MANEJO DO SOLO NA REVEGETAÇÃO DE ÁREA DEGRADADA PELA MINERAÇÃO DE BAUXITA

 Paulo Roberto Moreira¹, Nilson Augusto Villa², Osvaldo Aulino da Silva³, Jairo Mazza⁴

ABSTRACT: Bauxite mining promotes alterations on soil properties, destroying the vegetation and the biota present in superficial layers of soil, as well as delaying natural regeneration. The current study was carried out with the aim of evaluating the potential of a group of management practices to restore a bauxite mining area in Poços de Caldas, MG, Brazil. A randomized block experimental design with split plots was adopted. The main plots comprised the treatments with and without subsoiling while the subplots contained the treatments as follows: T – liming, without fertilization plus addition of litter at 28 kg/subplot; F – mineral fertilization and liming after planting of 18 local tree species; L – treatment F plus application of summer green fertilization; C- treatment F plus topsoil replacement. In order to improve the microbiota in the soil, a winter green fertilizing crop was sown prior to the installation of the experiment. Subsoiling significantly increased the dry matter production of the winter green fertilizer and the canopy area of trees. The replacement of topsoil and fertilization considerably improved soil fertility, the survival of trees and the quality of the environment in general.  The study of the bases saturation (V%) and the cation exchange capacity (CEC) showed that a maintenance fertilization is essential 24 months after planting.

Keywords: restoration; damaged areas; management; soil fertility.

INTRODUCTION

Nature comprises complex and integrated systems involving different environmental factors: climatic (air temperature, precipitation, photoperiod, wind, solar radiation, humidity and gases), edaphic (physical, chemical and biological properties, humidity, topography, declivity and soil exposure) and biotic (humans, plants and animals) factors. When considering the restoration of a degraded area, the alterations of such factors have to be assessed, analyzed and interpreted before and after the anthropic interventions.   

Mining activities lead to losses of the vegetative cover, in biotic regeneration (seed bank, plantlets and sprouting), of the soil superficial layer, which is rich in organic matter, and of deeper soil horizons, altering the edaphic properties and reducing the potential ecosystem productivity (Franco 1993; Ruivo 1998).

Successful restoration of degraded areas depends on adequate soil management, a good landscape recovery plan, previous experiences in the area, public awareness toward the environment, favorable political and social conditions and fulfillment of local needs (Primack & Massardo 1998; Kopezinsk 2000).

Soil properties are the key element of terrestrial ecosystems, as they comprise organic and inorganic environmental factors that are essential to the good functioning of this ecosystem (Las Salas 1986; Lal 1998; Wallace & Terry 1998; Pianka 2000).

The purpose of the present study was to evaluate the influence of a group of management practices, including subsoiling, superficial horizon replacement, liming, mineral and green fertilization, and gypsum application on the restoration of an area degraded by bauxite mining planted with tree species of the regional flora.

MATERIAL AND METHODS

Characterization of the Studied Area

The experiment was established in April 2000 in a site called Morro das Arvores, east Poços de Caldas plateau, MG, (21^o 47’14’’S and 46^o 34’10’’ W), Brazil, altitude varying from somewhat below 1,000m to about 1,300m, property of Companhia Geral de Minas, subsidiary of Alcoa Aluminum S/A, which had undergone bauxite mining. The site was previously covered with a Semideciduous Seasonal Forest, Semi Umbrophilic Forest, as well as transitional intersections of both physiognomies, and showing significant occurrence of wood Cerrado grass species Cerrado (Brasil 1983).

According to Köeppen’s classification, the climate is humid subtropical (Cfb), presenting rainy summers and dry winter periods in July and August (IBGE 1977). The average annual temperature is 24.3^oC, with average maximum and minimum temperatures of 25.9^oC and 74.0^oC, respectively. Precipitation in the area is significantly higher than in the surrounding region due to orographic rains of around 1,800 mm/year, concentrated mainly from October to March (IBGE 1997; Girodo 2000). According to the Soil Survey Staff (1999), the soil in the region studied is classified as TYPIC DYSTROCHREPTS associated to a LITHIC UDORTHENTS, though predominantly DYSTROCHREPTS. The soil physical, hydric and chemical characteristics are shown in Tables 1, and 4 through 7, as well as in Figures 1 and 2. Two trenches (1.5m wide x 1.50m long x 0.6m deep) were dug in the experimental area for soil classification purposes. The original soil profile up to 1.50m depth surrounding the experiment in undisturbed areas was described by Lemos & Santos (1984) (Table 1).

Table 1 – Original soil profile prior to bauxite mining according to the Brazilian System of Soil Classification (Embrapa, 1999), ALCOA, Poços de Caldas, MG.

S =Soft; VF = Very friable; PS = Plastic and sticky.

Geology and Geomorphology

In Poços de Caldas there is a complex of pre-Cambrian alkaline intrusions of Nepheline Syenite rocks covered by Mesozoic remains and sediments (Shumann 1993).

Bauxites in Poços de Caldas represent the final stage of a decomposition process of alkaline rocks, releasing alkalies and silica from feldspars and feldspatoides belonging to the mother rock, giving way to hydrated alumina and possible impurities remaining in the ground. The topography is smoother over the mining sites where the study was carried out, with less active drainage and more intense leaching than in the ridge mining sites (Girodo 2000).

Comparison between the Original and Mined Areas

Comparative analyses of the soil physical-hydric and physical parameters of the original and the mined areas were conducted in order to evaluate the degrading effects of bauxite mining on the area studied.

Soil Physical Analysis

Samples of the soil profile were collected from trenches opened across the experimental area and its undisturbed surroundings. The samples were analyzed as to their granulometry, by the pipette methodology (Grohman & Raij 1974), density, according to Miller (1976), and macro and micro porosity through volume rings, according to Kiehl (1979). Color classification was carried out according to the Munsell Color Co. System (1975). The soil chemical characteristics (pH, organic matter, potential acidity (H+Al), phosphorus, potassium, calcium, magnesium and total nitrogen) were determined according to Raij et al. (1987).  

Soil Physical-Hydric Analyses

Characteristic water retention curves were drawn from undeformed soil samples collected from the original (undisturbed) and from the mined areas to represent the average soil profile. The results allowed the estimate of the available water capacity (Libardi 1995): AWC = [(Ucc% – Umu%) Da (H)]/100, where AWC is the available water storage capacity (mm), Ad is the soil apparent density (g/cm³), H is the horizon thickness (mm), Ucc% is humidity at field capacity (1/3 atm or 30 kPa) and Umu is the wilting humidity at 15 atm or 1,500 kPa.

Description of the Restoration Treatments Conducted in the Experimental Mined Area

Experimental Design

A randomized blocks split-plot experimental design with five replicates was used. The main treatment consisted of the use or absence of subsoiling while the subplots received the secondary treatments described below (Figure 1).

Figure 1 – Field layout of the experiment.

T – Liming and gypsum application, without fertilization, plus addition of litter (28 kg / 168 m^-2 plot, or 167 gm^-2);

F – Mineral fertilization and liming, followed by the transplanting of 18 native tree species of the local flora (Table 2) with planting-hole fertilization (2.0 kg NPK 20:10:20/planta and 15 kg of mature cattle manure;

L – Same as treatment F plus summer green fertilization (Crotalaria juncea) after planting of tree species;

C – Same as treatment F plus replacement of superficial horizon (20-cm deep layer of soil scraped from the surface previous to mining, heaped in lines and returned to the recovering area).

The same combination of the 18 tree species belonging to the regional flora was used in treatments F, L and C. Plants were placed 3.0 x 2.0m apart, which represented a density of 1,667 trees/ha. The survival of the individuals was checked twelve months after planting and the field card adopted was adapted from Silva & Lopes (1984). Plots were allocated to 672m² areas comprising 72 viable plants with an external row of plants left as border, while subplots measured 168m² and comprised 18 viable plants.

Prior to planting, a mixture of winter green fertilizing propagules was manually scattered over the experimental area. The fertilizer was composed of 20 kg of vetch (Vicia sativa), 40 kg de Black Oat (Avena strigosa), 10 kg of sunflower IAC – Uruguai (Helianthus annuus), 20 Kgof radish Cati-Al 1000 (Rhapanus sativus)and20 Kgof white lupin (Lupinus albus), which was applied to treatments F, L and C at the proportion of 20 seeds per linear meter (40 kg/ ha^-1). The mixture was incorporated 126 days after planting, which was coincident with the blossoming stage.

Table 2- Tree species of the regional flora planted in treatments F, L and C located in the area studied and their respective number.

Initials = pioneer and early secondary; Non-pioneer = late secondary and climax.

Abbrev. = Abbreviation of scientific name; EG = Ecological Group; I = initials; N = Number of species in the experiment; T = non-pioneer.

Soil Sampling and Assessment of Restoration Treatments in the Experimental Area

Soil Fertility

Compound samples were firstly collected at 0-20 and 20-40cm depths throughout the total area for physical and chemical analyses and the assessment of the needs for organic matter, lime, fertilizer and gypsum to be applied. The soil chemical analyses (pH, organic matter, potential acidity (H+Al), phosphorus, potassium, calcium and magnesium, boron, copper, iron, manganese and zinc) were carried out according to Raij et al. (1987).

Liming (1,000 Kg ha^-1), gypsum application (2,400 kg ha^-1), phosphatic fertilization (100 kg ha^-1 P, corresponding to 500 kg ha^-1 simple superphosphate) potassic fertilization (50 kg ha^-1 K, corresponding to 83 kg KCl), and the application of nitrogen (10 kg N kg ha^-1 , corresponding to 16.6 kg urea), and the micronutrients zinc (3 kg ha^-1 Zn), boron (1 kg ha^-1 B) and copper (2 kg ha^-1 Cu) were conducted in the whole experimental area according to the chemical analyses carried out. However, treatment T received 2.0 kg NPK 20:10:20 + 15 kg mature cattle manure applied into 50 x 50 x 50 cm planting holes.

Soil Fertility Monitoring

Samplings under the projection of canopies of the tree species used for restoring the local vegetation were carried out yearly in order to monitor and evaluate the variations in soil fertility in the experimental area. Compound soil samples were obtained from 10 sub-samples collected with the aid of a SONDA-TERRA probe, according to Raij (1983), at 0-20 and 20-40cm depths, twelve and twenty months after planting. For treatment T, where regional tree species were sowed and to which litter was applied, sampling was carried out using a Dutch probe, in a zigzag pattern throughout the effective area of the sub-plots.

Statistical Analysis

An analysis of variance was conducted for each factor studied by using the statistical software SAS 8.2. Means were compared by Tukey test at 5% probability.

RESULTS AND DISCUSSION

Physic-Hydric and Chemical Soil Parameters: Comparison between the Original Soil Surface before and after Mining

Granulometry

The results of soil granulometry analyses are presented in Table 3. Clay amounts in the original soil profile ranged from 520 to 600 g kg^-1 (“silt-clay” texture), while silt amounts varied from 250 to 310 g kg^-1 (“medium-clay” texture). The mined surface (B/C horizon) showed lower clay amounts (400 g kg^-1) and greater silt amounts (390 g kg^-1), implying lower weathering in relation to horizons A and B, which was expected due to the greater depth.

Table 3 – Physical parameters for the original soil profile and for the mined soil surface, ALCOA Poços de Caldas, MG.

(Sd) = soil density, (Pd) = particle density, (Tp) = total porosity, (Mip) -= micropores and  (Map) = macropores.

Density and Porosity

Soil density (Sd) figures were below 1.1 g/cm³ (Table 3), which, according to Kiehl (1979), are considered low considering mineral soils. This happens because the soil original material (Nepheline Syenite) shows low density. Lower Sd figures in superficial soils promote water retention, root growth, gas exchanges and microbial life. When Sd is known, it is easier to decide which management practices are best to least affect the soil environment, as Sd influences the distribution of soil particles, which, in turn, defines the characteristics of the porous system. All interventions influencing the organization of particles will influence Sd values (Alvarenga & Souza 1997). On the other hand, particle density (Pd) ranged between 2.3 and 2.9 g/cm³ (average of 2.65g/cm³), similar to values for the samples from the original and mined areas. Micropore proportion (Mip) was higher than the macropore proportion (Map) in all horizons of the soil profile studied (Table 3). Therefore, it can be concluded that the soil considered herein shows good water retention, once microporosity is the key factor responsible for such characteristic and is within the expected limits for clay soils, from 400 to 600 g kg^-1 (Kiehl 1979).  

Water Retention Curves

Water retention curves at 40cm depth for the original and the mined areas are shown in Figure 2. As it can be observed, there was a water retention loss in the soil mined surface probably due to organic matter loss and soil compaction caused by machines and the removal of superficial horizons. The same was observed in a similar situation by Korbiyama et al. (2001).

Figure 2 – Water retention curve for the superficial soil (experimental area) x Water retention curve for the original soil profile.

The available water capacity (AWC) up to 40cm deep in the profile studied was 64.8mm/ 0.40m, while in the mined surface it was 56.4mm/0.40m (Figure 2). Soil humidity was higher in the original area (Table 4), probably due to greater organic matter amounts.

Table 4 – Average values for physical parameters of the original soil profile and the B/C horizon of the mined area.

(Dep.) = depth, (Fc) = field capacity; (Wh) = wilting humidity, (Sd) = soil density and LAW = layer of available water in the original soil profile and in the mined area.

Hydric Balance

No serious soil water deficit that could lead plants to show severe effects of water stress was observed. A slight water deficit, which caused no harm to plants, was verified in April, June, July and August 2001/2002 (Figure 3), when the actual evapotranspiration (AE) line was below the potential evapotranspiration (PE) line. Precipitation (P) was abundant and well distributed during all the other months.

P = precipitation, PE = Potential evapotranspiration, AE = actual evapotranspiration.

Figure 3 – Graphic representation of the hydric balance from January 2001 to December 2002, Thornthwaite & Mather (1955) – 150mm.

Table 5 – Chemical analyses results for the original soil profile and for the mined surface prior to the establishment of the experiment and for the top soil. ALCOA, Poços de Caldas, MG, Brazil.

P = phosphorus, N = nitrogen, K = potassium, O.M. =organic matter; SB = sum of bases (Ca⁺²+ Mg ⁺²+ K⁺), CEC= cation exchange capacity (SB+ H⁺+ Al⁺³), V% = bases saturation (100 S/T), m = aluminum saturation, B = boron, Cu = copper, Fe = iron, Mn= Manganese and Zn = Zinc.

Assessment of Soil Chemical Characteristics for the Restoration Treatments

The mined soil surface showed a severe reduction in fertility levels when compared to the superficial layer (Ap) of the original soil prior to the establishment of the experiment, presenting lower amounts of P, S, K, Ca, Mg, B, Cu and Fe (Table 5). Such condition is directly related to the lower sum of bases (SB) and bases saturation (V%), which decrease the potential nutrient supply of the soil. However, the most significant effect was observed with the organic matter, whose reduction by just 3 gdm^-3 or 0,3% reduced the water and nutrients retention capacity and, thus,  reduced vegetal development. The superficial horizon replaced to the experimental area presented similar nutrient amounts to those observed for the horizon Ap of the original area, despite showing higher amounts of O.M. (around 4%) due to the storage of such material mixed with other vegetable remains.

There was a significant increase in phosphorus, potassium and organic matter (O.M.) amounts in the soil 12 months after soil correction and the application of fertilizers. The increase in soil fertility led to an increase in the bases saturation (V%) and in the cation exchange capacity (CEC), especially in the latter due to the increase in O.M. amounts. This favored the nutritional conditions for the establishment of the vegetation, contributing to an effective environmental restoration in the area (Table 6). There was a decrease in the nutrients (Ca, Mg and K) and O.M. amounts 24 months after planting the area, when compared to levels 12 months after planting (Table 6). On the other hand, the treatment where mineral fertilization was applied to the superficial horizon showed O.M. amounts 30% greater after 24 months of planting than treatments where such horizon was not replaced. As it was also mentioned by Franco et al. (1992), the restoration models for degraded areas must be based not only on the use of fast growing species, but also on the improvement of soil conditions through the additions of organic matter, which favors the soil restoration and the establishment of  secondary vegetation.               

Costa et al. (1998), working in areas degraded by bauxite mining in the Amazon Forest, Oriximina, PA, noticed that even ten years after replanting the area, organic carbon levels were lower than those observed in the pristine native forest. The studies showed the difficulty in restoring the organic matter in the original soil, which implies in greater difficulties in reestablishing the original amounts of organic matter found in the areas covered by the original vegetation. The studies also evidenced the need for a continuous monitoring of the soil.

Two years after the planting of the vegetation, treatments involving subsoiling showed greater phosphorus concentrations at 20 to 40cm depths. At the same time, differences in K amounts among treatments virtually disappeared, with a significant decrease in K amounts probably due to potassium leaching. Figures for m (% of aluminum saturation) were low two years after planting and should not hinder the vegetative development.

CEC increased in the first 12 months after planting, mainly in the treatment involving green fertilization, leading to lower cation losses at greater depths. However, there was a severe decrease in CEC 24 months after planting due to the combined effects of nutritional requirements and natural leaching processes. The increase of CEC is a key factor in the restoration of mined areas, once the O.M. present in the soil superficial layer is completely removed. V% figures varied from 14% at planting to 55% and 30%, 12 months and 24 months after planting, respectively. This shows a significant improvement in V% due to green fertilization and liming when the experiment was established, resulting in better fertility conditions and, consequently, in a better development of the initial vegetation. The decrease in V% at the end of the second year indicates the need of a maintenance fertilization, which was also mentioned by Lal (1998), emphasizing that nutrient stocks are among the key properties for soil restoration in a degraded area.

B and Zn amounts, 0.1 and 0.3mg dm^-3, respectively, were originally low. With the introduction of such elements, increasing B and Zn figures to levels above 0.2mg dm^-3 and 0.6 mg dm^–³, respectively, the conditions stopped limiting plant development.

The results obtained in our study corroborate the recommendations suggested by Sanches (1977), Salas, (1986), Sparovek et al. (1991) and Sparovek (1998), showing that the main management practices to be performed in a degraded area include fertilization, acidity correction, green fertilization, introduction of organic matter, subsoiling and soil conservation practices.

The mineral and organic fertilizations conducted in the mined area aimed at restoring the soil potential through the addition of organic matter and also at recovering the soil quantitative potential, with special emphasis on phosphorus and calcium, besides eliminating the aluminum excess from deep soil (Casagrande 2003).

The monitoring of soil fertility, as well as of physical and biological attributes, should be conducted until the litter layer covering the mineral soil builds up on the surface of the revegetated area (mined surface). From that moment on, most of the nutritional needs will be supplied by nutrient recycling.

Table 6 – Chemical analyses results for the degraded mined soil under different treatments in the area studied, 12 and 24 months after planting. ALCOA, Poços de Caldas, MG.

Treatments → T: Control, C: Top Soil + F, L: Mineral fertilization + green fertilization, F: Mineral fertilization + planting hole fertilization (NPK + manure).

Soil Parameters → O.M. = Organic Matter, SB = sum of bases (Ca⁺²+ Mg ⁺²+ K⁺), CEC= cation exchange capacity (SB + H⁺+Al⁺³), V% = bases saturation and (m) = aluminum saturation.

INFLUENCE OF SOIL MANAGEMENT ON VEGETATION

Fertilization is a management practice easily performed in an area to be restored, which reveals promising results at the beginning of an environment restoration regarding soil fertility and vegetative establishment (Tables 5 and 6).

Gochmatia polymorpha (species number 7) showed greater and more homogenous standard height 12 and 24 months after planting for treatments F, L and C. Lafoensia pacari (species number 3) and Chorisia speciosa (species number 4) showed intermediate performance for height and homogeneity figures. The growth patterns of the species above evidence greater plasticity and better adequacy for the environmental conditions of the area studied.

Luehea divaricata, Rapanea umbellata, Acacia polyphylla, Vitex polygama, Machaerium nyctitans, Tapirira guianensis, Jacaranda macrantha and Eugenia florida (species 2, 5, 6, 8, 9, 10, 12 and 17, respectively) presented homogeneous growth in relation to their height, showing lower plasticity under the conditions of the treatments conducted 12 and 24 months after planting (Table 7).

Treatments F, L and C did not show significant differences as to tree height 12 and 24 months after planting (Table 8). The high coefficient of variation (69%) for this variable evidences great variability within the experimental area. For future experiments on this issue, it is recommended the establishment of smaller experiments with a greater number of replications.

Treatment T is not shown in Tables 7 and 8 due to litter loss and propagules, which where carried away by the runoff, once the experimental area lies on a slope. No plantlets emerged in this area, indicating the need to improve the technique aimed at litter retention. Silva et al. (2000) collected litter up to 5 cm deep and stored it in open raffia bags and were able to successfully restore the vegetation in steep areas.

Table 7 – Results for average height (m) of tree species for treatments F, L and C, 12 and 24 months after planting.

S/st.: Average was not calculated due to high mortality level of the sp in the treatment;

sp: species;  

Averages followed by the same letters do not differ by Tukey test at 5% probability.

Table 8: Average height results for tree species in treatments F, L and C, 12 and 24 months after planting.

Averages followed by the same letters do not differ by Tukey test at 5% probability.

C: replacement of superficial soil horizon + F

F: mineral fertilization + indigenous species + planting hole fertilization (2.0  Kg  NPK 20:10:20 kg/plant) +15 kg  manure. 

L: mineral fertilization + Crotalaria  juncea  + F

Subsoiling in the area was aimed at breaking the physical obstructing layers that compacted the soil and at promoting higher water infiltration and good development of root systems, which favor water and nutrient absorption by plants, mainly the sub-superficial absorption. Such effects were achieved by Willians (1995) when restoring an area degraded by bauxite mining, and by Durigan (1996) when revegetating Cerrado areas. Although contributing to a better dry matter production during the winter fertilization, subsoiling showed no effect on the species survival twelve months after planting by Tukey test at 5% probability (Table 9). However, this finding was already expected, as roots were limited to the substrate volume within the planting holes, whose effect was similar to subsoiling during this evaluation period. Nonetheless, subsoiling showed a significant effect by Tukey test at 5% probability on the area of canopy 18 months after planting (Table 10).

Table 9 – Effect of subsoiling on the survival of tree species twelve months after planting, ALCOA, Poços de Caldas, MG.

Averages followed by the same letters do not differ by Tukey test at 5% probability.

Table 10 – Influence of subsoiling on average canopy areas for tree species 18 months after planting, ALCOA, Poços de Caldas, MG.

Averages followed by the same letters do not differ by Tukey test at 5% probability.

The replacement of the 15 to 25-cm superficial layer of the original soil to the area to be recovered favored the survival of plants in treatment C when compared to treatments F and L (Tukey test at 5% probability), which did not undergo original soil replacement (Table 11). Regeneration was also more intense in treatment C than in treatments L and F, when compared to the bare mined area, due to the seed bank, greater organic matter content and better physicochemical conditions present in the original soil, which created a more suitable environment to new propagules brought by the seed rain (Figures 4 and 5).  No significant statistical differences were observed among treatments for tree heights 24 months after planting by Tukey test at 5% probability (Table 12). However, Parrota & Knowles (2003) observed that the replacement of topsoil significantly increased tree heights 10 years after planting of combined tree species in the recovery process of bauxite mined areas in the Amazon region.

Figure 4 – General profile of plant regeneration in treatment C (with topsoil replacement).

Figure 5- General profile of plant regeneration in treatments L and F (without topsoil replacement).

The winter green fertilization applied to the area studied promoted good cover and protection of the soil during the dry season, increasing the dry matter content when organic matter was absent in the soil. Green matter production was more intense (Tukey test, p < 0.05%) in treatments where subsoiling had been carried out (Table 13).

Table 11– Survival of tree species of the regional flora in different treatments 12 months after planting.

C = topsoil + F

F = mineral fertilization + indigenous species + fertilization in the planting hole (2.0 Kg NPK 20:10:20/plant) +15 kg mature cattle manure

L = Mineral fertilization + Crotalaria  juncea  + F

Averages followed by the same letter do not differ by Tukey test at 5% probability.

Table 12 – Effect of subsoiling on tree heights 12 months after planting, ALCOA, Poços de Caldas, MG.

Averages followed by the same letter do not differ by Tukey test at 5% probability.

Table 13 – Influence of subsoiling on dry matter production (kg.ha^-1) from green fertilizer, with and without subsoiling. ALCOA. Poços de Caldas, MG.

Averages followed by the same letter do not differ by Tukey test at 5% probability.

CONCLUSIONS

The management practices conducted in treatments influenced the amounts of P, K and O.M. in the soil. When V% was considered, maintenance fertilization showed to be indispensable 24 months after planting. 

Subsoiling favored the tree canopy development, as well as the production of dry matter in the winter green fertilizer. The topsoil replacement improved the organic matter amounts in the soil and the survival rates of trees.

Subsoiling increased the effective use of rainfall in soils subject to serious runoff due to declivity, as it enhanced water infiltration rates and nutrients absorption.

Topsoil replacement improved fertility, increasing organic matter amounts and biological characteristics essential to the restoration of degraded areas regarding soil microbiota.

More studies are required on the use of litter in the restoration of similar mined areas.

ACKNOWLEGMENTS

The authors thank FAPESP, Fundation of Support for Researche in the State of São Paulo (process # 00/00503-2) for sponsoring the first author in the conduction of his doctorate studies.

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SOIL MANAGEMENT IN THE REVEGETATION OF A DEGRADED AREA BY BAUXITE MINING

*Paulo Roberto Moreira¹; Osvaldo Aulino da Silva²; Nilson Augusto Villa Nova³ – “Im Memorian”; José Carlos Casagrande⁴; Jairo Antonio Mazza⁵.

¹Floresta Negócios Ambientais. Rua Major Antonio Machado de Campos, 301 Ap. 42 –  Cep:13484-315   Jd. Piratininga. Limeira. SP – Brasil.

²UNESP/IB – Depto. de Botânica. Avenida 24-A. 1515- Cep: 13506-900 Bela Vista, Rio Claro, SP – Brasil.

³USP/ESALQ -Departamento de Ciências Exatas. Mail Box 9 – 13418-900 – Piracicaba, SP – Brasil.

⁴UFSCAR – Depto. de Recursos Naturais e Proteção Ambiental Araras. Via Anhangüera. Km 174- Cx.P. 153 – Cep:13600-970 Araras. SP – Brasil.

⁵ ESALQ/USP – Depto de Solos e Nutrição de Plantas. 

* Corresponding author < paulofloresta@terra.com.br