Changes in total organic carbon and organic carbon fractions of reclaimed minesoils in response to the filling of different substrates

Short-term high-temperature pretreated compost increases its application value by altering key bacteria phenotypes

Short-term high-temperature pretreatment can effectively shorten the maturity period of organic waste composting and improve the fertilizer efficiency and humification degree of products. To investigate the effect and mechanism of the end products on the saline-alkali soil improvement and plant growth, the short-term high-temperature pretreatment composting (SHC) and traditional composting (STC) were separately blended with saline-alkali soil in a ratio of 0-40 % to establish a soil-fertilizer blended matrix for cultivating Lolium perenne L. The pot experiments combined with principal component analysis showed Lolium perenne L. planted in 20 % SHC-blended saline-alkali soil had the best growth effect, and its biomass, chlorophyll content, and plant height were 109-113 % higher than STC. The soil physicochemical property analysis showed that SHC and STC increased the soil nutrient content, humification degree, and enzyme activity at any blending ratio. The microbial analysis showed that 20 % SHC in the saline-alkali soil stimulated the growth of functional microorganisms and the addition of SHC promoted the sulfur cycle, nitrogen fixation, and carbon metabolism in the soil-plant system. The correlation analysis showed that pH; nutrient contents; and urease, catalase, sucrase, and phosphatase activities in the saline-alkali soil were significantly correlated with plant growth indexes (p < 0.05). Georgenia and norank_f__Fodinicurvataceae had a stronger correlation with four types of enzyme activities (p < 0.01). SHC improved the saline-alkali soil and promoted plant growth by adjusting soil pH, increasing soil nutrients, and influencing soil enzyme activity and dominant flora. This study provides a theoretical basis for applying SHC products in soil improvement.

Effects of land reclamation on soil organic carbon and its components in reclaimed coal mining subsidence areas

The accumulation of soil organic carbon (SOC) is crucial for the development and ecosystem function restoration of reclaimed mine soils (RMSs). To optimize reclamation management practices, this study aims to explore the factors and underlying mechanisms influencing the recovery of SOC and its components in RMSs from a systemic perspective using complex network theory (CNT). This study focused on coal mining subsidence areas in the eastern mining regions of China, comparing reclaimed cultivated land with surrounding non-subsided cultivated land. Soil samples were collected at depths of 0-20 cm, 20-40 cm, and 40-60 cm, and 25 soil indicators were measured. CNT was applied to explore the intricate relationships between soil indicators and to identify the key factors and underlying mechanisms influencing SOC and its components in RMSs. The results revealed that the compaction-induced soil structural damage during the reclamation process led to a chain reaction, resulting in increased soil bulk density (11.92 % to 15.03 %), finer soil particles (5.00 % to 9.88 % more clay and silt), and enhanced SOC mineralization (SOC decreased by 10.70 % to 15.62 % with a lower C/N ratio by 2.30 % to 28.55 %). Microbial activity also decreased, with a 6.25 % to 13.16 % drop in MBC and a 0.91 % to 27.68 % decrease in enzyme activity. The utilization of active SOC fractions by more adaptable bacterial communities was crucial within this chain reaction process. The intermediate role of soil structure in the RMS ecosystem, particularly in carbon cycling, becomes more prominent. RMSs exhibited heightened sensitivity to soil structure changes, with the response of microorganisms and enzymes to soil structure changes being pivotal. In the carbon cycling process of RMSs, microbial-driven enzyme activity in response to soil structure was more critical during SOC transformation, while the role of physical-chemical protection and microbial inhibition mediated by iron‑aluminum oxides became more pronounced in stabilizing SOC.