Sandy Land Research Articles

Multisource Remote Sensing Monitoring and Analysis of the Driving Forces of Vegetation Restoration in the Mu Us Sandy Land

The Mu Us Sandy Land is a key region of man-made desert control and farmland to forest (grass) return in China. Despite global change and the strong influence of human activities, the vegetation in this region has been significantly improved and restored. In this study, multisource remote sensing data and multiple indicators were used to quantitatively monitor and evaluate the vegetation restoration status in this area. The driving factors were also analysed. The results show that in the past 20 years, nearly the entire Mu Us Sandy Land significantly and substantively recovered. The regional fractional vegetation cover increased, with an average annual growth rate of 0.59% and obvious spatial heterogeneity. The nine most important driving factors could comprehensively account for 58.38% of the spatial distribution of the vegetation coverage. Factors such as land use and land cover, the aridity index, and gross domestic product had the most significant impact, followed by precipitation and temperature. The results confirmed that the vegetation was restored and improved in the Mu Us Sandy Land and determined the main driving factors, which is helpful for vegetation restoration and ecological improvement on sandy land similar to the Mu Us Sandy Land.

Double Production of Shallot (Allium cepa L var. aggregatum) based on Climate, Water, and Soil Management in Sandy Land

The objective of this study was to double production by True Shallot Seed (TSS) in sandy land agro-ecosystems, widely adapted especially in temperate climate regions. Even though vegetative planting has been carried out using tubers in rice fields and dry land in Indonesia, not much has been done on sandy land. Another research gap also presents from the considerably low actual productivity (10-15 t ha-1) that still can be doubled (>20 - 30 t ha-1) in sandy land. The study used three varieties (Lokananta, Bima, and Trisula) and carried out in three stages: characterization and identification of soil biophysical properties, an in-site study of the seed nursery system of TSS, and an assessment of cultivation development based on plant populations increasing production. This study resulted in TSS productivity 30.66-236.00% higher than average national productivity for all three varieties; this is a novel finding. TSS productivity on sandy land ranging from 14.831 to 28.178 t ha-1 was above the national average production at 10.48 t ha-1 of bulb-seed originated shallots. Thus, this result indicates that TSS seed planting system is more profitable, particularly for shallot seed producers (traders and farmers), aside from saving transportation costs. Another benefit is supporting planning and agronomy development, especially the progress of planting shallot from seeds in Indonesia.

Grain-size composition of the surface sediments in Chinese deserts and the associated dust emission

Chinese deserts are one of the essential source areas for global dust emission, and the intensity of dust emissions varies significantly depending on the grain-size composition of sediments, wind force, and vegetation coverage. To obtain complete and accurate information on the grain-size compositions of the surface sediments in these deserts and to assess the contribution of Chinese deserts to Asian dust emission, we systematically collected surface sediments from 12 deserts in northern China, and analyzed their grain-size composition. We also calculated dust emissions from 2010 to 2019 based on the sand transport rate and clay content. The mean grain-size of surface sediments was 2.34Φ, and the clay and silt contents were only 0.6 and 6.7%, respectively. The Taklimakan Desert had the finest surface sediment, with a mean grain-size of 2.75Φ, whereas the Kumtag Desert had the coarsest sediment, with a mean grain-size of 2.00Φ. The total annual dust emission of the Chinese deserts from 2010 to 2019 was 70.6 Tg y-1. The Taklimakan Desert in the western region, the Badain Jaran Desert and the adjacent Tengger and Ulan Buh deserts in the central region, and the Otindag Sandy Land in the eastern region were the greatest contributors to dust emission. These core areas of dust emission are also the regions with the highest dust storm frequency, indicating that the deserts are significant regions for dust storms in northern China and an important surface type for dust emission in China. We found a significant positive correlation between dust emission and dust storm frequency.

A comparison of multiple methods for mapping groundwater levels in the Mu Us Sandy Land, China

Study regionMu Us Sandy Land, China. Study focusThe groundwater table in unconfined aquifers is often a subdued replica of the topography or land surface. In hilly terrain, spatial interpolation methods are prone to errors such as higher interpolation water level than the ground surface due to sparse observation wells. Meanwhile, in ridge areas, groundwater depth can easily be overestimated with limited groundwater observations. To address these issues, this paper proposes a framework to learn groundwater depth using related groundwater variables based on the extreme gradient boosting (XGB) machine learning method. Moreover, the groundwater level map is drawn based on the predicted groundwater depths and elevation data.New Hydrological Insights for the RegionThe results obtained by the XGB algorithm are compared with those of common interpolation methods (including inverse distance weighting, ordinary kriging, and collaborative ordinary kriging) and machine learning methods (including multiple linear regression, geographically weighted regression, support vector regression, and random forest). The results showed that the XGB using the Tweedie loss function performs best in learning groundwater depth compared with interpolation methods and other machine learning methods, and almost completely overcomes the effects of imbalanced data. The topographic factors such as elevation, topographic position index, and topographic roughness index are key factors for groundwater depth. This study provides a reference for improving regional GL mapping, especially in areas of complex terrain.

Inoculation of Merapi Indigenous Rhizobacteria as A Substitute Compost for Application in Rice Cultivation on Coastal Sandy Under Drought Stress

This study aimed to determine the role of the indigenous rhizobacteria from Merapi as a substitute for compost in rice cultivation on coastal sandy land under drought stress. The study was a single-factor experiment, with types and doses of compost as treatments, arranged in a completely randomized design (CRD) consisting of seven treatments and three replications. The seven treatments tested were cow manure compost at doses of 30 and 40 tons/ha, chicken manure compost at doses of 30 and 40 tons/ha, Azolla compost at doses of 20 and 30 tons/ha, and without compost as a control treatment. Each experimental unit consisted of three plants for destructive sampling, three sample plants, and a substitute plant. The application of cow manure compost at a dose of 30 tons/ha to the rice plants inoculated with MB and MD isolates of Merapi indigenous rhizobacteria resulted in the best growth at five weeks after planting, which was not significantly different from that without compost application. This result indicated that the rice plants cv. Segreng Handayani inoculated with Merapi indigenous rhizobacteria, cultivated on coastal sandy soil under drought stress, even without the application of compost, could give the same responses as the plants treated with various types and doses of compost.

Dust emissions in the Beijing-Tianjin sandstorm source and their regional differentiation

<p indent="0mm">Dust emissions caused by soil wind erosion are the primary natural source of inhalable particulate matter in dust source areas and downwind atmospheric environments. Accurate estimations of dust emissions are foundational for understanding the mechanism of sandstorm occurrences and their transport processes. They are also the basis on which planning and decision-making for sand control and atmospheric environment governance are made. Based on field surveys, surface soil collections, laboratory experiments, remote sensing images, meteorological data, and model simulation, this paper estimated the amount of dust emissions for four different particle size groups (0–2.5, 2.5–5, 5–10, <sc>10–20 μm)</sc> in four different periods (2000, 2005, 2010, 2015), revealed the temporal and spatial distributions of dust emissions from Beijing-Tianjin sandstorm sources and their responses to particle size changes, and clarified the contributions to dust emissions by different land uses. The main conclusions are as follows: (1) Due to climate change, the amount of dust emissions in the Beijing-Tianjin sandstorm source has fluctuated since the implementation of the Beijing-Tianjin sandstorm source control project. In 2000, 2005, 2010 and 2015, dust emissions were 3.24 × 10⁷, 2.76 × 10⁷, 3.44 × 10⁷, and 3.26 × <sc>10⁷ t,</sc> respectively. These emissions demonstrated a clear pattern throughout the year. From January to April, they increased monthly, peaked in April, decreased throughout May, maintained the lowest yearly value from June to September, and increased again in November. These results indicate that dust emissions in Beijing-Tianjin sandstorm sources have obvious seasonal characteristics. The emission amounts descended in the following order: spring, winter, autumn and summer. Their average proportions were 45.45%, 28.14%, 15.99% and 10.42%, respectively. (2) The three subareas, such as the agricultural and animal husbandry interlaced belt subarea, the desert steppe, and the northern Shanxi mountain hills subarea, were the main source of dust emission in Beijing-Tianjin sandstorm sources, accounting for 55.29% of the total amount. The total amount of dust emissions for the above three subareas was 2.64 times those of the four deserts or sandy land in Beijing-Tianjin sandstorm sources, which included the Kubuqi Desert, the Mu Us Sandy Land, the Hunshandake Sandy Land and the Horqin Sandy Land. (3) Although the proportion of cultivated land in Beijing-Tianjin sandstorm sources was only between 13.89% and 14.81%, dust emissions from cultivated land accounted for 71.56% of the total emissions in Beijing-Tianjin sandstorm sources. The corresponding proportions for deserts (or sandy land) and other vegetation surface covers (such as grassland, shrubland, etc.) were 19.78% and 8.66%, respectively. (4) In order to control both dust emissions in Beijing-Tianjin sandstorm sources and their impacts on atmospheric inhalable particulate matter, especially in the Beijing-Tianjin area, this paper showed that the key areas are the agriculture and animal husbandry interlaced belt subarea, the Yanshan Hills Water Source Reserve subarea, the desert steppe, and the northern Shanxi mountain hills subarea, and the core of land use in governance is cultivated land, not sandy land. The results in this paper would provide basic data for accurately assessing the benefits of the Beijing-Tianjin sandstorm source control project and also present a scientific basis for its optimal layout.

Diversity of soil seed banks under different vegetation types in the southeastern margin of the Tengger Desert, China

To explore the dynamics and distribution of soil seed banks under different vegetation types in desert, and reveal the community succession tendency and diversity characteristics of different vegetative types, we took Populus euphratica community, Caragana intermedia community, Leymus secalinus community and Agriophyllum squarrosum community as the research objects in the southeastern margin of the Tengger Desert. Samples of 0-2 cm, 2-5 cm, 5-10 cm, and 10-20 cm soil layers were collected. We examined the characteristics of soil seed banks and their relationships with vegetation. The results showed that there were 13 plant species in the soil seed banks of the four vegetation types, belonging to 3 families and 12 genera, with the annual and biennial herbs dominated and much Chenopodiaceae species. The soil seed bank density was generally low, with an order of C. intermedia community > L. secalinus community > P. euphratica community > A. squarrosum community. The seed bank density and species richness decreased with increasing soil depth. Based on the Shannon index, Simpson index, Pielou index and Patrick richness analysis, the order of species diversity in soil seed banks was P. euphratica community > L. secalinus community > C. intermedia community > A. squarrosum community. The similarity coefficient between soil seed bank and vegetation was the highest in C. intermedia community, followed by P. euphratica community, and the lowest in P. euphratica community and L. secalinus community. On the whole, the arbor forest P. euphratica community was the most stable one, while the sandy land A. squarrosum community was the most vulnerable.

Responses of intraspecific and interspecific variations of plant functional traits to grazing in degraded grassland

Understanding the responses of functional trait variation for grassland plants to grazing disturbance is highly helpful to clarify the community assembly mechanism, functional diversity maintenance, plant adaptation and their strategies. We investigated plant functional traits (plant height, root length, leaf area, root area, leaf dry matter content, shoot dry matter content, root dry matter content, specific leaf area, specific root length and root/ shoot ratio) and the responses of their variation characteristics to grazing disturbance in enclosure and grazing grasslands in Horqin Sandy Land. The results showed that the interspecific variation of functional trait was obviously higher than the intraspecific variation in degraded grassland. The relative contribution of interspecific variation to the overall trait variation ranged from 70.2% to 95.1%, while that of intraspecific variation only contributed 4.9% to 29.8%. However, that did not imply the intraspecific variation could be ignored in the community assembly. The interspecific variation in grazing grassland was lower than that in enclosed grassland, while the intraspecific variation increased but the interspecific variation decreased in grazing grassland. Grazing resulted in the decrease of leaf area and leaf dry matter content but the increase of specific root length for pastoral-resistant grasses. However, pastoral-tolerant forbs would improve their dominance in the community by decreasing specific root length and increa-sing leaf area and leaf dry matter content. The traits sensitive to grazing were leaf area, leaf dry matter content, specific root length, and specific leaf area. Leaf traits and root traits were significantly positively correlated within and with each other. Grazing would enhance the synergy of root traits while reduce the synergy of leaf traits. That meant grazing could change the trade-off strategy of functional traits in individual and population levels, and thus affect vegetation structure and function in community level.

Comprehensive evaluation and scenario simulation of carrying capacity of water resources in Mu Us Sandy Land, China

Abstract With the rapid improvement in socioeconomic conditions globally, the demand for water resources has dramatically increased. Evaluating water resource carrying capacity (WRCC) is crucial for regional sustainable development. To date, limited attention has been paid to WRCC in areas of predominantly sandy land, with the impact of vegetation restoration in ecologically degraded areas on WRCC remaining unclear. In this study, using a comprehensive evaluation index and a system dynamics model, we evaluated the WRCC of the Mu Us Sandy Land, Inner Mongolia, China, from 2000 to 2019 then projected to 2030. Our results show WRCC has decreased since 2000, reaching a general state by 2019. In a future scenario where historical development remains unabated, WRCC will continue to decline to a poor carrying state by 2030. The comprehensive scheme based on industrial restructuring and water conservation performed the best in terms of WRCC, continuously increasing and returning to a general carrying state by 2030. Our findings highlight the WRCC of the Mu Us Sandy Land is not optimistic and subsequent ecological restoration should proceed with caution. A comprehensive scheme is an optimal development strategy for the future.

Effects of Ecological Water Conveyance on Soil Salinization in the Shiyang River Basin’s Terminal Lake—Qingtu Lake—Area

(1) Background: Recently, secondary soil salinization has frequently occurred in ecological water conveyance and irrigation areas. Therefore, monitoring the information on soil salinization in the conveyance irrigation area and analyzing the change process of soil salinization are of great significance to both environmental improvement and salinization management. (2) Methods: This study takes the Shiyang River’s terminal lake—Qingtu Lake—and its surroundings as the research area. The salinization index was extracted by remote sensing data and methods, and a comprehensive salinization model (CSI) was established. Firstly, the spatial distribution regular of soil salinization, since ecological water conveyance was explored, and the change trends in soil salinization were analyzed. Secondly, the relationship between the change characteristics of soil salinization and groundwater, water area changes and land use types were analyzed. (3) Results: The Kappa coefficient between the soil salinization extracted by CSI and the measured data reached 0.703, and CSI can accurately monitor soil salinization information. From 2011 to 2020, the non-salinized land increased by 2.1%, mild and moderate salinization decreased by 5.7% and 3.9%, respectively, and severe salinization increased by 7.5%. The salinization in the lake area showed a decreasing trend, and the periphery of the lake area showed an increasing trend. Groundwater, water area changes and land use type have certain influences on soil salinization in the study area. (4) Conclusion: Since ecological water conveyance, the total proportion of soil salinized area in Qingtu Lake and its surrounding areas has not changed much, but there are certain changes between different grades of salinized land. The areas with changes to the level of salinization are mainly shallow, unstable water areas, saline–alkali land, wetlands and sandy land, and there are secondary salinization problems in these areas.

Morphological changes and dynamic mechanism of blowouts on fixed dunes in the Otingdag sandy land, China

<p indent="0mm">Blowouts are a major indicator of fixed dune reactivation, and their continuous occurrence and expansion aggravate the process of regional desertification. Therefore, research on the morphological evolution and dynamic processes of blowouts is paramount not only to understanding reactivation processes in stabilized and semistabilized dune fields but also to accurately assessing regional desertification trends. At present, much research has focused on blowouts in coastal dunes and flat grasslands, and little research has focused on the evolution mode of blowouts that have developed on fixed dunes in semiarid inland areas. Moreover, the morphological changes and airflow dynamics of blowouts are usually analyzed separately, and research integrating the two is still insufficient. In this paper, a fixed dune on the southern edge of the Otingdag sandy land was selected as the research object. A high precision real-time kinematic global positioning system (RTK-GPS) and 17 2D ultrasonic anemometers were used to measure the topography and airflow of four blowouts with different morphologies on the fixed dunes, and the multiperiod imaging data and multiyear meteorological data were used to monitor the morphological changes of each type of blowout and the regional meteorological conditions. The goal of this research is to reveal the morphological evolution, erosion-accumulation characteristics and airflow distribution patterns of each type of blowout and to discuss the relationship among the topography of fixed dunes, morphology of various blowouts and airflow variation. The results showed that the length, width and area of each type of blowout continued to increase from 2010 to 2021, and the overall shapes of each type of blowout tend to be oval or trough-shaped. The expansion direction of the blowout shape has a general corresponding relationship with the erosion-accumulation pattern in the deflation basin. The eastern and southeastern edges of the deflation basins are the most severely eroded, and their overall shapes expand from west to east. Relative to the wind direction of the field reference station, the approaching wind direction of the blowouts hardly deflects at the foot of the windward slope of the fixed dune, while it deflects significantly at the middle and top of the fixed dune, and the deflection angle changes with the regional wind direction. Both the blowout shapes and the approaching wind directions determine the airflow pattern within the blowouts. Based on a detailed analysis of both the regional climate and the morphological changes in blowouts, this study considered that the effect of the topography of fixed dunes on regional airflow could be the fundamental reason for the morphological differences in blowouts. The shape of blowouts determines the airflow pattern in the deflation basin, and the change in the wind speed and wind direction in turn affects the erosion-accumulation pattern and finally changes the evolution direction of blowouts. The research results can act as a good supplement for studying blowouts in semiarid inland areas.

Spatial and Temporal Variations in the Ecological Vulnerability of Northern China

Ecological vulnerability is the focus of research on global environmental impact, regional sustainable development, ecological civilization, and green development. There are eight deserts and four sandy lands in northern China. The ecological environment is sensitive to climate change and human activities. It is of great significance to carry out long-term sequential ecological vulnerability assessments. Therefore, taking northern China as the research area, this paper selects 13 data indicators such as climate, topography, and soil based on the ecological sensitivity-ecological recovery-ecological pressure model (SPR) and uses the spatial principal component analysis method (SPCA) to quantitatively evaluate the spatial and temporal differentiation characteristics and driving forces of ecological vulnerability in this area from 1980 to 2020. The results showed that areas with extreme, severe, and moderate vulnerability dominated northern China, accounting for 74.58% of the total area. The analysis revealed a decrease in ecological vulnerability from west to east and north to south. Meanwhile, from the perspective of timing, the overall level of ecological vulnerability showed an upward trend before 2000, and the overall level of ecological vulnerability continued to decline after 2000, and the quality of the ecological environment improved. During the study period, areas in northern China with severe vulnerability and slight vulnerability showed a change of 15.53% and -14.01%, respectively. The main reason for the change in ecological vulnerability is the frequent transformation between forest land, grassland, water, and cultivated land. In addition, the study found a spatial autocorrelation of ecological vulnerability of northern China and a significantly positive correlation. After 2000, the spatial aggregation of vulnerability was high-high cluster, which was mainly distributed in northwest China. The study’s findings will provide a robust scientific basis for ecosystem management and sustainable development.

Spatial distributions of salt-based ions, a case study from the Hunshandake Sandy Land, China.

Soil water soluble base ion salt-based ion concentrations are critical parameters for estimating soil buffer capacity and vegetation productivity. Ionic content clearly covaries with the distribution of plant communities. Previous studies on salt-based ions in soils focused primarily on ion migration and its relationships with vegetation growth. Few studies have sought to characterize larger scale spatial distribution of salt-based ions or correlation with climatic and plant community characteristics. This study used ion chromatography to analyze the salt-based ion content (Ca2+, Mg2+, Na+ and K+) of surface soils from the Hunshandake sandy lands. Statistical methods were used interpret spatial variation. Results showed that the average content of salt-based ions in Hunshandake sandy land was 86.57 mg/kg. Average values ranked as Ca2+ > Na+ > K+ > Mg2+ but concentrations also exhibited uneven spatial distributions. Horizontal spatial variation in Ca2+, Mg2+ and Na+ ions showed these ions gradually decrease from northwest to southeast. Potassium ions (K+) showed no obvious spatial variation trends. Ions varied significantly across different soil layers but their average concentrations ranked as K+>Na+>Ca2+>Mg2+ (from shallow to deep). The 20–30 cm soil layer contained the highest salt ion concentrations. Of the four base ions, only K+ ions appeared in surface samples. In terms of water soluble base ion available salt-based ions, Ca2+ occurred in the highest concentrations along the north and west side of the study area. K+ ions occurred in the highest concentrations along the south and east sides of the study area. Na+ concentrations did not show a consistent spatial pattern. Statistical analysis detected significant correlations of normalized ion concentration parameters (Ca2+/CECT, K+/CEC, effective water soluble base ion salt-based ions) and the total species number, average species number and total biomass of the plant communities (P <0.05). This study can help inform understanding of soil water transport in sandy areas and provide a reference for interpreting ecosystems in arid regions.

Decoupling between circulation pattern and dust path since the last glacial in the Songnen Plain, NE China: Insights from quantitative provenance reconstruction of the Harbin dust sediments

• Potential sources of the Harbin loess during the last glacial and modern dust were quantitatively tracked. • The sandy lands of NE China figure importantly in acting as a dust transfer station. • Decoupling between circulation patterns and dust export since the last glacial in the Songnen Plain were revealed. • The SW-direction sandy land of the Songnen Plain should be treated as a priority for environmental management. Knowledge of the provenance of dust deposits in the easternmost margin of the Eurasian loess belt is essential for understanding the connection between circulation patterns and dust source-to-sink route in the Songnen Plain, NE China. Here, a total of 131 samples, from the loess-paleosol sequence since the last glacial (20) and the modern dust-storm sediments (7) in Harbin area together with potential dust source areas (104), were collected for elemental geochemical analysis to quantify the source apportionment and compare the performance of the Frequentist and Bayesian models. Fourteen geochemical properties (V, Zn, Ga, Sr, Mo, Ba, Pb, Y/Ta, MREE N /MREE N *, Th/Sc, Th/U, La/Sc, Zr/Hf and Co/Th) were selected as the optimum composite fingerprint after a range test, non-parametric Kruskal-Wallis H-test and stepwise discriminant function analysis. Based on both the models, the source contributions to the loess sequence and dust-storm deposits were in the following order: southwestern Songnen Sandy Land (57–95%, 49–97%), Horqin Sandy Land and Onqin Daga Sandy Land (2–43%, 0–31%), northwestern Songnen Sandy Land (0–21%, 0–20%) and Hulun Buir Sandy Land (0%, 0–8%). Following the goodness-of-fit and virtual mixtures, combined with root mean square error and mean absolute error, we argue that the Frequentist model is slightly more accurate than the Bayesian model in quantifying dust sources. The sandy lands figure importantly in acting as a dust transfer station. The comparison between the loess sequence and modern dust-storm source reconstructions reveals a decoupling between circulation pattern (northwesterly wind domination in the glacial) and dust path (dominantly southwestern direction), and small areas, high vegetation coverage and topographical barrier are considered to be the main reasons for the significantly limited dust emission in the NW-direction source area. Finally, the study highlights that improving land management practices in the SW-direction but not NW-direction sandy land may help ameliorate the effects of the Harbin dust pollution.

Spatial and temporal evolution of soil wind erosion in the Beijing-Tianjin sandstorm sources

<p indent="0mm">Dust emissions due to soil wind erosion and its transport are the most important natural sources of inhalable particulate matter in the atmospheric environment of sandstorm sources and the regions where sandstorms occur. To control the impact of dust emissions caused by soil wind erosion on the atmospheric environment in the Beijing-Tianjin resources, the Chinese government implemented a strategic significance ecological governance project in the Beijing-Tianjin sandstorm sources at the beginning of this century. However, there is still much controversy about soil wind erosion in the Beijing-Tianjin sandstorm sources and the resulting dust emissions. Based on field surveys, laboratory tests, remote sensing images and meteorological data, this paper calculated soil wind erosion in the Beijing-Tianjin sandstorm sources under three conditions, including the typical years of 2000, 2005, 2010, and 2015, land-use change conditions (land use in 2000, 2005, 2010, and 2015 but other factors with 2015), and climate change conditions (land use in 2015 but other factors with 2000, 2005, 2010, and 2015), by using the specified soil wind erosion model in the National Plan for Dynamic Monitoring of Soil and Water Loss from 2018 to 2022 and the Technical Regulations for Dynamic Monitoring of Regional Soil and Water Loss (Trial Version). In 2000, 2005, 2010, and 2015, the fluctuation in wind erosion modulus in the Beijing-Tianjin sandstorm sources decreased. Wind erosion modulus gradually decreased from northwest to southeast, and the value in desert or sandy land was higher than that in the surrounding areas. With the advancement of governance projects in the Beijing-Tianjin sandstorm sources, the distribution of wind erosion modulus changed significantly. Wind erosion modulus in the desert steppe was the largest and was approximately 2.67–2.98 times that of the Beijing-Tianjin sandstorm sources. Wind erosion modulus in the Hetao Plain and Hunshandake Sandy Land, were roughly the same as that in the Beijing-Tianjin sandstorm sources. Wind erosion modulus in other subregions was 42.69% of that in the Beijing-Tianjin sandstorm sources. Wind erosion area and variability in the above years in the Beijing-Tianjin sandstorm sources were <sc>385800–464500 km²</sc> and −9.35%–9.14%, respectively. The area of ​​mild and moderate wind erosion accounted for 91.56%. Overall, wind erosion area in the northwestern Beijing-Tianjin sandstorm sources was large, and its area proportion was high, followed by that in the middle area, and the southeast area had the smallest area. The wind erosion area in ​​desert steppe accounted for the largest proportion, with a value of 25.88%, and that in the southern part of the Greater Khingan Mountains was only 3.18%. Intense and extremely intense soil wind erosion was concentrated in the desert steppe and the western part of the Hetao Plain. Intense soil wind erosion was mainly distributed in the Kubuqi Desert and Hunshandake Sandy Land. Moderate and mild erosion involved each subregion in the Beijing-Tianjin sandstorm sources. There were obvious differences in the changes in the wind erosion area and intensity in each subregion during 2000–2005, 2005–2010, and 2010–2015. Climate change and land-use change had important impacts on soil wind erosion in the Beijing-Tianjin sandstorm sources. The variability of the wind erosion modulus and the area affected by climate change was equivalent to the corresponding variability of the year but greater than the influence of land-use change. In addition, the area of wind erosion under land-use change generally decreased, especially from 2010 to 2015, which had a decrease of 4.10%, indicating that the Beijing-Tianjin sandstorm source control project played an important role. These results provide a scientific basis for the evaluation of the benefits of the Beijing-Tianjin sandstorm source control project and the optimization of its layout.

Wind-proof and sand-fixing effects of Artemisia ordosica with different coverages in the Mu Us Sandy Land, northern China

Wind-proof and sand-fixing effects of Artemisia ordosica with different coverages in the Mu Us Sandy Land, northern China

Analyses of the Dust Storm Sources, Affected Areas, and Moving Paths in Mongolia and China in Early Spring

Dust storms are common in Mongolia and northern China, this is a serious threat to the ecological security and socioeconomic development of both countries and the surrounding areas. However, a complete quantitative study of the source area, affected area, and moving path of dust storm events (DSEs) in Mongolia and China is still lacking. In this study, we monitored and analyzed the spatiotemporal characteristics of the source area and affected areas of DSEs in Mongolia and China using the high-spatiotemporal-resolution images taken by the Himawari-8 satellite from March to June 2016–2020. In addition, we calculated the moving path of dusty weather using the HYSPLIT model. The results show that (1) temporality, a total of 605 DSEs occurred in the study area, with most of them occurring in April (232 DSEs), followed by May (173 DSEs). Spatially, the dust storm sources were concentrated in the arid inland areas such as the Taklimakan Desert (TK, 138 DSEs) and Badain Jaran Desert (BJ, 87 DSEs) in the western, and the Mongolian Gobi Desert (GD, 69 DSEs) in the central parts of the study area. (2) From the affected areas of the DSEs, about 60% of the DSEs in Mongolia started locally and then affected downwind China, as approximately 55% of the DSEs in the Inner Mongolia Desert Steppe and Hunshandake Sandy Land came from Mongolia. However, the DSEs in the TK located in the Tarim Basin of northwest China affected the entire study area, with only 31.3% belonging to the local dust. (3) From the moving path of the dusty weather, the dusty weather at the three meteorological stations (Dalanzadgad, Erlian, and Beijing), all located on the main transmission path of DSEs, was mainly transported from the windward area in the northwest, accounting for about 65.5% of the total path. This study provides a reliable scientific basis for disaster prevention and control, and has practical significance for protecting and improving human settlements.

Soil Properties under Artificial Mixed Forests in the Desert-Yellow River Coastal Transition Zone, China

Mixed forests play a key role in the environmental restoration of desert ecosystems and in order to address the improvement of soil properties by different mixed vegetation types. We selected four typical mixed vegetation types (including: Populus alba var. pyramidalis × Caragana korshinskii, P. pyramidalis × Hedysarum mongdicum, P. pyramidalis × Hedysarum scoparium and Hedysarum scoparium × Salix cheilophila) that have been restored for 22 years and the moving sandy land in the transition zone between the desert and the Yellow River in northern China. We compared the differences in soil properties using a total of 45 soil samples from the 0–30 cm soil layer (10 cm units). We found that revegetation had a significant positive effect on fine particles, soil nutrients, soil bulk density (SBD), and soil fractal dimension (D) values. Soil D values under different types of vegetation range from 2.16 to 2.37. Soil nutrients and fractal dimension showed highly significant or stronger negative correlations with SBD and sand and highly significant or stronger positive correlations with clay and silt. The construction of P. pyramidalis × C. korshinskii improved the soil texture better than other vegetation restoration types. Compared to the mobile sandy land, organic carbon (SOC), available phosphorus (AP), available potassium (AK), alkaline hydrolysis nitrogen (AN), total nitrogen (TN), total potassium (TK), clay, and silt increased by 161%, 238%, 139%, 30%, 125%, 69%, 208%, and 441% respectively. As mentioned above, P. pyramidalis × C. korshinskii is a suitable type of mixed vegetation restoration for the area. In addition, establishing vegetation with high nitrogen fixation rates in desert ecosystems tolerant to drought and aeolian conditions is beneficial in reversing the trend of desertification. This research will suggest vegetation building strategies for controlling desertification.

Spatiotemporal evolution of desertification based on integrated remote sensing indices in Duolun County, Inner Mongolia

Desertification causes not only a reduction of vegetation cover and surface moisture but also the expansion of sandy land. Considering that the modified soil adjusted vegetation index (MSAVI) is linearly related to canopy cover, albedo plays a significant role in the surface energy balance, and the sandy feature index (SFI) can identify sandy land. This paper proposed a desertification monitoring index (DMI) based on MSAVI, albedo and SFI to accurately monitor desertification. In addition, three classification methods (quantile grading, the susceptibility index segmentation method, and Jenks Natural Breaks) were used to divide the DMI into non-desertification, mild desertification, moderate desertification, and severe desertification. The relative exponential entropy model was adopted to select the optimal method for desertification classification. Spatiotemporal distributions of desertification in Duolun County were finally observed from 2005 to 2020. The results show that (1) although MSAVI, albedo and SFI have their own advantages in monitoring desertification, a single indicator is not suitable for various land uses. The DMI can combine the advantages of MSAVI, albedo and SFI in desertification monitoring and is more consistent with the real desertification levels. (2) Compared with quantile grading and susceptibility index segmentation methods, Jenks Natural Breaks has the smallest relative exponential entropy (2.124), with an overall classification accuracy of 88.21%, indicating that Jenks Natural Breaks is an optimal method for desertification monitoring. (3) Although approximately 1708.60 km2 of desertification areas have improved from 2005 to 2020, accounting for 44.23% of the whole area, the remaining areas are still under fluctuating or degraded conditions. This shows that the local government has made some progress in desertification protection, but the areas under fluctuating or degraded conditions still require protection or management.

Sand fixation mechanism and effect evaluation of sand barriers in Mu Us sandy land, China

<p indent="0mm">Sand barriers are an engineering measure for sand fixation, and play an important role in promoting dune fixation and vegetation restoration. As the most widely used means of sand control, sand barriers have a variety of materials and configurations. In recent years, some new sand fixation materials have appeared, but their benefits of sand fixation have not been compared and evaluated. Moreover, there is an insufficient amount of research on the sand fixation mechanism of sand barriers. Therefore, an accurate understanding of the sand fixation mechanism of sand barriers and the optimization of its configuration mode is conducive to improving the techniques of wind prevention and sand fixation. In this paper, four barchan dunes developed in the Mu Us sandy land were selected as the research carrier. One of the dunes is a reference dune without sand barriers, and the remaining three dunes are covered with sand barriers of different materials and specifications. There are 9 types of sand barriers, which can be divided into 3 materials (Salix, straw rope and PLA) and 3 specifications (1 m<sc>×1 m,</sc> 2 m<sc>×2 m</sc> and 3 m<sc>×3 m).</sc> This study revealed the surface processes of dunes under each type of sand barrier and evaluated the benefits of each type of sand barrier on sand fixation and ecological restoration through topography measurements, sand drift observations, sediment sampling, vegetation investigations and laboratory analyses. The results show that the sand barriers have the functions of reducing the height of dunes, reshaping the surface micromorphology, decreasing near-surface wind speed, blocking the sand transport and promoting vegetation restoration, and the strength of the functions is controlled by the material of the sand barrier, the configuration mode of the sand barrier and the relative positions on the dune. Detailed analysis of the benefits in sand fixation and vegetation restoration of each type of sand barrier suggests that the Salix barrier is the best choice in this area, the straw rope barrier is the second best choice, and the PLA barrier is the worst. The best configuration mode of the Salix barrier and straw rope barrier is 1 m<sc>×1 m,</sc> while that of the PLA barrier is 2 m<sc>×2 m.</sc> Moreover, this study considered that the effect of sand barriers on wind prevention and sand fixation are decided by multiple factors, and it is not sufficient to take the near-surface wind speed or micromorphology as the measurement standards of these effects. The selection of sand barrier materials and configurations needs to comprehensively consider many issues, such as the efficiency of sand fixation, the ability to promote vegetation restoration, sustainable time, economic cost and secondary pollution. Thus, sand barrier projects should take the regional sand fixation demand and field environment into account and select the most suitable configuration forms according to the main objectives or demand.