Ulrich Irmler

The spatial and temporal pattern of carabid beetles on arable fields in northern Germany (Schleswig-Holstein) and their value as ecological indicators

Abstract Ground beetles have been often used as indicators for agricultural practices in ecological studies, but little is known about the spatial and temporal variation independent from the agricultural practices. Between 1985 and 1995 the ground beetles (Carabidae) of 53 fields in Schleswig-Holstein (northern Germany) were investigated using three replicate pitfall traps at each site. One field was studied over a period of 9 years from 1988 to 1996, and in addition two adjacent fields subjected to ecological or conventional farming methods were investigated in 1999 using 12 pitfall traps each. Overall, five assemblages of ground beetles could be differentiated, primarily by sand content of the soils and field size. The separation of the assemblages was weak (eigenvalue of 1st axis: 0.39) compared to natural ecosystems. The most common assemblage on loamy soils was dominated by Pterostichus melanarius. On both sandy soils and loamy soils in small fields the species Poecilus versicolor and Platynus dorsalis, Bembidion lampros, respectively, dominated. Eight ecologically differentiated groups of ground beetles were found. Most species correlated positively with the sand content of the soils. Only two species, P. melanarius and Loricera pilicornis showed a positive correlation with the field size. A higher species richness was observed on fields which have practised for 30 years ecological farming. Comparing the two adjacent fields with ecological and conventional farming, no difference in species richness was detected. Four species showed higher abundance on the field with ecological farming. In this analysis of a long-term dataset ground beetles did not respond to the cultivated plants, but only to the yearly climate conditions.

Changes in the fauna and its contribution to mass loss and N release during leaf litter decomposition in two deciduous forests.

Summary Investigations on the mass loss of leaf litter were carried out between 1992 and 1994 using litter bags of 0.02 mm and 5 mm mesh sizes in a beech and a mixed forest in northern Germany. The two forests on moder humus differed in soil faunal composition, vegetation type, and nutrient supply. Mass loss and N and C concentrations were determined from the litter at bimonthly intervals. From subsamples macrofauna were sorted by hand and mesofauna was extracted by heat. The biomass and N content of the litter bag fauna was estimated. Mass loss, particularly that attributed to the fauna, was different between the two sites with highest rates in the mixed forest and lowest at the beech site. A significantly higher rate of N release was found for the litter extracted from 5 mm mesh size litter bags in the mixed forest but not in the beech forest. Collembola and Cryptostigmata changed in numbers during litter breakdown. Collembola reached high numbers in the beginning, whereas Cryptostigmata dominated later. The diversity of Cryptostigmata increased at both sites during litter breakdown, whereas collembolan diversity only increased in the beech forest and remained at the same level in the mixed forest. Several species of Collembola and Cryptostigmata occurred earlier in the mixed forest than in the beech forest. Mass loss rate attributable to the fauna did not correspond to total faunal biomass. Only Isopoda, Diplopoda and Cryptostigmata appeared to affect the mass loss positively, whereas the biomass of Lumbricidae was negatively correlated with mass loss, particularly in the beech forest. On the other hand, the release of N attributable to the fauna was positively correlated with the total faunal biomass in the beech forest and Lumbricidae in particular were positively correlated with N-release at both sites.

Zonation of ground beetles (Coleoptera: Carabidae) and spiders (Araneida) in salt marshes at the North and the Baltic Sea and the impact of the predicted sea level increase

The ground beetles and spiders of two salt marshes at the German Northand Baltic Sea coast were investigated by pitfall traps in 1997 and 1998. Whilethe sites at the North Sea coast are tidal salt marshes, the salt marshes at theBaltic Sea are not influenced by tides. Pitfall traps were installed in agradient from 20 to 150 cm above MHT (mean high tide: 157cm + NN, NN: 500 cm above 0 at Amsterdam gauge) atthe North Sea coast or NN at the Baltic Sea coast at six or sevensampling elevations, each with five replicates. Conductivity, water content, organic substance,frequency or duration of floodings, sand content and pH of the soil weredetermined. The flooding regime is the major factor controlling the zonation ofinvertebrates. Two and three invertebrate assemblages at the North and BalticSea, respectively, were distinguished. These corresponded well with thevegetational zones. The border between the two zones was at 60–80cm above MHT at the North Sea. The three zones at the Baltic Seaextended between 20 and 30 cm, 40 to 80 cm and 100 to150 cm above NN. The elevation of the mean abundance of speciesabove MHT or NN was calculated. A tide simulation experiment resulted in ashifting population and in an increasing activity under a tidal regime aspredicted for the global climate change conditions in 2050. From the actualelevation of the mean abundance, the habitat size of salt marsh species wascalculated for a moderate and worse scenario of global climate change. Habitatreduction becomes highest for species of the lower salt marsh zone. Under worseconditions the gradiental length of habitat will only amount to a maximum of 20m at the slopes of the dikes.

Assignment and evaluation of ground beetle (Coleoptera: Carabidae) assemblages to sites on different scales in a grassland landscape

Carabid beetles and environmental parameters were investigated in 52 grassland sites with three replicate pitfall traps in each site and in the valley of the River Eider in Schleswig–Holstein (northern Germany) with 61 pitfall traps. Environmental parameters included water content of soil, sand content, organic matter content and pH. Ground beetle assemblages were derived by detrended correspondence analyses (DCA) and characterised by the specific environmental conditions as means for each assemblage. On the regional scale including all investigated sites of Schleswig–Holstein, five assemblages were differentiated. On the local scale including the investigated sites in the valley of the River Eider, three assemblages were found corresponding well with those found on the regional scale. Environmental conditions at the sites of the five assemblages were correlated with land use data, soil types, and water level stages provided by three maps of a geographic information system (GIS). The GIS maps were combined to develop smaller areas with land use, soil type and water level stage information. The characteristic environmental conditions were assigned to each area to derive the spatial distribution of the five ground beetle assemblages. Spatial prediction was correct for 65% of investigated sites. The potential area of each assemblage was estimated for the valley. The different grassland areas were evaluated as potential habitats for ground beetle species comparing total species richness with the regional species richness of each assemblage. The comparison shows that species richness in the evaluated assemblages is relatively low compared to the regional potential.

Movement of carabids from grassy strips to crop land in organic agriculture

The colonisation process of carabid beetles from field margins to crop fields under organic agriculture was investigated in 2010 and 2011 in northern Germany in order to find the supporting effects of grassy strips in the agricultural landscape. Displacement and speed of Pterostichus melanarius, Carabus auratus and Poecilus spp. were higher in the crops than in the grassy strips, except for the speed of C. auratus. Among the four species C. auratus, P. melanarius, Pterostichus niger, and Poecilus spp., C. auratus revealed the highest displacement and speed, whereas no significant differences were found between the other three species. P. melanarius showed higher displacement and speed in wheat than in red-clover or pumpkin. Speed and displacement of P. melanarius differed between spring and autumn generations in wheat or red-clover. When they were released at a junction of arable crop and field strips, C. auratus moved indifferently to either arable field or field margins/strips, whereas P. melanarius moved directly to crop centres. At the field margin, Poecilus spp. preferred to move along a grassy strip, while it moved irrespective from the grassy strips in a central site. C. nemoralis and P. niger preferred to move within the grassy strips. Our studies reveal that grassy strips do not affect the dispersal of typical arable field species; however, the species demanding grass vegetation can only overcome the barriers of arable fields either by grassy strips alone or by grassy strips with an adjacent hedge.

Niche differentiation and preferences of Elaphrus cupreus Duftschmid, 1812 and Elaphrus uliginosus (Fabricius, 1792) (Coleoptera: Carabidae) as reason for their different endangerment in Central Europe

Ecological demands were studied in Elaphrus cupreus, a frequent species, and E. uliginosus, one of the most endangered carabids in Europe. Ecological experiments were performed in the laboratory and the field in northern Germany. Abundance was measured using the mark-and-recatch method. Both species prefer sites with water content changes lower than 25%. E. uliginosus prefers higher temperatures than E. cupreus and niche breadth was on average wider in E. cupreus than in E. uliginosus. E. uliginosus is restricted to grassland sites with a low fraction (>0 and 25%) of bare soil. E. cupreus was mainly found on sites having >75–100% bare soil. This preference of E. uliginosus can be referred to its high temperature demands using open regions for warming up and its predatory behaviour using hideouts for a rapid predatory push. The wider niche structure and lower temperature demand of E. cupreus allows the inhabitation of cooler alder woods. It prefers large fractions of bare soil because its predatory behaviour is to run randomly on the soil. Thus, E. uliginosus demands wet extensively grazed grassland where cattle produces low fractions of bare soil, while E. cupreus prefers intensively grazed sites in grassland or alder woods.

Impacts on biodiversity at Baltic Sea beaches

Sandy and shingle beaches were investigated in 2009 and 2010 along the coast of the Baltic Sea in northern Germany with the purpose of assessing biodiversity gradients from shingle to sandy beaches, from beach to primary dunes, and the impacts of tourism on biodiversity. On nine beach sites, ranging between 100% shingle and 99% sand without shingle, Carabidae, Staphylinidae, and Araneae were studied. Two of the six sandy beaches were open and four were closed to tourists. Additionally, trampling effects from tourists, species richness of plants, and plant cover were investigated on sixteen beaches. According to results, primary dunes showed higher species richness in carabids and spiders, but not in staphylinds. Shingle beaches exhibited lower species richness in Staphylinidae and Araneae, but not in Carabidae. As estimated by the Jackknife II method, shingle beaches were the lowest in total species richness. Trampling intensity ranged from 0 footprints m−2 day−1 on closed beaches, up to a maximum of 30 footprints m−2 day−1. On “intensively” used beaches (12 footprints m−2 day−1, on average), reduction of plant cover was more pronounced than on “extensively” used beaches (7 footprints m−2 day−1, on average). Both plant cover and plant species richness were lower on intensively and extensively used beaches than on closed beaches. In arthropods, only staphylind and spider species richness was significantly lower on open beaches than on closed beaches, but no differences were found in carabids. Referring to our results, trampling effects from tourists have high impact on species richness of sandy beaches, on both intensively and extensively used sites.

Effects of habitat and human activities on species richness and assemblages of Staphylinidae (Coleoptera) in the Baltic Sea coast.

In 2009, the staphylind fauna was studied in six habitats of the Baltic Sea coast of Schleswig-Holstein (northern Germany). The following habitats lagoon, sandy beach, shingle beach, primary dune, wooded cliff, and woodless cliff were significantly separated by their species composition. Vegetation and soil moisture were the most important factors separating the assemblages. Lagoons exhibited the most species-rich habitat. Sandy beaches provided the highest number of endangered species. Both sandy beaches and woodless cliffs showed the highest number of exclusive species. A loss of species was determined in the gradient from sandy to shingle beaches. Few species preferred shingle beaches; abundance of Cafius xantholoma increased with the increasing amount of shingle. More species preferred the sandy conditions, for example, Polystomota grisea, P. punctatella, and Phytosus spinifer. Anotylus insecatus and Bledius defensus require distinct mixtures of sand and silt on woodless cliffs. Tourist impact on sandy beaches accounts for approximately 50% loss of species.

Two New Species of the Genus Thoracophorus Motschulsky, 1837 (Coleoptera: Staphylinidae, Osoriinae) with Remarks on Ecology of the Genus in the Neotropical Region

The new species Thoracophorus venezuelanus and T. silvaticus are described. The ecological information from labels and that produced by more detailed studies in Central Amazonia indicate that tree canopies and tree trunks are main habitats of Thoracophorus species, and that many species might be associated with ants or termites.

Biocoenotic Interactions between Different Ecotopes

another part of the fauna, e.g. wood-living beetles, only use separate layers of the tree strata. Ecosystem size is an important parameter influencing biotic dynamics. As all ecosystems of the study area are comparatively small, marginal effects on the structure of the biota are quite remarkable. Furthermore, the beech forest is additionally intersected by several forest tracks which also affect the biotic dynamics, e.g. the vegetation cover, the distribution of invertebrates and birds and thereby the dynamics of food resources. As a result of the small-sized ecosystems several species can easily subsist on different ecosystems in correspondence with the seasosonal or interannual fluctuations of environmental conditions. Thus, many species of the agrarian systems use the forest to hibernate, populations migrate according to moisture conditions between dry and wet sites. The changing land use results in succession processes and alters the composition of the community. Biotic dynamics is, therefore, difficult to analyse on the landscape level. They cannot be explained by the normal seasonal changes or the overall climatic differences between successive years alone. The biotic interactions within the complex landscape, in particular the environmental changes from the lake to the hill top and from intensively tilled agrarian systems to little-managed forests, substantially influence ecosystem dynamics. Chapter 7 Biocoenotic Interactions between Different Ecotopes