The sustained intensification of agricultural production to meet increasing food, feed and fibre demands has aggravated soil deformation, thereby accelerating soil degradation. The conversion of some of these degraded arable lands to permanent grassland has been recommended to recover the soil functions. However, there is still a considerable gap in understanding the timeline for the effective recovery of degraded land in terms of its stability (resistance and resilience to disturbance). Moreover, the dynamics of the recovery process in ameliorative grasslands are still not fully understood. In this study, the physical, hydraulic, and mechanical properties including the coefficient of compressibility (Cn) and precompression stress were investigated in degraded arable land at three different depths (0-5, 10-15 and 20-25 cm) after 1-, 2-, 8-, 13-, 19-, and 25-years ameliorative grassland conversion. To fully understand and finalise the dynamics of the recovery process as a function of time since the amelioratory conversion, we combined the analysed data from 2 different sets of measurements (loading conditions) on samples predrained to - 60 hPa matric potential. The loading conditions were (a). static confined compression with normal stresses applied for 4 h in steps of 1, 20, 50, 100, 200, and 400 kPa without stress relaxation on each sample, and (b). dynamic - cyclic loading at 50 kPa with 30 seconds of loading and unloading (relaxation). We included data concerning porewater pressure dynamics under the cyclic loading condition to document possible changes in elasticity. Our results showed that settlement during loading and the elastic rebound during unloading were related to the sward age and the sampled depth. Before the cyclic loading experiment, higher values of effective stress were recorded in the older swards, but the values changed after loading in response to the change in the porewater pressure. The effective stress values were less negative during loading than when unloading. At soil depth of 0-5 cm in the 25 years old sward, the rebound rate (values) and the coefficient of compressibility were higher due to changes in soil properties, particularly the soil bulk density, while at the 10-15 and 20-25 cm depths, the mean values were much closer. When the rebound rate was considered, the highest mean value occurred at 13 years after conversion. In addition, significantly higher values of pre-compression stress were observed in the 8-year-old sward under static loading, which decreased by 19 years. Higher values of pre-compression stress were mostly recorded at the lower depths under static loading. Finally, the results showed that a period between 8 and 13 years is needed to document the starting of strength regain and the recovery of the physical properties and functions, after conversion to grassland. This recovery was observed even up to deeper depths of 20-25 cm for precompression stress and for the soil compressibility/ rebound in the top 5 cm

Antimony smelting activities damage the soil and vegetation surroundings while generating economic value. However, no standardized methods are available to diagnose the extent of soil degradation at antimony smelting sites. This study developed a standardized framework for assessing soil quality by considering microbial-induced resilience and heavy metal contamination at Xikuangshan antimony smelting site. The soil resilience index (SRI) and soil contamination index (SCI) were calculated by Minimum Data Set and geo-accumulation model, respectively. After standardized by a multi-criteria quantitative procedure of modified Nemerow's pollution index (NPI), the integrated assessment of soil quality index (SQI), which is the minimum of SRINPI and SCINPI, was achieved. The results showed that Sb and As were the prominent metal(loid) pollutants, and significant correlations between SQI and SRI indicated that the poor soil quality was mainly caused by the low level of soil resilience. The primary limiting factors of SRI were Fungi in high and middle contaminated areas, and Skermanella in low contaminated area, suggesting that the weak soil resilience was caused by low specific microbial abundances. Microbial regulation and phytoremediation are greatly required to improve the soil quality at antimony smelting sites from the perspectives of pollution control and resilience improvement. This study improves our understanding of ecological effects of antimony smelting sites and provides a theoretical basis for ecological restoration and sustainable development of mining areas. (c) 2024 The Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences. Published by Elsevier B.V.

Flooded rice cultivation, accounting for 75% of global rice production, significantly influences soil redox potential, element speciation, pH, and nutrient availability, presenting challenges such as extensive water usage and altered soil properties. This study investigates bacterial community dynamics in rice soils subjected to repeated draining and flooding in Rio Grande do Sul, Brazil. We demonstrate that bacterial communities exhibit remarkable resilience (the capacity to recover after being altered by a disturbance) but cannot remain stable after long-term exposure to environmental changes. The beta diversity analysis revealed four distinct community states after 11 draining/flooding cycles, indicating resilience over successive environment changes. However, the consistent environmental disturbance reduced microbial resilience, causing the bacterial community structure to shift over time. Those differences were driven by substitutions of taxa and functions and not by the loss of diversity. Notable shifts included a decline in Acidobacteria and an increase in Proteobacteria and Chloroflexi. Increased Verrucomicrobia abundance corresponded with lower pH levels. Functional predictions suggested dynamic metabolic responses, with increased nitrification during drained cycles and a surge in fermenters after the sixth cycle. Despite cyclic disturbances, bacterial communities exhibit resilience, contributing to stable ecosystem functioning in flooded rice soils. These findings enhance our understanding of microbial adaptation, providing insights into sustainable rice cultivation and soil management practices.