The ecological restoration of slate waste tips in Wales, UK
Electronic versions
Documents
64.4 MB, PDF document
Abstract
Many hundreds of hectares of slate waste have accumulated in north Wales as a result of hundreds of years of quarrying. Due to its resistance to weathering and susceptibility to flushing, no fines or organic materials accumulate on slate waste tips and they remain largely devoid of vegetation cover. Various methods aimed at restoring vegetation to slate waste tips have been tested but no single method can claim to have achieved results that could be applied on a large-scale. To address this problem an integrative experimental approach to the ecological restoration of slate waste was taken, focussing on the reassessment of past experiments, the sourcing of planting stock and the identification of the best mixture of materials for applying to slate waste to increase plant-available nutrients and water. The reassessment of past restoration experiments at Penrhyn Quarry, north Wales, showed that only by introducing large quantities (for example, a 75 cm depth of boulder clay) of materials to provide nutrients and increase water-holding capacity could acceptable levels of plant establishment be achieved (e.g. survival in LIFE experiment A ~96.43 %). The greatest levels of success were achieved by the hydraulic distribution of peat-based slurry followed by planting of tree saplings. The surviving trees in this treatment show sustained growth (e .g. highest growth rate recorded between 2002 and 2007 = 391.26 % increase in crown area (tree 23)) more than 30 years after planting. To test the potential of using very local (quarry) provenances in quarry restoration activities, shoot cuttings of willow ( Salix caprea x Salix cinerea = Salix reichardtii) and seed from seven species of tree and shrub (Acer pseudoplatanus, Betula pendula, Cytisus scoparius, Fagus sylvatica, Sorbus aucuparia, Quercus petraea and Ulex europaeus) were collected from both quarry (Penrhyn Quarry) and non-quarry populations. Survival and growth rates showed no clear differences between quarry and non-quarry populations when grown in slate waste. Although it cannot be advised that all planting stock for quarry restoration is collected from quarry provenances, further research is recommended. Field application of green waste compost (GWC) (produced by Conwy County Council) and hydrated polyacrylamide (PAM) gel in a 50:50 (v/v) mixture produced significantly greater species richness, vegetation cover and dry biomass over 18 months than a control treatment. Vegetation cover in the GWC-PAM treatment showed an increase of more than 90 % over that prior to applications of soil-forming materials. In conclusion, rapid, sustainable, low-cost methods of successfully restoring vegetation cover to slate waste tips are achievable without the need for costly site preparation or disturbance of established successional assemblages. Development of nurse crops and early colonising vegetation cover of this type is an important step in the sequential ecological restoration of slate waste tips. And with careful consideration of site-specific requirements, past restoration successes and sources of planting stock, the efficiency and success of ecological restoration projects can be greatly increased.
Details
Original language | English |
---|---|
Awarding Institution | |
Supervisors/Advisors | |
Award date | Dec 2009 |