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Biological Recultivation Of
"industrial Deserts" Or "lunar Scapes"
By:
M.N.V. Prasad*
"Industrial deserts" or "Lunar scapes"
are large territories over-loaded with technogenic waste. Soil
washing and cleaning in such situation is cost prohibitive.
Therefore, one of the emerging approaches is "biological recultivation". It has been satisfactorily implemented in USA and
Russia by seeding of perennial grasses, tree and bushy species.
The environmental problems associated
with mining and
industrialization are the cause for concern in India.
Recently, the environment minister of India announced that
the MOEF has planned to add five million hectares of forest cover
and improve its quality in another five million hectares in the next
ten years. All this is possible when we have robust lab-cum-field
research program in biological recultivation.
Despite the wide ranging constraints
at hazardous waste dump sites and substrates, there have been some
important success stories in the direct restoration yielding
significant biodiversity benefits. The principal restoration
options, on a site-specific basis, are the ameliorative approach
(improving the physical and chemical nature of the site) and the
adaptive approach which seeks to achieve the ecological restoration
goal of establishing ecosystem structure and function and thus
biodiversity. Ecological restoration without ameliorative and
adaptive approaches usually depend on:
-
careful selection of suitable
substrates for plant growth
-
species with good
adaptability and suitability for ground stabilization
-
the value of the species as
wildlife habitat (and as forage for domestic animals),
-
aesthetic value.
Indigenous species available as
propagules do not always satisfy the above criteria, in which case
native, but not locally indigenous, species can be sown as a
supplement, usually in a way that provides a rapid solution to
short-term problems such as erosion, but one which enables
colonization by local volunteer species and thus facilitates
succession to eventually restore the native ecosystem and
biodiversity
The use of metal tolerant plants, in
particular of the temperate grasses Agrostis capillaris and
Festuca rubra, is a proven reclamation technology of 20 years
for a variety of mine tailings and metal contaminated soils
More recently, a technology has been
promoted whereby the tolerance to metals of some plants is used in a
different way. Some species are described as "hyper accumulators" in
recognition of their ability to accumulate elements that are usually
present in trace concentrations in plants. For highly toxic metal
mine wastes, it has been suggested that such species could be
manipulated to clean-up or 'bioremediate' soils and at the same
time stabilize and reclaim land for other purposes. Long term
trials are also underway in the U.S.A. and Chile.
Revegetation is the basis for most
contaminated land reclamation programs. The revegetated contaminated
area must meet two basic objectives; (i) forage and habitat for
livestock and wildlife suitable for the approved post mining land
use must be provided, and (ii) erosion from the mined lands must be
controlled to the same extent that erosion is controlled on
undisturbed native lands. Vegetation grown on the mined area is the
forage for animals, a basic part of the habitat for animals, and the
principal means of controlling erosion from mined lands.
There is not a single "best" method in
all circumstances for any of the reclamation operations. The
procedures and techniques described in this article have proved
successful in at least one and possibly more situations.
1. Revegetating contaminated site
The objective of a revegetation
program is to establish desirable vegetation. The procedures
described for establishing vegetation include the aspects such as,
seed-bed preparation, farming practices, seed handling, planting,
mulching, shrub establishment and reforestation. Revegetation
involves the following points/exercises.
a)
Preparing a revegetation
package
b)
Cultivation practices
c)
Drill seeding practices
d)
Hydro seeding practices
e)
Mulching practices
f)
Seed handling
g)
Planting methods for permanent
reclamation
h)
Broadcast seeding
i)
Transplanting live plants and
planting plant parts.
j)
Seeding shrub seed
2. Seed technology
Seed quality is vitally
important. The quality of the seed many a time determines the
success or failure of a revegetation effort. This includes the
following points/aspects.
a)
Seed procurement
b)
Preparing a seed bed and
seedlings
c)
Procuring seeds/propagules of
seasonal grasses
d)
Sowing the seeds of good
shrubs, under trees and trees
3. Surface Stabilization
It is an important facet of
restoration ecology. If the reclaimed land surface is stable, then
soil erosion from that land is controlled to the extent possible.
Vegetative and non-vegetative methods for stabilizing the land
surface or controlling erosion are practiced in different sites.
4. Husbandry (management)
After the vegetation is
established, the husbandry (management) of the vegetation becomes
critical for its survival and longevity. The revegetation will
degenerate to less than desirable cover and production and to a less
desired species composition without some type of management to
sustain it. Native plant species evolved under same type of foraging
pressure should be included in the revegetation programs. Therefore,
some type of management that at least simulates "use" is vital for
the maintenance of the revegetated stand. The husbandry practices
should include mowing for weed control, regulated grazing, and
burning.
5. Monitoring
It is important to know
how the vegetation is progressing toward the desired stage. The
monitoring should focus on status of weed infestation, invasion by
alien plants, protection afforded to native species, record keeping
and document management.
Sodding
It is a bioengineering technique that
uses vegetation mats for soil stabilization and erosion control.
Plant salvage and transplant techniques with perennial grasses have
been used with success. Perennial grasses with sturdy adventitious
root mat anchoring them in place are preferred. The following is a
list of recommendations for using vegetation mats as bioengineering
materials:
-
To anchor perennial solid/soil
binding grass mats to a slope, mats can be cut to form any shape
desired. A shallow, narrow trench built along the contour of a slope
and planted with a vegetation mat may become an effective terrace.
-
The mat should remain attached
to stable vegetation and thus be held in place from the top. The mat
can be pegged to prevent ripping and sliding. This technique would
be used to stabilize the contaminated soil.
-
Vegetation mats can be used as
building bricks. Slice the mats into rectangular pieces and use them
to construct a very steep, living wall. The bricks can be pegged to
each other and to the underlying substrate. This technique may be
useful around culverts or sunken walkways and controls erosion.
Following three basic techniques are
being used in different parts of the world:
a) Land filling: Putting the
top fertile soil on the surface of the hazardous waste. An ash dump
site is overlaid in strips (strip sodding) each 3 to 6 m wide. Such
strips are sown with perennial grasses or planted with shrubs and
trees in a parsimonious technique
b) Ferlilizer application:
Mineral fertilizers (NPK) are necessary in certain instances.
Application of phosphate fertilizer at a dose of 30 kg per hectare
and nitrogen fertilizer @ 30 kg per hectare is a normal sodding
practice in different parts of world.
c) Irrigation: Watering of the
surface disposal areas with domestic effluents. This is done through
the growing season. High productivity perennial grasses, trees and
bushy shrubs are planted in strips or in clumps or patches which is
important for erosion control.
Examples of Plants that have
successfully revegetated the land of mine spoils in different parts
of India are mentioned below.
Bauxite mined area of Madhya Pradesh:
Grevillea pteridifolia. Eucalyptus camaldulensis, Shorea robusta.
Coal mine spoils of Madhya Pradesh:
Eucalyptus hybrid, Eucalyptus camaldulensis, Acacia
auriculiformis, Acacia nilotica, Dalbergia sissoo, Pongamia pinnata
Lime stone mine spoils of outer
Himalayas: Salix tetrasperma, Leucaena leucocephala, Bauhinia
retusa, Acacia catechu, Ipomea carnea, Eulaliopsis binata,
Chrysopogon fulvus, Arundo donax, Agave americana, Pennisetum
purpureum, Erythrina subersosa
Rock-phosphate mine spoils of Musoorie:
Pennisetum purpureum, Saccharum spontaneum, Vitex negundo, Rumex
hastatus. Mimosa himalayana, Buddlea asiatica, Dalbergia sissoo,
Acacia catechu, Leucaena leucocephala and Salix tetrasperma,
etc.
Lignite mine spoils of Tamil Nadu:
Eucalyptus species, Leucaena leucocephala, Acacia and Agave
Mica, copper, tungeston, marble,
dolmite, limestone, and mine spoils of
Rajasthan:
Acacia
tortilis. Prosopis juliflora, Acacia Senegal,
Salvadora oleodes, Tamarix articulata. Zizyphus
nummularia, Grewia tenax, Cenchrus setigerus. Cymbopogon, Cynodon
dactylon. Sporobollis marginatus and
Dichanthium annulatum
Iron ore wastes of Orissa: Leucaena
leucocephala
Haematite, magnetite,
manganese spoil from Karnataka: Albizia lebeck
*Department of
Plant Sciences, University of
Hyderabad,
Hyderabad 500
046 (A.P.) India;
E-Mail -
[email protected]; [email protected] | 
