Abstract
The remediation of opencast bauxite mines in the natural forests of Indonesia is difficult. We have investigated and contrasted the chemical characteristics of soils from natural forests and mining sites and their effects on plant growth. The soil pH, total carbon (C), nitrogen (N) and available phosphorus (P) concentrations, cation exchange capacity, C/N ratio, and exchangeable K, Na, Mg, Ca, Fe, and Ni concentrations were determined. Falcataria moluccana and Albizia saman were then grown in these soils for 15 weeks, and their shoot heights, shoot dry weights, and root dry weights determined. The post bauxite mining soils’ N, C, and available P concentrations and exchangeable Ca, Mg, and Na concentrations decreased by 75, 75.7, 15.7, 92, 100, and 52%, respectively, in comparison with the natural forest soils. The shoot and root dry weights of F. moluccana when grown in the post bauxite mining soils were also lower than those from the natural forest soils. However, there was no difference in the shoot and root dry weights of A. saman when grown in the two soil types. The results suggest that opencast mining decreases the soil fertility, which in turn inhibits the initial growth of tree seedlings, and reduces the carbon stock in the land.
Highlights
Introduction e tropical rainforests on theIndonesian islands of the Riau Archipelago (Sumatera) vary greatly in their biodiversity but have soils that are generally poor in nutrients
While the material organic content of tropical soils is low overall, the decomposition processes on the forest floor and nutrient uptake are fast [1]. e organic carbon in tropical forests declined with depth, in the topsoil layer of East Kalimantan, Indonesia [2]
Opencast bauxite mining decreased the soil fertility overall and the TN concentrations by 75% (Table 1). e reduction was due to the removal of tree cover, litter, and topsoil by the processes used to create the opencast mines. e reduction was higher than the 53% reduction reported for soil from an opencast coal mining site in India [16] and the 53–80% reduction in soil from an opencast coal mining site in the U.S.A. [17]. e effect of opencast mining on soil fertility in tropical areas is higher than that in nontropical areas. e reduction in TN was higher than the 45% reduction in farmland compared with forests [18] and the 36% reduction after forest fires [19]
Summary
Introduction e tropical rainforests on theIndonesian islands of the Riau Archipelago (Sumatera) vary greatly in their biodiversity but have soils that are generally poor in nutrients. The biomass is the major pool for nutrients and not the forest soil content, as is found in temperate forests. While the material organic content of tropical soils is low overall, the decomposition processes on the forest floor and nutrient uptake are fast [1]. E organic carbon in tropical forests declined with depth, in the topsoil layer of East Kalimantan, Indonesia [2]. Knowing the characteristics of the soil in tropical rainforests is important to take a strategic step in the process of rehabilitation of degraded land. Is process affects the landscape of the local environment and its social well-being, as it causes tremendous physical, chemical, and biological damage to forests, impacting on their vegetation and animal biodiversity [5]. A study provides a selection of 20 forest plant native species for increasing biodiversity and restoration of area disturbed by petroleum extraction activities in the Ecuadorian Amazon [8]
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