The stability of alpine grassland ecosystem is closely related to the stability of soil structure. The objectives of this study were to analyze the characteristics of soil aggregates and organic carbon in different degradation stages of alpine grassland in northwest Sichuan, and to build the relationship between soil organic carbon and aggregates. The results showed that the non-degraded grassland was dominated by macro-aggregates (>0.25 mm), while the degraded grassland was dominated by micro-aggregates. Both soil aggregate stability and soil organic carbon content were significantly reduced with the intensification of grassland degradation. The soil organic carbon content in degraded grassland was significantly lower than that in non-degraded grassland, and the fastest decline stages of the soil organic carbon occurred in the transformation processes from non-degraded to lightly degraded. The highest value of the soil aggregate organic carbon appeared in the 0.5-2 mm size, and the organic carbon content of each aggregate also decreased with the grassland degradation. The soil organic carbon and soil aggregate organic carbon were significantly correlated with the stability index of soil aggregate in the process of grassland degradation (P<0.01).

Repeated biogas slurry application in soil may cause accumulation of heavy metals. In the experiment, repeated biogas slurry application for 4 (N1) and 10 years (N2) in two vegetable fields, to detect heavy metal content (Zn, Cu, Cr, Pb) and assessment the risk of shortand long-term fertilizing on ecology and health. The result showed, long-term fertilization has increased the content of heavy metal. Zn and Cu in topsoil (0-20 cm) in field N2 exceed the standard, resulting in mild contamination. The value of hazard quotient (HQ) in the same land were as follows: Cr>Pb>Cu>Zn. In general, the noncarcinogenic risk and carcinogenic risk index in N2 were higher than those of N1. In the survey area, there was no noncarcinogenic risk and carcinogenic risk for adults and children. However, children are more sensitive to environmental changes than adults and should pay more attention to protect their health. Longterm monitoring and evaluation of heavy metal hazards is necessary to ensure the safety of biogas slurry used in farmland.

Very few studies have investigated the factors affecting soil displacement and tillage erosion by hoeing tillage. This study adopted a magnetic tracer method to investigate the influences of hoe form and tillage depth on soil translocation over steep hillslopes in Southwest China using a new type of magnetic tracer, i.e., ilmenite powder. Ilmenite powder enhanced the magnetic sensitivity of soil at the end position of tracer distribution, and improved the accuracy and efficiency of tillage translocation measurements. Tillage translocation by wide and perforated hoes was found to be significantly correlated with slope gradient (P < 0.01), however, no significant correlation was found for narrow and bidentate hoe tillage (P > 0.05). Compared with wide hoes, the tillage erosion rates resulting from the use of narrow, perforated and bidentate hoes were reduced by 12.4%, 11.0%, and 16.3%, respectively, indicating that changes in hoe forms resulted in a marked decrease in downslope soil translocation and tillage erosion. Tillage erosion rate decreased by 64% when the tillage depth was reduced from 0.26 to 0.14 m. These results suggest that innovations in hoe form and reductions in tillage depth are important means to manage tillage erosion due to hoeing.

In arid mountainous areas with stony soils in the Eastern Tibetan Plateau, intensively managed orchards (which include the need for plowing, irrigation, and soil stone removal), eco-forests, and grasslands, all converted from croplands, are becoming increasingly popular. We randomly collected soil samples at 0–15, 15–30, 30–45, and 45–60 cm depths from the four land-use types on the northern and southern slopes in the region. Differences in soil organic carbon (SOC) content/stock, soil water content (SWC), and rock fragment content (RFC) in land-use types and slopes were analyzed using two-way ANOVA. The factors’ contributions to SOC variation were assessed using mixed-effect models. Results showed the following: (1) In topsoil (0–30 cm), SOC contents followed the order eco-forest > orchard > grassland ≈ cropland; in subsoil (30–60 cm), the order was orchard > eco-forest > cropland ≈ grassland. SOC stocks (0–60 cm) were higher in orchards (93.72 Mg ha⁻¹) and eco-forests (92.44 Mg ha⁻¹) than in grasslands (53.65 Mg ha⁻¹) and croplands (53.05 Mg ha⁻¹). Contributions of SOC stocks at the 0–15 cm depth level to total SOC were above 40% for GL and EF and between 27 and 35% for OL and CL; at the 45–60 cm level, OL contributed 16–20% and was higher than 10–15% for the other land-use types. (2) Eco-forests and grasslands showed increased SOC contents/stocks at all soil layers on the northern slope than on the southern one. Orchards and croplands, however, showed no differences in contents between slopes. (3) Land-use types, TN, SWC, RFC, slope aspect, and management practices significantly affected SOC variation. Our results suggest that forest plantations (orchards and eco-forests) in arid mountainous regions, through active management practices (e.g., irrigation and fertilization), are vital for improving soil carbon sinks and achieving peak carbon/carbon neutrality goals.

The objectives of this study were to analyze the research trends and research hotspots of biogas slurry utilization and treatment in the past 20 years (1996-2018) by literature metrology. In the early 21st century, relevant research has increased rapidly. A total of 175 SCI papers with biogas slurry as the keyword were retrieved on the Web of Science. Keywords co-occurrence graphs showed the biogas slurry, growth, yield and nitrogen were the core keywords. The top four journals in the number of articles are Bioresource Technology, Pakistan Journal of Botany, Applied Soil Ecology, Environmental Science and Pollution. The top three cited authors with high central node are Ryckebosch E, Serejo ML, Abdeen Frh. The top four countries with the number of published articles are China, India, Pakistan and Germany. In conclusion, the core development direction of this field is "biogas slaque-quality", and subordinate line is "biogas slurry, waste water treatment, nutrient removal and activated sludge".

Despite the prevalence of postrift volcanoes and underlying igneous plumbing systems in rifted basins at proximal and hyperextended crustal configurations, well-preserved volcanoes and related intrusions are rare within minimally stretched continental blocks (i.e., continental ribbon). It is now possible to investigate the size, age, and geographical distribution of the buried volcanoes from multibeam, single-, and multichannel seismic data recently collected beneath the South China Sea Xisha massif, which we argue is a continental ribbon. These data made it evident that the Middle Miocene volcanoes frequently generated massive volcanic fields that erupted along the rift fault zones in contrast to the Early Miocene volcanoes, which typically built clusters of small-volume volcanic cones in the rift half-graben. Details include the presence of numerous volcanoes above and to the side of the dome-shaped main edifice that constitutes the middle Miocene volcanic field. Intrusive sills beneath volcanoes are isolated and have a dispersed distribution pattern at different levels, whereas dikes beneath volcanoes are numerous and have vertical zones of disruption that connect to underlying faults or extend through the sediments to the crust. The relationship between the volcanoes and intrusions suggests that shallow igneous plumbing systems within the Xisha massif are most likely dike domains. The Xisha massif has favorable conditions, including a relatively thin sedimentary sequence over a slightly extended continental crust (20–28 km) that might provide sufficient magma pressure for an igneous plumbing system that is primarily fed by dikes. In addition, rifted faults in the upper crust and possibly subvertical foliations in the basement rock mass are thought to be viable routes for magma transport vertically. In conclusion, we emphasize the importance of crustal structure on the continental ribbon in controlling igneous plumbing styles and the distribution of postrift volcanic systems along magma-poor continental margins, including crustal thickness, preexisting faults, heterogeneous basement, and sediments.