The nature of mycorrhizal benefit in reclaimed ecosystems
The nature and importance of vesicular arbuscular mycorrhizae and ectomycorrhizae was determined for a range of different sites and mycotrophic plant species. Sites were chosen in the south-east, east and Midlands of England and South Wales so that different situations were represented in terms of historical management and biotic and edaphic parameters. Two major types of environmental disturbance were included; restored opencast coal mines and reclaimed landfill sites which had distinct reclamation problems associated with them. A number of undisturbed systems were also included in the survey including mature and ancient woodland on a number of different soil types, mature hedgerows and mature meadows. Several soil physico-chemical parameters were determined for each site and the relationship with the degree and type of mycotrophy for the flora were related to these features. Other edaphic factors were also taken into account including variations in the weather and the age of a given plant. The extent of mycotrophic development was found to be strongly linked to age of site and the preferred type of mycotrophy of the plant partner. Edaphic factors had a lesser, but significant, effect which was particularly important in reclaimed situations. Different methods were assessed on a small scale for the mycorrhizal inoculation of plant species commonly used for amenity purposes on reclaimed landfill sites. A simple scheme employing root fragments and certain soil components was selected on the basis of two required criteria: it was important that the scheme was not only effective but could be implemented within the financial and technical constraints imposed by a county council restoration programme. The chosen inoculation system was then implemented on a large scale in a field based experiment using lysimeters that were subject to a continuous input of landfill gas derived from a newly reclaimed landfill. The success of inoculation was related to both the plant species and the soil type. The importance of mycotrophy in terms of the success and sustainability of plant growth on a landfill reclamation was shown to be significant for certain species. Mycotrophy was more important to predominantly ectomycotrophic species than VA endomycotrophic species. A revision of current theories on the succession of ectomycorrhizal fungal species is suggested in the light of mycobionts identified during the course of the work.