Terrestrial Model Ecosystems Research Articles

Application of a small scale-terrestrial model ecosystem (STME) for assessment of ecotoxicity of bio-based plastics

In this work a small-scale terrestrial model ecosystem (STME) filled with 4 kg of soil mimicking the natural ecosystem was constructed, and then successfully applied to evaluate the effect of bio-based plastics on soil biota at the community level. It was inhabited by higher plants monocotyledonous (Sorghum saccharatum) and dicotyledonous (Lepidium sativum), and earthworms (Eisenia andrei). Two innovative bioplastics based on polylactic acid (PLA) were tested. This work is one of the first studies, in which potential impacts of bioplastic particles on soil organisms were determined at the community level. Owing to the application of the STME the ecotoxicity data for plants and earthworms were simultaneously collected and the mutual interactions might be taken into account.PLA-based plastics studied did not affect the percentage of seed germination of higher plants that was on average not lower than 88.9%. Neither the length nor fresh mass of shoots of cress were affected. One out of two PLA-based plastics (BPE-RP-PLA) inhibited sorghum growth so that it was statistically significant. PLA-based plastics did not cause to the mortality of earthworms as all ten organisms introduced to each STME survived each experiment. However, the presence of PLA-based plastic particles influenced the depth distribution of earthworms in the STMEs. Most of earthworms (60–70%) exposed to PLA-based plastics migrated downwards to the bottom soil zone, while 80% of the earthworms not exposed to PLA-based plastics lived in the top soil zone of the STME. This avoidance behaviour of earthworms known earlier for other contaminants (e.g. metals, pesticides) was for the first time reported with regard to bioplastic particles present in soil. It is a dangerous phenomenon not only for earthworms but also for the functioning and structure of terrestrial ecosystems. The STME proved to be an appropriate tool to detect it.

Are structural and functional endpoints of soil communities similarly affected by metal mixtures? – A terrestrial model ecosystem approach

Soils are habitat to a variety of flora and fauna in a linked ecosystem which provides essential ecosystem services. In soil, metals can accumulate at high concentrations, because of anthropogenic activities, leading to toxic effects, threatening the ecosystem and the services it provides. In most real-world contamination scenarios, metals occur as complex mixtures which can interact and produce different toxicity than predicted from individual metal data. Current regulatory guidelines are based on single species responses to individual metals and ignore indirect effects inherent to the inter-linked nature of ecosystems. Also, the evaluation of anthropogenic impacts to the soil communities is usually measured through structural endpoints (e.g. abundance) disregarding functional measurements (e.g. organic matter decomposition rates), which are often seen as tightly related, and thus, similarly affected. In this study we tested three mixture ratios of five metal oxides (lead, copper, nickel, zinc, cobalt) at three dose levels (Low, Med, High) in a terrestrial model ecosystem experiment and measured structural and functional endpoints. Exposure to metal mixtures for 16 weeks did not affect the microarthropod community, but produced severe effects on soil microbial activity (PNR and DHA) reducing activity below 50% compared to control levels, in all dosed treatments. Metal contamination also significantly affected feeding activity and organic matter decomposition, but effects were not as pronounced as on microbial activity. Data suggest that, in the risk assessment of metals and their mixtures, effects on ecosystem structure and functions must be considered to provide adequate environmental protection.

Compared to conventional, ecological intensive management promotes beneficial proteolytic soil microbial communities for agro-ecosystem functioning under climate change-induced rain regimes

Projected climate change and rainfall variability will affect soil microbial communities, biogeochemical cycling and agriculture. Nitrogen (N) is the most limiting nutrient in agroecosystems and its cycling and availability is highly dependent on microbial driven processes. In agroecosystems, hydrolysis of organic nitrogen (N) is an important step in controlling soil N availability. We analyzed the effect of management (ecological intensive vs. conventional intensive) on N-cycling processes and involved microbial communities under climate change-induced rain regimes. Terrestrial model ecosystems originating from agroecosystems across Europe were subjected to four different rain regimes for 263 days. Using structural equation modelling we identified direct impacts of rain regimes on N-cycling processes, whereas N-related microbial communities were more resistant. In addition to rain regimes, management indirectly affected N-cycling processes via modifications of N-related microbial community composition. Ecological intensive management promoted a beneficial N-related microbial community composition involved in N-cycling processes under climate change-induced rain regimes. Exploratory analyses identified phosphorus-associated litter properties as possible drivers for the observed management effects on N-related microbial community composition. This work provides novel insights into mechanisms controlling agro-ecosystem functioning under climate change.

Impact of no-tillage versus conventional maize plantation on soil mesofauna with and without the use of a lambda-cyhalothrin based insecticide: A terrestrial model ecosystem experiment

Different soil management in crop cultures like maize can produce a variety of effects on soil fauna. Conventional cropping includes soil tillage, promoting organic matter losses and destruction of soil structure, whereas no-tillage cropping includes a herbicide application which can potentially affect soil fauna. In both management systems, insecticides are often used, such as pyrethroid insecticides, to prevent insect pests. Understanding the impact of these different cropping systems in their different phases on soil mesofauna and investigating the ability of soil communities to recover may provide important information to select cropping strategies which are more protective of soil biodiversity. With this aim, a terrestrial model ecosystem experiment was performed over eighty-nine days. The test treatments, all including maize, were: undisturbed soil; conventional tillage; conventional tillage with insecticide; no-tillage soil with herbicide; no-tillage soil with herbicide and insecticide. In each TME, soil samples from 0 to 5 and 5–10 cm of the top layer were collected from which collembolans and mites were identified to species, genus or subfamily level, and enchytraeid abundance was determined. Soil tillage did not affect soil communities, but insecticide application did. For collembolans and enchytraeids, the impact of the insecticide was independent of soil management, but for mites, insecticide impact was longer in conventional tillage than in no-tillage system. Changes on collembolan abundance, in general, did not promote changes in mean community trait values and functional diversity. Data suggest that no-tillage management is more protective to soil fauna than conventional tillage.

Salinization effects on coastal ecosystems: a terrestrial model ecosystem approach.

In coastal areas, intrusion/irrigation with seawater can threaten biodiversity along with crop yields, and the leaching of salts from areas affected by these processes can increase the salinity of water bodies nearby. The aims of this study were to evaluate the effects of salinization on coastal soil ecosystems due to saline intrusion/irrigation. Terrestrial model ecosystems were used to simulate two soil salinization scenarios: (i) seawater intrusion and irrigation with distilled water and (ii) seawater intrusion and irrigation with saline water. Three sampling periods were established: T0-after acclimation period; T1-salinization effects; and T2-populations' recovery. In each sampling period, the abundance of nematodes, enchytraeids, springtails, mites and earthworms, and plant biomass were measured. Immediate negative effects on enchytraeid abundance were detected, especially at the higher level of saltwater via intrusion+irrigation. Eight weeks after the cessation of saline irrigation, the abundance of enchytraeids fully recovered, and some delayed effects were observed in earthworm abundance and plant biomass, especially at the higher soil conductivity level. The observed low capacity of soil to retain salts suggests that, particularly at high soil conductivities, nearby freshwater bodies can also be endangered. Under saline conditions similar to the ones assayed, survival of some soil communities can be threatened, leading to the loss of biodiversity.This article is part of the theme issue 'Salt in freshwaters: causes, ecological consequences and future prospects'.

What Limits Predictive Certainty of Long‐Term Carbon Uptake?

AbstractTerrestrial biosphere models can help identify physical processes that control carbon dynamics, including land‐atmosphere CO2 fluxes, and have the potential to project the terrestrial ecosystem response to changing climate. It is important to identify ecosystem processes most responsible for model predictive uncertainty and design improved model representation and observational system studies to reduce that uncertainty. Here we identified model parameters that contribute the most uncertainty to long‐term (~100 years) projections of net ecosystem exchange, net primary production, and aboveground biomass within a mechanistic terrestrial biosphere model (Ecosystem Demography, version 2.1) ED2. An uncertainty analysis identified parameters that represent the quantum efficiency of light to photosynthetic conversion, leaf respiration and soil‐plant water transfer as the highest contributors to model uncertainty regardless of time frame (annual, decadal, and centennial) and output (e.g., net ecosystem exchange, net primary production, aboveground biomass). Contrary to expectations, the contribution of successional processes related to reproduction, competition, and mortality did not increase as the time scale increased. These findings suggest that uncertainty in the parameters governing short‐term ecosystem processes remains the most significant bottleneck to reducing predictive uncertainty. Key actions to reduce parameter uncertainty include more leaf‐level trait measurements across multiple sites for quantum efficiency and leaf respiration rate. Further, the empirical representation of soil‐plant water transfer should be replaced with a mechanistic, hydraulic representation of water flow, which can be constrained with direct measurements. This analysis focused on aboveground ecosystem processes. The impact of belowground carbon cycling, initial conditions, and meteorological forcing should be addressed in future studies.

Disentangling the effects of the aqueous matrix on the potential toxicity of liquid pig manure in sub-tropical soils under semi-field conditions

Inadequate application of liquid pig manure (LPM) may pose risks to the soil due to the potential contaminants that exists, as well as by the large water input that can originate excessive moisture. By using Terrestrial Model Ecosystems, this study aimed to evaluate the effect of application of LPM (82% moisture) using the application rates of 20, 50 and 150 m3 ha−1 and also of the corresponding amount of water to understand the origin of effects on the soil fauna of two sub-tropical soils. In general, the results obtained for the two soil types indicated that LPM (150 m3 ha−1) changed the composition of soil fauna, with an increase in the abundance of insect larvae and dipterans, but a decrease in the number of earthworms and enchytraeids. Microbial biomass, soil respiration and the nutrients Mg, K and P increased with the amount of LPM supplied to the soil. When analysing the effects of adding large volumes of water via the LPM, results showed that application did not originate significant effects on the parameters measured. The differences obtained when comparing both treatments were mainly attributed to the organic load brought by the LPM and not to the amount of water without LPM.

Season-Long Experimental Drought Alters Fungal Community Composition but Not Diversity in a Grassland Soil

Using terrestrial model ecosystems (TMEs), we investigated how reduced moisture conditions impact soil fungal communities from a temperate grassland over the course of an entire season. Starting at about 65% of the soil's maximum water holding capacity (WHCmax), TME soils were adjusted to three moisture levels for 15weeks: 70% WHCmax, approximating starting conditions, 50% WHCmax, and 30% WHCmax, representing reduced moisture conditions. Diversity and abundances of soil fungi at the start and at the end of the experiment were characterized using Illumina meta-barcoding. Community diversity at the end of the experiment did not differ between experimental moisture levels and was comparable to diversity measures from the field. However, fungal communities did change compositionally in both abundances and presence/absence of species. Analyzing class-level and individual contributions of fungi to these changes revealed that only a minor portion reacted significantly, indicating that most compositional change was likely driven by many consistent small-scale shifts in presence/absences or abundances. Together, our results show that prolonged reduction in soil moisture conditions will trigger compositional changes in soil fungal communities but not necessarily change overall diversity. We highlight the cumulative contribution of minor but consistent changes among community members, as opposed to significant responses of individual species. We also detected a strong general experimental effect on soil fungi that are moved from the field to experimental TMEs, suggesting the importance of acclimatization effects in these communities under laboratory conditions.

A TME study with the fungicide pyrimethanil combined with different moisture regimes: effects on enchytraeids.

Today's ecosystems are influenced by different factors that could evolve into stressors. Effects of pesticides, especially in agricultural areas, may interact with environmental factors, such as soil moisture fluctuation caused by global climate change. In this contribution, two semi-field studies conducted in Germany and Portugal with terrestrial model ecosystems are presented. Their aim was to assess the effects of the fungicide pyrimethanil under different soil moisture levels on Enchytraeidae. In Portugal a no observed effect concentration design was chosen, using two concentration levels: the maximum application rate (MAR) according to the safe use registration within the European Union and five times the MAR (1.82and 9.09mg/kg dry soil, respectively). Both concentrations did neither affect the total enchytraeid abundance nor single populations. In Germany an ECx design (effect concentration) was conducted, using 11 concentrations. In general, 14 EC50 values for different combinations of single species, moisture level and sampling date were determined. The strongest effects were found in dry soil, particularly for Fridericia connata (EC50: 3.48mg/kg dry soil after 8weeks of exposure). The advantages and challenges of these test designs are discussed with regard to the registration process of pesticides in the European Union. In any case, enchytraeids are suitable test organisms in such higher tier studies for the combined evaluation of chemical and climatic stressors due to their usually high diversity and abundances and their close contact with the soil solution.

MICROCOSM EXPERIMENTS AS A TOOL IN SOIL ECOLOGY STUDIES

Soil microcosms are also called Terrestrial Model Ecosystems (Carbonell and Tarazona, 2014) . There is a large diversity of microcosm studies from simple systems to sophisticated terrestrial ecosystems. Many disciplines have utilized microcosms as a powerful research tool especially microbiologists, ecotoxicologists, limnologists (Fraser et al. 2004) and soil ecologists (Sandor and Schrader, 2012). This study is in attempt of a better understanding terrestrial model ecosystem and some causal effects that can be simulated. For this purpose advantages and drawbacks are assessed. Setting up a microcosm was often achieved using plastic containers of different sizes related with the size of the studied organisms or the number of species included. Nevertheless it is recommended to be no smaller than 25x50cm (Fraser et al. 2004). Microcosms can be placed indoor or outdoor using sieved soil or undisturbed cores. Experiments variables have included: moisture supply, soil depth, temperature, mineral nutrient supply, carbon dioxide concentration, mycorrhizae, rhizobia, plants, herbivores and carnivores animals. The time of the study depends on the ecological processes under investigation. Usually microcosms are not suited for long-term studies. All the experimental designs have advantages like the ease of replication and manipulation of the parameters and treatments involved and some disadvantages like restricted space. Further factorial microcosm experiments can explore combinations of factors for a better understanding of causal relationships and interactions between plants species and soil communities. Comparison is helped by separating complex causal effects. Â

Do organic inputs alter resistance and resilience of soil microbial community to drying?

Grassland ecosystems in south-eastern Australia are important for dairy and livestock farming. Their productivity relies heavily on water availability, as well as the ecosystem services provided by soil microbial communities including carbon and nutrient cycling. Management practices such as compost application are being encouraged as a means to improve both soil water holding capacity and fertility, thereby buffering against the impacts of increasing climate variability. Such buffering consists of two complementary processes: resistance, which measures the ability of an ecosystem to maintain community structure and function during a period of stress (such as drying); and resilience, which measures the ability of an ecosystem to recover community structure and function post-stress. We investigated the effects of compost on the resistance and resilience of the grassland soil ecosystem under drying and drying with rewetting events, in a terrestrial model ecosystem. Overall, compost addition led to an increase in soil moisture, greater plant available P and higher plant δ15N. Soil C:nutrient ratios, mineral N content (NH4+ and NO3−) and soil microbial PLFA composition were similar between amended and unamended soils. Rainfall treatment led to differences in soil moisture, plant above-ground and below-ground biomass, plant δ15N, soil mineral N content (NH4+ and NO3−) and microbial biomass C, N and P composition but had no effects on soil C:nutrient ratios, plant available P and soil microbial PLFA composition. There was little interaction between rainfall and compost. Generally, the soil microbial community was resistant and resilient to fluctuations in rainfall regardless of compost amendment. However, these properties of the soil microbial community were translated to resilience and not resistance in soil functions. Overall, the results below-ground showed much greater response to rainfall than compost amendment. Water was the key factor shaping the soil microbial community, and nutrients were not strong co-limiting factors. Future projections of increasing rainfall variability will have important below-ground functional consequences in the grassland, including altered nutrient cycling.

Does altered rainfall regime change pesticide effects in soil? A terrestrial model ecosystem study from Mediterranean Portugal on the effects of pyrimethanil to soil microbial communities under extremes in rainfall

In this century, agroecosystems are subjected to multiple global change stressors acting in concert such as alterations in rainfall regimes and pesticide use. Alterations in rainfall regimes, characterised by more extreme intra-annual rainfall regimes, have been forecasted for the Mediterranean region. At the same time, the use of pesticides continues to rise. Here, we report the responses of soil microbial community to a model pesticide, i.e., fungicide pyrimethanil (PYR) under altered rainfall regimes (i.e., drought and heavy rainfall) two and eight weeks after PYR application. We measured the functional responses as enzyme activities, potential nitrification and BIOLOG carbon substrate utilisation. We also characterised the soil bacterial communities using polymerase chain reaction–denaturing gradient gel electrophoresis (PCR–DGGE) method. After two weeks, enzyme activities were mainly responsive to PYR and kinetic parameters, calculated from BIOLOG carbon substrate utilisation, indicated interaction effects from PYR and rain treatments. Bacterial band richness increased with PYR treatment under normal rain and drought regimes, but bacterial band richness was higher at 1X than 5X PYR under heavy rainfall. Bacterial community structure was also different with the PYR and rainfall treatments. By week eight, PYR treated soils remained functionally different from untreated soils. Bacterial band richness was consistent across PYR treatment regardless of rain regime. However, the bacterial community structure remained significantly different among the PYR treatments under different rain regimes. We conclude that rainfall extremes can alter the effect of PYR on the soil microbial community structure without altering PYR effects on soil functions (measured as enzyme activities, potential nitrification and BIOLOG carbon substrate utilisation).

Application of standard statistical methods in the analysis of complex data generated from soil bioassays to assess the impacts of agrochemical-containing sludge amendments

The use of sludge as soil amendment is widely encouraged by its high contents in organic matter and plant nutrients. Nevertheless, agrochemicals potentially present in sludge could be harmful to terrestrial ecosystems. The present work aimed to apply standard statistical methods for suitable assessment of the ecotoxicological impacts of sludge amendments on soil, involving the following factors: the type of treated sludge, their application dose, and their contents in agrochemicals. Terrestrial Model Ecosystems were used to assess the effects of sludge amendments on endpoints from different trophic levels of the soil ecosystem, including an in vitro estrogenic bioassay on soil leachates. Here, we show the significant negative effects of the highest dose of sludge in most of the soil bioassays. Thermally dried sludge increased significantly the microbial activity leading to lower contamination of leachates with endocrine disrupting molecules. Agrochemicals contents of sludge have only significant impacts on increasing the delay of germination of plant seeds. Soil bioassays are thus complementary to sludge chemical analysis when the impacts of its application on soil should be assessed: significant negative impacts were related to the intrinsic composition of sludge rather than its agrochemicals contents. We conclude that standard statistical methods are relevant tools for the analysis of complex data generated from this type of experiment.

The response of soil organism communities to the application of the insecticide lindane in terrestrial model ecosystems

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.

Assessing impacts of copper on soil enzyme activities in regard to their natural spatiotemporal variation under long-term different land uses

Enzymes are known to be sensitive indicators of soil quality. Nevertheless, the natural variability of their activities needs to be considered for a relevant interpretation of activity levels, especially in contaminated soils. We first monitored the variability of enzymatic activities (acid and alkaline phosphatases, β-glucosidase, N-acetyl-β-glucosaminidase, urease and dehydrogenase) in two agricultural sites in north-western France during a seasonal April–October cycle. For both sites, two types of long-term different agricultural managements, grassland and intensive cropping were considered. Our results revealed great variability of enzymatic activities in space and over time, yet more pronounced for grassland than for cropped soils. Then, we assessed the impact of copper on enzymes activity on Terrestrial Model Ecosystems (TMEs) filled with undisturbed soil, and incubated for 70 days in open-field conditions. Copper was added at two concentration levels corresponding to a regulated annual agronomic input (2 mg kg−1) or to a high soil contamination (200 mg kg−1). In comparison to effects of natural spatiotemporal variability of soil conditions, copper addition did not show significant impacts on enzymatic activities. Finally, our results confirmed that for assessing effective impacts of contaminants in soils under real field conditions, natural spatiotemporal soil variability must be considered.

Outdoor Terrestrial Model Ecosystems are suitable to detect pesticide effects on soil fauna: design and method development

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.

ISTA 14—Impact of antibiotics from pig slurry on soil microbial communities, including the basidiomycete Trametes versicolor

Livestock slurry containing antibiotics is a source of contamination of agricultural soils, with possible effects on soil function and micro-organisms. Extracellular oxido-reductases and hydrolases from the fungus T. versicolor and fungal growth were monitored in liquid cultures in the presence of tetracycline, lincomycine, sulfadiazine and ciprofloxacin for 10 days, in order to assess the suitability of these enzymes as biomarkers. Among the conditions of treatment, statistical analysis demonstrated an increase in manganese-dependent peroxidase after exposure to sulfadiazine at 1 mg/L when compared with the control. Acid phosphatase activity was decreased by lincomycine at 1 or 10 mg/L. Conversely, β-glucosidase activity increased in the presence of this antibiotic at 10 mg/L. In Terrestrial Model Ecosystems spiked with contaminated pig slurry, lincomycine at the concentration of 8 or 80 μg/kg dry soil, and ciprofloxacin at 250 ng/kg dry soil decreased the activity of soil dehydrogenase, when compared with a green slurry treatment, over 28-day incubations. Laccase activity was similarly decreased in the presence of the highest concentration of antibiotics. We determined bacterial and fungal biomasses using Q-PCR. Bacterial biomass was increased in the presence of lincomycine at 80 μg/kg whatever the time of exposure, and to a lesser extent in the presence of ciprofloxacin at 250 ng/kg, but only at day 28. In contrast, both antibiotics, whatever their concentrations, did not modify fungal biomass in soil. In conclusion, we were unable to demonstrate important effects of antibiotics at concentrations found in the agricultural environment.

Fate and effects of ivermectin on soil invertebrates in terrestrial model ecosystems

The effect of ivermectin on soil organisms was assessed in Terrestrial Model Ecosystems (TMEs). Intact soil cores were extracted from a pasture in England and kept for up to 14 weeks in the laboratory. Ivermectin was applied to the soil surface via spiked cow dung slurry at seven concentration rates ranging from 0.25 to 180 mg/TME, referring to concentrations of 0.19-227 mg ivermectin/kg soil dry weight in the uppermost (0-1 cm) soil layer. After 7, 28 and 96 days following the application soil cores were destructively sampled to determine ivermectin residues in soil and to assess possible effects on microbial biomass, nematodes, enchytraeids, earthworms, micro-arthropods, and bait-lamina feeding activity. No significant effect of ivermectin was found for microbial respiration and numbers of nematodes and mites. Due to a lack of dose-response patterns no effect concentrations could be determined for the endpoints enchytraeid and collembolan numbers as well as total earthworm biomass. In contrast, EC50 values for the endpoint feeding rate could be calculated as 0.46, 4.31 and 15.1 mg ivermectin/kg soil dry weight in three soil layers (0-1, 0-5 and 0-8 cm, respectively). The multivariate Principal Response Curve (PRC) was used to calculate the NOEC(community), based on earthworm, enchytraeid and collembolan abundance data, as 0.33 and 0.78 mg ivermectin/kg soil dw for day 7 and day 96, respectively. The results shown here are in line with laboratory data, indicating in general low to moderate effects of ivermectin on soil organisms. As shown by the results of the bait-lamina tests, semi-field methods such as TMEs are useful extensions of the battery of potential test methods since complex and ecologically relevant endpoints can be included.

CREAM: a European project on mechanistic effect models for ecological risk assessment of chemicals

Current risk assessments are mainly based on ecotoxicological endpoints at the level of individual organisms, but according to the EU directives, the protection goal aims at achieving sustainable populations (European Commission 2002a, b; Forbes et al. 2009; Preuss et al. 2009a; Thorbek et al. 2009). Population-level effects depend not only on exposure and toxicity, but also on important ecological factors that are impossible to fully address empirically. At present, a number of testing approaches exist that provide endpoints on the community and the population level, respectively (nontarget arthropod and earthworm field tests, aquatic and terrestrial model ecosystem tests). However, not all fields and regulatory questions can be covered by these approaches. To fill these gaps and to enhance the scientific quality of ecological risk assessments, we suggest implementing mechanistic effect models (MEMs), as these also

Tropical terrestrial model ecosystems for evaluation of soil fauna and leaf litter quality effects on litter consumption, soil microbial biomass and plant growth

The aim of this work was to evaluate whether terrestrial model ecosystems (TMEs) are a useful tool for the study of the effects of litter quality, soil invertebrates and mineral fertilizer on litter decomposition and plant growth under controlled conditions in the tropics. Forty-eight intact soil cores (17.5-cm diameter, 30-cm length) were taken out from an abandoned rubber plantation on Ferralsol soil (Latossolo Amarelo) in Central Amazonia, Brazil, and kept at 28ºC in the laboratory during four months. Leaf litter of either Hevea pauciflora (rubber tree), Flemingia macrophylla (a shrubby legume) or Brachiaria decumbens (a pasture grass) was put on top of each TME. Five specimens of either Pontoscolex corethrurus or Eisenia fetida (earthworms), Porcellionides pruinosus or Circoniscus ornatus (woodlice), and Trigoniulus corallinus (millipedes) were then added to the TMEs. Leaf litter type significantly affected litter consumption, soil microbial biomass and nitrate concentration in the leachate of all TMEs, but had no measurable effect on the shoot biomass of rice seedlings planted in top soil taken from the TMEs. Feeding rates measured with bait lamina were significantly higher in TMEs with the earthworm P. corethrurus and the woodlouse C. ornatus. TMEs are an appropriate tool to assess trophic interactions in tropical soil ecossistems under controlled laboratory conditions.