Andrea Ruf

A maturity index for predatory soil mites (Mesostigmata: Gamasina) as an indicator of environmental impacts of pollution on forest soils

Abstract A long-term biomonitoring programme has been established for many years in Baden-Wurttemberg, southern Germany, focussing mainly on environmental impacts of pollutants on vegetation and the analysis of heavy metals in litter, plant and animal tissue. The soil ecological research group at the Staatliches Museum fur Naturkunde, Karlsruhe have investigated the soil fauna at 11 selected forest sites within this programme with the specific objective of establishing a system of soil quality classification based on biological criteria. These sites represent different climatic and pedological regions as well as different levels of adverse environmental impact. Results relating to the incidence of predatory mesostigmatid mites in the study sites are reported here. Our methodology begins by ranking mesostigmatid mite taxa according to their life-history traits on an r/K-scale. A faunal maturity index, which expresses the proportion of species in a community with predominantly K attributes to those with more r attributes, can then be calculated for the fauna of any particular site. The less environmentally perturbed a soil is, the higher the value of this index. Comparative norms for the index in different forest types can be deduced by analysing published species lists from unperturbed sites. The index is a sensitive bioindication tool and a more integrative measure of the severity of environmental impact in forest ecosystems than is the more traditional measurement of heavy metal concentrations in soil litter and earthworm tissues.

Sensitivity of different taxonomic levels of soil Gamasina to land use and anthropogenic disturbances

1 The effect of taxonomic level on the sensitivity of bioindicators has been widely investigated in aquatic ecosystems and, to a lesser extent, in terrestrial ecosystems. However, no studies have been conducted on the sensitivity of the different taxonomic levels of soil mites, especially Gamasina, to human activities. 2 The present study aimed to assess the sensitivity of different taxonomic levels of soil Gamasina mites to anthropogenic disturbances in Europe and Argentina. We arranged the data from previous projects in a hierarchical system and conducted a study to identify the critical taxonomical levels that had the highest discriminative potential between sites (Europe and Argentina) or management types (forests, grasslands, fallows, succession, recultivation and agricultural sites). 3 For the Gamasina community, geographical location was by far more important than the influence of any land use type. The analysis including only the European sites demonstrated that communities belonging to sites subjected to different land uses were also significantly different. 4 The species data set provided a clearer separation of sites according to both the geographical and the land‐use gradients than the genus and family data sets. The genus and, to a lesser extent, the family approach may be sufficient to elucidate the influence of great geographical differences and also of certain land uses (e.g. grasslands from the forests and arable sites). 5 Species presence/absence data provided valuable information in our analyses, although the use of quantitative data yielded a clearer separation of sites.

Beurteilung von Bodenqualität mit Hilfe von Bodentieren

Es gibt einige Ansatze, Bodentiere zur Beurteilung von Boden heranzuziehen. Allen liegt die Annahme zugrunde, das Bodenorganismen an Eigenschaften der Boden gebunden sind, das es also typische) Bodenorganismen fur bestimmte Boden gibt. Wie Dunger (1998) ausfuhrt, war es bereits die Uberzeugung der „Klassiker“ der Bodenbiologie in den 40er und fruhen 50er Jahren unseres Jahrhunderts (Kubiena, Kuhnelt, Franz, Ghilarov), das es einen Zusammenhang zwischen Boden und der Besiedlung mit Bodenorganismen gibt. Dieses Forschungsfeld wird nunmehr seit uber 40 Jahren beackert, und es hat Ertrage und neue Erkenntnisse gebracht. Jedoch scheinen wir erst jetzt in einer Phase zu sein, in der die Datengrundlage beginnt solide genug zu werden, so das ubergreifende Konzepte zum tragen und zu neuer Blute gelangen konnen. Dunger (1998) schreibt:„... Das bedeutet, das trotz einer Flut von aktueller bodenbiologischer Literatur noch keine ausreichende Prazisierung der Bindung gelungen ist, die doch offenkundig zwischen Bodenorganismen und dem Boden als ihrem Lebensraum besteht.“ Parallel werden in einigen Landern und in vielen Forschungsinstituten Verfahren erarbeitet, wie einzelne Organismengruppen oder ein groserer Ausschnitt aus der Lebensgemeinschaft des Bodens zur Indikation von Bodenqualitat eingesetzt werden kann. Beim XII Internationalen Kolloquium uber Bodenzoologie in Dublin 1996 gab es eine Sitzung, die sich dem Thema widmete.

An Object-oriented Simulation Approach to Analyze the Bionomics of a Predatory Soil Mite

In order to investigate the bionomics of the gamasid mite Hypoaspis aculafer studies in the laboratory were conducted. Parallelly an object-orientated simulation model was constructed to explain the observed phenomena. By using an object-orientated modelling concept individuals are represented as single, independently acting data-objects, which can be qualitatively and quantitatively differentiated. Thereby the influence of parameters describing the activity of the individuals onto the resulting dynamics at the population level were investigated. Moreover the simulation of a large number of repetitons shows that concerning the population development a necessary range of unpredictability remains although the characteristics of all participating components are known.