Research in Cold and Arid Regions最新文献

Assessment of land sensitivity to desertification is an important step to support desertification monitoring and control. Based on the Mediterranean Desertification and Land Use (MEDALUS) model, we defined four quality indicators (soil, climate, vegetation and management) to evaluate the sensitivity of land in northern China to desertification. We improved MEDALUS via excluding cities from the areas at risk of desertification by means of defining a threshold value for population density. The framework, validated in northern China, further optimizes the model to link priority areas and land restoration programmed to support desertification control. We found that the four indicators influenced and restricted each other, which jointly affected the distribution of desertification sensitivity in northern China. The spatial distribution of sensitivity in northern China showed large regional differences, with clear boundaries and concentrated distributions of regions with high and low sensitivity; the overall sensitivity decreased, with some areas rated as having moderate, severe, and extremely severe sensitivity changing to slight sensitivity; and the influence weight was much higher for the management quality index than for the climate, vegetation, and soil indexes. This suggests that management was the main factor that affected desertification sensitivity in northern China, and that climate factors exacerbated sensitivity, but the factors that are driving the spatial heterogeneity of the influencing factors need further study.

Over the last few decades, the ecological quality of the Qinghai–Tibet Plateau (QTP) has significantly changed due to climate warming, humidification, and increasing human activities. Thus, evaluating this region's ecological quality and dominant factors is crucial for sustainable development. In this study, the changes in the ecological quality on the QTP from 2000 to 2020 were evaluated based on aggregated indices and Sen–MK trend analyses, and the dominant factors affecting the ecological quality of the QTP were quantitatively analyzed using decision tree classification. The results revealed that (1) the ecological quality of the QTP exhibited an overall high trend in the east and a low pattern in the west; (2) the ecological quality of the QTP significantly increased from 2000 to 2020, and human activities were the dominant factors causing this change; and (3) the changes in the ecological quality and dominant factors exhibited obvious spatiotemporal heterogeneity. The area with an improved ecological quality occurred mainly in the northern QTP region. It was governed by human activities and precipitation. In contrast, the area with a deteriorated ecological quality occurred largely in the southern QTP region and was dominated by human activities and temperature. The 2000–2010 period was the most significant period of heterogeneity regarding of ecological quality and its driving factors. (4) The change in the ecological quality was mainly affected by the synergistic relationship between human activities and climate change in this region, which encompassed multiple dominant factors. This study provides important information on the spatiotemporal heterogeneity of ecological quality change and its dominant factors on the QTP and offers systematic guidance for the planning and implementation of ecological protection projects.

Salinized soil is an important reserved arable land resource in China. The management and utilization of salinized soil can safeguard the current size of arable land and a stable grain yield. Salt accumulation will lead to the deterioration of soil properties, destroy soil production potential and damage soil ecological functions, which in turn will threaten global water and soil resources and food security, and affect sustainable socio-economic development. Microorganisms are important components of salinized soil. Microbial remediation is an important research tool in improving salinized soil and is key to realizing sustainable development of agriculture and the ecosystem. Knowledge about the impact of salinization on soil properties and measures using microorganisms in remediation of salinized soil has grown over time. However, the mechanisms governing these impacts and the ecological principles for microbial remediation are scarce. Thus, it is imperative to summarize the effects of salinization on soil physical, chemical, and microbial properties, and then review the related mechanisms of halophilic and halotolerant microorganisms in salinized soil remediation via direct and indirect pathways. The stability, persistence, and safety of the microbial remediation effect is also highlighted in this review to further promote the application of microbial remediation in salinized soil. The objective of this review is to provide reference and theoretical support for the improvement and utilization of salinized soil.

Oil leakages cause environmental pollution, economic losses, and even engineering safety accidents. In cold regions, researchers urgently investigate the movement of oil spill in soils exposed to freeze-thaw cycles. In this study, a series of laboratory model experiments were carried out on the migration of oil leakage under freeze-thaw action, and the distributions of the soil temperature, unfrozen water content, and displacement were analyzed. The results showed that under freeze-thaw action, liquid water in soils migrated to the freezing front and accumulated. After the pipe cracked, oil pollutants first gathered at one side of the leak hole, and then moved around. The pipe wall temperature affected the soil temperature field, and the thermal influence range below and transverse the pipe wall (35–40 cm) was larger than that above the pipe wall (8 cm) owing to the soil surface temperature. The leaked oil's temperature would make the temperature of the surrounding soil rise. Oil would inhibit the cooling of the soils. Besides, oil migration was significantly affected by the gravity and water flow patterns. The freeze-thaw action would affect the migration of the oil, which was mainly manifested as inhibiting the diffusion and movement of oil when soils were frozen. Unfrozen water transport caused by freeze-thaw cycles would also inhibit oil migration. The research results would provide a scientific reference for understanding the relationship between the movement of oil pollutants, water, and soil temperature, and for establishing a water-heat-mass transport model in frozen soils.

Development of urban human settlement environments (HSEs) is an integral part of promoting high-quality and sustainable regional development and constructing a beautiful China. The city of Lanzhou, located at the geometric center of China, is the only provincial capital traversed by the Yellow River. Given the constraints posed by the valley topography and the need for economic development, the development of this HSE, which is located within an arid region, poses considerable challenges. Evidently, an understanding of the evolution of HSEs and drivers of changes in them contributes to high-quality, sustainable urban development in arid and semi-arid regions. An analytical model was developed using the parameters of relief degree of land surface, human comfort days, the land cover index, nighttime light index, and precipitation. This model was used in combination with population density and the gross domestic product to analyze the spatial distribution of Lanzhou's HSE and its drivers. The results showed that landscapes in Lanzhou underwent significant changes between 2000 and 2022, with an increase in building-up land (+0.946%), cultivated land (+0.134%), and forest land (+0.018%) and a decrease in grassland (−1.10%). There was significant outward expansion of the main urban zone of Lanzhou and of various county towns, with the increase in building-up land being most prominent. During this period, there were significant changes in the periphery of the core urban area and county towns in Lanzhou, with decreases moving from the urban center (the highest value) to the surrounding areas (Yongdeng County had the lowest value). The correlation between the HSE and population density grew stronger in Anning and Chengguan Districts but became weaker in Xigu and Qilihe Districts. Spatiotemporal variations in the HSE were primarily caused by climate change, followed by human activities, and were also influenced by the valley topography. Overall, the spatial distribution of population density and the HSE in Lanzhou demonstrated good consistency under the influence of economic development and urbanization.

The annual distribution characteristics of river runoff in arid regions have significant implications for water resource stability and management. Based on the mountain runoff data from 1965 to 2018, this study examines the annual change characteristics of monthly runoff of the Shiyang River Basin, Heihe River Basin, and Shule River Basin in the Hexi Corridor, Northwest China. Many indexes are used and analyzed, including the coefficient of variance, the complete regulation coefficient, the concentration degree and concentration period, the magnitude of change, the skewness coefficient, and the kurtosis coefficient of the annual distribution curves. The results reveal the following: (1) The inhomogeneity of annual runoff distribution in the Taolai River and the rivers to the west of it, except the Shiyou River, show an increasing trend. Conversely, the inhomogeneity of the rivers to the east of the Taolai River generally show a downward trend, but the coefficient of variance value is still very high. (2) In the Shiyang River Basin, the annual distribution of the concentration period is characterized by a relatively discrete pattern. Conversely, the Heihe River Basin exhibits a relatively concentrated pattern, and the distribution pattern of the Shule River Basin is quite different. Notably, all concentration periods in the three basins have shifted backward after the 2000s. (3) The Shiyang River Basin exhibits disordered annual distribution curves of runoff in different years. In contrast, the Heihe River Basin presents a typical ‘single-peak’ pattern with a prominent right-skewed. The Shule River Basin has regular distribution curves, with a gradually significant ‘double-peak’ pattern from east to west. Overall, there has been a slight change in runoff in the Shiyang River Basin, while the Heihe River Basin and Shule River Basin have experienced significant increases in runoff. The annual distribution curves of runoff in the Liyuan River and the rivers to the east of it exhibit a gentle peak pattern, and the appearance probability of extreme runoff during the year is low. Conversely, the rivers to the west of the Liyuan River, excluding the Danghe River, display a sharp peak and thick tail pattern, indicating that the appearance probability of extreme runoff during the year is high. These findings have practical implications for the planning and management of water resources in the Hexi Corridor. Moreover, they provide a solid foundation for predicting future changes in regional water resources.

Biological soil crusts (BSCs) play an important role in soil development and ecological function, and it is more important for quantitatively analyzing the processes and trends of BSCs to identify the advantages and disadvantages of BSCs research for the development and application of BSCs theory. Bibliometric analysis of 2,186 BSCs literatures from Web of Science showed an exponential growth trend, as China and the United States as the top 2 in terms of publication volume. High quality publications are mainly from European and American countries, such as the United States, Germany and Spain. The top 3 publishers are Journal of Arid Environments, Soil Biology & Biochemistry and Plant and Soil, and disciplines include ecology, environmental science, and soil science, etc.. Research institutions mainly affiliate to the Chinese Academy of Sciences, United States Department of the Interior, United States Geological Survey, Hebrew University of Jerusalem, Consejo Superior de Investigaciones Cientificas, and Universidad Rey Juan Carlos. Authors mainly come from United States, Israel, Spain and China. Funds are mainly from the National Natural Science Foundation of China, Spanish Government, Chinese Academy of Sciences, and National Science Foundation of the United States. Biological soil crusts (biocrusts, cyanobacteria, lichens, moss crusts, bryophytes), drylands, climate change, photosynthesis and desert are high-frequency keywords. Future research will focus on the driving mechanisms of BSCs on global biogeochemical cycles, maintaining global biodiversity on important ecological processes, global C, N, and P cycles. The impact on biological invasion, sandstorms, and water balance, multifunctional and reciprocal mechanisms for maintaining the stability of desert and sandy ecosystems, and impact on the formulation of management policies for arid ecosystems, corresponding to global climate change, and the estimation of regional, local, and microscale distribution of BSCs based on machine deep learning modeling gradually focus on. The ecosystem service functions of BSCs, the soil and water conservation and soil stability mediated by BSCs in arid and semi-arid regions, and the excavation of stress resistant genes for BSCs will be emphasized.

This paper aims to comprehensively analyze the influence of the principal stress angle rotation and intermediate principal stress on loess's strength and deformation characteristics. A hollow cylinder torsional shear apparatus was utilized to conduct tests on remolded samples under both normal and frozen conditions to investigate the mechanical properties and deformation behavior of loess under complex stress conditions. The results indicate significant differences in the internal changes of soil particles, unfrozen water, and relative positions in soil samples under normal and frozen conditions, leading to noticeable variations in strength and strain development. In frozen state, loess experiences primarily compressive failure with a slow growth of cracks, while at normal temperature, it predominantly exhibits shear failure. With the increase in the principal stress angle, the deformation patterns of the soil samples under different conditions become essentially consistent, gradually transitioning from compression to extension, accompanied by a reduction in axial strength. The gradual increase in the principal stress axis angle (α) reduces the strength of the generalized shear stress and shear strain curves. Under an increasing α, frozen soil exhibits strain-hardening characteristics, with the maximum shear strength occurring at α = 45°. The intermediate principal stress coefficient (b) also significantly impacts the strength of frozen soil, with an increasing b resulting in a gradual decrease in generalized shear stress strength. This study provides a reference for comprehensively exploring the mechanical properties of soil under traffic load and a reliable theoretical basis for the design and maintenance of roadbeds.