Organic Matter Fractions and Quality of the Surface Layer of a Constructed and Vegetated Soil After Coal Mining. II - Physical Compartments and Carbon Management Index

Abstract

soils constructed after mining often have low carbon (c) stocks and low quality of organic matter (OM). cover crops are decisive for the recovery process of these stocks, improving the quality of constructed soils. therefore, the goal of this study was to evaluate the effect of cover crops on total organic c (tOc) stocks, c distribution in physical fractions of OM and the c management index (cMi) of a soil constructed after coal mining. the experiment was initiated in 2003 with six treatments: Hemarthria altissima (t1), Paspalum notatum (t2), Cynodon dactylon (t3), Urochloa brizantha (t4), bare constructed soil (t5), and natural soil (t6). soil samples were collected in 2009 from the 0.00-0.03 m layer, and the tOc and c stocks in the physical particle size fractions (carbon in the coarse fraction -ccF, and mineral-associated carbon -Mac) and density fractions (free light fraction -FlF; occluded light fraction -OlF, and heavy fraction -hF) of OM were determined. the cMi components: carbon pool index (cPi), lability (l) and lability index (li) were estimated by both fractionation methods. no

Initial Recovery of Organic Matter of a Grass-Covered Constructed Soil after Coal Mining

“…According to the authors, this was due to the higher efficiency of the density method in the recovery of the labile OM fraction. These data corroborate results of Leal et al (2015b). In a soil constructed after coal mining and covered with grasses for six years, these authors found a high correlation (r = 0.95; p<0.05) between CMI estimated from particle-size and from density (separated with SPT) OM fractions, and greater sensitivity of the density-based CMI to distinguish the most appropriate plant species for the recovery of the quality of the constructed soil.…”

“…On average, the cover crop treatments accounted for only 24 % of the stock in natural soil, indicating that it will probably take years/decades of cultivation until the C stock in the FLF of covered constructed soil reaches that of natural soil. Results in this direction were observed by Leal et al (2015b) in the 0.00-0.03 m layer of a constructed soil covered with grasses after coal mining. After six years of cover crops cultivation, the authors observed that the C stocks in the FLF of covered constructed soil were on average 237 % higher than those in bare constructed soil, but represented only 39 % of the stock in the natural soil.…”

“…The MAC fraction consists of less labile organic material, subject to different protection mechanisms involved in OM stabilization, including protection within microaggregates, in this case <0.053 mm (Carter and Stewart, 1996;Bayer et al, 2004) and interactions with the surface of mineral particles (electrostatic attraction -outer sphere complex, sorption by cation bridge -internal sphere complex, protonation, hydrophobic interactions), forming organo-mineral complexes (Dick et al, 2009). These factors make the MAC fraction less sensitive to different soil management/crop systems and more stable in comparison to the CCF fraction (Bayer et al, 2004;Leal et al, 2015b). Therefore, the MAC fraction often contains higher TOC proportions, playing a key role in maintaining the soil TOC stocks.…”

“…In recently constructed soils, where OM consists predominantly of less labile material, I LIF is expected to decrease over the first years of revegetation, due to the reduced soil disturbance, the protection of the soil surface against erosion, the incorporation of plant residues into the soil, and the OM protection within aggregates (Leal et al, 2015b). Studies on OM including spectroscopic techniques associated with fractionation methods are common in soils under agricultural cultivation (Roscoe et al, 2001;Bayer et al, 2002;Dieckow et al, 2005;Boeni et al, 2014).…”

Reclamation of a Degraded Coal-Mining Area with Perennial Cover Crops

“…A constructed minesoil is usually compacted by excessive machine traffic, which results in inadequate physical conditions for plant growth and development (Lunardi Neto et al, 2008;Sheoran et al, 2010;Borůvka et al, 2012;Stumpf et al, 2014;Sena et al, 2015), as well as a decrease in the biodiversity of soil fauna (Oliveira Filho et al, 2014) and carbon losses due to mechanical mixing of soil horizons (A, B, and/or C) during the operations of removal, transport, and placement of the soil (Ussiri and Lal, 2005;Leal et al, 2015). In addition to these impacts, in mine waste piles derived from coal processing (usually enriched in pyrite), the process of soil aggregation and structuring by the root system of cover crops can promote input of oxygen and water and increase the development of acid mine drainage in the reclaimed area (Quiñones et al, 2008;Campaner and Luiz-Silva, 2009;Costa and Zocche, 2009;Inda et al, 2010;Daniels and Zipper, 2010;Moura, 2014) Reclamation of a mined area should return a degraded ecosystem to a non-degraded condition, which may be different from the original environment (Ibama, 2011).…”