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The EU plant protection regulation 1107/2009/EC defines the requirements for active ingredients to be approved, specifically including the assessment of effects on biodiversity and ecosystems. According to that, semi-field methods are expected to be more important in the near future. Therefore, a higher-tier experiment suitable to assess the risk for soil organisms was conducted to further develop the TME (terrestrial model ecosystems) methodology in a dose-response design with the persistent insecticidal model compound lindane (gamma-HCH). The effects of lindane on soil communities such as collembolans, oribatid mites, nematodes, soil fungi and plant biomass were determined in 42 TME. Intact TME-soil cores (diameter 300 mm, height 400 mm) from undisturbed grassland were stored outdoor under natural climatic conditions. Lindane was applied in five concentrations between 0.032 mg active ingredients (ai)/kg dry soil and 3.2 mg ai/kg dry weight soil, six-fold replicated each. Twelve TME served as untreated controls. Abundance and community structures of oribatids, collembolans, enchytraeids, nematodes and fungi were recorded. Oribatid mites' community responded 3 months after treatment, although they were not significantly affected by the overall treatment regimen. Collembolans in total and species-specific abundance as well as the community endpoints (principal response curves, diversity measures) were adversely affected by moderate dosages of lindane. Effects were transient between 3 and 5 months after treatment with a recovery within 1 year. No significant effects could be detected for enchytraeids, nematodes and fungi. The study design and the obtained results allow for calculations of no observed effect concentrations below the highest treatment level for populations and for soil communities as defined entities, as well as effective concentrations. The paper discusses the limits of effect detection in the light of achievable coefficients of variation and by means of minimum detectable differences. Outdoor TME are useful to analyze and assess functional and structural endpoints in soil organisms' communities and their possible recovery after pesticide treatment within 1 year.

Terrestrial Model Ecosystems (TME) were developed as one higher-tier option to detect and assess effects of pesticides on soil communities in a 1 year study using lindane (gamma-HCH) as a persistent and toxic reference pesticide. TME contained intact soil cores (diameter 300 mm, height 400 mm) including indigenous soil communities of undisturbed grassland. Forty units were placed outdoors between spring 2005 and 2006. The TME experiment was designed to provide data that fulfill the requirements of the revised European regulation on plant protection products (regulation 1107/2009/EEC replacing guideline 91/414/EC) with a focus on structural endpoints such as soil organisms and their community structure in case higher-tier evaluation is triggered. The key objective was to evaluate the dynamics and stability of species-diverse microarthropod communities of undisturbed grassland over at least 1 year after application. In grassland soils, less selection pressure towards insensitive species compared to arable land was presumed. Sufficient numbers of organisms and numerous TME replicates ensured that a statistical evaluation could be performed to estimate the sensitivity of the organisms upon application of lindane applied at high rates of 7.5 and 75 kg ai/ha. The application rates resulted in nominal concentrations of 10 and 100 mg ai/kg dry soil referred to the top 5 cm soil layer of 10 TME each; 20 untreated TME served as controls and were used to study the natural dynamics and the variability of populations under field conditions. Results showed that the grassland from which the soil cores were sampled contained communities of soil organisms marked by typical diversity of improved grassland. Lindane applied at excessive rates caused clear dose-related and long-lasting effects on the communities of microarthropods. On the contrary, lumbricids, the total feeding activity (bait lamina) and the growth of plant biomass were not affected up to 1 year after application. Based on the results of this study using a toxic reference insecticide, the methodology seems to be suitable for use in the regulatory context of the assessment of pesticides once protection goals, data requirements and the conceptual framework are defined.