Exploring land use/cover (LULC) change is essential for the sustainable development of ecologically fragile areas. The main objective of this study was to clarify the characteristics and differences in the spatiotemporal changes of LULC on the Loess Plateau (LP) based on the transfer matrix and land use dynamics and to quantitatively describe the impact of natural factors on LULC using a geodetector. The results indicated that the overall LULC change in the LP was characterized by a decrease in the area of cropland, grassland, and bare land, and an increase in the area of woodland and built-up land. This trend shows a clear phase-change characteristic around 2000. LULC changes were primarily affected by human activities in the southeastern agricultural region. The project of returning farmland to forest and grassland had a great impact on LULC change in the central region. Vegetation was sensitive to temperature and precipitation, and the impact of LULC change was significantly higher than that in the humid region in the northwest arid region. NDVI, PRE, and TEM were determined to be the main contributors to LULC changes in the LP. These results provide a scientific basis for the sustainable development of LP.

Purpose: Data support and theoretical basis for bioremediation and treatment of petroleum-contaminated soils in the Loess hills of Yan’an, northern Shaanxi. Methods: The evolutionary characteristics of soil microbial diversity and community structure under different levels of oil pollution were studied by field sampling, indoor simulation experiments, and analyzed through assays, using the mine soils from Yan’an, Shaanxi Province, as the research object. Results: Compared with clean soil, the microbial species in contaminated soil were significantly reduced, the dominant flora changed, and the flora capable of degrading petroleum pollutants increased significantly. The soil microbial diversity and community structure differed, although not significantly, between different pollution levels, but significantly from clean soil. In the uncontaminated soil (CK), the dominant soil microbial genera were mainly Pantoea, Sphingomonas, Thiothrix, and Nocardioides. The abundance of Pseudomonas, Pedobacter, Massilia, Nocardioides, and Acinetobacter in the soil increased after oil contamination, while Thiothrix, Sphingomonas, and Gemmatimonas decreased significantly. Conclusions: After the soil was contaminated with petroleum, the microbial species in the soil decreased significantly, the dominant genera in the soil changed, and the relative abundance of bacteria groups capable of degrading petroleum pollutants increased. The genera that can degrade petroleum pollutants in the petroleum-contaminated soil in the study area mainly include Pseudomonas, Acinetobacter, Pedobacter, Acinetobacter, and Nocardioides, which provide a scientific basis for exploring It provides a scientific basis for exploring remediation methods suitable for petroleum-contaminated soil in this region.

Purpose: This study investigates the feasibility of bio-enhanced microbial remediation of petroleum-contaminated soil, and analyzes the effect of different plant wastes as exogenous stimulants on microbial remediation of petroleum-contaminated soil and the effect on soil microbial community structure, in order to guide the remediation of soil in long-term petroleum-contaminated areas with nutrient-poor soils. Methods: The study was conducted in a representative oil extraction area in the Loess Hills, a typical ecologically fragile area in China. Through indoor simulated addition tests, combined with the determination of soil chemical and microbiological properties, the degradation efficiency of petroleum pollutants and the response characteristics of soil microbial community structure to the addition of different plant wastes in the area were comprehensively analyzed to obtain the optimal exogenous additive and explore the strengthening mechanism of plant wastes on microbial remediation of petroleum-contaminated soil. Results: Compared with the naturally decaying petroleum-contaminated soil, the addition of plant waste increased the degradation rate of petroleum pollutants, that is, it strengthened the degradation power of indigenous degrading bacteria on petroleum pollutants, among which the highest degradation rate of petroleum pollutants was achieved when the exogenous additive was soybean straw; compared with the naturally decaying petroleum-contaminated soil, the addition of soybean straw and dead and fallen leaves of lemon mallow made the microbial species in the contaminated soil significantly reduced and the main dominant flora changed, but the flora capable of degrading petroleum pollutants increased significantly; the addition of exogenous nutrients had significant effects on soil microbial diversity and community structure. Conclusions: Soybean straw can be added to the contaminated soil as the optimal exogenous organic nutrient system, which improves the physicochemical properties of the soil and gives a good living environment for indigenous microorganisms with the function of degrading petroleum pollutants, thus activating the indigenous degrading bacteria in the petroleum-contaminated soil and accelerating their growth and proliferation and new city metabolic activities, laying a foundation for further obtaining efficient, environmentally friendly and low-cost microbial enhanced remediation technology solutions. The foundation for further acquisition of efficient, environmentally friendly, and low-cost microbial-enhanced remediation technology solutions. It is important for improving soil remediation in areas with long-term oil contamination and nutrient-poor soils.

Based on the MOD16A3GF data, spatial regression analysis was conducted to explore the trends of the annual change of AET and the characteristics of its spatial distribution in Mu Us Sandy Land between 2001 and 2020. Combined meteorological data and NDVI data to analyze its effects on AET by trend analysis and correlation coefficient. The results showed that (1) The AET exhibited significant regional differences in Mu Us Sandy Land, with an overall low northwest and high southeast distribution pattern; (2) The AET showed a rapid upward trend from 2001 to 2020, with an average rate of change of 5.68 mm·a-1; (3) The correlation coefficient between AET and precipitation was 0.74, and there was no obvious correlation with temperature; (4) AET was consistent with the NDVI spatial distribution and interannual variation curves. Under the combined influence of precipitation and NDVI, AET increased significantly in Mu Us Sandy Land from 2001 to 2020. Precipitation was the main factor affecting climatic conditions of AET, and NDVI was the dominant factor affecting AET in the same period. This provides a theoretical basis and scientific basis for the conservation and protection of ecological water source in Mu Us Sandy Land.

Northwest China mining area is an important coal production base and ecologically fragile area in China, and it is of great significance to explore the ecological environment quality and influencing factors in the mining area. Focusing on the Northwest China mining area as the study object, an ecological environment quality change evaluation model based on remote sensing ecological index (RSEI) was constructed to comprehensively and intuitively analyze the RSEI change process and influencing factors in the Northwest China mining area. The results indicate: (1) From 2000 to 2021, the ecological environment quality in the Northwest China mining area showed an overall trend of initial increase followed by fluctuations. (2) The evolution of ecological environment quality in the study area was mainly influenced by human factors, affected by the implementation of ecological engineering from 2000 to 2005, and by mining area development from 2005 to 2021. (3) Mining area development has a negative impact on the ecological environment quality of the study area, but subsequent ecological restoration can mitigate the destructive effects of mining development on the ecology. (4) The explanatory power of NDSI (normalized differential soil index) for ecological environment quality is 0.826, and its influence is the most significant. The explanatory powers of WET and NDVI are 0.690 and 0.709 respectively, which play a key role in improving the quality of the ecological environment. It is recommended to implement effective measures, such as afforestation and grass planting for ecological restoration, removal of impervious surface facilities, and controlling the expansion and development speed of built-up areas. These measures can effectively improve the overall ecological environment quality of the study area by enhancing NDVI (normalized difference vegetation index) and WI (wetness index) and reducing NDSI.

Purpose: The present study envisaged the stoichiometry of microbial biomass in petroleum-contaminated soil, in order to study the influence of the petroleum-contaminated soil on the ecosystem stability. Methods: A typical oil well area in the Northern Shaanxi was considered the research object and the oil pollution status was assessed by studying the physical, chemical, and microbiological characteristics of the soil in the area. Results: From the measurement and analysis of the petroleum pollutants in the soil samples, it was observed that the concentration of the petroleum pollutants around all the oil well areas was higher than the critical value of 500 mg/kg. Furthermore, the C to N ratio of 8 soil samples around the oil wells (0.8:1~13.3:1) was lower than that of the control soil samples in most cases and could not reach the nutrient proportion level required by soil microorganisms. It was observed that the oil organic carbon content at 0~10 m from the wellhead was obviously higher than that in other areas, and decreased with an increase in the distance from the well. Based on the determination of soil organic carbon, total nitrogen, total phosphorus, and the soil microbial biomass carbon (SMBC), soil microbial biomass nitrogen (SMBN), and phosphorus content analysis, it was observed that only the soil organic carbon was significantly positively correlated to the oil pollutants in soil. Conclusions: Imbalance in the C to N, SMBC, and SMBN ratio can lead to an acute shortage of the required nutrients than microorganisms, limit the soil microbial reproduction and growth, and thereby slow down the rate of indigenous microbial degradation of petroleum hydrocarbons, so as to reduce the impact of oil pollution on the stability of the entire ecosystem. Therefore, during the remediation of petroleum-contaminated soil in this study area, adequate nutrients need to be reasonably added to the soil.