Native multispecies and fast-growing forest root biomass increase C and N stocks in a reclaimed bauxite mining area.

This study is aimed at evaluating C and N stocks in fractions of soil organic matter (SOM) in an area of bauxite mining under recovery with tree species. We have analyzed the long-term recovery of C and N stocks of organic matter fractions from five types of forest cover (Eucalyptus, Anadenanthera peregrina, mixed plantation of 16 native species, a mined area without vegetation cover as a control site, and a natural forest cover as a reference site). The total organic C (TOC) and N (TN) stocks and also organic matter fractions, particulate organic matter (POM), mineral-associated organic matter (MAOM), microbial biomass (MB), and labile C (LC), were determined, as well as the C/N ratio and the carbon management index (CMI). Although the stocks of TOC and LC, CMI, and MB did not differ between the types of forest cover in the 0-60 cm layer, they were lower than the values in the native forest. Forest cover increases the stocks of TOC, LC, MB, and CMI in the area of bauxite mining compared to the control site. In addition, we found that the TOC C and TN stocks and also SOM fractions (LC, C-MAOM, C-POM, N-MAOM, and N-POM) are positively correlated (r ≥ 0.71 for all cases) with volume of roots larger than 2 mm. Therefore, Eucalyptus, A. peregrina, and a mixed of 16 native trees contribute for restoring stocks of soil C and N following bauxite mining in the Brazilian Atlantic Forest.

Estoque de carbono orgânico total e fracionamento granulométrico da matéria orgânica em sistemas de uso do solo no cerrado / Total organic carbon stock and granulometric fractioning of organic matter in soil use systems in cerrado

Os sistemas de uso do solo apresentam potencial de alterar os estoques de carbono orgânico, podendo permanecer estáveis, aumentar ou diminuir em relação à área sem interferência antrópica. Com isso, objetivou-se quantificar e comparar os estoques de carbono orgânico total, carbono orgânico associado aos minerais, carbono orgânico particulado e calcular o índice de manejo de carbono em solos cultivados sob diferentes sistemas de uso. Os tratamentos foram representados por seis sistemas de uso do solo: vegetação nativa de cerrado, seringueira solteira, seringueira consorciada com abacaxi, pastagem de Brachiaria sp. com 30 anos, pastagem de Brachiaria sp. com três anos e sistema de plantio convencional.  Em cada sistema foram coletadas amostras de solo nas camadas de 0-10, 10-20 e 20-30 cm para avaliar os teores e estoques de carbono no solo, e amostras indeformadas com anéis volumétricos para estimar a densidade do solo. Os resultados foram submetidos à análise pelo teste de Scott-Knott (p≤0,05). O carbono orgânico total e as frações granulométricas da matéria orgânica mostraram ser um atributo promissor para avaliação da qualidade do solo. O carbono orgânico total, carbono orgânico particulado e carbono orgânico associado aos minerais foram superiores para vegetação nativa, pastagem de Brachiaria sp. 30 anos, seguidos pelos sistemas com seringueira. O índice de manejo de carbono...(AU)

Soil use systems have the potential to alter organic carbon stocks and may remain stable, increase, or decrease relative to the area without anthropogenic interference. The objective of this study was to quantify and compare the total organic carbon stock, organic carbon associated with minerals, particulate organic carbon, and calculate the carbon management index in soils grown under different systems of use. The treatments were represented by six systems of soil use: native vegetation of cerrado, single rubber tree, rubber tree with pineapple, Brachiaria sp. with 30 years, a pasture of Brachiaria sp. with three years, and conventional planting system. In each system, soil samples were collected in the 0-10, 10-20 and 20-30 cm layers to evaluate soil carbon contents and stocks, and undisturbed samples with volumetric rings to estimate soil density. The results were analyzed by Scott-Knott test (p≤0.05). The total organic carbon and the grain size fractions of the organic matter showed to be a promising attribute for soil quality evaluation. Total organic carbon, particulate organic carbon, and organic carbon associated with minerals were higher for native vegetation, Brachiaria sp. 30 years, followed by systems with rubber trees. The calculated carbon management index indicated that the use of rubber trees adds benefits to the soil in the medium and long term, followed by the...(AU)

Estoque de carbono orgânico total e fracionamento granulométrico da matéria orgânica em sistemas de uso do solo no cerrado / Total organic carbon stock and granulometric fractioning of organic matter in soil use systems in cerrado

Os sistemas de uso do solo apresentam potencial de alterar os estoques de carbono orgânico, podendo permanecer estáveis, aumentar ou diminuir em relação à área sem interferência antrópica. Com isso, objetivou-se quantificar e comparar os estoques de carbono orgânico total, carbono orgânico associado aos minerais, carbono orgânico particulado e calcular o índice de manejo de carbono em solos cultivados sob diferentes sistemas de uso. Os tratamentos foram representados por seis sistemas de uso do solo: vegetação nativa de cerrado, seringueira solteira, seringueira consorciada com abacaxi, pastagem de Brachiaria sp. com 30 anos, pastagem de Brachiaria sp. com três anos e sistema de plantio convencional.  Em cada sistema foram coletadas amostras de solo nas camadas de 0-10, 10-20 e 20-30 cm para avaliar os teores e estoques de carbono no solo, e amostras indeformadas com anéis volumétricos para estimar a densidade do solo. Os resultados foram submetidos à análise pelo teste de Scott-Knott (p≤0,05). O carbono orgânico total e as frações granulométricas da matéria orgânica mostraram ser um atributo promissor para avaliação da qualidade do solo. O carbono orgânico total, carbono orgânico particulado e carbono orgânico associado aos minerais foram superiores para vegetação nativa, pastagem de Brachiaria sp. 30 anos, seguidos pelos sistemas com seringueira. O índice de manejo de carbono...

Soil use systems have the potential to alter organic carbon stocks and may remain stable, increase, or decrease relative to the area without anthropogenic interference. The objective of this study was to quantify and compare the total organic carbon stock, organic carbon associated with minerals, particulate organic carbon, and calculate the carbon management index in soils grown under different systems of use. The treatments were represented by six systems of soil use: native vegetation of cerrado, single rubber tree, rubber tree with pineapple, Brachiaria sp. with 30 years, a pasture of Brachiaria sp. with three years, and conventional planting system. In each system, soil samples were collected in the 0-10, 10-20 and 20-30 cm layers to evaluate soil carbon contents and stocks, and undisturbed samples with volumetric rings to estimate soil density. The results were analyzed by Scott-Knott test (p≤0.05). The total organic carbon and the grain size fractions of the organic matter showed to be a promising attribute for soil quality evaluation. Total organic carbon, particulate organic carbon, and organic carbon associated with minerals were higher for native vegetation, Brachiaria sp. 30 years, followed by systems with rubber trees. The calculated carbon management index indicated that the use of rubber trees adds benefits to the soil in the medium and long term, followed by the...

Quantity and quality of soil organic matter as a sustainability index under different land uses in Eastern Amazon

Soil organic matter (SOM), which influences chemical, physical and biological soil attributes, is the main form of C found in the soil which can also be used as a soil sustainability index. The aim of this study was to use the quantity and quality of SOM as an indicator to determine the sustainability of different land uses (native vegetation, secondary vegetation, fruit orchards, horticultural areas, degraded pasture, improved pasture, and fields with annual crops) in the eastern Amazon. Improved pasture had higher soil C stock than the other land uses and was similar to the native vegetation, and also presented the highest quantity of C in a stable form in the soil (fraction < 53 μm). According to the C management index, improved pasture is the most similar in use to native vegetation. Changes in land use reduced the soil microbial C content, although the more conservationist systems (fruit orchards, secondary vegetation, and improved pasture) had contents similar to those of the native vegetation. The highest soil microbial quotients were found in fruit orchards and horticultural areas. Well-managed pastures were effective in accumulating C as stable forms in the soil, which demonstrates the sustainability of this land use in the region studied.(AU)

Quantity and quality of soil organic matter as a sustainability index under different land uses in Eastern Amazon

Soil organic matter (SOM), which influences chemical, physical and biological soil attributes, is the main form of C found in the soil which can also be used as a soil sustainability index. The aim of this study was to use the quantity and quality of SOM as an indicator to determine the sustainability of different land uses (native vegetation, secondary vegetation, fruit orchards, horticultural areas, degraded pasture, improved pasture, and fields with annual crops) in the eastern Amazon. Improved pasture had higher soil C stock than the other land uses and was similar to the native vegetation, and also presented the highest quantity of C in a stable form in the soil (fraction < 53 μm). According to the C management index, improved pasture is the most similar in use to native vegetation. Changes in land use reduced the soil microbial C content, although the more conservationist systems (fruit orchards, secondary vegetation, and improved pasture) had contents similar to those of the native vegetation. The highest soil microbial quotients were found in fruit orchards and horticultural areas. Well-managed pastures were effective in accumulating C as stable forms in the soil, which demonstrates the sustainability of this land use in the region studied.

The conversion of grassland to acacia forest as an effective option for net reduction in greenhouse gas emissions.

This study aimed to evaluate the effect of forestation with leguminous Acacia mearnsii De Wild in native grasslands on the soil greenhouse (GHG) fluxes and their main driving factors. The experiment was conducted in the Brazilian Pampa over the period of one year in a six-year-old Acacia plantation, evaluating four treatments: Acacia (AM), Acacia with litter periodically removed (A-l), Acacia after harvest (AH) and native grassland (NG) (reference treatment). Air samples were obtained by the static chamber method, and gas concentrations were evaluated by gas chromatography. Soil and climate factors were monitored. The accumulated fluxes of methane (CH4) and nitrous oxide (N2O) were statistically similar between the soils in the AM and NG treatments, which tended to oxidize CH4 (-1445 and -1752 g C-CH4 ha(-1) yr(-1), respectively) and had low emission of N2O (242 and 316 g N-N2O ha(-1) yr(-1)), most likely influenced by the low water-filled pore space and the low content of mineral N in the soil. However, the soil in the AH treatment presented higher emissions of both gases, totaling 1889 g C-CH4 ha(-1) yr(-1) and 1250 g N-N2O ha(-1) yr(-1). Afforestation neither significantly affected the total organic C stocks nor their lability, keeping the C management index for the forested area similar to that in the NG treatment. The conversion from grassland to Acacia forest represents an effective option for mitigating the net reduction in greenhouse gas emissions, which is basically determined by C accumulation in biomass and wood products.