The health of our soils is vital for the sustainable delivery of a wide range of ecosystem services such as food and fibre provision, carbon sequestration, habitat support, flood prevention and detoxification. The ability of our soils to perform the functions that support these services is underpinned by complex relationships between the diversity and activity of the soil’s biological community and the soil’s physical structure1. New Zealand flatworms (Arthurdendyus triangulates) are thought to have arrived in the UK in horticultural imports sometime in the 1960’s and were first identified at the Edinburgh Botanical Gardens. Over recent decades this non-native flatworm species has been identified in gardens, allotments, and agricultural grasslands across large parts of northern England, Scotland and N Ireland2. They are known to be voracious predators of native earthworm species and in particular impact on deep-dwelling anecic species such as Lumbricus terrestris and Apporrectodea longa3,4 and thus, New Zealand flatworms are listed by the EU, DEFRA and the Scottish Government as an invasive non-native (alien) animal species of concern.
Despite decades of research, and the documented impact of this invasive species on native earthworm populations, their potentially cascading impacts on wider soil ecology and soil structure are less well understood. Evidence of their impact on soil functions such as hydrology and organic carbon and nutrient cycling has tended to be anecdotal and mechanistic links assumed based on the intimate relationship between soil ecology, soil structure and soil biochemical processes. It has been noted for example that Scottish pasture fields infested with New Zealand flatworm were often covered in rushes and more prone to waterlogging, presumably because of impact on soil structure and porosity3. However, beyond the documented impacts on specific earthworm species the impacts on the functional soil biodiversity may be less pronounced due to niche filling by other species5, and the effects of the flatworms themselves on soil structure and biochemical processes have not been determined. The impacts on soil function therefore may be more complex than has been assumed.
A. triangulates is one of more than 20 flatworm species known to be in the UK, of which only 4 are native, and concerns persist over the potential for climate change to assist the spread and colonization by further species such as the New Guinea flatform (Platydemus manokwari)6 or the South American Obama nungara7. Thus, developing a better understanding of how our soil communities are already changing in response to flatworms and the consequences for how our soils function is vital.
This project will explore the impacts from micro-scale to landscape scale of New Zealand flatworm on soil ecology, soil structure and soil function, seeking to better understand the interactions and drivers of changes in soil function. This will inform management and policy concerning invasive soil fauna and enable improved modelling of soil functioning in response to likely ecological change. The project will include 3 study elements:
1) Field survey of agricultural grassland sites in N-S and E-W transects across N England and Scotland to update our knowledge of the distribution of the species and environmental and geographic controls on their spread.
2) Field scale studies of agricultural grasslands known to be infested with New Zealand flatworms will involve the manipulation of populations of anecic earthworms and New Zealand flatworms through selective removal to demonstrate the impact of New Zealand flatworms on not only earthworm populations, but also on the wider soil macro and meso fauna community and soil biological activity. Changes in soil structure, infiltration and water-holding capacity, SOM and soil nutrient dynamics will be used to assess impacts on soil function.
3) Mesocosm experiments will allow the impacts of New Zealand flatworm on soil structure, soil organic matter and soil nutrient cycles under controlled conditions to support the field-scale studies helping identify specific drivers of change in soil function.
The application deadline is January 7th at 17:00. By this deadline applicants must have filled in the IAPETUS online application from following instructions here: https://www.iapetus2.ac.uk/how-to-apply/. The application form requires you to write several sections of text about your interest in this PhD and your suitability for PhD research. Serious applicants are strongly advised to make contact with Dr Clare Wilson by email well before the deadline to discuss their application. After making the application, candidates will be shortlisted for the next stage of the IAPETUS DTP selection process.
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