Woodland Restoration on Landfill Sites: Earthworm Activity and Ecosystem Service Provision

Tree measuringSummary

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. 

Research objectives

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.

Results

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.

Next steps

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.

Status

Complete (2013-2016). 

Contact

Dr Frank Ashwood

Funders and partners

This PhD project was funded and supported by the University of Central Lancashire, and Forestry Commission Thames Chase.

Forestry Commission policy

Climate change represents a significant threat to urban infrastructure, environmental quality and the health of city dwellers. Green infrastructure is itself at risk through greater extremes in temperature fluctuation, consequent flourishing of tree pests and diseases, drought and perceived increased risk of subsidence leading to tree removal.

There is no clear system for determining the biophysical interactions, benefits, or managing potential trade-offs within a risk-benefit context, so as to optimally support the protection and sustainable regeneration of UK towns and cities. The Urban Trees and Greenspace in a Changing Climate Programme intends to develop such a system through consolidating and building upon existing work to provide the evidence base for urban trees, definition and communication of best practice guidance, and robust assessment, evaluation and dissemination tools so that the risks and benefits of urban tree placement can be more fully assessed by society, policy makers and planners.

The Programme also maintains the centre of excellence which Forest Research has developed over several decades on land regeneration practices to establish and maintain urban greenspaces on former brownfield and contaminated sites.

Urban trees and greenspace in a changing climate