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Title: A review of the history of restoration ecology of degraded semi-natural agro-ecosystems : case study of the Woburn Sands Fuller's Earth Quarry
Author: Aloupie, Maria-Stella
Awarding Body: University of Reading
Current Institution: University of Reading
Date of Award: 2011
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Abstract:
While the agricultural surplus in Europe has left us with a legacy of abandoned or set-aside land and efforts have been made to even reduce its high input-induced fertility, so that competition (mainly by grass) is reduced and broad leaved species (e.g. wildflowers) can establish, restoration legislation has long been requiring that post industrial land is returned to society by developers, after use, in its productive (in agricultural terms) previous state. Relatively recently, this has been challenged by new generation ecologists, who, however, base their arguments on previously established ecological principles, which had not yet found their way to materialize into practice, due to a general culture that saw high fertility as a self-evident goal. It is thus now proposed that instead of trying to make post- industrial land fertile as the rest of biodiversity-impoverished green fields, it is better that land use possibilities are expanded towards different end-"uses", which would comprise more diverse habitats and land uses. Trees, especially conifers, are usually better tolerators of harsh post-industrial land conditions, and have been used extensively in restoration. Broadleaved tree species and wildflower species have been employed in restoration too. Is there scope to retain their systematic use in restoration? If so, in order for those plants to establish successfully, some initial inputs may be necessary, so that disturbed or damaged nutrient cycles start functioning, and, at the same time, some initial grass-leguminous mixtures are often recommended to be sown, so that erosion is prevented. The concern, in this case, is to find what these inputs' levels must be, so that erosion control is achieved, without the development of overwhelming vegetation and fertility, because if this happens, certain sown or naturally colonizing species will prevail at the expense of species that are more valuable from a biodiversity point of view. The Woburn Sands Fuller's Earth Quarry in Aspley Heath (Bedfordshire,1994- 1998) was seen as a valuable terrain to study plant growth and survival in three spoil substrates with different vegetation. Substrates used exhibited typical spoil characteristics, lacking construction, nutrients, organic matter, water retention capacity etc. Additional bioassays with Woburn Sands substrates and also with sand, were done at the University of Reading Grounds and Glasshouses. As well as surveying soil characteristics and present vegetation and its evolvement during four consequent years, several plant forms (sycamore and alder seedlings and saplings, grasses, clover and wildflowers), namely regular protagonists in restoration projects, were screened for performance in the three substrates (which might -or might not- represent different successional stages on post industrial land, dominated by woody leguminous species - broom and gorse), and a calibration was sought for minimum nutrient inputs, so that the above goals of a) induction of nutrient cycles and b) discouragement of excessive fertility build-up (leading to competition and species loss), are served. Plant nutrients (N, P, K ) and lime were used in sub-optimal to near optimal levels (in agricultural terms) in multi-factorial bioassays, and thresholds were sought for, in which, nutrient actions and interactions were observed to promote or reverse the process of plant survival and I or growth: gradual nutrient increase was often observed to induce or inhibit plant survival and growth responses disproportionately, after a critical dosage threshold. In the field and in mixtures, such observations were examined through the framework of possible competition (notably by grasses) and facilitation manifestation. Spoils heterogeneity and 'immaturity', can produce inconsistent bioassay results. Thus, the amount of labour etc input in such studies hardly ever corresponds to the number of interpretable, let alone publishable, findings. Also, since this study concerned only one region, results cannot be generalised, but only help to knowledge built-up. While some thresholds have been detected, and some insights have emerged concerning the actual scope of planting what we plant on harsh substrates, further study is needed to clarify this work's findings towards a broader framework. In this work, there has also been an effort to place restoration into a broader historical, aesthetic, sociological, ethical and scientific context, relating it to issues of British Landscape conservation etc. The discourse of a palette of views amongst laypeople, concerned parties, politicians and scientists about restoration and conservation was also explored.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.553018  DOI: Not available
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