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Aspects of Applied Biology 82, 2007
Vegetation Management
Vegetation dynamics on oil-shale bings; implications for
management of post-industrial sites
By B A HARVIE and G RUSSELL
Centre for the study of Environmental Change and Sustainability, School of GeoSciences,
The University of Edinburgh, King's Buildings, Edinburgh EH9 3JN, UK
Summary
We assessed the distribution of vegetation, pH and nutrients on six sites in
relation to three different management regimes. The results demonstrated that
the ranges of pH and available macronutrients on ecologically managed sites
were not significantly different from those on unmanaged sites. Lower levels of
nutrients and higher pH were recorded on traditionally managed sites. In
addition, groups of common plant species were identified that are indicators of
ranges of physical and chemical environmental conditions. This information can
be used to determine best suited sowing and planting regimes in the restoration
and vegetation management of post-industrial waste sites.
Key words: amelioration, assisted planting, mine spoil, policy, restoration, seed
sources, indicator species
Introduction
A comprehensive study of the vegetation dynamics on the oil-shale bings of West Lothian,
Scotland (Harvie, 2005a) demonstrated that although variation in substrate chemistry and the
large scale physical environment (aspect, altitude and angle of slope) each explained some of the
variation in species distribution, differences in past management of individual sites was also a
considerable contributing factor. This paper analyses relevant data from the earlier study. The
objectives are to identify groups of plant species that are influenced by different management
practice, and by variations in the physical and chemical structure of the spoil substrate, and to
discuss the implications of this information on the restoration and vegetation management of
post-industrial sites in general.
Study sites
The 19 oil-shale bings are post-industrial waste heaps arising from the industrial process of
retorting crude oil from deep-mined oil-bearing shale and were created between 1851 and 1963.
Like many similar spoil sites they are situated close to large urban populations. From cessation
of dumping the individual bings have been managed in different ways (due to vagaries of
ownership and a series of historical circumstances) making them ideal study sites to gauge the
effectiveness of a range of management regimes.
Geographically the bings lie within an area of 13.5 ha in the east and south of the county of
West Lothian and the greatest distance between any two sites is 9 km (Seafield and Oakbank).
The mounds of spoil can be low lying over a large area or steep sided, single or multiple peaked.
Height above the surrounding landscape ranges from 9 m to 95 m (summit altitude above sea
58
level from 100 m to 240 m). The bings are in the early recruitment stages of primary succession
and no recognisable vegetation types (e.g. NVC, Rodwell, 2000) have developed. There are no
obvious signs of competition for space as even in the most populated areas there is still a high
percentage of bare ground.
The bing substrate is basic in comparison to the surrounding agricultural land. The substrate
has a large particle size with low water holding capacity and the shale particles are cohesive;
factors that make the bings free draining and stable, even on steep slopes (Harvie 2005b).
Materials and Methods
Collecting and collating the data
Past management for each bing site was determined from planning applications, site maps and
planting regimes (West Lothian Council, various dates). The bings were then categorised by
management type and representative sites were selected for further investigation.
In the earlier study (Harvie, 2005a) vegetation and environmental data were collected in a
systematic stratified sampling of these bing sites. Plant species and bare ground were recorded
as percentage cover within 2 m x 2 m quadrats at regular intervals (horizontally) from the top,
middle slopes and base of each site. The aspect and angle of slope of each quadrat were also
recorded. Samples of the substrate were collected adjacent to each quadrat and analysed for pH
and available macronutrients; Na, Mg, K, P and N.
The relevant data from this study were collated and analysed to determine the distribution and
abundance of species in relation to the management regime on each site. Species were grouped
according to their restriction to particular management regimes or to measured physical and
chemical criteria.
Results
Management types and selected sites
Three broad management types were identified, ranging from no management to long term
ecological restoration programmes for wildlife and amenity (Table 1). Seven bings were
unmanaged, nine were conventionally managed and three were ecologically managed. From the
19 sites, six bing were selected as representative of the range of past management practices for
further study; two examples each of bings that had been unmanaged, traditionally managed and
ecologically managed (Table 2).
The soil chemistry
Chemical analysis of the substrate recorded a wide range of nutrients and pH (Table 3), with
measurements significantly higher and lower than the requirements for optimum plant growth
suggested by Bradshaw and Chadwick (1980) recorded on all sites. Available nitrogen in the
substrate is especially low at all sites regardless of management regime, even after amelioration.
Lowest levels of sodium, potassium and phosphorous were recorded on traditionally managed
sites and highest on unmanaged sites. The reverse was true for pH.
Potassium (K) is used to exemplify variance in nutrient availability between four bings from
the six selected (Table 4). Clapperton, the traditionally managed site, has the lowest available
potassium, despite extensive fertilisation less than 10 years previously. The two unmanaged
sites (Greendykes and Mid Breich) and the ecologically managed site (Oakbank) are more alike
but the analysis reveals significant differences between the two unmanaged sites.
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Table 1. General description of the three main management regimes on the oil-shale bings of
West Lothian, Scotland
Regime Description of the regime
No management On cessation of tipping all machinery, plant and rail tracks removed: site made safe
to prevent spoil slippage and spontaneous combustion. Management objective =
minimal reclamation and reshaping, no amelioration or planting to present.
Traditional
management
On cessation of tipping all machinery, plant and rail tracks removed. Reclamation -
large scale removal of spent shale (for road foundations and infill) – ongoing.
Restoration - flattening and rounding off of remaining spoil, covering with top-soil,
ameliorating (adding fertiliser) then sowing with commercial rye-grass mix and/or
direct planting with tree species (native and non-native). Management objective =
cover up – from 1970’s to present, after reclamation
Ecological
management
On cessation of tipping all machinery, plant and rail tracks removed, site made safe
to prevent spoil slippage and spontaneous combustion. Restoration – minimal
rounding off of some slopes, some amelioration of summits, implementing planned
seeding and planting regime using best suited native species. Management objective
= providing green space for amenity and recreation - from 1980’s to present (often
after earlier traditional restoration)
Table 2. The six selected bings, their location (OS grid reference), bing height (above
surrounding landscape), management regime, date of cessation of dumping and approximate
date of restoration, species numbers and unique species (adapted from Harvie, 2005a).
Name of bing
Greendykes Mid Breich Clapperton Drumshoreland Addiewell Oakbank
OS reference NT 087 736
NT 009 646
NT 079 697
NT 075 700 NT 002 631
NT 076 664
Bing height 95m 12m 38m 61m 9m 46m
Management Unmanaged
Unmanaged
Traditional Traditional Ecological Ecological
Closure date 1925 1915 1925 1925 1932 1932
Restoration none none <10 yrs ago <10 yrs ago >15 yrs ago >15 yrs ago
Total spp. 86 92 92 60 99 84
Unique spp. 4 13 13 2 20 11
Table 3. The minimum, maximum, mean and standard deviation of the of the available Na, Mg,
K, P, Ca ( in ppm) and pH measured across all bing sites. Available nitrogen was measured as
NH
4+
and NO
3-
also in ppm. Letters in brackets denote the type of management at the bing
where the minimum and maximum measurements were recorded. U = unmanaged, T=
traditionally managed (adapted from Harvie 2005a).
Na Mg K P Ca pH NH
4
+
NO
3
-
minimum 1 (T) 16 (U) 5 (T) 5 (T) 50 (U) 5.72 (U) 0.05 0.03
maximum 275 (U) 1289 (U) 371 (U) 180 (U) 20300 (U) 8.17 (T) 0.47 4.67
mean 41 308 146 29 3284 6.84 0.13 0.91
SD 4 312 94 24 3736 0.70 0.09 0.89
Table 4. The minimum, maximum and mean of potassium (K) recorded at four of the six
selected bings (adapted from Harvie 2005a).
Bing site Greendykes Mid Breich Clapperton Oakbank
K min 65 52 8 84
K max 353 179 110 282
K mean 208 108 37 190
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The bing vegetation
The vegetation survey recorded 275 quadrats and 202 species from the six selected bings.
There were 60-99 species recorded on each bing and 2-20 unique species associated with each
site (Table 2). Addiewell (ecologically managed) had the highest number of both total species
and unique species and Drumshoreland (traditionally managed) the lowest. The numbers of
species recorded did not, however, correlate with the management regime of the bings although
there were groups of species that were recorded only on sites with particular management
regimes (table 4).
Table 5. Indicators of management. Examples of species that are solely recorded under one of
the three management regimes on the bings. Asterisk (*) denotes species that are also
indicators of chemical environment: dagger (†) denotes species are also indicators of the
physical environment (adapted from Harvie 2005a).
No management Traditional management Ecological management
Heracleum sphondilium Cerastium glomeratum Agrostis gigantea
*Linum catharticum Galeopsis tetrahit Alnus glutinosa
*Trifolium campestre Matricaria discoides †Calluna vulgaris
†Rosa canina Stellaria media †Poa trivialis
†Rubus fruticosus †Potentilla erecta
Senecio jacobea *Sanguisorba minor
Six species were associated with unmanaged bings and not recorded on other bing sites.
These are species that are also common in the landscape surrounding the sites. The four species
associated with traditional management were all annual, ruderal species; common agricultural
weeds. There were six species associated with ecological management. Agrostis gigantea and
Poa trivialis are present as a result of assisted planting schemes on one bing and Calluna
vulgaris has spread from surrounding moorland at another site.
Table 6. Indicators of the chemical environment. Examples of species that are solely recorded
at high pH and high measurements of available sodium (Na), phosphorus (P), potassium (K)
and magnesium (Mg). Asterisk (*) denotes species that are also indicators of management;
dagger (†) denotes species that are also indicators of the physical environment (adapted from
Harvie 2005a).
pH Na P Mg
†
Medicago lupulina *Linum catharticum Chamerion angustifolium
†
Arctium minus
Sagina procumbens Tragopogon pratensis Hesperis matronalis *Sanguisorba minor
†
Stellaria media *Trifolium campestre
Tripleurospermum inodorum Lotus corniculatus
There were additional species recorded only when levels of individual nutrients, or pH, were
higher than considered suitable for optimal plant growth (Table 6), others were recorded only on
the upper or lower slopes of the sites, and at slopes less than or greater than 30
o
(Table 7). Some
of these species were limited by more than one set of environmental factors.
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Table 7. Indicators of physical environment. Examples of species that are solely recorded
within a range of elevation (mid slopes to summit or base) or angle of slope (<30
o
or 30
o
).
Asterisk (*) denotes species that are also indicators of management; dagger (†) denotes species
that are also indicators of the chemical environment (adapted from Harvie 2005a).
Elevation Angle of slope
mid slopes to summit base < 30
o
30
o
Arenaria serpyllifolia Medicago lupulina Matricaria discoides *Arctium minus
Cardamine hirsuta Taraxacum officinale Rhinanthus minor Linaria vulgaris
Festuca ovina †Rosa canina †Calluna vulgaris
†Poa trivialis †Rubus fruticosus *Stellaria media
†Potentilla erecta Tussilago officinale †Potentilla erecta
Myosotis arvensis Vicia hirsuta Veronica persica
Discussion
Management has been shown to be a major factor in the distribution species on the oil-shale
bings of West Lothian, Scotland (Harvie, 2005a). There have been three different management
regimes practised on these bing sites, traditional management, no management and ecological
management, and the character of the resulting vegetation reflects these management practices.
The substrate of the bings is different from the surrounding agricultural land, with a higher
pH, low nitrogen and considerable variation in the availability of other nutrients providing a
range of niches and microhabitats within each site. The variation in nutrient availability
measured in the oil-shale substrate is comparable with the results from chemical analysis of
volcanic ash on Ascension Island (Gray, 2006). The substrate on all bing sites is receptive to the
seeds of species that would otherwise be unsuited to local soil conditions. Indeed the bings add
considerably to the diversity of plant species in West Lothian and the vegetation includes both
nationally and locally rare species (Harvie, 2005b). The characteristically poor flora associated
with some bings and other industrial spoil sites is more likely to be due to their isolation from
similar habitats than to any deficiencies of the substrate (Miles and Walton, 1993). Studies of
unmanaged anthracite mining spoils in Pennsylvania showed that large numbers of species were
found on all spoils (except highly acid black shales) indicating that most post-industrial
materials were suitable for the growth of higher plants even without amelioration (Cornwell,
1971).
The individual sites
Clapperton and Drumshoreland have both been traditionally managed. Restoration on these
bings follows the same pattern as much of the restoration work carried out post-industrial sites
across Britain; rigidly adhering to fifty-year old policies. Policy in 1956 followed a standard
recipe of reducing the height and gradient of the heap, rounding peaks and ridges, covering with
topsoil, applying fertilizers (liberally) and sowing with commercial rye-grass mix. On low
lying heaps trees, usually birch and alder, were planted directly into the spoil at the base of the
heap without any amelioration. The sole purpose was “to obtain a satisfactory visual effect”
(Oxenham, 1966). The results of this management strategy can be seen on these two shale
bings. The end product is species poor and visually boring. Many of the planted species die
(Harvie, 2005b) and are replaced by the weedy species (ruderals) recorded on these (Table 5)
and other similarly managed bing sites (Harvie 2005a). The results of chemical analysis of the
substrate on these sites (Table 4) suggest that any advantages gained from costly reshaping,
adding topsoil and amelioration are lost within a few years. Without continuing input of
fertilisers the substrate of traditionally managed sites becomes depauperate in many of the
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nutrients that were available in the untreated shale. The weedy species that were uniquely
recorded on the traditionally managed sites (Clapperton Table 2 and Table 5) are unlikely to
remain successful as a result of lack of nutrients and many of the planted and sown species have
already died resulting in vegetation lacking in diversity (Drumshoreland Table 2).
Mid Breich and Greendykes were unmanaged from cessation of dumping more than 80 years
ago and the resulting vegetation is from natural colonisation and is therefore a primary
succession. No fertilisers or amelioration have been used on these sites therefore they are not
colonised by the ruderal (weedy) species that require nitrogen rich soils and were uniquely
recorded on the traditionally managed sites. The unmanaged bing sites retain a greater range of
available nutrients, with very high and very low levels being recorded within individual sites,
than managed bings. This in-site variation in substrate chemistry adds to the available
microhabitats and niches available for colonisation. The numbers of species recorded on these
sites was higher than traditionally managed sites where seeding and planting had been carried
out (unsuccessfully) and was similar to ecologically managed sites.
Addiewell and Oakbank have been ecologically managed, each with a specific objective.
Restoration of post-industrial sites in the United Kingdom is rarely associated with amenity and
recreation or with plans for long-term vegetation management yet Addiewell is a Scottish
Wildlife Trust nature reserve and Oakbank is managed as part of Almondell and Calderwood
country park. These bings grant access to much needed green space for the residents of nearby
towns and, due to conscientiously planned assisted seeding and planting with carefully selected
species, they also provide a refuge for a wide range of plants and animals that are becoming
increasingly marginalised by increased pressure for housing and agricultural land.
Ecological management has been highly successful on these sites. Species that have colonised
naturally have been supplemented by strategic assisted planting of those same species. In
addition some native plant species not common locally, but that are suited to the alkaline, free
draining substrate on the bings, have been seeded (e.g. Sanguisorba minor). When grass mixes
are used they are carefully selected and not standard rye grass mix (West Lothian Council,
various dates). This careful management regime has resulted in sites with diverse habitats (from
birch woodland to scree slopes) and a diversity of plant and animal species.
Indicator Species
The indicators of managed bings are predominantly species that are known to be planted, from
management records (West Lothian Council, various), or heathland species that have established
on sites in close proximity to large surrounding areas of heath. The indicators of unmanaged
bings are all species that are frequently recorded in the surrounding landscape, Linum
catharticum, Trifolium campestre, Rosa canina, Rubus fruticosus and Senecio jacobea (Smith et
al., 2002). L. catharticum and T. campestre also indicate high levels of sodium and could be
important indicator species within management regimes.
Several species are indicative of components of the physical environment and others are also
indicators of high levels of nutrients within the chemical environment. The indicator values of
these species are only expected to be relevant within the bing habitat and are possibly only valid
in the bings that have been surveyed in the Harvie (2005a) study, however, the generality of the
association needs to be tested on other sites. Many of these species are also recorded in
vegetation surveys on a range of post-industrial sites including stone quarries (Hepburn, 1955;
Davis, 1982) and disused pits (Hall, 1957) making them, potentially, an integral component of
restoration policy.
Vascular plants are considered to be the most useful indicator species for identification of
habitat quality: mammals and birds are too mobile and lower plants are often too difficult to
identify in the field (Rose, 1999). Vascular plants were used as indicator species in a method of
assessing woodland flora (Peterkin, 1974) that was adopted by the Nature Conservancy Council
in the 1980’s to identify ancient and semi-natural woodland habitats that should be protected.
63
The Forestry Commission has recently adopted an ecological system of classification (ESC) of
British forests based on ground vegetation and humus type as indicators of soil nutrient regime
(Wilson et al., 2001).
It is disappointing that Oakbank and Addiewell are rare examples of ecological restoration
management of post-industrial waste. By surveying the vegetation that establishes naturally on
derelict land managers can determine a great deal about a substrate. Restoration plans can then
be developed that make use of existing conditions with assisted planting and seeding to produce
self managing sites with high recreation and amenity value that also add to the diversity of the
local landscape.
Conclusions
Management decisions on the restoration of the bings and similar post-industrial sites are often
considered to be constrained by available sources of funding but frequently the real constraints
on restoration managers are imposed by an unrealistic public perception of what post industrial
and other waste sites should be restored to, and how quickly they should be restored. In Britain
it is not the quantity of spoil that causes public concern but that it is situated in or near centres of
population where it is seen as an immediate problem.
The three management regimes on the West Lothian bings produce habitats with different
vegetation types and species. Each of the bings selected for discussion in this paper has fewer
than 100 plant species yet the total species recorded on all six sites is more than 200. A
compilation of plant species records for all of the West Lothian bings results in a list of more
than 350 species (Harvie, 2005a) making the bing habitat a major source of biodiversity in the
county.
Vegetation management should not be about ameliorating a site to temporarily accommodate a
random selection of commercial plant species, many of which are not going to survive. This
results in species poor vegetation as was recorded on the traditionally managed bing sites at
Clapperton and Drumshoreland. When suitable seed sources are nearby the best management
may be no management. Allowing natural succession by species that are best suited to the novel
environment of a post-industrial site can result in rich and varied vegetation as was recorded at
Greendykes and Mid Breich. When there are no suitable local seed sources due to distance from
established vegetation or because the surrounding landscape is physically and chemically
different from the spoil heap then ecological management, making a well-informed decision to
sow and plant appropriate species that are best suited to the substrate and compliment the
existing vegetation, may be the best option. This is particularly true of spoil heaps that are close
to cities and towns. These sites provide an opportunity to provide new amenity and recreation
areas like Oakbank and Addiewell. Ecological management also has the potential to improve
sites that have previously been unsuccessfully restored using traditional methods. Whatever the
type post-industrial site, there must be a clear plan of what the location is to be managed for, a
specific objective and an end product that the manager intends to achieve.
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