agilis (ca. 0.12) and not evident in the subterranean species Ch. elongata.All three species compensated for the vagaries of climate through bet-hedging tactics. Bet-hedging is so pervasive that a recent substantial increase in temperature seems to have a negligible effect on the distribution pattern of all three species. Based on life-history data it is conceivable that both soil-inhabiting Choleva species, which require a relatively low thermal sum for their development, were already present in western Europe during the sub-arctic conditions when ice shields reached their maximum extension during glacial periods by shifting their activity from the cold to the warm season. The Atlantic fringe north of the Pyrenees, where the climate was not cold enough for permafrost during glacial stages, was probably the only refuge where Ch. elongata might have survived. In contrast, the Mediterranean region should have been the northernmost refuge for C. nigricans during glacial periods. This species has relatively high day-degree requirements (= 1150 d°) for individual development when compared to both Choleva species (= 700 d°).

In feeding experiments, leaf litter of different tree species and isopod feces derived from these leaf litter materials were offered to the common woodlouse, Porcellio scaber . Consumption indices were used to elucidate the nutritional significance of coprophagy. Consumption rates of P. scaber clearly differed between feeding assays with alder ( Alnus glutinosa ) litter and those with isopod feces derived from alder. Differences between feeding assays depended on microbial activity of the food sources when oak ( Quercus robur ) litter or isopod feces derived from oak were offered. Further, microbiota increased the digestibility of oak material, but did not change digestibility of alder litter and reduced digestibility of feces derived from alder. Thus, the significance of litter- or feces-colonizing microbiota decreased with increasing nutritive value of the leaf litter. Inoculated feces derived from oak provided better growth than any other oak-derived food. In contrast, isopods grew better on alder litter than on alder-derived feces. In sum, we found little evidence to support the notion that P. scaber gains from coprophagy. We reject the hypothesis that coprophagy meets a need for nutrients that, due to digestive incapabilities, cannot be satisfied by feeding on leaf litter alone. The hypothesis that microbial colonizers render feces attractive as a source of microbial enzymes or nutrients is only partly corroborated. P. scaber gains from coprophagy through microbial activity or biomass only if leaf litter quality is low.

In microcosms containing soil from a mixed deciduous forest, we examined the nutrient release from feces of phytophagous insects through coprophagous behavior of saprophagous soil animals during 12 weeks of decomposition. The decomposition of feces of Operophthera fagata (Lepidoptera: Geometridae) fed on beech (Fagus sylvatica) released more cations (Ca2+, Mg2+, K+) into the soil than the decomposition of beech litter, whether or not woodlice, Porcellio scaber and Oniscus asellus (Isopoda: Oniscidea), were present. Similarly, the C/N ratio of the soil was lower in assays with feces than in those with leaf litter. Coprophagy by isopods resulted in decreased C/N ratio of the soil. Respiratory activity of soil microbiota was greater when woodlice degraded Operophthera feces than when they degraded beech litter for 12 weeks. The present study provides evidence for nutrient release from the feces of phytophagous insects into the soil through the feeding activity of coprophagous soil animals.

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.

The jumping plant-lice fauna of seven different willow species growing adjacent to the Rhine River and nearby was investigated in a two-year study. In four of five distinct sites all the seven plant-lice species were found, which feed on willows in central Europe. Number and density of species per host varied tremendously depending on the year, host plant species and site. There was no plant-lice species which characterised a distinct host or a distinct site. Cacopsylla pulchra (Zetterstedt 1838) was the most common psyllid species: it dominated at four of the five sites studied, and preferred either Salix viminalis, S purpurea or S alba at each site, even when the other host plants were also present. The canonical correspondence analysis (CCA), which takes the year of study, the site and the host plant species including secondary plant chemistry into account, resulted in 45% of the variance in psyllid diversity, leaving up to 55% to unexplained variance which could potentially be accounted for by a stochastic dispersion pattern and the low ability to find host plants. The number of species and individuals of the Salix-feeding psyllids usually surpassed that one of the tourist species. However, several examples of this study exhibited higher tourist guild inputs than of psyllid species associated with their hosts. This was found not only for single host trees but also for total groups of single willow species growing at a site. The study clearly demonstrates that plant-lice assemblages and herbivory are dynamic processes that reflect influences of variable environmental conditions and erratic colonization.

The study area is located in the low mountain range of Central Europe (Eifel) and characterized by a marked relief and high game densities. Especially red deer populations, calculated at 20 ind./100 ha, surpass the carrying capacity of the forests observed. Trampling (by red deer and moufflon) and rooting (wild boar) result in extensive soil disturbances, visible as soil profile mixture and soil erosion.

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.

This paper is focused on diapause and polyphenism of development of Lagria hirta L. and tries to unravel its mechanism of life-history adaptation. Lagria hirta, distributed widely in Europe, has a strictly univoltine life cycle. The results showed that larval diapause and moulting polymorphism were the deciding factors that made L. hirta maintain its univoltinism and keep a flexible relation between seasonal changes and life-history phases. In the laboratory, larvae of this species were not able to pupate if kept at constant temperatures of 5 °, 10 °, 15 °, 20°, 25 ° or 30 °C combined with a photoperiod of either LD (L16:D8) or SD (L8:L16). Pupation only occurred if larvae were reared at 15 °-25 °C when intervened by a three-month chilling at 5 °C in stages L 3 , L 4 , L 5 or L 6 . A chilling treatment was shown to be obligatory for the termination of its larval diapause and had an accelerating and synchronizing effect on larval development. Larval diapause of L. hirta was characterized by no pupation and more moulting in advanced instars, longer duration of each single stage, and moulting desynchronization. Larval development was found to be variable with respect to the total number of instars: most larvae underwent a total of seven or eight moults; some larvae might even moult once or twice more, but they seldom pupated. It seemed that the choice for the 7-instar or the 8-instar development did not directly relate to any of the external conditions, such as temperature, photoperiod, and stages with chilling treatment. This polyphenism was observed in the same group under identical conditions and even in a single egg clutch. In L. hirta, overwintering in different stages of L 3 -L 6 . and choosing the 7- or 8-instar pathway of development are two features that increase the plasticity and flexibility in coordinating its life cycle with seasonal change, that varies unpredictably from year to year.

Summary Long-term observations of Trichoniscus pusillus revealed that chemical composition and microbial activity of the leaf litter serving as food influenced the reproductive success of females and the mortality rates of juveniles as well. Of the food sources investigated, only alder litter, exhibiting high microbial activity, allowed the maintenance of a stable population with frequently reproducing females. This study concludes that the food type is a significant factor for population parameters of this parthenogenetic isopod. Our results on T. pusillus, belonging to the taxon Synocheta, are compared with data on terrestrial isopod species of the taxon Crinocheta.

Summary We analysed field data on the occurrence of woodlice and millipedes in abandoned grassland in southwestern Germany using multivariate ordination statistics to extract information on single environmental factors influencing the distribution of particular species in the field. Different methods (DECORANA, CANOCO) revealed slightly different patterns of ordination, but led to similar conclusions. These conclusions coincide with previously observed ecophysiological requirements of isopods, and confirm the significance of the soil pH for their distribution. Howewer soil pH did not appear to be significant for diplopods. The distribution of diplopod species mainly corresponds with mean annual air temperature. Besides assigning particular species to single study sites that are characterised with respect to environmental factors, we statistically associate a group of three isopod species having similar ecological requirements.

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.

In the common woodlouse Porcellio scaber different parts of the gut were observed with respect to microbial counts, cellulose activity, and degradation of cellulose. Cellulose is mainly digested in the anterior part of the hindgut, as was indicated by the distribution of cellulolytic activity and the decrease of cellulose content inside the gut. The cellulases woodlice utilize for the degradation of litter are mainly produced by endosymbiotic bacteria in the hepatopancreas rather than by microorganisms ingested with the food. Microorganisms ingested with the litter are digested in the anterior part of the hindgut and may provide an important food source. In the posterior hindgut, bacterial proliferation ensures microbial colonization of feces.

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

Choleva agilis Illiger 1789 is a cold season species which reproduces and develops in winter months and obligatorily aestivates in the early adult stage from IV until IX. Aestivation delays, and tends to synchronize, the developmental cycle with the season rather than avoids deteriorating climatic conditions. Females [FF] oviposit for about 150 days. However, at the end of pre-imaginal development in the spring the adults emerge within a relatively narrow time interval of about 35 days. Synchronisation of individual development within the population is caused by the differences in thermal thresholds in subsequent pre-imaginal stages, and by the changing temperatures during winter months as well. The narrow time interval of adult emergence is not maintained until the age of first reproduction. By contrast, diapause intensity varies and gives the capability to spread the onset of reproduction over a time interval of more than 200 days, even between full sibs. Spreading the age at first reproduction even within families, and the relatively low heritabi-lity in the duration of diapause (h 2 = 0.12 + 0.018), are interpreted as bet-hedging mechanisms to cope with the vagaries of weather conditions in an unpredictable environment. Temporal spreading of reproduction is so pervasive that it provides the opportunity for at least some daughters of each single dam to match the correct date of oviposition, independently of birth dates and weather conditions which could be expected in the area of study. There is insufficient synchronisation of the developmental cycle with the season by diapause intensity when (a) oviposition is very early in the season, and (b) the entire pre-imaginal development occurs at extremely high temperatures. Under these circumstances an ecological tuning by photoperiod and temperature is neccessary.

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).

The sandy beaches of British Columbia are inhabited by a small number (11 species) of indigenous Staphylinidae which live near the drift line in the mid to upper littoral zone. They prefer fine-grained sandy beaches and most species feed on other intertidal invertebrates. All species investigated survived submersion in seawater by becoming quiescent, thereby reducing their metabolic rate. Oxygen consumption in seawater was greatly reduced. On re-exposure to air, a large overshoot in oxygen consumption occurred (in Thinopinus pictus), signifying a prior oxygen debt. In Cafius canescens, Cafius seminitens, and Hadrotes crassus the time required to reach full recovery was directly related to the duration of submersion, with 50% mortality in the population when recovery time exceeded 25 min. At a seawater temperature of 10 °C, LT50 was reached at 12–16 h submersion and at 20 °C, after 6.5 h. In Thinopinus pictus, however, recovery time was independent of duration of submersion, although the mortality curves were almost the same as for the three previously mentioned species, with LT50 occurring at 13 h at 10 °C and 7–8.5 h at 20 °C. Bledius monstratus showed symptoms of oxygen depletion only after a considerable time lag. Experimental submersion of this beetle resulted in an LT50 of 18 h at 20 °C.