Ecological Engineering 11 (1998) 221–229

A case study of ecological restoration at theXiaoyi Bauxite Mine, Shanxi Province, China1

Lin Gao a,*, Zewei Miao a, Zhongke Bai b, Xiaoyuan Zhou a,Jingkui Zhao b, Yinmei Zhu b

a Research Center for Eco-En6ironmental Sciences, Chinese Academy of Sciences,Beijing 100085, People’s Republic of China

b Department of Soil Science, Shanxi Agricultural Uni6ersity, Taigu,Shanxi 030801, People’s Republic of China

Received 15 December 1996; received in revised form 2 September 1997; accepted 30 December 1997

Abstract

This paper introduces theories and methods for ecological restoration of mines andpresents a case study of the ecological restoration in the Shanxi Bauxite Mine. In the processof ecological restoration, an integrated technical system consisting of stripping, mining,peeled-off and rehabilitation was established with the integration of engineering reclamationand biological reclamation; some techniques such as advanced farming techniques andbiotechnology were also employed. These measures considerably improved crop yield andsoil fertility of the mine, accelerated ecological rebuilding processes, and controlled soilerosion effectively. © 1998 Elsevier Science B.V. All rights reserved.

Keywords: Ecological restoration; Open-pit mine; Mineland restoration

* Corresponding author.1 Paper presented at ICEE 96—International Conference on Ecological Engineering, Beijing, China,

7—11 October 1996

0925-8574/98/$ - see front matter © 1998 Elsevier Science B.V. All rights reserved.

PII S0925-8574(98)00036-6

L. Gao et al. / Ecological Engineering 11 (1998) 221–229222

1. Introduction

Land is one of the most important resources on which humans depend. China,with the highest population worldwide, has experienced a decline in its totalcultivated land area. Currently, cultivated land occupies one tenth of the total landarea in China and cultivated land per capita (1.3 ha) is only one third of that forthe world. With economic development, industrial expansion, acceleration ofurbanization and growth of population as well as cultivated land area will continueto decrease. Thus, it is an urgent and important task to protect cultivated land andto restore converted or degraded land.

Exploitation of mineral resources has resulted in the destruction of vast amountsof land and has caused very serious environmental problems which have receivedattention from most countries in the world, including China. Ecological restorationand mine reclamation have become important parts of the sustainable developmentstrategy of many countries (Robert, 1992)

Land reclamation of mines in China began in the late 1970’s but has beenpracticed more widely since ‘the regulation of land reclamation’ was issued inNovember 1988 (Gao et al., 1995). Based on data from the National Bureau ofLand Administration, it is estimated that at present, the rate of land reclamation is10%. But China still has a long way to go, compared with reclamation rates as highas 50% in developed countries. For example, in bauxite mines in America, reclama-tion rates as high as an 80% were achieved by the 1970s, whereas this rate in Chinais only 20% on average. This comparatively low reclamation rate represents one ofthe largest ferrous metal mines in China.

2. Theories and methods of ecological restoration

Theories of ecological succession can be applied to mine reclamation. Whengrassland is converted into bare land, natural succession subsequently proceedsfrom weeds to sparse herbs to dense herb grassland. After deforestation, the naturalsuccession of Picea forest proceeds from cut land to grassland, to Betula forest, toPopulus forest and finally to Picea forest. This process can last for several decades.However, human activities may regulate the process and thus expedite succession orchange its direction.

In order to hasten ecological succession, an emphasis should be put on thefollowing aspects: (1) Selection of drought-resistant, sterility-tolerant and fast-grow-ing crops or herbage to grow on mining wasteland; (2) after stabilisation ofwasteland substrate to an acceptable level, planting of several kinds of grasses toquickly cover the wasteland or intercropping/rotating grass with leguminous cropsto combine cultivation with restoration of soil fertility; (3) based on elementcomposition and soil, fertility reconstruction of a self-sustained ecosystem withassistance from proper application of water and fertilizers, especially microbefertilizers; (4) planting of diversified crops and fruit trees, and integration ofagriculture with forestry, animal husbandry and sidelines according to local condi-tions to comprehensively utilize mining wasteland.

L. Gao et al. / Ecological Engineering 11 (1998) 221–229 223

Rehabilitation of mining wasteland is a complicated systematic project (Liu,1995). The following six fundamental principles should be observed: (1) legislation;(2) ecological risk evaluation; (3) minimization; (4) resource regeneration; (5)harmlessness and purification; (6) restoration of ecosystem.

Reclamation of open-pit mines includes two stages, engineering reclamation andbiological reclamation. Also, it requires that mining technology, ecological technol-ogy and biotechnology be integrated. The processes involved in reclamation areshown in Fig. 1 (Ma, 1995).

3. Case study of ecological restoration at Shanxi Bauxite mine

3.1. Description of the study area

Containing :40% of the total aluminum reserves in China, Shanxi is one of therichest provinces for aluminum resources. Xiaoyi Bauxite mine, which produces1–8 million tons of bauxite annually, is the largest bauxite mine in China. It issituated in Xiaoyi county on loess hilly land with sharp terrain cut and is part ofthe Shanxi province, which is a transitional region from Jinzhong basin to theLuliang Mount. Xiaoyi Bauxite mine, with an area of �1158 ha, consists of boththe Kee mine field and the Xihedi mine field. Clay shale, carbon shale, and gritconstitute the majority of soil at the strip-mined field, of which, one-third is thefourth period of alluvial loess. The presence of clay with poor erosion-resistance

Fig. 1. The process and methods of ecological restoration in mines (Ma, 1995).

L. Gao et al. / Ecological Engineering 11 (1998) 221–229224

and equally poor washed-resistance is one factor that causes soil erosion and makesthe slop unstable the strip mined. Annual precipitation in the mining area is450–550 mm, 60% of which is concentrated as rainfall between July and September.Spring is characterized by drier conditions and the annual evaporation is 3–4 timesas much as annual precipitation.

3.2. Integrated technological system for stripmine reclamation

To increase the efficiency of industrial land use and land reclamation processes itis essential that an integrated system of mining and reclamation be initiated.

Both the interior and exterior peeled-off fields use truck and bulldozers to peeloff at the Kee mine field, and loosener and scraper are used at the Xihedi minefield.

Loess, the upper rock layer covering the mined ore, makes up about one third ofthe stripping topsoil and is adequate for use as reclamation material (Ma, 1995).This makes it possible for mining and land reclamation to be carried out simulta-neously. Its features include; using the same equipment by engineering reclamationand peeled-off, a close combination of stripping, peeled-off and land reclamation intime, space and process, the regulation of working plan of peeled-off field inaccordance with the principle of shortening the period of occupying land andrestoring waste land to cultivated land in advance.

3.3. Materials and technology of land reclamation

To get high yield, good soil texture and easily fertilizing soil section are essential.Meanwhile, the cost of backfilling and landmaking accounts for :40% of the totalcost. In terms of technical demand and economic benefit, it is very important tostudy the optimum reclamation material and technology of landmaking.

Physical, chemical and biological properties of mine soils (the fourth period) areanalyzed and pot culture experiments are made. Malan soil, the upper of the fourthperiod loess, is a yellow white clay and middle soil. Its good permeability favoursfertilizer-leaking, water-leaking and the poor washed resistance and erosion-resis-tance make the arable layer barren. The lower Lishi soil, thicker than Malan soil,is a red clay and its total N content and quick-acting N are 1–2 times higher thanyellow pink soil, also, it has a strong ability to preserve water and fertilizer. Thus,the clay is a practical material for land reclamation in the Xiaoyi region. However,its poor properties like poor permeability and easy hardening are unfavourable forcrops to emerge and grow. The complementary properties of these two soilcategories make it feasible to mix them as a material for land reclamation.

Pot culture test showed that the mixed soil of red soil and yellow pink soil in theproportion of 7:3 is superior to the original topsoil on the mining area. Theemergence rates of grass and leguminous plant are increased by 64%, the survivalrate of a seeding increased by 120%, and the fresh weight per plant increased by160%. Improved results of the experiment are found by adding crushed coal to thestripping layer. The demonstration shows that this mixed arable layer favours the

L. Gao et al. / Ecological Engineering 11 (1998) 221–229 225

Table 1Comparison of yield and productive properties between different corn varieties

Barren SpikeVarieties Number ThousandSpike Period ofGrainsFresh Yield(kg/ka)of samples length per row graindiameternet weight growthhead

(cm) (days)(cm)(kg/spike)(cm) weight (g)

298 5670Zhongdan 5.1471 15022.99 0.303 4.56 38104

4.94 155Zhongdan 28648 21.64 0.294 54840.94 4514

217.3Control 48 21.74 0.220 1.71 40.44 4.18 3714167

growth of crops; yields per m of tested sorghum, millet, cowpea, soybean, and mungbean are 125, 100, and 40 kg, respectively.

In order to conserve more water and avoid slope washout, after the terrace ofpeeled-off field is levelled, the basis of the terrace must keep a certain back-slopeangle, generally not \4°. The basis should have 5–10 cross fall so that in case ofrainstorms, runoff may flow into the flood-discharge system to avoid the terracecollecting too much water. To protect slope, a ridge is built along the edge of theterrace and then cultivated soil is covered whose optimum thickness is 0.6–0.8 m.

3.4. To screen 6egetation 6arieties

When comparing basic conditions of reclaimed land with that of arable land,there exists a great difference between arable soil of reclaimed land and that of localfarm fields (Robert, 1992). Reclaimed land has higher soil bulk weight, biggerelevation, thinner soil layer and poorer soil structure, as well as lower activity ofmicrobes. Vegetation on mining reclaimed land can only rely on mining similarcrops like corn, millet, bean, sorghum, wheat, bean and buckwheat, etc.

3.4.1. To screen food crop 6arieties. For screening vegetation varieties, the propertiesof strong stress-resistance, such as strong poorness-tolerance, drought-resistance,lodging-resistance and disease-resistance are demanded. High yield and high fertil-ization rates are considered important for screen plant varieties. Developed rootsystems and high biomass yield are important factors too. The methods forscreening vegetation varieties include the following steps: At first, experiments ofpot-culture in the laboratory are implemented, then pilot and field tests areconducted. Among 96 maize varieties, several fine varieties were singled out,including those with many fine properties, such as extensive adaptability, strongdrought-resistance, low ear position and good high-yield properties. The yield in theexperimental field increased 47.7% more than that of the control (Table 1). From 24tested bean varieties, a series of fine varieties including Beinong 50098, Zhongzuo84, Zhongzuo 85 and so on, were selected to fertilize and conserve soil. Theircommon features include strong stress-resistance, high-yield properties, developed

L. Gao et al. / Ecological Engineering 11 (1998) 221–229226

root system, longer main root and greater fungal colonies. Their yield was 55%higher than the control. The amount of nodule bacteria was 5–6 times that of thecontrol (Table 2).

3.4.2. To screen herbage and shrub. In order to enhance the capability of soilconservation and slope protection on the slops of peeled-off fields, the sameimportant technical method as that constructed for flood-discharge systems is used:establishing glass-shrub vegetation communities.

The ways of screening vegetation varieties are: (1) experiments for drought-resis-tance and screening of roots are performed in the laboratory with 15 candidatevarieties; (2) their field tests are executed. The screening perennial glasses include:Madicago satica6a, Astragalus adsuzgens, Onobrychis 6icifolia, Caragana intermedia,Festuca, and Artemisia scoparia. Among the shrub varieties, Caragana and falseindigo are the best.

3.5. Natures of 6egetation techniques for land reclamation

(1) Applying cultivation techniques of drought-resistance and moisture-preserva-tion. In Xiaoyi area, during the period of spring-sowing, the climate is characterizedby little rainfall, high evaporation and poor topsoil moisture. The program teammade an adjustment to traditional farming methods, including the change of springcultivation to plough after autumn and cross ridge culture so as to improve topsoilroughness of the cultivated area, and to create a condition to preserve snow andmoisture. By applying the techniques including less cultivation in the spring, holdseeding, and absorption of deep moisture, crop emergence rates of test fields andreclaimed land increased more than 85%.

(2) Rational close planting. Through changing the local traditional planting torational close planting, such as 12000–14000 bean plants/m or 2500–3000 cornplant/m, high yield was achieved and no lodging was presented.

(3) Crop rotated and intercropping systems. In experimental fields of intercrop-

Table 2Yields and productive properties of beans in various fields

Numbers ofVarietiesFields YieldAverageAverageAverage Thousand(ka/ha)numbermeasuring number grain weightnumber of(platform)

points (g)points (m2) of grainsof pods(m)

183 2134.956 6 22.711125 2.2550 098910.052051.959.351125 3340 237

222 1716.650 0981150 10 10 17.5 2.09Control 966.61841.7516.94331125

L. Gao et al. / Ecological Engineering 11 (1998) 221–229 227

ping of maize and bean, the individual yields of corn and bean were 567 and 152kg, respectively, which set a yield record of reclaimed land separately.

3.6. Introduction of mature techniques to increase production

The program team employed many new agricultural techniques in experimentson reclaimed land in the Xiaoyi area which have been successful in agrosystems inour country in recent years. Most of the experimental techniques are good andlisted as follows.

3.6.1. Fertilizing techniquesIt is very significant to input chemical fertilizer reasonably. In the Xiaoyi

region, urea, ammonium nitrate (NH4NO3) and ammonium bicarbonate(NH4HCO3) are usually utilized as base and topdressing fertilizer. However, thistechnique is not helpful to alleviate soil alkalinity. In terms of the principle of soilnutrition balance, in reclaimed land, a two-element complex fertilizer of nitrogenand phosphorous was used as a base fertilizer. Sufficient phosphorous was addedone time to meet the demands of the seeding period to phosphorous thresholdperiod. In general, the threshold period of nitrogen emerges in the middle andearly period of crop growth. By choosing urea as a base fertilizer instead of localammonium bicarbonate (NH4HCO3), fertilizer efficiency increased. During theflourishing period of crop development, the method of spraying fertilizer on leaveswas adopted to supplement the crops trace elements like Mo (Molybdenum), Zn(Zinc), B (Boron), etc. As an economical and effective measure to increase yield,the method was to use less fertilizer and benefit from the quick effects of thefertilizer.

As a complete nutritious manure, organic manure is useful to improve soil andchemical fertilizer efficiency. With the enlargement of the mining area and re-claimed land, straw of food crops herbage will become a very good organicmanure source.

3.6.2. Experiments on the effects of nodule bacteria on crop yieldNodule bacteria may ameliorate plant nutritious conditions and give full play

to soil potential by the activity of microbes.Experiments on the effects of nodule bacteria on yield were conducted on test

fields in the Xiaoyi Bauxite mine with a pilot area of 240 m2. The treatments ofnodule bacteria occupied half of the above-mentioned area separately. The testedcrop was bean, and the weight of used nodule bacteria only amounted to 5% ofthe crop seed weight. Seed dressing was followed by seed sowing, and the amountof fertilizer and field management measures were the same as that of other fields.While crops were harvested, samples were collected. The yield of beans dressed bynodule bacteria increased by 48% compared to the control (Table 3).

In Xiaoyi Bauxite mine, nodule bacteria techniques are also employed toenhance emergence rate of seedling and vegetation recovery rates of on steepslopes of peeled-off fields.

L. Gao et al. / Ecological Engineering 11 (1998) 221–229228

Table 3Experiments on nodule bacterial manure

YieldTreatments AveragePlant fresh AverageNodule fresh CalculatedThousand-increaseyieldgrain weightnumbersweight weight numbers

of pods (g)(g/4 plants) of grains (%)(g/4 plants) (kg/ha)

39.25 2.26Seed dressing 239 2530 148365 5.80with nodule

100Control 220250 17004.95 25.07 2.14

3.7. Utilization of mycorrhiza techniques

Based the characteristics of soil and rock on Xiaoyi Bauxite mine, it has beensuggested that endomycorrhiza should be used to increase crop yield, accelerate soilmaturity and shorten the period of land reclamation.

Experiments were made with four strains from G. mossae and G. 6esriformeadapted to alkali soils in northern China, VA-1 and VA-2 were selected to multiplyin the laboratory, then the strains were sowed with potato as tested crops in Julyand October 1994, respectively. The containment experiment was conducted inAugust and December in the same year. Results showed that the fungus agent hadreached the quality standard abroad and could be used for land reclamation. In1994, VA1 and VA-2 were inoculated to soybeans and transplanted date trees andmaize in 1995. Good results were seen; containment rates of soybeans and datatrees were 60 and 72%; moreover, the date trees bore fruits in the same year (Table4).

4. Conclusions

A whole set of engineering and biological reclamation approaches were appliedto land reclamation of the Xiaoyi Bauxite mine. After 4–5 year cultivation, the

Table 4Experiments for effects of inoculated VA bacteria agents

Treatments VA-2VA-1 Control

5.7 6.4 4.4Total numbers of buds per pot21.68Plant height (cm) 21.68 17.79

1.51Root fresh weight (g/plant) 3.372.8118.03Fresh weight per plant (g/plant) 19.27 11.59

2.804.204.20Dry weight per plant (g/plant)100Comparison of phosphorus content (%) 189.5173

+Infringed extent Slightly infringed+

L. Gao et al. / Ecological Engineering 11 (1998) 221–229 229

original soil has matured, and its properties have reached the fertilizer level of localmatured soil, close to the fourth standard of Chinese soil fertilizer. The results ofland reclamation are summarized as follows:1. There is a remarkable increase in organic matter, active P and quick-acting K in

arable layer.2. During cultivation, as a result of the return of plant root systems and leaves

restoring to the soil as well as acid manure being applied, the soil pH valuedecreased from the 8.29 to 7.26, and soil bulk weight decreased from 1.45 to1.23 g/cm3. However, soil porosity increased. After 3 years of reclamation, somegranular structure developed.

3. After a 3- and 5-year cultivation period, the amount of bacteria, fungus andactinomyces have reached the level of local farm fields.

4. After the 4-year reclamation on the Xiaoyi Bauxite mine, the fertility of the soilarable layer has reached the middle and upper level of local farm fields. Cropyields of the reclaimed lands are also close to, or more than, local fields. Ingeneral, they increased by :10%.

5. After reclamation of slopes and platforms of the peeled-off field, the vegetationrecovery rate of the platform was \90%, the slope reached 50–60%. Due to thedeveloped root system of slope herbage and its good network properties andhigh mechanic strength, it possessed a strong capability of soil-conservation andslope-protection. After slope management, the amount of soil erosion decreasedby as much as 60%, so soil erosion was controlled effectively.

References

Gao, L., Shi, Z., Zhang, W., 1995. Reclamation of mining land in China: Policies and practices. In:Wang, R. (Ed.), Wealth, Health and Faith. China Environmental Science Press, Beijing, pp.130–141.

Liu, R., 1995. Review of reclamation of waste land in China. Reclamation and Greening of Waste Landof Mine, pp. 1–6.

Ma, Z., 1995. Research on Reclamation of Surface-Mined Lands in the Loess Plateau (No 1). ScientificPress, Beijing, 199 pp.

Robert, E.D., 1992. Prime Farmland Reclamation. In: Dept. Agronomy, IL Agric. Experiment Station,editors. University of Illinois Press, Urbana, 184 pp.