Keywords

1 Introduction

Deforestation, mining, land use change, rapid industrialization, overgrazing, non-sustainable extraction of forest produce for fodder and fuel wood and simultaneous loss of biodiversity due to direct or indirect factors lead to degradation of environment and ecosystems (Daily 1995). These activities bring major environmental challenges which mankind is facing at the moment. Situation is bound to worsen going with current rate of blind, ecologically disturbing, anthropogenic activities in the name of development. India is among the major mining hubs in the world. Mining is one of the biggest cause for large-scale deterioration (that too, in a very short span) of forest ecosystems, wild life and also of the healthy soil layers which harbour life sustaining properties (Walker and Willig 1999). Large areas get deforested, denuded, and the soil is lost or polluted with mined-out ore waste. Such environmentally poor, degraded, mined-out areas subsequently become derelict and are of little benefit for local inhabitants. Apart from ecosystem imbalance, and loss of biodiversity, open cast mining activities also harm a country’s natural beauty (Ehrlich 1993). Such area when seen in a satellite imagery or using applications such as Google Earth appears as a blot on the country’s geographical and vegetational continuity. After the commercial extraction or land use change, these areas are left on the mercy of nature resulting in weed infested areas which further degrade the surrounding habitats being invasive, only increasing the total area under degradation. Consequently, there is loss of native biodiversity, ecological services, affecting the locals, aboriginals, and tribals who are compelled to mass migrate to urban areas in search of livelihood, thus extinguishing hopes of preservation and maintenance of cultural diversity, language diversity. To avert such changes , Ecological Restoration is the only feasible human induced effort which can be taken up to treat the degraded site to prevent it from getting infested with weeds and also to undo the damages caused to certain extents (Holl et al. 2003; Doren et al. 2009; Feng et al. 2013). This chapter provides a succinct introduction on the basics of Ecological Restoration as a concept and as a technological tool with which it can be practised on degraded environments to manage them effectively and minimize the long- and short-term damages by restoring the area.

2 Ecological Restoration

Though there are many definitions of ecological restoration, the most relevant one was defined by Society for Ecological Restoration (SER ) in 2004 . According to SER (2004), ecological restoration is defined as “an intentional activity that initiates or accelerates the recovery of an ecosystem with respect to its health, integrity and sustainability and attempts to accelerate the natural recovery process artificially to achieve the otherwise long term goals in a short time” (SER 2004). It is an intentional activity to recover the ecosystem towards its original structure and function (SER 2004; Rajdeep et al. 2011). Eco-restoration also aims to increase soil fertility in terms of nutrients as well as richness in soil biota, and increased biotic control over biogeochemical fluxes faster than time period required for natural recovery (Parrotta 1992). Eco-restoration of mined-out areas and wastelands thus aims to return the degraded ecosystem to its natural, pre-mining state, thereby bringing stability and sustainability in associated human activity. Restoration Ecology provides clear concepts, models, tools, and methodologies to practice ecological restoration of degraded ecosystems.

2.1 Need to Ecologically Restore Sites

Most encroachments in natural forest areas and natural ecosystems are for some special yet peculiar land use such as denudation for industrialization, mining, extraction of oil, or other natural resources, etc. All these extractions/developmental activities are based on resources which are finite and so is the land use, i.e., the so-called developmental activity is one day going to shut down, but by that time the damage will be almost irreparable and irreversible, if left as it is. Therefore, it becomes imperative to undertake “social, environmental and legal” steps to ensure proper reclamation once the desired extraction is over. In India, such steps have been initiated. Restoration of wastelands, or degraded lands has become a national prerogative and part of Corporate Social Responsibility (CSR ) to institute a dedicated department on Environmental Impact Assessment and mitigation cum protection from the possible damages as well as post-use reclamation/restoration. However, proper restoration tools and techniques have not yet been normalized. To meet the major goals of sustainable development, restoration is crucial as it is the restored land that remains available indefinitely for future generations. Ecological restoration of environmentally degraded areas is the only successful long-term approach to promote both sustainability and the maintenance of ecosystem biodiversity. The environmental problems arising out of large-scale developmental activities such as Open Cast Mining, Residential and Corporate Construction, Cement factories, etc., involve all three major types of pollution, i.e., air, water and soil pollution. For instance, suspended particulate matters (SPM ) and gases released in these areas bring about air pollution (Gautam et al. 2012). Similarly, discharge of fine dust, organic compounds, oil and grease (and in some cases acidic water and chemicals) as well as exposure of the parent rock material to the surface water bodies makes it contaminated with toxic and heavy metals compounds causing pollution (Barbour 1994; Mishra et al. 2004). Soil gets polluted due to increasing concentration of parental rock in soil and also due to mixing of unused form of ore (fine dust or fine ore which is commercially not viable for meeting extraction cost) with the top layers, and forming overburdened dumps over top soil due to open cast mining activities with high concentrations of heavy metals and toxic elements coming on the surface. Open cast mining or quarrying activities cause change in the general topography of the terrain due to formation of overburdened dumps, depletion of top soil, destruction of woody vegetation inducing a high risk of erosion, drainage, and increasing failure of rehabilitation attempts (Gams et al. 1993; Sort and Alcañiz 1996).

2.2 Factors Influencing Ecological Restoration of Degraded Mined-Out Areas

Different sites and their site factors such as Climatic, Edaphic, Topographic and Biotic influence the vegetation at ecological and physiological levels. Climatic factors mainly include Light, Temperature, Precipitation, Wind, and atmospheric injuries. Soil physicochemical properties such as soil texture, structure, profile, soil depth, stoniness, pH, organic matter content, organic carbon, electrical conductivity, bioavailable cations, anions, etc., comprise the edaphic factors. Configuration of the physical relief, altitude, slope, aspect etc., determine the topographic factors while all the interactions between Plant-Plant, Plant-Animals, Plant-Microbes, Plant-Man and his animals constitute the Biotic factors within a site. The interactions are such that these factors affect the composition and distribution of the above and below ground biotic communities and in turn the above and below ground communities bring about a change in these factors. The influence of the factors is so supreme that the entire choice of species, methods of planting and the order in which different groups of plants are going to be planted is dependent on the site factors only.

To make any ecological restoration programme a successful one, whether it is a long term or a short term one, needs to be critically evaluated from the very beginning. Every site is different and so is the nature of techniques applied in the area for restoring it. The success mainly depends on scientific evaluation of the site factors entailing Climatic, Topographic, Edaphic and Biotic Factors and subsequent careful selection of plant species to be introduced in the site (Hassan et al. 2007). Some features considered for choosing a species for introduction to a site selected for restoration are: (1) species should be native to the area, (2) it should be of some socio-economic importance, viz. a multipurpose tree (MPTs e.g. Leucaena leucocephala) or nitrogen fixing tree (NFTs e.g. Casuarina sp.,), (3) better adapted to poor soils (ability to survive under stress conditions), and (4) the debris or leaf litter should be biodegradable (for increasing soil organic matter (SOM ) content and to positively influence soil microbial biomass). Floral records from previous surveys for the vegetation type and structure, if available, provide valuable information for planning a restoration strategy as they undoubtedly indicate the pre-mining climax or seral communities (Chari et al. 1989). Native species and early colonizers (such as nitrogen fixing legumes) known to improve soil health and nutrient status have been used as part of various eco-restoration and rehabilitation programmes for degraded environments in the past. Such approaches constitute good initiation points for restoring degraded mined-out sites (Babu et al. 1985a, b; Nair et al. 1988; Babu et al. 1993).

The species composition, distribution, community structure, species richness, rate of growth of above- and below-ground biota at a site undergoing eco-restoration respond to changes in environmental variables. Changes in climate and season affecting conditions of light, temperature, precipitation, relative humidity, etc., are obviously important even at an un-restored setting. Shifts in edaphic factors like soil structure, soil moisture, pH, soil organic matter (SOM ), cation exchange capacity (CEC ), electrical conductivity (EC), levels of bio-available cations and anions, trace elements, heavy metals, are associated with growth of plants and rhizospheric biota. All or some of these factors are essential for monitoring eco-restoration efforts (Schoenholtz et al. 2000; Fierer and Jackson 2006; Andrew et al. 2012).

Among the many site factors, two factors are considered extremely important for the colonization and establishment of the biotic community. These are Soil pH and Soil Organic Matter (SOM). Soil pH determines acidity or basicity of the soil environment. Most plant species have a requirement of an optimum pH range for growth. For instance, tree species Xylia xylocarpa, Shorea robusta (pH 4.5–5.5) and Tectona grandis (6.5–7.6) prefer to grow in acidic soils, while Acacia arabica, Azadirachta indica and Terminalia arjuna, Acacia catechu, Acacia nilotica, Adina cordifolia, Anogeissus latifolia, Dalbergia sissoo and Bauhinia variegata prefer to grow in basic soils and can be found commonly growing in calcareous soils in natural as well as in ecologically restored areas (Soni et al. 1994; Singh et al. 2002; Verma 2003; Rajdeep et al. 2011). Soil pH determines the degree of maturity of soil, the successional stages and distribution of plant communities (Gianello et al. 1995; Favreto and Medeiros 2006; Meurer 2007; Sanchez-Azofeifa et al. 2014). In moist localities acidic pH is an indicator of soil maturity and climax vegetation, while basic pH indicates immaturity. Soil organic matter (SOM ) is another very important and rather decisive factor for success of eco-restoration. Decomposition of leaf litter, dead decaying organisms, animal refuse, plant parts constitutes the organic matter content which increases the nutrient load and moisture holding capacity as well increases the cation exchange capacity, further enhancing the selective uptake of the cations in the plant systems. SOM releases nutrients to the soil environment, making it a useful resource for plant roots and soil microbes. SOM is important for bacterial and fungal decomposers, as well as for soil fauna that influences nutrient cycling and plant growth (Wardle 2002; Moore et al. 2004; Bardgett and Wardle 2010).

2.3 Indicators of Successful Ecological Restoration Effort

To monitor an ecological restoration programme for its progress, there are many ways with which one can establish the success of the human-induced restoration efforts. The methods of monitoring may consist of floristic composition analyses, species composition surveys, community structure changes over time (temporal) and space (spatial), species richness, rate of growth of above- and below-ground biota, change in above-ground plant biomass using various indices such as NDVI (Normalized Vegetation Differential Index) depicted by Remote Sensing technologies using Geographical Information System (GIS ) and also changes in environmental variables such as soil physicochemical properties and microclimatic profile such as soil and air temperature, relative humidity, spore concentration and the kind of bacteria and fungi above and below ground. A combination of the previously mentioned variables needs to be monitored in parallel over seasons and years to conclude success or failure of the effort. Apart from these indicators, reference sites should also be kept such as a native forest ecosystem or a degraded unrestored site to establish effects of human induced restoration to be real and not just a natural process, as one might argue.

2.4 Selection of Species to Be Introduced as Part of Restoration

There are no set rules of choice of tree or ground cover species (forbs, as some may refer to) to be planted/regenerated to restore sites. The site itself or the nearby semi-disturbed, native sites/habitats are the best guide as to what needs to be planted and in what proportion of distribution. However, some leads are taken from the general site profile using the microclimatic, water and soil profile of an area to sort out what kind of species and in what order should be planted to have a successful restoration. This part is decisive for any restoration effort and so needs to be validated by experts. An account of how a very basic site factor such as soil pH affects choice of the species is mentioned previously.

Similarly, there are evidences that soil microbial parameters may be useful as early and sensitive indicators for stressed soil and its alleviation. Composition of soil biota has been seen as a biological indicator of soil health. The treatment or management of soil with application of arbuscular mycorrhizal fungi (AMF ), free living, associative and symbiotic nitrogen fixers and other plant growth promoting bacteria (PGPRs ), Chitin amendments, green manure or agricultural waste, application of pesticides and the introduction of transgenic crops have been shown to affect rhizospheric soil microbial community structures. Soil type and cropping practices also influence the microbial community composition thus leading to sooner establishment of plant communities in a site undergoing eco-restoration.

3 The Ecological Restoration Work Done in India and the Techniques of Restoration Applied

There are some success stories of ecological restoration work done in India. A number of environmentally degraded sites were not only ecologically restored, but were also declared self-sustainable, having a number of ecological services at their disposal making the locals engage in their traditional occupational activities thus preventing their migration and protecting the cultural diversity of the tribal folk. Some of the recently successful ecological restoration works in India are Ecological Restoration of Chilika Lake (Odisha), Limestone quarries of Musoorie Hills (Uttarakhand), conversion of Asola Bhati mines area into Asola Bird Sanctuary on Delhi-Haryana border, Aravalli Biodiversity Park on the Prosopis infested Aravalli ranges bordering Delhi, and the restoration and creation of Yamuna Biodiversity Park on the Old Yamuna basin in Delhi (Burari, Delhi region). A brief description of the site, nature of restoration and techniques applied in some of the selected case studies is given here.

3.1 Chilika Lake, Odisha

Chilika lake is a brackish water lagoon with coordinates 19°43′N 85°19′E. This lake is on the eastern coast of India in the state of Odisha. It was declared India’s first Ramsar Site on 1st October 1981 and a wetland of international importance. This lake is considered India’s largest brackish water lagoon (1185 km2) and World’s second largest lagoon. The lake enjoys an estuarine ecosystem with tidal inundations and river opening into the lake. It has its importance in terms of ecological, economic and socio-cultural features. However, over time, with non-regulated use of the lake resources, illegal shrimp culture and due to anthropogenic alterations in the lake hydrology, the ecological services of the lake were severely affected and consequently the lake was added to the Montreux Record, the threatened list of Ramsar sites in 1993, merely 13 years after it was declared a wetland of international importance. Briefly, to ecologically restore the status of the lake, Chilika Development Authority (CDA) followed Ramsar guidelines and carried out establishment of a water inlet thereby having hydrological intervention administered to the lake. Finally, in 2000 the lake was re-monitored for its ecological services and was declared restored with its name removed from the Montreux Record. This was the first lake in Asia, to have its status retracted from threatened Ramsar site to a standard Ramsar site.

3.2 The Asola-Bhatti Wildlife Sanctuary

The Asola-Bhatti Wildlife Sanctuary (declared as wildlife sanctuary in 1991) is located between 28° 24.2′ N and 77° 13.6′ E, encompasses an area of 4000 acres in the south-eastern part of the Southern ridge near Tughlaqabad in Delhi. The Delhi Ridge represents the spur of Aravalli mountain range covering an area of 7000 acres and has performed several ecological functions in the past such as ground water recharge; an area for grazing activities, Acacia woodland and 3–5 storeyed tropical dry deciduous forests; provide fodder and firewood for the local communities; regulated local weather patterns and served as CO2 sink.

Prior to ecological restoration, the Bhatti Mines areas was known for its open cast morrum mines having quartzite soil with hard red crust due to oxidation of iron which has poor moisture retention capacity and little organic matter. The landscape of the area ranges from gentle undulating terrains with deep gorges and gullies, steep cut slopes to overburden dumps. The entire area was dominated by Prosopis juliflora – an exotic invasive species with scattered xerophytic vegetation, weedy species and lacked characteristic (native) Aravalli vegetation type. The environmentally challenged site was taken up to restore degraded lands to their pristine ecosystems and make it sustainable over the years. The exemplary work of ecologically restoring the site was done under the aegis of Prof. C.R. Babu and his team at Center for Environmental Management of Degraded Ecosystems, University of Delhi.

The main restoration techniques applied in this area were:

  • Removal of weeds and other invasive species (woody and non-woody).

  • Addition of farmyard manure (FYM) to the top layers of soil.

  • Steep slopes were stabilized by planting grasses and legumes, as mentioned below. Approximately nine perennial grass species namely, Cenchrus ciliaris, C. setigerus, Eremopogon sp., Eragrostis tenella, Dactyloctenium aegyptium, Chyrsopogon fulvus, Dichanthium annulatum, Sporobolus diander, Aristida sp., nine tree legumes namely Acacia senegal, A. leucopholea, A. nilotica, A. catechu, Albizzia lebbeck, Butea monosperma, Cassia siamea, Cassia fistula, Dalbergia sissoo, three shrubby legumes (Indigofera tinctoria, Tephrosia purpurea, Dichrostachys cineraria), two herbaceous legumes (Trigonella spp., Melilotus spp.) and eight non-leguminous woody species (Wrightia tinctoria, Grewia tenax, Ficus spp., Syzigium cumini, Balanites roxburghii, Maytenus, Fluggia, Holoptelia integrifolia) were selected for processing the habitat leading to the development of ecosystem.

  • AMF (arbuscular mycorrhizal fungi) and a number of plant growth-promoting bacteria isolated from the rhizospheric soils of grasses and legumes were also used as inoculants in the top soil for enhancing mineralization, decomposition and other useful soil processes.

3.3 Yamuna Biodiversity Park and Aravalli Biodiversity Park

Under the aegis of Professor C.R. Babu and his team at CEMDE, Delhi University, working on similar lines mentioned as above, two environmentally challenged sites in Delhi were taken up and ecologically restored. One was near Old Yamuna River Basin along the Burari region of North Delhi and one was near Vasant Kunj Area. The first area has been developed into Yamuna Biodiversity Park (https://dda.org.in/greens/biodiv/yamuna-biodiversity-park.html) and the second one is now developed into Aravalli Biodiversity Park (https://dda.org.in/greens/biodiv/aravalli-biodiversity-park.html). Post restoration these sites are now harbouring a number of forest communities such as (Source: Delhi Development Authority Database available at www.dda.org.in)1. Subtropical mixed evergreen forest ecosystem Top canopy - Toona ciliata, Dalbergia latifolia, Mitragyna parvifolia, Syzygium cumini Middle storey - Trewia nudiflora, Artocarpus lakoocha, Cinnamomum camphora Shrub layer- Dillenia indica, Coffea benghalensis, Murraya paniculata, Bauhinia malabarica Herbs and Grasses- Barleria cristata, Flemingia bracteata, Desmodium triflorum Climbers- Vigna capensis, Combretum decandrum, Vitis paniculatum 2. Moist tropical deciduous forest ecosystem with Teak as a dominant species Top Canopy- Tectona grandis, Pterocarpus marsupium, Diospyros melanoxylon Middle storey- Buchanania lanzan, Albizia lebbeck, Bauhinia variegata Shrub layer- Flemingia rugosus, Vitex negundo, Nyctanthus arbortristris, Zizyphus mauritiana Herbs and grasses- Desmodium triflorum, Crotolaria juncea, Bothriochloa pertusa Climbers- Pueraria phaseoloides, Asparagus racemosus 3. Tropical dry decuduous forest ecosystem with Sal as a dominant species Top canopy – Shorea robusta, Diospros melanoxylon, Putranjiva roxburghii Middle storey – Erythrina indica, Cassia fistula, Albizia sp., Sterculia urens Shrub layer – Carissa spinarum, Zizyphus oenoplea, Nyctanthus arbortristris Herbs & Grasses – Chloris, Eragrostis, Fimbristylis ferruginea, Indigofera tinctoria Climbers – Smilax zeylanica, , Clittoria turnatea, Marsidenia, Cocculus hirsutus 4. Tropical Dry Deciduous forest with Teak as a dominant species Top Canopy – Tectona grandis, Butea monosperma, Sterculia urens, Terminalia chebula Middle storey – Emblica officinalis, Bauhina variegata, Cochlospermum religiosum Shrub layer – Gardenia turgida, Randia dumetorum, Grewia asiatica Herbs & Grasses – Barleria prionitis, Bothriochloa pertusa, Dicanthium Hetropogo Climbers – Abrus pulchellus, Cocculus hirsutus 5. Tropical thorn forest Top Canopy- Acacia sp., Prosopis cineraria, Anogeissus pendula Underwoods- Zizyphus mauritiana, Maytenus emarginatus, Wrightia Herbs and Grasses- Vicovestata, Vico auriculata, Desmostachya bipinnata, Climbers- Valletia, Leptochloa fusca, Tinospora cordifolia 6. Scrub jungle Top Canopy- Acacia catechu, A. senegal, A. leucophloea Underwoods- Euphorbia neriifolia, Cassia auriculata, Maetenus emarginatus Herbs- Tephrosia purpurea, Justicia simplex, Cyperus rotundus, Eragrostis tenella Climbers – Cocculus laurifolius, Rhynchosia minima

In most cases, the general techniques used in ecological restoration can be summed up by the following:

  1. 1.

    Identification and extensive surveys in the site/plot selected for ecological restoration followed by enlisting the floristic composition (if any) and also recording the degree of infestation by weeds, degree of degradation such as properties of surface (with or without soil) and the levels of degradation of the general landscape. Also, in the process identified the key weed species which needed to be eradicated from the site using physical, chemical or biological means and for this gather pertinent information on the ecological and biological information on the said weed species, e.g. Phenological data, means of dispersal of the pollens and seeds, etc.

  2. 2.

    From the floristic documentation of the area done in past such as Forest Types for the area in past, such as the one from a flora record, or even an Environment Impact Assessment (EIA) Committee report list out the species that will be used to raise a forest/grassland community. This is important to resurrect a native community which will be ecologically sustainable and will help in augmenting biodiversity. With this data one can outline the kind of ecosystem one is aiming to develop effectively “restoring” the area. It will be also important to devise means to monitor the effects of the techniques applied. For this, a native forest ecosystem found in a similar site needs to be kept as a positive control or the reference site. Other means of monitoring the ecosystem could be by on ground vegetational surveys and monitoring changes in above-ground biomass from remote sensing techniques using geographical information system (GIS ) and also correlating the same with the changes in ecological processes provided by changing composition such as changes in soil properties, moisture levels in soil, moisture rentention period per year etc. In this manner, a detailed monitoring program specifying the chosen indicators on which information will be recorded during the restoration period to assess the recovery of ecosystem over time needs to be done.

  3. 3.

    Initiate restoration by choosing a proper intervention method to eradicate weeds and other undesirable non-natives species. This needs to be followed by addition of biological inputs to the substratum with farmyard manure, microbial inoculum enrich in plant growth-promoting rhizobacteria (PGPRs ) and other saprophytic microbes, decomposers, mineralizers, nitrogen fixers, mycorrhizal fungi, etc.

  4. 4.

    To begin with plantation inputs, an exhaustive planning needs to be made regarding digging of pits, the spacing between pits, time of plantation, establishment of a temporary nursery to generate a massive amount of planting material of trees, bamboos, ground cover species, etc., and planting material from other relevant sources such as a nearby natural forest area from where planting material could be brought in by “wilding”.

  5. 5.

    Stabilization of the slopes should be the emphasis of the programme in the initial years to prevent erosion by wind and water. For this, grass species such as Heteropogon, Bothriochloa and Tetrapogon need to be planted during early monsoons.

  6. 6.

    Next step should be stabilization of the general surface by forbs comprising of annual and perennial grasses, legumes, and other herbaceous plants, so that litter formation and basic ecological processes can augment. This helps in building a microbial flora and fauna and creates a below-ground conducive environment for the tree roots to develop.

  7. 7.

    Planting of the woody species in well-spaced pits of 1 to 3 feet depth. The spacing should be optimum, not too close or wide, e.g. a spacing of 1.5 × 2 m is ideal. The planting material should be minimum 1 year old and if originating from a nursery should be properly hardened-off for at least 3 weeks before transplantation.

  8. 8.

    Regular monitoring after transplantation should be carried out to record success rate of seedling-sapling establishment and mortalities/casualties need to be replaced immediately from the nursery material.

  9. 9.

    Monitoring and mid-course correction, if and when required should be laid out explicitly for ensuring no failures in the efforts of the human-induced restoration.

  10. 10.

    Depending on the degree of degradation and the approximate time required, strategy needs to be made for long-term protection and maintenance of the restored ecosystem.

4 Soil inhabiting Microbial Communities and Ecological Restoration

4.1 Soil as a Microbial Habitat

Soil is one of the most diverse habitats on earth. It provides highly heterogeneous environments for organisms inhabiting it (Gans et al. 2005; Zwolinski 2007). Microbial diversity indicates the number and abundance of species comprising a community in a given habitat. At the molecular level it is the sequence diversity for a given gene family in a community DNA sample isolated from an environment (quintessentialy, the metagenomic approach)(Liesack et al. 1997; Garbeva et al. 2004). Microbial community structure is a qualitative term. It indicates the number of individuals of the diverse taxa which share a common habitat and perform key functions at a trophic level. The functions performed by different trophic levels of microbial communities (bacterial and fungal) include decomposition of organic matter, involved in mineralization and nutrient cycling (van Elsas and Trevors 1997; Garbeva et al. 2004). Below-ground soil communities also maintain essential ecosystem functions in both managed and unmanaged soils (Hairston et al. 1968; Doran et al. 1996; van Elsas and Trevors 1997; Garbeva et al. 2004), by participating in soil structure formation and toxin removal (van Elsas and Trevors 1997), by promoting plant growth, suppressing a number of soil borne pathogens and bringing about changes in above-ground vegetation (Nitta 1991; Abawi and Thurston 1992; Doran et al. 1996).

There are evidences that soil microbial parameters may be useful as early and sensitive indicators for stressed soil and its alleviation (Dick 1992, 1994; Dilly and Blume 1998). The composition of soil microbiota has been established as a biological indicator of soil health and quality (Dick 1994; Fauci and Dick 1994; Filip 1998). The treatment or management of soil with application of pesticides (Heilmann et al. 1995), amendment with chitin (Hallmann et al. 1999), compost or manure (Schonfeld et al. 2002) and the introduction of genetically modified microorganisms (De Leij et al. 1994; Mahaffee and Kloepper 1997) have been shown to affect soil microbial community structures. Soil type and cropping practices also influence the microbial community composition (De Leij et al. 1994; Latour et al. 1996; Westover et al. 1997; Grayston et al. 1998; Horwath et al. 1998; Lupwayi et al. 1998).

4.2 Rhizospheric Microbial Biodiversit y

In 1904, a German agronomist and plant physiologist, Lorenz Hiltner, coined the term “Rhizosphere”. He defined a rhizosphere as a zone of soil close to the plant root in which the activity of the microbial community was enhanced, with consequent effects on nutrient (mainly nitrogen) availability to the plant (Hiltner 1904; Smalla et al. 2001; Sanguin et al. 2006; Hartmann et al. 2008). The definition is now slightly modified to mean the volume of soil directly in contact with plant roots, or the zone of influence of plant roots on the associated biota (Lynch 1998). The influence may be chemical, biological or physical (Jones and Schmitz 2009; Walker et al. 2003; McNear 2013). This zone supports an active microbial population distinct from the bulk soil and is mainly selected by the rhizospheric environment (Sørensen 1997; Marilley et al. 1998; Hawes et al. 1998, 2000; Hinsinger et al. 2009; Raaijmakers et al. 2009; Chaudhary et al. 2012). The bulk soil is that soil which is not associated with plant root-soil interaction zone. Bulk soil is remarkably diferent from rhizospheric soil in not one but many ways. The rhizosphere can cover large areas if the roots are extensive (Bolton et al. 1993). The rhizosphere is highly complex because of the numerous interactions co-existing within constituent biotic groups (van der Heijden et al. 1998, 2008). These interactions may be beneficial or harmful to the plant (Brimecombe et al. 2001).

5 Linkage of Above- and Below-Ground Biodiversit y

Community structure, biomass and specific functions of soil microorganisms can indicate soil health and quality (Hooper et al. 2000; Wolters et al. 2000). Soil biota is assumed to be responsible for soil ecosystem processes, especially nutrient cycling and decomposition of soil organic matter (Wardle and Giller 1996; Brussaard et al. 2004; Coleman et al. 2004). Soil organic matter in turn is an important attribute that shows positive correlation with above-ground plant diversity (Le Houerou 1969; Lugo et al. 1986; Cesar 1989; Aronson et al. 1993). Organic matter and carbon is mainly contributed by crop refuse, leaf litter, animal refuse and detritus influencing microbial communities (Schaeffer and Whitford 1981; Bardgett 2005; Bardgett and Wardle 2010). In a nutshell, the composition of the soil microbial assemblage can (i) affect plant growth, (ii) alter species composition and distribution, and (iii) change the colonization pattern of plant species (Turkington et al. 1988; Bever 1994). Likewise, rhizospheric microbial communities are influenced by various plant processes viz. root exudates, respiration and absorption of chemical ions that affect rhizospheric chemistry (Grayston et al. 1998; Paul and Clark 1996a, 1996b; Marschner et al. 2001). In simpler words, it can be concluded that the success of establishing above-ground plant communities as part of an ecological restoration programme essentially depends on site and the taxonomic and functional diversity of native or introduced below-ground communities and therefore understanding microbial community structure and improving/enhancing the richness will bear fruits in terms of successful establishment and perpetuation of above ground communities, which is the very goal of restoration effort. (Zak et al. 1992; Wardle et al. 2002, 2004; Moore et al. 2004; Bardgett et al. 2005; Bardgett and Wardle 2010; Miki et al. 2010).