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Lindsay Carrington has completed her PhD in ecology.  The overall aim of her research was to investigate methods by which semi-natural habitats can be successfully created on clay capped landfill and to explore mechanisms by which the establishment of these habitats can be accelerated.

Background to research

A major loss of semi-natural habitats has been seen in the United Kingdom over the last century.  Decommissioned landfill presents excellent opportunities for habitat creation to help compensate for this loss.  However, landfills are usually capped with a highly impervious clay substrate which is then deliberately compacted to form a seal.  This presents a unique and hostile environment for plants in which standard techniques of habitat creation require modification.

A major constraint to habitat creation which is often overlooked is insufficient social acceptance of landscape changes during restoration processes.  The aesthetic appeal of the landscape is often affected for a number of years.  Methods of reducing the time taken to establish vegetation, and thus reducing the impact on the landscape aesthetic appeal, would therefore be of benefit in promoting community social acceptance and support within the local community.

Therefore the research was aimed at finding the best methods of habitat creation on landfill sites in order to accelerate the rate of re-vegetation, whilst at the same time maintaining ecological integrity through the establishment of swards indicative of unimproved or species-rich semi-improved grassland.

Ongoing experiments

Lindsay’s study focused on two properties that are influential in the development of grassland that can be manipulated under experimental conditions: the substrate and micro-topography.  Experiments were set up comparing sward establishment between sites seeded directly onto the bare clay substrate and for sites to which ameliorant and topsoil have been added.  The research also investigated the impact of ridge and furrow of varying dimensions on sward establishment as well as the role of two ecological levers: earthworms and arbuscular mycorrhiza.  The establishing grassland was monitored with quadrats over a seven year period.

Initial Results

Progress demonstrated that substrate has an effect of the soil in terms of its physical and chemical attributes and on plant community in grassland creation on clay capped landfill.  The addition of topsoil and ameliorant has resulted in non-seeded competitive grass species dominating the sward within three years following creation.  Where no topsoil or ameliorant was added the plant community continued to support the more desirable forb species.  However, in the absence of ameliorant and topsoil plant growth was found to be impeded with a mean of 36% bare ground five years following creation.