Supervisors: Simon Potts, Paul Eggleton (Natural History Museum)
The soil biota mediates a number of essential ecological processes that are vital to the entire ecosystem such as the degradation of organic matter, cycling of nutrients, sequestration of carbon, and the development and maintenance of soil structure which influences gas and water transportation
- In addition to these important ecological functions, the soil is home to the majority of terrestrial insects at some stage in their life-cycle, therefore indirectly influencing above-ground services such as pollination, and directly or indirectly linking in with above-ground food-webs
- Macroinvertebrates such as earthworms and millipedes can process up to 30% of the annual dead organic matter input to most soils and facilitate decomposition by bacteria and fungi by mechanically breaking up residues and dispersing microbial propagules. As ecosystem engineers, soil macroinvertebrates create channels, pores, aggregates and mounds that influence the transport of gases and water and thus create or modify microhabitats for other smaller soil organisms. In anthropogenically modified environments, such as agriculture, forestry and horticulture, they are essential for maintaining the structure of soil, and may be significant in preventing or controlling outbreaks of soil-born diseases and pests
- Intensive agriculture can result in lower soil fertility, increased soil erosion and reduced biodiversity. This is thought to be unsustainable in the long-term, as the functions performed by the soil biota must be increasingly replaced by chemical and mechanical inputs
- Agri-environment schemes encourage the adoption of agricultural practices favourable to the conservation of wildlife. Non-cropped field margins enhance species diversity and act as refuges from which beneficial organisms such as earthworms and biological control agents are thought to spread out into the adjacent field
- The choice of seed mix sown and subsequent management may affect the value of these field-margins for enhancing agro-ecosystem biodiversity. The SAFFIE project (Sustainable Arable Farming For an Improved Environment) is investigating the influence of field margin vegetation and management on the biodiversity of arable systems. Field margins have been planted with three different seed mixes and managed in three different ways, and the aboveground biota, including birds, vegetation and arthropods, has been monitored. This PhD will complement this work by examining the belowground system.
- To test the hypothesis that different field margin management practices result in differences in soil invertebrate diversity and abundance. Does this correlate with aboveground plant & invertebrate diversity? Does functional group composition differ between management regimes? Are field margins an important habitat for taxa with potential as biological control agents?
- To investigate the temporal heterogeneity of soil macroinvertebrates. Do the field margins act as a reservoir for re-colonisation of cultivated fields? Do the margins provide a refuge for over-wintering invertebrates? Do soil invertebrates provide a resource for farmland birds, either as chick food during the breeding season or for over-wintering migrants?
- To examine the influence of spatial heterogeneity on soil invertebrates. Is landscape heterogeneity a more important influence on soil invertebrate diversity than farm management?
METHODS
Initially, work will concentrate on developing a suitable sampling protocol appropriate for arable field margins. Soil invertebrates are difficult to sample comprehensibly, the method employed usually being dependent on the size of the target taxa. A comparison of three methods will be carried out – soil invertebrates will be extracted from soil cores by handsorting, Tullgren funnel extraction and Winkler bags.
Target taxa will include mesofauna such as collembola, and macrofauna including earthworms, millipedes, centipedes, woodlice, ants and beetles. Soil properties, such as moisture content, pH, soil structure and texture and volume of organic matter, will also be measured.
Based on the conclusions from this work, sampling will then take place in the field margins in spring and autumn to investigate the influence of margin management on soil invertebrate diversity and abundance. Sampling will initially take place at ADAS Boxworth, Cambs, where the SAFFIE field margin has been in place for three years.
Subsequently, sampling throughout the year will allow an assessment of temporal and spatial heterogeneity. This will be conducted on a transect running from the field margin into the field to investigate the role of field margins as a source for migration into the field following cultivation. The influence of landscape heterogeneity on soil invertebrate diversity will be examined by expanding sampling to SAFFIE sites across the country.
Analysis of data will employ multivariate techniques including MANOVA and ordination.
OUTPUTS
Research papers will focus on (i) the influence of field margin management on soil invertebrate diversity and abundance, (ii) the links between above- and below-ground systems, (iii) temporal heterogeneity in soil invertebrate communities and (iv) spatial heterogeneity in soil invertebrate communities.
The study is funded by ...
