Paul Henning Krogh

The effect of glyphosate and nitrogen on plant communities and the soil fauna in terrestrial biotopes at field margins

Publication: Research - peer-reviewReport

The aim of the study was to improve our understanding of and be able to quantify and predict the effects of glyphosate and nitrogen and their interaction on small terrestrial biotopes in the agricultural landscape, e.g. hedgerows and field margins. For both vegetation and soil fauna, the effects were assessed at the ecosystem level by measuring biodiversity and functional traits.
We have obtained an increased understanding of the causal relationship between plant communities and the soil fauna at the ecosystem level and increased knowledge on how and by what mechanisms important drivers that are known to affect plant communities may affect pollination and the soil fauna. The combined use of plant trait and soil fauna trait data in a full-factorial field experiment of glyphosate and nitrogen has never been explored before. The focus on plant and soil fauna traits rather than species enabled a robust description of the ecological processes at the functional level.
More specifically, both fertilizers and herbicides affected species composition. Generally, species cover decreased with increasing glyphosate doses, although cover of Festuca ovina and Euphorbia esula forms exceptions. Increasing nitrogen, generally, resulted in increasing total plant cover and biomass, especially of fast-growing and competitive species as grasses and a few herbs such as Tanacetum vulgare.
Using plant traits we found that increase in nitrogen promoted an increase in the average specific leaf area (SLA) and canopy height, whereas glyphosate promoted a decrease in those traits. Additionally, the present analysis found an increase in competitive ability (increase in Ellenberg N and Grimes C and a decrease in Grimes S) with increasing nitrogen. With increasing doses of glyphosate, the present analysis also found an increase in Grimes S. For the two composite species Tanacetum vulgare and Leucanthemum vulgare, the two most heavily affected traits were floral density and flowering phenology, in turn leading to marked changes in plant-pollinator interactions.
Nitrogen application caused a shift towards earthworms feeding on litter. There was a negative relationship between glyphosate and habitat width of Collembola, whereas nitrogen had the opposite effect. Deep root biomass was positively correlated with trophic position of Collembola. We observed both stimulation and declines of microarthropod populations in response to the high N fertilization.
The empirical data of vegetation and soil fauna biodiversity and traits was linked to the underlying ecological processes at the functional level of the ecosystem using the modelling approach of structural equation modelling.
Original languageEnglish
Place of PublicationCph.
PublisherThe Danish Environmental Protection Agency
Number of pages75
ISBN (print)978-87-93283-85-5
ApplicantMiljøstyrelsen
StatePublished - 2016
SeriesPesticide Research
Number163

    Keywords

  • Agro-ecosystem Competition model Effect of environment on competitive interactions Hedgerow flora Pin-point Plant cover State-space model Vertical density

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