Journal American Society of Mining and Reclamation, 2013 Volume 2, Issue 2
UNDERSTANDING AND DELIVERY OF THE COMPONENTS OF
STRUCTURE, DIVERSITY, AND FUNCTION IN THE RESTORATION
OF ECOSYSTEMS ON MINED LAND: WORKING TOWARDS A
PRACTICAL METHODOLOGY1
R. N. Humphries2
Abstract: With the full implementation of the Convention on Biological
Diversity (CBD) by 2020, surface mining and other industries in the UK will have
to embrace the concept of ecosystems and ecosystem services, and be ready to
deliver satisfactory schemes with all the necessary elements where important
natural vegetation and habitats are involved.
It is debatable whether there is sufficient understanding of the ecosystems being
considered and clarity in what needs to be achieved leaving practitioners and
regulators with little guidance when faced with designing or evaluating a mining
proposal or the evaluation of the success of restoration schemes.
This paper introduces and examines a measurable and workable methodology
based on the Tansley concept of vegetation communities (being the basic unit of
ecosystems) and the application of the national monitoring standards (CSM) for
the key requisite ecosystem structural elements. These are encompassed in the
proposed Canopy-Age-Regeneration-Genetic-Indicator–Exotic design and
assessment model.
It is argued that the Joint Nature Conservancy Council (JNCC) derived CARGIE
Model is applicable to the restoration of ecosystems in the UK. It could enable
better design and evaluation of the restoration of ecosystems and their services,
and the mining industry to meet the challenges posed by CBD and the new and
emerging legislation and policies.
Additional Key Words: biological diversity, ecosystem services, vegetation classification, plant
community traits
_________________
1.
Paper presented at the 2013 National Meeting of the American Society of Mining and
Reclamation, Laramie, WY Reclamation Across Industries, June 1 - 6, 2013 and accepted for
the online Journal of The American Society of Mining and Reclamation, Volume 2, No. 2,
2013. R.I. Barnhisel (Ed.) Published by ASMR, 3134 Montavesta Rd., Lexington, KY 40502.
2
Neil Humphries, Environmental Co-ordinator, Celtic Energy Ltd, Castlegate Business Park,
Caerphilly, CF83 2AX, UK. and Visiting Professor, National Soils Research Institute,
University of Cranfield, Cranfield, MK43 0AL, UK.
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Journal American Society of Mining and Reclamation, 2013 Volume 2, Issue 2
Introduction
Human kind, for good reason, has become increasingly preoccupied with the (bio-) diversity
component of ecosystems; particularly in respect of the loss of rare species and the degradation
of life supporting ecosystem services that living entities provide.
The consideration of
ecosystems is now beginning to determine how we exploit sustainably the natural resources of
Planet Earth and consequently the consenting of future mine developments and the detailing of
their reclamation.
By 2020 planning authorities and regulators in the UK will have had to review the impact
and mitigation of development and management of natural resources and to have had fully
implemented the Convention on Biological Diversity (CBD). This involves the enactment of
legislation and policy to protect, enhance, and restore ecosystems and ecosystem services
(Department of Environment, Farming and Rural Affairs, 2013). Surface mining and other
industries in the UK will have to embrace the concept of ecosystems and ecosystem services, and
be ready to deliver satisfactory restoration schemes with the recognised ecosystem elements.
Whether we have sufficient understanding of the ecosystems being considered and clarity in
what needs to be achieved may be debated for some time to come. Whilst there is growing
enthusiasm for a more ecological approach to restoration, we are seemingly stumbling around for
clear guidance beyond repeatedly rehearsing “what a good thing this might be.”
This paper is concerned with the re-establishment of semi-natural ecosystems on mined land
in the UK and to determine if there are useful and guiding principles that might be put to
practical and beneficial effect. An outcome could be measurable and workable criteria to enable
better design and evaluation of the restoration of semi-natural ecosystems and their services,
thereby enabling the UK mining industry to meet the emerging challenges posed by CBD.
The Ecosystem Concept
Over the millennia, globally, there has become a myriad of species at both the macro- and the
microscopic habitat scales within the same abiotic environments, and even the evolution of biotic
ecosystems within ecosystems (Thompson, 2010). In the simplest of terms, the conceptual
definition of an ecosystem is a (biotic) community of living entities (comprising of individuals
and populations of animals, plants, fungi, bacteria species) within a non-living (abiotic)
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environment (Odum, 1963). The concept embraces a bewildering range and complexity of living
entities across a range of spatial scales from continental coral reef systems to the microscopic
level of microorganisms and protists of soil aggregates. Some systems are temporal in nature,
such as the migratory Caribou with spatially different supporting communities depending on
season.
The search for a unifying understanding of ecosystems and its application to the sustainable
exploitation of natural resources developed considerably in the 1950s and 1960s with the study
of energetics and trophic structures and functions (Odum, 1963). This was followed by studies
of the dynamics of interactions between individuals and populations from the 1970s (e.g.,
Harper, 1977) through to today.
The conceptual structure and function of the biotic component of ecosystems is based on a
pyramid of trophic levels (Odum, 1963), comprising populations of producers (autotrophs) and
consumers (heterotrophs - including predators and decomposers). For any particular ecosystem
there are populations of associated plants, fungi, bacteria, and animals. For these to exist and
function there are a number of fundamental life cycle processes comprising immigration,
establishment (niche), growth and development, and reproduction and dispersal (Harper, 1977).
This is further embellished through genetic differentiation in terms of competitive ability through
life form and phenology, physiological adaptation to environmental and biotic (disease, predator)
stresses, and niche differentiation and resource availability (Grime et al., 1988).
The complexity of the topic makes it a seemingly impossible task to marshal a workable
approach to grasp and apply in practice. So is there a pragmatic way forward to this conundrum?
A possibility is to define the scale the reclamation approach needs to work. To this end, the
thinking of Arthur G. Tansley (the reputed originator of the term ‘ecosystem’ (Moore, 2012) is
most helpful. He used the term ecosystem to form a rational system for vegetation succession
from pioneer (pre-sere) or secondary (sub-sere) stages to climax/plagio-climax stability between
its plant (autotroph), animal, and decomposer (heterotroph) components. The merit of this
definition of ecosystems and their complexity is the easily recognisable scale of plant vegetation
communities (e.g., beech woodland, basic grasslands, dry heaths (see Tansley, 1949). It is at this
scale and complexity that the restoration of ecosystems on mined land is considered further as a
practical way forward for reclamationists.
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The Restoration of Ecosystems
John Harper (1987) aptly likened ecosystem restoration to repairing a damaged watch. To do
this he considered the repairer needed “… a kit of parts and knowledge of how to fit together”
and “… if this is done properly the watch will have acquired the emergent property of the whole
….”
Harper’s parts are synonymous with Odum’s structure and how they fit with his functional
element. Magnuson et al. (1980) proposed a simple two-dimensional graphical model for the
restoration of the Great Lakes’ aquatic ecosystems, which predicted spatially the outcome
between structure and function (Odum, 1963).
Bradshaw (1987) adopted his approach to
illustrate the hypothetical directional development of restored and replacement terrestrial
ecosystems. Here, he defined structure as species and/or complexity and function as biomass
and/or nutrients, and worked as follows:





Degraded ecosystems are low in species complexity and therefore low in
biomass/nutrients
Original ecosystem are high in species complexity and therefore high in biomass and/or
nutrients
Degraded ecosystems recover through natural processes to the original by increasing in
species complexity and therefore biomass and/or nutrients
Ecosystems are restored when they have the same level and balance in species
complexity and biomass and/or nutrients
Other (replacement) ecosystems increase in level of species complexity and biomass
and/or nutrients, but in a different balance to the original
In the absence of further elaboration or definition, these might be taken as being
representative of species number and trophic levels/food web for structure and carbon
assimilation, sequestration, and decomposition capacities for function. Bradshaw goes on to
describe how the development from a degraded (low level) ecosystem to a restored (high level)
ecosystem can be driven in the reclamation process through increasing the biotic structure by
adding species and increasing ecosystem function by such measures as soil replacement, physical
treatment, nutrient addition, and treatment of toxicities. If we take literally what this suggests,
all that is required is to simply provide the requisite species and ensure the abiotic environment is
not limiting to restore a particular ecosystem.
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Burger (2012) in his recent paper on ecosystem reclamation and mining made similar
suggestions based on the Bradshaw principles. Here, species diversity, habitat and water quality
(as structural elements); and biomass/carbon accumulation, hydrologic function, flood control,
etc. (functions) could contribute to higher levels of ecosystem reclamation where practices of
geomorphic-landform design, replacement of topsoil, stream reconstruction and reforestation
were implemented. In commenting on the general achievements of ecological and ecosystem
restoration, Thompson (2010) considered that the restoration practices for the abiotic (physical)
environment to have been largely perfected. This, in his view, was in contrast to the biotic
element (particularly biodiversity). Given an apparent consensus there is sufficient knowledge to
specify the required abiotic environment, this raises the question, what are the essential biotic
structural elements in reclamation schemes?
If the ecosystem structural elements are
reassembled properly, then so will their functional elements, and the ecosystem and its services
as a whole.
Developing a Methodology
Three temperate ecosystems are explored below as to their biotic structural elements at the
plant-community scale and their application in the design and implementation of mine
restoration schemes, and the assessment of the ecosystem restoration achievement. The three
temperate ecosystems considered are woodland, a dwarf shrub heathland, and upland acid
grassland.
Woodland Ecosystems
In considering the application of Tansley’s vegetation-community-based ecosystem
approach, the overreaching functional parts of mature woodland communities are essentially the
autotrophic tree, shrub, and ground-layer vegetation components. The structural elements being
vegetation height, density, growth form etc., which create and modify microclimate (humidity,
temperature, and light), and provide food and breeding habitat providers for a range of
heterotrophs and decomposers. In terms of woodland ecosystems, this embodies an array of
structures and functions at the species level (Morris and Perring, 1974). In order to apply as a set
of design and monitoring principles in the practical world this needs to be simplified.
Tansley’s structural model of woodland vegetation types, the vertical spatial distribution of
the component higher plant species (i.e., horizontal canopy layers of tree, shrub, field, and
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ground layers) is obviously simplistic in that it overlooks the belowground components. Despite
this it has been subsequently refined over the past decades to be more representative of the
complexity of woodland ecosystems by introducing additional structural elements such as treelayer, age class, regeneration potential, genetic pool, local features, and the presence of exotic,
alien or weed species (Table 1). This six-element structural model has been adopted by the UK
Forestry Commission in their surveys to compile the National Inventory of Woodland and Trees
(Forestry Commission, 2001). Importantly, it has also been used by the UK Government’s
scientific and oversight advisory body, the Joint Nature Conservation Committee (2004), in
setting management actions/targets and monitoring of statutory protected internationally and
nationally important woodlands in the UK. The following discussion considers the application
of the JNCC derived Canopy-Age-Regeneration-Genetic-Indicator-Exotic model (referred to
subsequently as the CARGIE Model) in the reclamation of terrestrial ecosystems using Sessile
Oak woodland.
Table 1: Canopy-Age-Regeneration-Genetic-Indicator –Exotic Model for Restoring Woodland
Ecosystems
Structural Elements
Canopy Cover:
Age Class:
Regeneration Potential:
Genetic Pool:
Indicators of Local Distributions:
Exotic / Alien and Weed Species:
Definitions*
Has a range of 30-90% of canopy cover for the tree layer with
an understory cover of 20% of the total stand, and with a
minimum of 10% open space.
A range of age classes (seedlings, saplings, young trees,
mature trees, decaying trees, dead trees) where, at least three
age classes are to be represented by the commonest trees with
10% or 5-10 trees/ha of commonest mature tree species
represented by old growth (>150 years for deciduous species,
>110 years for coniferous species) and a minimum 3 fallen
trees of >20cm dbh and 4 dead standing trees per hectare.
Strictly as the capacity of the woodland’s main structural tree
species to produce and regenerate from seed and to develop to
sapling class. Age maturity …. Seed bearing years
Not less than 95% cover in any structural layer to be solely
native or naturalised species, and local provenance where
local variations.
Characteristic local micro-habitat features (other than dead
wood), presence of notable species (other than tree species) to
maintain distinctive local woodland characteristics.
No prescribed limits. Exotic/alien weed species eg
Rhododendron spp to be progressively eradicated.
*Source – Joint Nature Conservation Committee, 2004
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Sessile oak woodland (Quercus spp – Betula spp – Deschampsia flexuosa woodland,
National Vegetation Classification type W16, Rodwell, 1991a) is one of several types of lowland
woodland occurring typically on ranker, brown-podsol and podsol soils in the warm-dry
conditions of south eastern UK. The mature woodland comprises tree, shrub, and herbaceous
ground layers having a range of number of species (3-29) present. The constant characteristic
tree layer species are either Sessile Oak (Q. patraea) or Pedunculate Oak (Q. robur) and Silver
Birch (Betula pendula) or Brown Birch (Betula pubescens). The shrub layer is typically Holly
(Ilex aquifolium) and Rowan (Sorbus acuparia), with a ground layer of Wavy Hair-grass
(Deschampsia flexuosa), Bracken Pteridium aquilinem), Bilberry (Vaccinium myrtillus),Broad
Buckler Fern (Dryopteris dilatata), Heather (Calluna vulgaris), and Bramble (Rubus fruticosa
agg.).
Typically, these woodlands are of some age and the sites having been woodland for 200
years or more, with some examples predating Medieval times. In the UK, these woodlands have
not gone unmodified and have historically been a source of timber on an ad hoc, a rotational or
coppice basis, livestock grazing and hunting, and even as parts of a planned landscape (Marren,
1990). Others have been clear-felled and replanted from time to time. The oak trees are usually
of some stature, but at a low density and often seemingly even-aged, which reflects the
woodland’s history and exploitation. Where coppiced, the stools are of some size with the
regrowth multi-stemmed, even-aged stems. Oak is usually the dominant mature tree species, but
can be co-dominant with Birch or in some places Birch is the dominant (especially with clear
felling and the opening up of the woodland canopy). In these woodlands canopy cover is usually
not complete and characteristically comprise areas of ‘high wood’ with open areas (glades) and a
high degree of woodland edge.
The following applies the CARGIE Model (Table 1) as the requisites for having established a
Sessile Oak Woodland ecosystem on mined land. The five structural biotic elements are to be
the essential part of the delivery by the reclamation design and a means for an evaluation of
success.
Canopy Cover: According to the CARGIE Model, the requisite for this structural element of
woodland ecosystems is the provision of 30-90% ground cover by the canopy (leaf cover) of the
main constituent tree layer characteristic of the target woodland type (comprising of Birch and
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Oak in the example of Sessile Oak woodland being used as a reference example here). The
widely qualifying range of canopy cover could be made up of any or combinations of the
prescribed age classes of the Oak and/or Birch tree species. The primary purpose of the canopy
cover is to provide the light and humidity conditions required for a woodland ecosystem function
and diversity of associated woodland flora and fauna.
It also provides for the conditions
conducive for woodland regeneration (i.e., establishment of seedlings and maturation of
seedlings).
For the shrub layer (Holly and/or Rowan in the Sessile Oak woodland) there is a requirement
for a 20% canopy cover relative to the whole stand. The distribution of this qualifying element
can be at the woodland edge, scattered, and/or clumped within the woodland. The third requisite
is the 10% open space within the woodland as a whole, which may take the form of scattered
glades or larger areas.
This structural element of woodland could be provided by the design of the reclamation
scheme; for example, for an area of 100ha of woodland, 90ha would be wooded and the overall
tree canopy cover (of the main community tree species (Birch and Oak in the Sessile Oak
woodland) would be between 30 and 90%. Within the wooded area as a whole 20ha of shrub
layer canopy and 10ha of open space could be provided. The tree and shrub-layer canopy cover
criteria could be achieved in a number of ways, either by planting and/or sowing the component
woodland tree and shrub species or by leaving woodland regeneration to natural colonisation
(where there is a nearby and certain source of propagules and the required species have sufficient
dispersal mechanisms).
Where planted, compared with relying on natural colonisation, the tree and shrub canopy
cover can be rapidly and predictably achieved through planting design and specification (stock
size and planting density), and species growth habit and performance. For example for Birch –
Oak woodland with a qualifying canopy cover criteria can established within five years as
described by Humphries and McQuire (1994a).
Where dense planting is relied upon, the
understory can be provided in the woodland design as edges and openings. The attainment of
open space can also be delegated as a matter of design and achieved without difficulty.
In the UK, planted schemes are typically managed under planning consent agreements by
standard forestry practices (see Evans (1984) and Hibberd (1986)) for the first 10-20 years, and
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thereafter, under the owner’s or tenant’s stewardship, to achieve the intended use (e.g., timber,
catchment management, recreation, wildlife, or as visual landscape treatment). Here, density of
stems and canopy cover may be reduced or nurse species removed to alleviate competition and
facilitate tree and shrub maturity, and provide space for understory and ground layer
development. This is achieved by a cyclic programme of thinning, whilst maintaining tree and
shrub canopy cover.
Where there is reliance on seeding, the time to reach the required canopy cover will be longer
and maybe less predictable and more so where natural colonisation is relied upon. If a specific
woodland composition and structure is required, subsequent intervention by managing species
composition and density may be necessary.
Age Class: To meet the qualifying requirement of this second CARGIE Model element there
needs to be the presence of at least three of six prescribed age classes (see Table 1) of the
characteristic tree layer species (i.e., Birch and Oak in the example being used here). This is
primarily to provide important physical habitat structure and conditions, and a range of food
sources for the diverse assemblage of woodland flora and fauna. In this respect three age classes
are particularly important for woodland ecosystem function and diversity, these are: the sapling
growth stage, maturation to seed-bearing age, and old growth (particularly fallen/standing dead
trees) of the tree layer species.
In the design of restoration schemes either a spectrum of age classes are to be introduced at
the time of site reclamation, during the ‘aftercare period’ or later during the first complete life
cycle of the trees within the woodland. In application of this age-related structural element,
qualification would only be achieved with the manifestation of three or more classes within the
woodland.
Taking the sapling, seed bearing aged trees, and old growth classes as examples the
following might be considered. The sapling age class in reclamation schemes can be quickly
achieved (typically 5-10yrs) by planting young nursery stock (as is standard practice in the UK
(Moffat and McNeill, 1994), but thereafter it takes a number of decades (depending on species)
to reach the next mature stage (Evans, 1984). As the sapling cohorts mature into the next older
classes in the course of the development of the woodland, either further replacement saplings
will be required for this age class aspect of woodland structure to be maintained or a different
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age class will need to be present as a replacement. The next cohort of saplings could be provided
by further planting of young trees or recruited from seed and seedlings. The former would
require intervention at some point during the development and maturation of the woodland. This
may be several decades after the initial planting. The latter could also be by intervention through
introducing seed of the tree layer species to the woodland or reliance on the maturation of the
tree layer species (Birch and Oak in this example) to produce seed from which seedlings mature
into the replacement saplings. However, in the latter case, the time before the first cohort of
planted trees matures sufficiently to produce seeds and provide their own seedlings is a matter of
decades. For Birch it is typically 15 years and for the Oak species it is 40 or more years
(Hibberd, 1986). The provision of the old/dead wood element from the first cohort of trees will
be considerably longer, being in the order of 50-60 years for Birch and 200 or more years for the
Oaks (Evans, 1984).
In the interim decades before the Birch and Oak mature to produce seed and dead wood,
these two missing aspects of the woodland ecosystem might be catered for by intervention to
provide these age class structural elements and contribute to the early development of the
woodland ecosystem. Seed could be periodically sown or young trees planted during the early
development of the woodland to provide cohorts of the sapling age class. The provision of fallen
dead trees and upright decaying wood could be provided from areas of the mine development
being clear-felled as part of the forestry programme in advance of mining or felled or from
restored areas being thinned as part of the aftercare management. The timber could then be
stored for later reintroduction. Felled timber can be planted to satisfy the requirement for upright
dead wood. In some situations it may be possible in the wider mining plan to provide seed
bearing trees and mature/over-mature trees by translocation or through leaving islands or
corridors of existing mature woodland. In ecosystem restoration terms, the crucial seed, sapling,
and dead wood age classes and their contribution to the vertical structural components of the
woodland ecosystem could be provided within a 15-20 year period for Birch dominated
woodland and 50 years for Oak dominated woodland.
Where woodland is established by
seeding or to rely on natural regeneration will take longer to generate the qualifying tree canopy
cover because of slower immigration and establishment rates.
In applying the age class structural criterion, the type and amount of old growth is quantified
as the provision of fallen and dead trees at three and four per hectare respectively, whereas the
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amount of saplings and seed production is not, and is related to the next structural element of the
potential of the woodland to regenerate.
Regeneration Potential:
A key characteristic of ecosystems is their ability to re-new and
regenerate their constituent populations. In principle, this qualifying criterion is satisfied by
showing that the complete life-cycle processes are operational (as without this ability other
vegetation and ecosystems will develop). In the case of woodland, regeneration is typically by
seed with the regeneration potential being simply a function of the presence of the key tree
canopy species and the time it takes before they become seed bearing as set out above. There
will have to be a sufficient number of trees to provide an adequate amount of seed and sufficient
number of seedlings that provide the necessary replacement saplings and mature trees for the
required canopy cover to persist. In terms of the amount of seed produced and number of
saplings needed for woodland regeneration, this is dependent on many factors including seed
viability and dormancy, predation and disease, available suitable niches, etc..
Whilst the
qualifying criterion in Table 1 is not quantified in terms of numbers, density, or distribution, it
would be expected that the saplings and maturing trees would be apparent throughout the
woodland and capable of providing further mature/over-mature trees in due course.
Whilst the age class structure is informative of the regeneration potential of woodland
ecosystem restoration schemes, cognisance needs to be given in the design and specification to
the timing and amount of seed production by the first cohort of tree layer species planted. In
practice, this may be a case of ensuring there are a sufficient number of trees (in locations where
seed establishment is likely to be favoured) and a balance between generally uniform or clumped
distribution to promote the chances of pollination, seedling establishment, and ultimately the
replacement of the trees contributing to the woodland.
In the early years of woodland
restoration, regeneration could be promoted through intervention by periodic supplementary
planting and/or seeding (in concert with other interventions to diversify the woodland’s age class
structure as described above).
Genetic Pool: Reliance on foreign sources of seed and nursery plant material for the supply
of ‘native’ species has meant that alien elements have been introduced into the UK gene pool
over the past decades. Because of recent concerns for the conservation of species’ resilience and
diversity, and introduction of diseases and pests, the genetic pool is now considered and
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specified at regional/local levels for the sourcing of seed and nursery plant material for
reclamation schemes. This has resulted in the purposeful collection of seed and growing-on of
local plants for some schemes and particularly where there is sensitivity of introducing non-local
gene pools into the local landscape.
Where woodland establishment relies on natural
regeneration, it may be assumed that this will probably comprise of local gene pools.
Indicators of Local Distribution: Within the overall woodland ecosystem matrix of canopy
cover of the main tree layer, range of age classes, and genetic pools there is a range of woody
and non-woody species to be found giving distinct regional and local woodland characteristics.
In the UK, there are twenty-five recognised semi-natural woodland and scrub community types
(Rodwell, 1991a). Of these, there are four Oak Woodland types. Taking two Sessile Oak
woodland types (NVC W16 and W17 (Rodwell, 1991a)) as examples, these woodlands in the
UK have distinct ‘lowland’ and ‘upland’ Oak-Birch forms, Quercus spp - Betula spp Deschampsia fexuosa (NVC W16) and Quercus petrea – Betula pubescens – Dicranium majus
(NVC W17, Rodwell), respectively. The former W16 type is widespread through the relatively
warmer and drier central, south, and east parts of the UK whilst the W17 type is typical of the
cooler and wetter western and northern uplands of Wales and Scotland.
Within both types of Oak Woodland there are local variations in species composition of the
shrub and ground layers giving two distinct types of W16 (largely soil and/or climate variants)
and four types of W17 (largely climatic with oceanic and continental variants) and each variant
has its own indicator species (see Rodwell, 1991a). The example referred to above in this paper
is the W16a Quercus robur sub-community with an abundance of Bracken over a Wavy Hairgrass sward, but no particular indicator species, whereas W16b has a number of associated moss
indicator species (e.g., Isopterygium elegans).
In the design and specification of reclamation schemes cognisance needs to be given to the
woodland composition and to the local indicator species. At the wider regional level, Rodwell
and Patterson (1994) provide a list of species that can be selected from. It would be expected
that the restored woodland ecosystem would have the appropriate compositional elements.
Exotics and Aliens: In designing mine restoration schemes in the UK there has been a move
away from the use of non-native species. Their use in the past was largely because methods of
establishing native species on disturbed soils and mine wastes, was little understood and the non-
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natives were sometimes easier to establish. With the development of mine restoration practices
this is no longer necessary and besides the national nature conservation policy is now firmly
against introducing further alien species following their detrimental effects on native woodland
and other native ecosystems (UK Parliamentary Office of Science and Technology, 2008). Some
tree species like Sweet Chestnut (Castenea sativa) and Sycamore (Acer pseudoplatanus) were
introduced into the UK some 2000 years ago by the Romans. They are regarded as being
naturalised in the UK landscape, although these and others are often regarded as being
detrimental to native woodlands (Pearman and Walker, 2009). Many of the commercial conifer
crop species are non-native and of North American origin and may be regarded as becoming
‘naturalised’ in turn. In terms of restoration of non-coniferous commercial plantations, it is now
typical that only native dicotyledons and conifer tree and shrub species are to be established.
Dwarf Shrub (Heathland ) Ecosystems
The same Tansley based CARGIE Model principles described above for woodland can be
applied to other ecosystems. Here, the reclamation of Heather (Calluna vulgaris) dominated
heathland (as an idealised model for shrub ecosystems) is considered. The same Joint Nature
Conservation Committee (JNCC) source of vegetation monitoring information (as for woodland)
was referred to for the key structural elements for dwarf shrub ecosystems. For the dwarf shrub
communities (JNCC, 2009a) the information is presented in a different format from that for
woodlands (JNCC, 2004) and had to be extracted, and compiled in the woodland format as set
out in Table 2.
Calluna dry heathland (Calluna vulgaris – Deschampsia flexuosa heath, NVC H9 Rodwell,
1991b) is one of several types of lowland heathland occurring in the UK.
It is typically
associated with free-draining, strongly acid (pH 3 - 4) and base-poor, shallow ranker soils or
highly leached deep brown soils and typically on the Permian-Triasic Sandstones soils at low and
moderate altitudes in the cool and wet parts of central and north-central England. Mature dwarf
shrub heathland comprises shrub and herbaceous ground layers with a typical range in number of
species from 2-21. The constant shrub species is Heather (Calluna vulgaris) and the ground layer
Wavy Hair-grass (D. flexuosa) and the Nodding Thread-moss (Pohlia nutans). Typically these
heathland areas are of some age and may have originated from past woodland clearance and
maintained by the subsequent introduction of burning and grazing (Webb, 1986). This type of
heathland is often exploited commercially for its grazing and sporting returns.
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Table 2: Canopy-Age-Regeneration-Genetic-Indicator –Exotic Model for Restoring Dry Dwarf
Shrub (Heathland) Ecosystems
Structural Elements
Canopy Cover:
Age Class:
Regeneration Potential:
Genetic Pool:
Indicators of Local Distributions:
Exotic / Alien and Weed Species:
Definitions*
Shrub canopy cover of 25% - 90% comprising of at least two
ericaceous species, with <50% Gorse cover, a ground cover of
<25% - 30% graminoids-forbs-lichens & bryophytes, and 1% 10% bare ground.
A range of growth phases for ericaceous species:
Pioneer 10-40%; Building/Mature 20-80%; Degenerate <30%;
Dead <10%.
Strictly as the capacity of the heathland’s main structural dwarf
shrub species to produce and regenerate from seed
Not less than 95% cover in any structural layer to be solely
native or naturalised species, and local provenance where local
variations.
characteristic local micro-habitat features, presence of notable
species to maintain distinctive local dwarf shrub community
characteristics.
Less than 1% alien or weedy species; <5% Bracken; <10%
trees or scrub
*Source JNCC, 2009a
Canopy Cover: In the case of the NVC H9 dry heath community, there is only one CARGIE
Model qualifying shrub, Heather, with a requirement for a canopy cover of between 25 and 90%.
The ground layer is to have up to 30% herbaceous ground cover and 10% bare ground.
In dwarf-shrub restoration schemes in the UK the shrub layer is established from sown seed,
although in some cases natural colonisation may be relied upon where there is an adjacent seed
source. The ground layer may or may not be sown.
Age Class: The dwarf shrub component is relatively short-lived (typically 30 years). Four age
classes are recognised in dwarf-shrub heath ecosystems, these are: the pioneer, building/mature,
degenerate, and dead stages (Gimingham, 1972). Unlike woodland, the main source of dead
plant material is the accumulated leaf litter beneath the shrubs.
To qualify for the age class CARGIE Model criterion, the definition requires that all four
growth phases are to be present at the same time. Individual stands of these heaths tend to be
monocultures of the pioneer and building/mature phases in their physical form due to cyclic
management (burning) to promote their grazing and sporting (game birds) value. Hence, the
implied structural-mix occurring at the same time in these ecosystems may not be met in practice
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Journal American Society of Mining and Reclamation, 2013 Volume 2, Issue 2
in individual stands. However, where either less formal management is implemented or the
heath left to natural processes as in nature conservation areas, it would be expected there would
be more than one age class present.
In restoration schemes (where the heaths are not being commercially exploited) the spectrum
of age classes can be provided by either a phased cycle of establishment or differential
management (e.g., localised cutting/burning) over a period of 10-15 years. Areas of established
heath left without intervention of grazing or burning are readily invaded by tree and shrub
species and rapidly become scrub and woodland.
Regeneration Potential:
This structural element is not defined in the JNCC monitoring guidance. However, the key
to regeneration of the dwarf shrub heath is the production of seed and open habitat (bare ground
with little litter). Flowering and seed production occurs early in the life cycle of Heather and is
at its maximum during the building/mature phase.
In restoration schemes, management
programmes can be devised to promote these phases.
Genetic Pool: Whilst no JNCC guidance is given as to criteria for this structural element, it
would be expected that strict conservation of local genetic gene pools would be required. Seed
in the UK is typically sourced locally by harvesting from existing stands (as part of wider
heathland management programmes).
Indicators of Local Distribution: In the UK twenty-two dwarf-shrub (heathland) community
types have been described (Rodwell, 1991b). Like the woodland vegetation types, all the types
of dwarf shrub heathland have distinct regional and local characteristics, some of which are
extremely localised.
For example, NVC H5 Erica vagans – Schoenus nigricans heath is
restricted to the Cornish Lizard in the far southwest of England. Here, the Cornish Heath (E.
vagans) would be an indicator species as it is endemic and not found elsewhere in the UK.
Whereas, the NVC H9 covers tens of square miles over the southern Pennines and North York
Moors. The latter has five recognised sub-community types with their own characteristics and
indicator species. For the regional variant example in central-east of England (the Galium
saxatile sub-community) Lady’s Bedstraw (G. saxatile) and Tormentil (Potentilla erecta) would
be indicator species.
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Journal American Society of Mining and Reclamation, 2013 Volume 2, Issue 2
Hence, in reclamation schemes in the above localities it would be expected E. vagans would be
present for schemes on the Cornish Lizard and other species to be present in schemes in the
central England, these being introduced by sowing, or planting, or colonisation.
Exotic / Alien and Weed Species: The JNCC guidance is prescriptive regarding this structural
element where the heathland is to have less than the prescribed number/cover of alien or weedy
species, bracken and trees/scrub.
These are generally post-reclamation management issues and are controlled by grazing or
burning. The intensity of such programmes depends on whether the heathland is being exploited
or left to natural processes.
Upland Acid Grassland Ecosystems
The same Tansley based CARGIE Model ecosystem principles described above for
woodland can also be applied to grassland ecosystems. Here, the reclamation of upland acid
grassland (as an idealised model for grassland ecosystems) is considered. The same JNCC
source of vegetation monitoring information (as for woodland) was referred to for the key
ecosystem structural elements. For the upland habitats (JNCC, 2009b) the information for acid
grassland was presented in a different format from that for woodlands (JNCC, 2004) and had to
be extracted and compiled in the woodland format as set out in Table 3.
Sheep Fescue – Common Bent (Festuca ovina – Agrostis capillaris – Gallium saxatile
grassland, NVC U4, Rodwell, 1992) is one of several types of upland grassland occurring in the
UK. It is the most extensive type of pasture in the sub-montane cool, wet climate zone of Britain
and typical of acidic podsol and stagnogley soils. The typical range in species is 7 to 62. The
constant species are Common Bent (A. capilaris), Sweet Vernal-grass (Anthoxanthum odoratum)
and P. erecta with Sheep Fescue (F. ovina) and G. saxatile. These grasslands are exploited for
stock rearing and particularly as summer sheep pastures.
Canopy Cover: In the case of grasslands, the requisite canopy cover is concerned with the
herbaceous ground layer. Here, the JNCC guidance is prescriptive for the grassland canopy to be
dominated by grass species (70% – 80%). In the case of NVC U4 grassland this can be a
mixture of A. capilliaris, A. odoratum, and F. ovina along with 10% forb cover comprising G.
saxatile and/or P. erecta or other U4 characteristic species, and up to 10% bare ground.
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Journal American Society of Mining and Reclamation, 2013 Volume 2, Issue 2
In grassland restoration schemes in the UK the grassland is established by seeding, although
natural colonisation may be relied upon where there is an adjacent seed source.
Table 3: Canopy-Age-Regeneration-Genetic-Indicator-Exotic Model for Restoring Acid Upland
Grasslands Ecosystems
Structural Elements
Canopy Cover:
Definitions*
Less than 10% cover tree or scrub/Bracken canopy layers
Ground cover 70% - 80% graminoids with 10% forb species,
variable sward height range 1-25cm, <10% bare ground.
Age Class:
Greater than 25% mature flowering to be more than 5cm height
above the ground surface & >25% non-flowering maturity to be
less than 5cm height above the ground surface, <10% dead
material as litter layer
Strictly as the capacity of the grassland’s main structural species
to produce and regenerate from seed and/or vegetatively
Not less than 95% cover in any structural layer to be solely
native or naturalised species, and local provenance where local
variations.
Characteristic local micro-habitat features presence of notable
species to maintain distinctive local dwarf shrub community
characteristics.
Less than 1% alien or weedy species; <5% Bracken; <10% trees
or scrub
<1% neutral grassland species, <10% Soft Rush
<25% weed species
Regeneration Potential:
Genetic Pool:
Indicators of Local Distributions:
Exotic / Alien and Weed Species:
*Source – JNCC, 2009b
Age Class: Although not set out in these terms, it appears from the JNCC monitoring guidance
that there are three structural age classes, non-flowering pre-maturity, mature/flowering, and
dead material. To qualify for the age class criterion (using the CARGIE Model) all three class
have to be apparent and not less than the thresholds given in Table 3.
Unlike the productive neutral grassland types (Rodwell, 1992), these upland short-sward
grasslands are not usually suitable for haymaking.
Consequently, where these grasslands are
used by commercial farming enterprises as pasture, they are grazed for much of the growing
season and it is unusual to find flowering stands. However, like the dwarf shrub heathland
above, where either less formal management is implemented or the grassland left to natural
processes (as in nature conservation areas) it would be expected all three age classes would be
present.
Regeneration Potential: This structural element is not defined in the JNCC monitoring guidance.
Many species in this grazed grassland, particularly the grasses, spread and regenerate
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Journal American Society of Mining and Reclamation, 2013 Volume 2, Issue 2
vegetatively (e.g., tillering, stolons, rhizomes) and are not necessarily reliant on the production of
seed and seedling recruitment, and management programmes can be devised to promote these
vegetative growth forms (Spedding, 1971).
Genetic Pool: Whilst no current JNCC guidance is given for this structural element, where it is
proposed to establish native grasslands in reclamation schemes it is now expected that local
sources are required. Until quite recently, seed in the UK has been typically sourced abroad or
has been grown from horticultural stock or from seed collected elsewhere in the UK. Local
harvesting from existing stands for reclamation schemes is possible, as described by Humphries
(2012).
Indicators of Local Distribution:
In the UK there are twenty one types of acid grassland
communities (Rodwell, 1992). JNCC (2009b) identify five of these (NVC U2, U3, U4, U5 &
U6) as being upland types. Like the woodland and dwarf shrub heathland, all five types of acid
grassland have distinct regional and local characteristics. For example, NVC U4c Lathyrus
montanus – Stachys betonica sub-community is only found in a few locations in the Derbyshire
Dales in central England, here, the indicator species are the grasses: Oat Grass (Avenula
pratensis), Crested Hair-grass (Koeleria macrantha), Quaking Oat-grass (Briza media) and
Heath Grass (Danthonia decumbens).
Exotic / Alien and Weed Species: The JNCC guidelines are prescriptive as to the amount of
alien and weedy species, woody species, and other types of grassland species for the grassland to
qualify as acid grassland.
Discussion
The origin of this paper was a thought stimulating presentation given by Professor Jim
Burger at the annual ASMR meeting at Tupelo in 2012.
He considered the notion and
application to mine site reclamation that ecosystem structure and function were intrinsically
linked with the type and level of ecosystem recovery achieved (Bradshaw, 1987, Burger, 2012).
The purpose of this paper is to explore this further and attempt to define a workable methodology
whereby the successful restoration of the biotic component of important CBD (conventional or
biological diversity) ecosystems in the UK might be determined. In considering, the possible
application and value of the proposed JNCC derived CARGIE Model, there were a number of
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Journal American Society of Mining and Reclamation, 2013 Volume 2, Issue 2
issues that might be asked by academics, practitioners, and regulators. Some of the more
obvious ones are discussed below.
Does the CARGIE Model Meet CBD Standards?
Of foremost importance, a key requisite for the acceptance of the CARGIE Model is whether
it meets CBD expectations and standards. If not then the Model may not be accepted as a
measure of success in the assessment of restoration schemes. As the Model is derived directly
from the current and proposed government agency tool used for the monitoring and management
of biodiversity reference ecosystems in the UK (JNCC, 1998), there is no reason to believe it
would not be accepted (at least in principle) by the stakeholders. Hence, it is reasonable to
believe it could be applied to both the design and assessment of mine reclamation as set out in
this paper.
Ecosystem Structure May Not be Equitable to Function
It is implicit in the proposed CARGIE Model that levels of ecosystem structure are equitable
to levels in function. This is likely to be considered highly contentious amongst many ecologists
(C. Zipper, pers. com.), although it is also the basis of the readily accepted Bradshaw derived
model (Bradshaw, 1987). In this respect the JNCC Common Monitoring Standards (JNCC,
1998) stand out having identified the key structural biotic elements for the entire range of UK
terrestrial ecosystems and implicitly assumes there is consummate functioning of the ecosystem
as a result. The structural elements are at the vegetation community scale as originally suggested
more than sixty years ago by Arthur Tansley (1949). The vegetation communities provide the
habitat and food sources for the associated plant, animal, and microbe communities.
For
example, the decaying trees and dead wood were named as an essential component for woodland
ecosystems providing habitat and substrate for saprophytic invertebrates, fungi, and bacteria
(Jonsson and Stockland, 2012a). The JNCC approach reasonably assumes that the presence of
dead wood is an indicator of their presence within the woodland or at least provides an
opportunity for their occurrence.
The Approach Ignores the Belowground Components
The CARGIE Model and the JNCC criteria focus on the aboveground structural
characteristics and criteria.
As a result they are both open to criticism that important
belowground species’ rich biotic elements and essential functions such as decomposition and
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Journal American Society of Mining and Reclamation, 2013 Volume 2, Issue 2
nutrient cycling are ignored (Bardgett et al., 2005; Wurst et al., 2012), given the importance of
the soil as the supporting physical and biotic habitat. Whilst in this context the proffered
approach is somewhat simplistic, it may be that for some ecosystems, the functioning of the
belowground components could be manifest in the composition and condition of the
aboveground litter layer, hence its incorporation into the soil and involvement in the soil-carbon
and soil-nutrient transformation processes. This is demonstrated by the studies on the restoration
of the Jarrah (Eucalyptus marginata) forest on bauxite mines (Grant et al., 2007).
It could be argued in defence of the JNCC approach that the aboveground vegetation
communities are themselves an integration and expression of both the structure and functioning
of the aerial environment (climate) and the soil environment (including the biotic components),
thereby embracing decomposition and nutrient cycling processes in the soil. This notion is
supported by a view that it is the plant roots and buried aboveground derived plant detritus, and
their associated bacteria, fungi, protists, and animals that are the overarching biotic components
of soils (Bardgett and Wardle, 2010; Jonsson and Stokland, 2012a; Siitonen and Stokland, 2012).
Different species of plants and therefore plant communities have their root and soil associations,
some of which are known to have key roles in plant community development (Marx, 1991; Jose
et al., 2006; Piotrowski et al., 2008). Some of the other biotic components, such as those
involved in decomposition processes, may be essential for a fully functioning ecosystem,
whereas others are not and simply reflect the array of diversification of living entities within the
same habitat giving rise to notion of species redundancy in the functioning of ecosystems (Ritz,
2005; Thompson, 2010).
Given the current swell in research into soil diversity and function (Wall, 2012), this
particular criticism of the Model (the balance between above- and belowground biotic
relationships), merits further investigation and, if the Model is to be a valid representation,
further refinement to the Model may be possible to encompass the belowground structural
components.
What about the Abiotic Component?
Whilst the abiotic physical environment (climate, topography, soils, etc.) component of
ecosystems has not been explicitly considered in the Model, it is acknowledged as being the most
commonly considered factor determining the potential level of ecosystem type, development,
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Journal American Society of Mining and Reclamation, 2013 Volume 2, Issue 2
and function on restored mine sites. Here, much research and monitoring effort has been put into
defining these and the modification of the abiotic environment and the biotic response, and in
particular growth (productivity responses). Interestingly, Jonsson and Stokland (2012a) refer to
plants themselves as being the abiotic environment for a range of saproxlic species.
There are various methodologies whereby the potential of sites and soils might be determined
for a range of agricultural, forestry, and natural ecosystems, for example, that set out by
Humphries and McQuire (1994b). Such abiotic criteria can be used to predict the type and level
of ecosystem achievable and the type of amendment required for specific ecosystems to be
restored (the ecosystem being defined by NVC vegetation community type (Rodwell, 2006).
Rodwell in his NVC monographs defines the abiotic components for each of the community
types and their derivatives. As set out above for the below ground components, it can be
reasonably argued that the vegetation communities are themselves an integration and expression
of both the biotic structure and the abiotic aerial (climate) and soil environments as illustrated by
the following example. Festuca ovina – Carlina vulgaris calcareous grasslands (NVC CG1,
Rodwell, 1992) occurs on excessively draining, base-rich and strongly alkaline (pH 6.4 – 8.1)
oligotrophic rendziniform soils on calcareous bedrock. It is confined to areas with 800 to
1,000mm annual rainfall and low frequency of frost days. In contrast, Festuca ovina – Agrostis
capillaris – Galium saxatile calcifugous grasslands (NVC U4) occurs on moderately draining,
base poor moderately to strongly acidic (pH 4.0 – 5.5) oligotrophic shallow ranker soils over
bedrock in areas with 800 to 1,600mm annual rainfall. Whilst the sub-community variants of the
coastal CG1 vegetation type may be a result of geographic isolation, those of the more
ubiquitous upland U4 type reflect gradients in winter and summer temperature extremes, rainfall,
and nutrient levels with transition types of a mesotrophic Lolium perenne – Cynosurus cristatus
grassland character on more typical brown soils (NVC MG6b, Rodwell, 1992). Given that they
are reflecting both the aerial and the soil abiotic environments, and integrating climate-soil
interactions, it is possible to predict the type and range represented by the vegetation community
types. Hence, in characterising the vegetation community type, the CARGIE Model can be used
with confidence in the integration of biotic and abiotic elements.
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Equally Applicable to Vegetation Development, Succession and Natural Colonisation?
Because the JNCC derived, CARGIE Model is based on vegetation life cycles, it caters to
community development from juvenile seedling stages through to mature and over-mature
senescent stages, and the mixture of age classes to be expected in a restored ecosystem for a
given set of land use and management circumstances. Examples of these are set out in Tables 1,
2 and 3. Where the CARGIE criteria have been reached, this will be the point that restoration of
a particular ecosystem has been achieved because of vegetation and community development.
It might also be asked what is the Model’s use in the assessment of the success of natural
colonisation and succession in restoration schemes? Whilst the definition of success here is
dependent on the objectives and desired outcomes of a restoration scheme, in the UK context it is
possible to define and compare with the target NVC vegetation communities for a given location,
site, soil, and other circumstances. In doing so, a set of CARGIE criteria can be assembled
against which an assessment can be made.
Where vegetation development and further
immigration leads to succession, these can be defined again in NVC terms and allocated
CARGIE criteria for assessment of success. In these circumstances, a sequence of CARGIE
criteria would be expected.
Where natural colonisation is being relied upon, as for vegetation development and
succession, NVC types and CARGIE criteria can be set for appropriate outcomes. Success will
largely be a function of their abundance, mobility, and their local presence. Whilst mobile
species such as birds and flying invertebrates rapidly recolonize restored land (where there is
suitable habitat), other species like some woodland plant species (which spread vegetatively) and
some soil invertebrates typically spread very slowly, and may not recolonize areas for a very
long period of time, if at all. This may have consequences where there are Indicators of Local
Distributions for the achievement in all the CARGIE criteria.
Adaptive to Climate Change?
The UK NVC spans a range of climatic conditions and the interactions with soils and other
factors. Consequently, it is possible to redefine the likely vegetation communities and their subcommunity types according to climate. In the CARGIE Model, the most likely changes over
time are with the Canopy criteria (community characteristic main tree species), the Regeneration
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Journal American Society of Mining and Reclamation, 2013 Volume 2, Issue 2
Potential (increase or decrease in fecundity), Indicators of Local Distribution, and Exotic/Alien
and Weed Species.
For example, with warmer and drier conditions at the lower margins of the Quercus petrea –
Betula pubescens - Dicranium majus Oak Woodland (NVC W17, Rodwell, 1991a) a transition
to the Quercus – Betula – Deschampsia flexuoas Oak Woodland (NVC W16) would be
predicted. Probably little change in the Canopy, Age Class, Regeneration Potential, Genetic
Pool and Exotics, and Aliens might be expected in this case. However, the Indicators of Local
Distribution are likely to change with the invasion of Bracken and Bramble (Rubus fruticosa
agg.) with the woodland assuming more of a NVC 16 character. This example is of a relatively
insensitive kind, in contrast, the NVC CG1 grassland referred to above is on the other hand very
sensitive to rainfall levels. As a possible outcome of future climate change in the UK,
an
increase in annual rainfall may lead to the invasion of more competitive species in this short and
well drained open-turf community. This is likely to drive a change to the scrub community of
Crataegus monogyna – Hedra helix – sub-community Brachypodium sylvaticum scrub (NVC
W21c (Rodwell, 1991a)), comprising Wild Privet (Ligustrum vulgare), Bramble, Ivy (Hedra
helix) the tussocky grass False Brome (Brachypodium sylvaticum).
Hence, a JNCC based
CARGIE Model can be prepared for both the current and the future predicted vegetation
communities for design and assessment purposes.
Projected Time Scales for Ecosystem Restoration
The CARGIE Model can be used to explore and assess the projected time scales for the
restoration of ecosystem structural and function.
Taking woodland as an example, typically woodland reclamation starts with the planting of
nursery grown trees and shrubs which in time grow and mature to saplings, mature, and seed
bearing trees; then progress to decaying trees; and eventually become dead wood with each stage
providing their functional entities. Whilst the development of the trees and shrubs in themselves
provides for increase in structural complexity and graduation to a fully functioning ecosystem, it
is the coincidence of several of the structural forms over time that together provide the increasing
functional complexity associated with fully restored ecosystems (as illustrated by the notation in
Table 4). What is clear is the attainment of at least three requisite structural elements will only
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Journal American Society of Mining and Reclamation, 2013 Volume 2, Issue 2
occur sometime the first complete life cycle of the planted tree layer is completed or near to
completion.
Table 4: Sequential development of ecosystem structural elements in a traditionally planted
restoration scheme
Tree Layer
Development /
Life Cycle
Traditional Restoration Scheme
Planted Stock
Woodland
Ecosystem
Target
Subsequent Woodland Stand
Development from Planted Stock
S
SZMDF
Z
SZMDF
M
S
SZMDF
D
Z
SZMDF
F
M
S
SZMDF
Key : S - seed / seedlings / nursery stock; Z – sapling; M - mature /seed bearing; D - decaying;
and F - dead fallen trees
1
2
3
4
5
As might be expected (in the context of the life cycle dynamics of the biotic components of
ecosystems), time is an important variable and probably the ultimate determinant of when
ecosystems are actually restored. It is inherently longer in woodland systems where just nursery
stock is provided (Table 5). This is inherently longer in woodland systems compared to dwarf
shrub and grassland ecosystems where life cycles are shorter (Table 5).
Table 5 demonstrates clearly the difference in timescales that the attainment of the required
ecosystem structural elements might be achieved (i.e., all the life cycle stages at the same time).
In the case of grassland communities this might be achieved relatively quickly and within 15
years (where longer lived semi-woody components are present such as the rhizomatous
Potentilla erecta in the upland Festuca ovina – Agrostis capillaris – Galium saxatile acid
grasslands (NVC U4, Rodwell, 1992)) or sooner where woody herbaceous plant species are
absent.
For the dwarf shrub communities the period is longer still and in the order of 30-50
years.
In contrast, the Birch and Oak components of woodland may be as much as 150-200 and
250-350 years respectively, with Birch dominated woodland potentially completing two
complete life cycles within the first for Oak dominated woodland.
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Table 5: Comparative schematic temporal development of structural elements in woodland,
dwarf shrub and grassland ecosystems (bold symbols indicate when all age classes are
present)
Tree Layer
Development /
Life Cycle
Traditional Restoration Scheme
YEARS
Birch Woodland
Oak Woodland
0-5
5-10
10-15
15-20
20-30
30-50
50-70
70-80
80-100
100-120
120-150
150-200
200-250
250-350
S
Z
Z
M
BS
BS
DZ
FDM
FBS
BSZ
DMZ
FDBZBS
FDBZBS
FDBZBS
S
S
Z
Z
Z
M
BS
BSZ
BSZ
BSZM
MZBS
DZMBS
DZMBS
FDMBSZ
Key :
S - seed / seedlings / nursery stock
Z - sapling
M - mature
B - seed bearing
D - decaying
F - dead fallen trees
Dwarf shrub
(Heather)
heathland
S
ZBS
Z BS
MBSD
DBSM
FDBSM
Key :
S - pioneer
Z - building
M - mature
B - seed bearing
D - degenerate
F - dead
Upland
Grassland
SZMB
SZMBD
SZMBDF
Key :
S - seed/ seedlings
Z - tillering etc
M - mature &
B - seed bearing)
D - degenerate
F - dead
Applied at What Scale ?
The JNCC Common Standards for Monitoring (JNCC, 1998) is designed to be applied at the
vegetation community scale within typical landscape settings of, for example, wooded valleys,
and heather moorlands. Minimum qualifying areas for small isolated parcels of land are set out
for descriptive and monitoring purposes; generic vegetation types and sample sizes are
prescribed and can be applied to mine restoration schemes.
Where CARGIE criteria are
quantified, these units are to be applied on a pro rata basis.
Implications for Restoration Practices
An outcome of the CARGIE Model is an understanding of the importance of life cycle
completion and renewal, and its key role in determining ecosystem restoration of the natural
vegetation communities. Hence, it would be expected to find a mixture of appropriate age
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Journal American Society of Mining and Reclamation, 2013 Volume 2, Issue 2
classes in restored communities if they and the ecosystem were to be judged self-sustaining and
the scheme a success. Restoration schemes are typically simplistic in that the component species
are planted or sown at prescribed densities and then left to mature or are managed in some
manner with the result it can be decades or centuries before the semblance of mixed aged
communities are established. The implications are that certain parts of the ecosystem structure
and function may not be re-established in some types of vegetation community for a very long
period of time and long after any prescribed aftercare period when further inputs and
management are unlikely. Given this, it is important for practitioners to be aware and take
whatever actions they can to provide for the age class related structural elements. In the case of
woodlands the key elements being new cohorts of recruits and dead wood.
Whilst there is an opportunity to prime the new woodlands by introducing dead wood and
‘short-circuit’ this time limiting process for ecosystem restoration by thinning programs at the
sapling and early mature stage and leaving the cut-wood (rather than its removal as in
commercial woodlands), this option is likely to be much less beneficial (as it relies on
colonisation by dead wood saproxylic species from outside) than the introduction of dead wood
from mature woodland with its in situ dead wood species (Stokland, 2012; Jonsson and Stokland,
2012a and 2012b).
Where woodland has been cleared as part of the mine development, there is an opportunity to
introduce mature and over-mature felled timber as complete trees, root-plates, and branches with
their associated animal and microbe communities into the planting scheme thereby shortcircuiting the long process of dead wood production. This requires a change in general practice
where often woodland is being cleared to make way for mining. Here, the dead wood and litter
layers should be considered as valuable restoration resources and where possible retained and
reintroduced as good practice.
Concluding Comments
The original notion behind this paper was that some dimension (yet to be defined) was
probably the key to practical ecosystem reclamation on mine sites. What has come out of the
debate, firstly, and not unsurprisingly, time (because of the life cycle dynamics of the biotic
components of ecosystems) is probably the key dimensional scale and the ultimate determinant
of the achievement of ecosystem reclamation, and challenges our own perceptions of restoration
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Journal American Society of Mining and Reclamation, 2013 Volume 2, Issue 2
achievement and restorability. Secondly, vegetation communities are a practical and justifiable
scale to consider ecosystem restoration for mine sites. To this end, the CARGIE Model could
enable better design and evaluation of restored ecosystems and their services, before and after
surface mining, and enable the mining industry in the UK to meet the challenges posed by CBD
and the new and emerging legislation and policies.
At the outset, the aim of this paper was simply explorative. The CARGIE methodology
suggested is just an idea and is open to further examination and development if it is deemed to
have merit.
If not, maybe an outcome of this paper is that stimulates others to suggest
alternatives.
If the CARGIE Model is to have a wide application and to be generally useful, the next steps
could be to determine:
1 If the qualifying criteria can be identified and applied to other Biomes.
2
If it is justifiable to assume the soil ecosystems are integrated within the model, and if
not what above- or belowground-based criteria should be added to the CARGIE model.
3 The outcomes of applying the Model to restored mine sites.
In these and any other respect, the author welcomes comments, other’s experiences, and the
exchange of ideas.
Acknowledgements
I would like to thank the anonymous Reviewers and Carl Zipper (Virginia Tech, Blacksburg)
for their helpful comments on the original manuscript.
References
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