Beate Strandberg

Nordic Empetrum Dominated Ecosystems: Function and Susceptibility to Environmental Changes

Abstract This paper reviews the knowledge on crowberry (Empetrum nigrum ssp. nigrum and ssp. hermaphroditum) dominated ecosystems in the Nordic region. Empetrum leaves and litter have high phenolic content resulting in slow decomposition, and with the formation of an organic top soil, nutrients are kept in an organic nutrient bank in the soil mainly available for plants with ericoid mycorrhiza. Empetrum nigrum ssp. hermaphroditum is a strong nutrient competitor and outcompetes most plants in late successional stages. This is due to chemical interference (allelopathy) and resource competition. Crowberry as an organism is resistant to atmospheric pollution and may even increase in vigor by high atmospheric N deposition in nemoral coastal heaths, but is very sensitive to mechanical disturbances and fire. However, there are indications that the closed nutrient cycle established when Empetrum is dominant may be disturbed after airborne inputs of inorganic N.

Herbicide impact on non-target plant reproduction: what are the toxicological and ecological implications?

Declining plant diversity and abundance have been widely reported in agro-ecosystems of North America and Europe. Intensive use of herbicides within cropfields and the associated drift in adjacent habitats are partly responsible for this change. The objectives of this work were to quantify the phenological stages of non-target plants in in-situ field situations during herbicide spray and to compare plant susceptibility at different phenological stages. Results demonstrated that a large number of non-target plants had reached reproductive stages during herbicide spray events in woodlots and hedgerows, both in Canada and Denmark where vegetation varies considerably. In addition, delays in flowering and reduced seed production occurred widely on plants sprayed at the seedling stage or at later reproductive periods, with plants sprayed at reproductive stages often exhibiting more sensitivity than those sprayed as seedlings. Ecological risk assessments need to include reproductive endpoints.

The Impact of a Copper Gradient on a Microarthropod Field Community

In order to evaluate the power of laboratory toxicity tests to predict the situation in the field, soil microarthropods were studied at the population and community levels in a copper contaminated field, and data were compared to the outcome of single species laboratory tests in the same soil type from a companion study. In addition to copper, the influence of several soil characteristics and plant cover data on soil microarthropod abundance and distribution was tested. Total microarthropod abundance was highest at intermediate copper concentrations, and linearly related to grass biomass. For single species populations no clear picture of abundance in relation to soil copper was seen. Two collembolan species, Folsomia quadrioculata and Folsomia fimetaria, were among the most sensitive. The Shannon-Wiener index of biodiversity decreased linearly with increasing soil copper concentrations. The application of multivariate statistics showed copper to be the parameter best fitting the distribution of microarthropod species in the field. A distinction could be made between sampling points with 50–199 mg Cu/kg soil and those with higher copper concentrations. The species composition of the microarthropod community was not correlated with plant species diversity or total grass biomass, but was affected by a nearby row of tall trees. Community analysis of field data proved as sensitive as laboratory testing, and seemed superior to single species field population data concerning detection of copper effects on soil microarthropods.

Effect of a copper gradient on plant community structure

Vegetation data including plant cover, biomass, species richness, and vegetation height was sampled on a copper-contaminated field with total copper contents varying from 50 to almost 3,000 mg/kg soil. The field was covered by early succession grassland dominated by Agrostis stolonifera. Plant cover, biomass, species richness, and vegetation height generally decreased with increasing copper content, although the highest biomass was reached at intermediate copper concentrations. Multivariate statistical analyses showed that plant community composition was significantly correlated with soil copper concentration and that community composition at soil copper concentrations above 200 mg/kg differed significantly from community composition at lower copper levels. Comparison of single-species (Black Bindweed, Fallopia convolvulus) performance at the field site and in laboratory tests involving field soil and spiked soil indicates that the laboratory tests conventionally applied for risk assessment purposes do not overestimate copper effects. Interaction between copper and other stressors operating only in the field probably balance the higher bioavailability in spiked soil.

Effects of copper on enchytraeids in the field under differing soil moisture regimes

The aims of this study were to investigate the combined effects of drought stress and copper pollution on enchytraeids under natural conditions in the field and to compare the results of laboratory toxicity tests with results of the field study. Such studies were conducted to increase the understanding of interactions between chemicals and natural stressors and assess the predictive value of standardized laboratory tests with enchytraeids. The combined effect of copper and summer drought on enchytraeids was investigated in an old copper-contaminated field site at Hygum, Denmark, in three areas with different copper burdens. Each area consisted of five plots, which were divided into two subplots: one control and one drought subplot in which precipitation was excluded for a 45-d period during summer. Enchytraeids were sampled in spring (before the enforced drought began) and in autumn (after recovery from drought). Clear effects of copper were evident in both the field and the laboratory experiment. The field population density and species composition was highly affected by copper at concentrations in the range 300 to 500 mg Cu/kg dry soil and higher. In particular, a greatly impoverished species diversity was found in the copper-polluted areas. The effects of copper in the field compared reasonably well with the results of the laboratory tests. Surprisingly, possible effects of summer drought in the field were not detected in the autumn sampling, perhaps because of rapid recovery of the enchytraeid populations in both unpolluted and copper-polluted areas.

Herbicide and fertilizers promote analogous phylogenetic responses but opposite functional responses in plant communities

Throughout the world, herbicides and fertilizers change species composition in agricultural communities, but how do the cumulative effects of these chemicals impact the functional and phylogenetic structure of non-targeted communities when they drift into adjacent semi-natural habitats? Based on long-term experiment we show that fertilizer and herbicides (glyphosate) have contrasting effects on functional structure, but can increase phylogenetic diversity in semi-natural plant communities. We found that an increase in nitrogen promoted an increase in the average specific leaf area and canopy height at the community level, but an increase in glyphosate promoted a decrease in those traits. Phylogenetic diversity of plant communities increased when herbicide and fertilizer were applied together, likely because functional traits facilitating plant success in those conditions were not phylogenetically conserved. Species richness also decreased with increasing levels of nitrogen and glyphosate. Our results suggest that predicting the cumulative effects of agrochemicals is more complex than anticipated due to their distinct selection of traits that may or may not be conserved phylogenetically. Precautionary efforts to mitigate drift of agricultural chemicals into semi-natural habitats are warranted to prevent unforeseeable biodiversity shifts.

The effect of glyphosate on the growth and competitive effect of perennial grass species in semi-natural grasslands

Biodiversity within European semi-natural biotopes in agro-ecosystem is declining, and herbicide drift from neighbouring fields is considered as an important factor for the decline. The aim of the present study was to investigate whether the growth and competitive interactions in a model system of two perennial grass species, Festuca ovina and Agrostis capillaris, are affected by sub-lethal doses of glyphosate in field margins. In a glasshouse experiment with ample nitrogen, the interspecific competitive interactions were found to be significantly affected by glyphosate; the competitive effect of F. ovina on A. capillaris increased and the competitive effect of A. capillaris on F. ovina decreased with increasing doses of glyphosate. Furthermore, the importance of interspecific competition increased with the glyphosate dose. The results of the study of competitive interactions are in agreement with the observed plant community dynamics at the field site where F. ovina was found to be more dominant in plots treated with a relatively high dose of glyphosate. Importantly, the effects of glyphosate on the plant community dynamics critically depended on the effect of glyphosate on the plant competitive interactions. The study concludes that the current practice in the environmental risk assessment of non-target effects of herbicides, where single species are tested in the greenhouse, may be inadequate for assessing the effect of herbicides in semi-natural plant communities. The presented methods can be used for assessing the importance of competitive interactions for the sensitivity of non-target plants to herbicides in risk assessment.

The effect of nitrogen and glyphosate on survival and colonisation of perennial grass species in an agro-ecosystem: does the relative importance of survival decrease with competitive ability?

The ecological success of a plant species is typically described by the observed change in plant abundance or cover, but in order to more fully understand the fundamental plant ecological processes, it is necessary to inspect the underlying processes of survival and colonization and how they are affected by environmental conditions. A general ecological hypothesis on the effect of environmental gradients on demographic parameters is proposed and tested. The hypothesis is that decreasing fitness or competitive ability along an environmental gradient is associated with an increasing importance of survival for regulating the abundance of the species. The tested hypothesis is related to both the stress gradient hypothesis and whether the importance of competition increases along productivity gradients. The combined effect of nitrogen and glyphosate on the survival and colonization probability of two perennial grass species, Festuca ovina and Agrostis capillaris, which are known to differ in their responses to both glyphosate and nitrogen treatments, is calculated using pin-point cover data in permanent frames. We found that the relative importance of survival increased with the level of glyphosate for the glyphosate sensitive A. capillaris and decreased for the glyphosate tolerant F. ovina. Likewise, increasing levels of nitrogen increased the importance of survival for the relative nitrophobic F. ovina. Consequently, the proposed hypothesis was corroborated in this specific study. The proposed method will enable predictions of the effects of agricultural practices on community dynamics in a relatively simple setup eliminating the need to quantify all the interaction among the species in the plant community. The method will be immediately useful for the regulation of non-cultivated buffer strips between agricultural fields and semi-natural and natural biotopes such as hedgerows and waterways.

Contribution of organic farming to public goods in Denmark

The potential contribution of organic farming to the public goods, ‘Nature and Biodiversity’, ‘Environment’, ‘Energy and Climate’, ‘Human Health and Welfare’ and ‘Animal Health and Welfare’ in Denmark is guided and partly secured by the principles and specific requirements of the EU Organic Regulation. However, other factors, such as the production type, farm size, geographical location and—not the least—the management of the farm, also influence the contribution. Using the ban on synthetic pesticides and restricted use of antibiotics, including the requirements to compensate for and prevent such uses in organic farming, as examples, the positive and negative contributions of organic farming in relation to selected public goods were analysed. The contributions of organic farming to Nature and Biodiversity and Human and Animal Health and Welfare are mainly positive compared to conventional farming for all farm types, whilst the effects on Environment and Energy and Climate are mixed; i.e. some effects are positive and others are negative. The analysis revealed a need for further documentation and revision of the organic principles and specific organic requirements—in particular in relation to the public goods Energy and Climate, which at present are not addressed in the EU Organic Regulation. Moreover, some organic farming requirements and practices cause dilemmas; e.g. more space per animal and outdoor access improves Animal Health and Welfare but at the same time has negative effects on Environment, Energy Consumption and Climate Change. These dilemmas should be solved before OA may be fully attractive as an integrated policy measure supporting jointly several public goods objectives.

Identifying potential gaps in pesticide risk assessment: Terrestrial life stages of freshwater insects

1.Insecticides are important drivers of biodiversity loss and ecological impairment in freshwater ecosystems. Freshwater insects may be exposed to insecticides via water during larval/nymph stages and via air, habitats, and food during adult stages in the terrestrial environment. 2.The aquatic risk assessment (RA) of pesticides does not consider terrestrial life stages, and a literature review revealed that pesticide ecotoxicity data for adult freshwater insects are very scarce and outdated. Consequently, it is not possible to assess how adult freshwater insects may be protected through RA programs for terrestrial non-target organisms. 3.We give guidance to generating and using of such ecotoxicity data focusing on species selection, test design, and type of ecotoxicity information. 4.Policy implications. This commentary considers how terrestrial stages of aquatic insects are protected by pesticide risk assessment (RA) and highlights the necessity of performing holistic RA, focusing on organisms and populations as supplement to current subdivisions in element-based compartments (e.g. aquatic and terrestrial ecosystems). This article is protected by copyright. All rights reserved.