Frank Ashwood, PhD studentship, University of Central Lancashire (2013-2016)
This PhD project studied the interactions of earthworms, composted green waste (CGW) and trees on reclaimed landfill. It looked at whether woodland establishment and soil quality on reclaimed landfill can be improved, through CGW application and earthworm activity promoting soil development and encouraging tree growth.
Here is a short video summarising this project.
The overall aims of this research project were to investigate:
- the interactive effects of CGW addition and earthworm activity on tree growth and survival on reclaimed landfill,
- the interactive effects of CGW addition and earthworm activity on the biological, physical and chemical quality of reclaimed soil under woodland,
- the community dynamics of naturally and artificially introduced earthworms on landfill sites, and responses to tree establishment and CGW addition.
Composted Green Waste being transported to an experimental plot for incorporation to the soil.
A large-scale field experiment and a nursery-based experiment revealed the responses of the tree species Italian alder and Norway maple to CGW and earthworm addition in reclaimed soil. Findings included:
- A positive synergistic effect of CGW addition and earthworm activity leading to significantly growth of both tree species.
- CGW addition significantly increased levels of soil organic carbon and essential plant nutrients, with earthworm activity increasing the accumulation of organic carbon into the soil.
Additional laboratory-based research revealed the performance of four common UK earthworm species in reclaimed soil and the palatability of CGW and Italian alder and Norway maple leaf material. We demonstrated that CGW and leaf material from both tree species can support earthworm establishment on landfill, and that two particular species of earthworm (black-headed and green worm) are suitable candidates for inoculation to reclaimed soil.
Finally, a survey of a newly reclaimed site showed that natural colonisation of reclaimed land by earthworms can occur rapidly (within 2 years), where soil quality is sufficient and legacy soil materials are stockpiled and applied following best practice guidance.
Future research aims to investigate legacy reclaimed sites which used organic amendments during restoration. This is expected to yield information on the long-term effects of organic matter addition on restoration quality, soil carbon stocks and the soil ecology of such restored sites.