The Mechanisms and Processes of Vegetation Dynamics on Oil-Shale Spoil Bings in West Lothian, Scotland
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Date
12/2004Author
Harvie, Barbra
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Abstract
The work establishes the ecological importance of shale bings at both a local and global
scale by presenting the mechanisms and processes of succession. The bings are postindustrial
spoil heaps, the result of retorting mineral oil from deep-mined carboniferous shale
beds.
The structure of vegetation on the shale bings was determined by a review of published data
and a base-line survey of eight bings resulting in new floristic and environmental data from
340 quadrats and 261 plant species. The floristic data were analysed in the context of
ecological indicator values (Ellenberg), functional type (competitive, stress-tolerant,
ruderal), National Vegetation Classification and two-way indicator species analysis. The
results indicated considerable variation in plant communities both between and within
different bing sites.
The vegetation patterns were associated with the physical (altitude, aspect, slope and bare
ground) and chemical (pH, calcium, phosphorous, potassium, magnesium, and nitrogen)
environment of the shale substrate. Multivariate analyses (Detrended Correspondence
Analysis and Canonical Correspondence Analysis) were used to ascertain the amount of
species variation explained by each of the different environmental gradients. Although these
abiotic environmental factors were shown to have a statistically significant influence on the
plant community structure around 75% of the variation was still unaccounted for.
Nine species were selected to determine whether inherent plasticity within a species (plant
height, number of flowering heads and seeds produced), the influences of seed dynamics and
plant physiology could account for the variation in community structure not explained by
environmental variables. This showed that almost half of the variation between and within
bing sites was stochastic and probably dependent on the chance arrival of propagules in the
initial stages of succession.
The results from this study were compared and contrasted with theoretical successional
models and with similar studies of primary successions on both natural (glaciers, sand dunes,
islands in fresh water, coral islands and volcanoes) and man-made (china clay, coal, other
post-industrial sites, urban waste and arable land) sites. The similarities established the
relevance of the work to other regions and sites, to successional theory and to ecological
restoration and management practices.
On a local scale the bings are shown to have high ecological importance. They are refugia
for locally rare fauna and flora and are a major component of the West Lothian biodiversity
action plans. They are also of considerable social and historic importance.