Sandy Land Research Articles

Extension of the revised wind erosion equation (RWEQ) to calculate grassland wind erosion rates based on the 137Cs tracing technique

The commonly used wind erosion models, including the Revised Wind Erosion Equation (RWEQ), are mainly based on data from loose soils, for which the erodibility factor (EF) reflects the abundance of erodible aggregates, and cannot be applied to simulate erosion of compacted soils such as some grassland soils. Taking the Inner Mongolia Autonomous Region in northern China as the study area, we used the 137Cs tracing technique to estimate the soil loss of grassland by wind erosion from 1963 to 2021, and used the results as criteria to verify the wind erosion rate (WER) predicted by RWEQ for the same period. We found that RWEQ accurately calculated the WER of cultivated farmland, but overestimated grassland WER. We believe that the main reason is that the equation did not consider the impact of soil compaction (SC) on EF, since the calculation methods for the weather factor, vegetation factor, surface roughness factor, and soil crust factor in RWEQ are applicable for grasslands. Therefore, we used the 137Cs tracing results to extrapolate the grassland EF while keeping the climate, soil crust, vegetation cover, and roughness factors constant, and combined SC and the proportion of aggregates smaller than 0.84 mm in diameter to develop an empirical equation for grassland EF. Compared with the original model, the extended model (RWEQext) that included the factor of SC more accurately estimated the WER of compacted grassland soil and could be applied to the whole study area. The RWEQext results showed that tolerable and slight levels of wind erosion dominated the grassland and gobi surfaces in the study area, whereas moderate wind erosion occurred in grasslands with sparse vegetation cover, and severe, very severe, and destructive wind erosion mainly occurred on loose surfaces such as sandy land with low vegetation cover.

Quantifying the contributions of natural and anthropogenic dust sources in Shanxi Province, northern China

Dust storms have direct or indirect impacts on climate change and human health. Identifying and quantifying natural/anthropogenic dust sources can facilitate effective prevention and control of dust events. Based on surface real-time PM10 monitoring data, satellite remote sensing and the HYSPLIT model, this study determined the specific timing, coverage and sources of dust events in Shanxi Province, Northern China. Thus, a composite fingerprinting technique was established to quantify potential dust sources and dust contributions of single dust events. The dust oxidation model was validated, indicating that the composite fingerprinting technique was well suited to the study region. The results show that natural dust sources (67%) contributed more to the study region than anthropogenic dust sources. They were mainly from the northwest and north of the study region. Particularly, the contributions of Taiyuan (TY) and Linfen (LF) accounted for the largest (82%) and smallest (55%) proportions, respectively, both exceeding 50%. Anthropogenic dust sources contributed 33%, mainly from the east and south of the study region. The contribution of anthropogenic dust sources increased in the study region from north to south. In terms of potential dust sources, the Tengger Desert and Badain Jaran Desert (TDBD) contributed the most (26%), followed by the Otindag Sandy Land (OL) (22%). The Taklimakan Desert (TD) contributed the least (2%). The Middle Farmland region of the Hexi Corridor (HMF) in the west (15%) had the largest proportion of anthropogenic dust sources. Differences in the regional contribution of potential dust sources mainly resulted from winter winds, surface drought severity and particle size. At an insignificant distance from the study region, the contribution of potential dust sources was larger in the west than in the east and increased from south to north overall. These methods and findings can contribute to improving the ecological environment in Northern China.

Spatial patterns of soil stoichiometry and their responses to land use in a desertified area: A case study of China's Horqin Sandy Land

AbstractEcological stoichiometry facilitates the understanding of biogeochemical cycles by studying the balance among multiple elements in ecosystems. However, the spatial patterns of soil stoichiometry and their responses to land use in desertified land are unclear. In this study, we selected 525 sample points to collect topsoil (0–20 cm) samples throughout China's Horqin Sandy Land and measured soil organic carbon (SOC), total nitrogen (TN), and total phosphorus (TP). We then calculated stoichiometric ratios (C:N:P). SOC (8.7 g kg−1), TN (0.9 g kg−1), and TP (0.3 g kg−1) were lower in this region than in Chinese and global terrestrial ecosystems due to aeolian desertification. SOC, TN, C:P, and N:P were significantly (p < 0.05) higher in grassland, followed by woodland, cropland, and sandy land. This sequence may result from the large number of dead roots that participate in the SOC turnover in grassland. TP was significantly higher in cropland due to fertilization. C:N did not differ significantly (p > 0.05) among grassland, woodland, and cropland because of the strong coupling relationship between SOC and TN. The values of SOC, TN, TP, C:P, and N:P in the Horqin Sandy Land were high in the north (dominated by mountain woodland and grassland) and were low in the south (dominated by desertified land). SOC, TN, and TP contents and C:N:P ratios were mainly affected by mean annual temperature (29.6%), land use (11.5%), and bulk density (11.4%) through their influence on soil microbial metabolism, litter and nutrient input, and soil structure, respectively. The results provide information on the overall changes in soil stoichiometry in the Horqin Sandy Land and its responses to land‐use changes, and can therefore guide ecological restoration in semiarid regions affected by desertification in the modern context of climate change.

Response of Liquid Water and Vapor Flow to Rainfall Events in Sandy Soil of Arid and Semi-Arid Regions

In arid and semi-arid regions, rainfall takes on a critical significance to both agricultural and engineering construction activities, and the transport process and driving mechanism of soil water under rainfall conditions are in need of further investigation. To clarify the variations in soil moisture, temperature, and liquid and vapor flux under various rainfall scenarios, the Mu Us Sandy Land was selected as the study region, and a water–vapor–heat transport model was established using the Hydrus-1D software with in situ observed soil and meteorological data. The simulated results were in good agreement with the measured data during both the calibration and validation periods, suggesting that the model was accurate and applicable to the study region. The variations in the selected dry and rainy periods proved the significant effect of rainfall events on soil matric potential, temperature, and driving forces. When rainfall occurred, the hydraulic conductivity for liquid water rose by three to five orders of magnitude, driving the liquid water flow downward. In contrast, the vapor flux played a vital role in soil water movement, accounting for about 15% of the total water flux in the shallow layer when the soil was dry, while it became non-significant during rainy periods due to the reduction in hydraulic conductivity for vapor and the temperature gradient. These results clarified the mechanisms of soil liquid water and vapor movement in arid areas, which could provide scientific support for future studies on vegetation restoration and ecosystem sustainability in ecologically fragile areas.

An advanced coverage estimation method to quantify biological soil crust coverage using Sentinel-2 imagery in desert and sandy land of China

ABSTRACT Monitoring the distribution and area change of biological soil crusts (BSCs) can enhance our understanding of the interactions between nonvascular plants and the environment in drylands. However, using only pixel-based binary classification methods results in large-area estimation errors at large scales. The lack of available calculation methods for directly measuring BSC coverage using multispectral satellite images makes it challenging to obtain BSC area data for further studies at large scales. To address these issues, this study developed feature space conceptual models for desert and sandy land based on the characteristics of BSC in drylands. The desert feature space comprised the normalized difference vegetation index (NDVI) combined with the brightness index (BI), encompassing moss, lichen, and non-BSC. The sandy land feature space relied on the biological soil crust index (BSCI) and the NDVI, including vegetation, mixed BSCs and sandy soil. Using Sentinel-2 satellite imagery and a spectral unmixing model, the abundance of BSCs was quantified in four BSC growth areas located in the Gurbantunggut Desert and Mu Us Sandy Land of China. Validation of the method indicated that the root mean square error (RMSE) of the BSC coverage estimation results was 10% and 8% in desert and sandy land, respectively (estimation accuracies of 79% and 81%, respectively). This demonstrated that the proposed method can effectively estimate BSC coverage at a subpixel scale. The resulting BSC coverage data can provide the possibility to evaluate the functions of regional ecosystems.

Temporal and Spatial Changes in Soil Organic Carbon in a Semi-Arid Area of Aohan County, Chifeng City, China

Soil organic carbon (SOC) plays a crucial role in arid zones, while land-use change could lead to changes in the balance of SOC. Therefore, the aim of this study was to determine the impact of land-use change on the temporal and spatial variability in SOC at the county scale. A semi-arid zone (Aohan County, Northeast China) covering a surface of 3800 km2 was selected for this study. SOC data for 65 and 182 soil samples from 1985 and 2021, respectively, were collected for major land-use types (forestland, farmland, grassland, and sandy land) across Aohan County to a depth of 20 cm. The impacts of different land-use types and land-use changes on SOC were evaluated. The results showed that land-use change enhanced the spatial variability in SOC over the last 36 years. The mean SOC in 2021 (7.49 g kg−1) was significantly higher than that in 1985 (6.91 g kg−1). Converting sandy land into grassland and farmland into forest or grassland would lead to significant accumulation of SOC, while the depletion of SOC occurred after grassland afforestation. The balance between aboveground biomass inputs and SOC decomposition was the determining reason that affected the accumulation of SOC. Vegetation restoration due to land-use change could alter both soil texture and the C/N ratio and could have positive effects on ecosystem recovery.

Carbon dynamics of the plant-soil system during vegetation succession in dune-meadow cascade ecosystems in Horqin Sandy Land, China

Understanding the relationship between the plant-soil carbon dynamics and environment is important for the management of arid and semi-arid ecosystems. Under long-term overgrazing and reclamation, the landscape of the Horqin Sandy Land has transformed into a dune-meadow ecotone. However, the effects of landscape evolution on the carbon dynamics in this region remain poorly investigated. This study evaluated changes in plant-soil organic carbon content and stable carbon isotope ratios (δ13C) attributable to vegetation restoration in dune ecosystems and wetland degradation in meadow ecosystems, and evaluate the indicative implications and driving mechanisms of the 13C enrichment in the plant-soil system. The dune ecosystems comprised semimobile dune with 25- and 15-year-old Artemisia Halodendron communities (SMAH1, SMAH2), fixed dune with 30- and 40-year-old Caragana microphylla communities (FCM1, FCM2), semimobile dune with 40-year-old Salix gordejevii community (SMSG), and transitional zone with a 30-year-old artificial Populus forest (TPF) in the gentle lower part. The meadow ecosystems comprised a corn field that transformed from natural meadow over 40 years (MCF) and a natural meadow with Phragmites australis community (MPA). The results show that plant leaves in different landscapes in the cascade ecosystems had various δ13C. And the mechanism of the leaves carbon isotope fractionation with increasing leaf age was significant and consistent, but different vegetation communities had different nutrient utilization strategies during ontogeny. Landscape types and soil depths are the key factors affecting SOC content, its δ13C (δ13Cs) and SOC stock changes. And the overall soil carbon turnover was accelerated with vegetation restoration. Especially in TPF, vegetation restoration is particularly significant for SOC, which is mainly reflected in the upper 20 cm of soil profile. The degradation of MPA to MCF led to loss of SOC content and storage and accelerated the soil carbon turnover rate. The δ13Cs of the dune and meadow ecosystems were positively correlated with organic-rich litter nitrogen content and were significantly negatively correlated with SOC, soil moisture, clay content, and total organic carbon to total nitrogen ratio of organic-rich litter. The revegetation using native and introduced tree and shrub species increased SOC content in dune ecosystems and significantly promoted the degree of its coupling with soil nitrogen and water.

Holocene aeolian activity triggered by climate change and endorheic-exorheic drainage transition in the Headwater Region of the Yellow River, Tibetan Plateau

The Headwater Region of the Yellow River (HRYR) is located in the northeastern Tibetan Plateau at an altitude higher than 4000 m above sea level. Modern aeolian sandy land is widely distributed in the HRYR, and the reactivation of paleo aeolian sediments under the disturbance of climate change and human activities has become a hot issue since the past decades. However, the chronology of paleo aeolian sediments in this region remains poorly understood. In this study, 22 samples of aeolian sediments were collected from six sections and dated using optical stimulated luminescence (OSL). Combining the OSL data with 15 previously published OSL ages from three sections in the HRYR, the following results were obtained. The oldest aeolian sand sediments in the HRYR are dated at 7.12 ± 0.39 ka. The remaining aeolian sediments were deposited in the late Holocene, ranging between 3.29 ± 0.42 ka and 0.18 ± 0.01 ka. In the late Holocene, phases of intensifying aeolian activities were recorded by clusters of OSL ages at 2.12–1.81 ka, 1.30–1.26 ka, and the Little Ice Age. In our dataset (37 OSL ages), 27 ages correspond to the past millennium and the aeolian activity phases mainly occurred in the Little Ice Age. The relatively scarce aeolian sand deposits in the early Holocene is likely due to the existence of Maduo Paleolake, which maintained a high water stand, inhibiting the availability of sediments for wind erosion. The absence of mid-Holocene aeolian sediments in this region is attributed to the optimum climate during this period although the HRYR had opened around 7.0 ka BP. Coupled with the drier and cooler climate, the exposure of lacustrine sediments during the endorheic-exorheic drainage transition (EEDT) of the HRYR ultimately triggered enhanced aeolian activities in the late Holocene.

Impacts of Different Types of Vegetation Restoration on the Physicochemical Properties of Sandy Soil

Understanding the integrated effects of vegetation types on the physicochemical properties and quality of sandy soils is crucial for guiding vegetation reconstruction and ecological restoration in desertified areas. This study selected three vegetation types at the southern edge of the Mu Us sandy land, including fenced Leymus secalinus Tzvel. grassland (LS), natural Hedysarum mongolicum Turcz (HM) forest land, and Salix cheilophila Schneid. (SC) forest land, as well as sandy land as a control (SD). The differences in the soil physicochemical properties were investigated by collecting soils from three layers within 0–60 cm. The soil quality index (SQI) was calculated using principal component analysis to comprehensively evaluate the soil quality. This study found that the soil physicochemical properties differed significantly among the plots and layers, and the soil properties exhibited a vertical distribution, with chemical indicators concentrated in the surface layer. As depth increased, differences in soil properties between the vegetation and control plots diminished, with vegetation influence mainly in the 0–20 cm layer. Among all the sample sites, the 0–20 cm layer of LS had the highest organic matter content (5.98 g/kg), which was 2.25, 2.28, and 4.71 times that of HM, SC, and SD, respectively. Moreover, LS had the lowest bulk density (1.35 g/cm3), which was 0.89, 0.91, and 0.86 times lower than that of HM, SC, and SD, respectively. The effects of different vegetation restoration types on the comprehensive quality of soil were different, as shown in LS (0.15) > HM (0.11) > SC (0.10) > SD (0.08). In conclusion, all three vegetation restoration types significantly affected the soil physicochemical properties and led to different degrees of variability of soil indexes in the vertical profile, and the fenced grassland restoration type may be preferable for ecological restoration and reconstruction in this region.

A Study of Sandy Land Changes in the Chifeng Region from 1990 to 2020 Based on Dynamic Convolution

Desertification is the process of land degradation and the reduction or destruction of biological potential in arid, semi-arid, and semi-humid areas, and its impact on agricultural development and the ecological environment cannot be ignored. Therefore, many researchers have aimed to achieve the acquisition of large-scale sandy land areas using sandy land extraction algorithms based on remote sensing images. However, the sandy land extraction accuracy needs to be improved because of the variable contour features in the remote sensing images and the easy confusion with targets such as the Gobi and bare ground areas. In this study, we combine the dynamic convolution with a U-Net model and propose the DU-Net sandy land extraction model. The method is based on dynamic convolution, which can adaptively learn the complex features of the target and build a dynamic convolutional neural network to achieve high-accuracy extraction of complex targets. DU-Net achieved 86.32% in IoU, 93.22% in precision, 94.5% in recall, and 92.66% in F1-score in sandy land extraction accuracy, which are 4.68%, 2.33%, 3.09%, and 2.76% improvements, respectively, compared with the U-Net static neural network. Based on this, we obtained the spatial and temporal evolution trends of sandy land areas based on Landsat images in the Chifeng region in the Inner Mongolia Autonomous Region, China. Meanwhile, in order to investigate the mechanism of spatial and temporal changes in the sandy land area in the study region over the past 30 years, the direct and indirect effects of seven climatic and human socioeconomic activity factors on the changes in the sandy land area in the study region were evaluated based on a structural equation model. The results show that the sandy area in the Chifeng region tended to first increase and then decrease over the study period, with the sandy land area reaching its maximum around the year 2000. In addition, the main driving factor for the change in the sandy land area in the Chifeng region has been human socioeconomic activities, with climatic conditions as the secondary driving factor. The method proposed in this paper realizes the rapid extraction of sandy land areas with high accuracy at a large scale and with a long time series and provides a basis for assessing the effectiveness of ecosystem restoration projects.

Sand-fixing vegetation regulates deep percolation and soil water dynamics in semiarid sandy land: Evidence from a deep percolation recorder and in-situ test

Deep percolation (DP) determines the sustainable utilization of regional groundwater resources and provides large hydrological benefits to ecosystems in semiarid sandy regions. However, studies involving DP variability have rarely conducted in-situ tests with different vegetation coverages (VC) and vegetation types using direct measurements. This study measured soil moisture and DP for four years in five plots, with DP measured using a deep percolation recorder: mobile sand (MS) as the control group; Artemisia ordosica semifixed (AOSF) with VC of 30%–35% and Artemisia ordosica fixed (AOF) with VC of 70%–75% (AOSF and AOF stand ages: 30–40 years), representing different vegetation coverages; and Salix psammophila fixed (SPF) and Pinus sylvestrix var. Mongolica fixed (PSMF) with the same VC of 45%–50% (SPF and PSMF stand ages: 30 years), representing different vegetation types. The effects of sand-fixing vegetation on DP and soil water were evaluated using the relative extractable soil water (RESW) and soil water storage deficit metrics. DP occurrence in MS was closely related to rainfall amounts of > 10 mm and high-intensity rainfall rather than the total annual rainfall. Increases in vegetation coverages and forest selection significantly reduced DP and RESW compared with MS. DP in the shrub plot (SPF) was significantly higher than that in the forest plot (PSMF). Plants utilized water from different sources among the sandy land types: the shallow (0–80 cm) and deep layers (80–200 cm) in PSMF and AOF, and only from the shallow layer in AOSF and SPF. However, compared with MS, soil water storage deficit occurred to varying degrees in each plot. This study can provide a scientific reference for the restoration of the ecology and water cycle in sandy regions.

Geochemical evidence of provenance diversity in Holocene sandy land of Qinghai Lake Basin in the north‐eastern margin of Qinghai–Tibet Plateau and its implications for climate change

ABSTRACTThe Qinghai Lake Basin, located in the north‐eastern Tibetan Plateau, is crucial for understanding the East Asian monsoon evolution and its interaction with westerlies. Palaeoclimatic studies in this region since the Holocene have primarily focused on interpreting proxy significance from sediments, resulting in being highly controversial. However, exploring palaeoclimate evolution through sediment provenance and proxy integration remains rare. This study analysed the elemental geochemical properties of two fluvial–lacustrine–aeolian profiles in Hudong Sandy Land, east of the Qinghai Lake Basin, and compared these with published modern basin sediments and extensively investigated Late Quaternary aeolian deposits. It was found that Hudong Sandy Land sediments exhibit similar geochemical compositions to other modern basin sediments, primarily consisting of SiO2, Al2O3 and CaO. Contrary to previous understanding, lacustrine sediments in the Hudong Sandy Land are closer to the upper continental crust average than aeolian deposits. Geochemical ratios and parameters suggested that Hudong Sandy Land sediments primarily derived from mixed source rocks of felsic igneous, quartzose sedimentary and intermediate igneous provenances. A comparison with published elemental geochemical data from the basin reveals distinct sediment sources during different periods in the Hudong Sandy Land. From 9.6 to 4.0 ka bp, Hudong Sandy Land hosted numerous lake environments, with sediments displaying a dominant role in sedimentary recycling and reworking, implying a continuously stronger East Asian summer monsoon. During 8.2 to 5.1 ka bp, the Hudong Sandy Land was a fluvial depositional sink for sediments from the Dabanshan Mountains. Bedrock clastic material generated by intense erosion and monsoonal runoff transport contributed to Hudong Sandy Land sedimentation, indicating the East Asian summer monsoon's peak since 9.6 ka bp. After 4.0 ka bp, thick aeolian sands accumulated in the Hudong Sandy Land, primarily derived from Lake Qinghai sediments due to declining water levels, indicating that westerlies and East Asian winter monsoon dominated the basin, with a weaker East Asia summer monsoon. This study facilitates a deeper understanding of the interaction between the East Asia summer monsoon and East Asia winter monsoon/westerlies.

Sustainable restoration in sandy lands is challenged by the divergent responses of grassland functional types to disturbance

The effective management of regional grassland degradation requires a deep understanding of how different grassland types respond to climate change and human disturbance over different spatial and temporal scales. This study examined the dynamics and underlying driving mechanisms of various grassland types in the Otindag Sandy Land over 36 years (1986–2021) by integrating time-series Landsat images and extensive climate and socio-environmental data. We found that the dynamics and driving factors of different grassland types varied significantly. In low-cover grasslands, the area of desert grassland fluctuated with a decreasing trend after the breakpoint, while that of sandy grassland increased continuously without any breakpoints. In high-cover grasslands, the area of typical grassland only increased after the breakpoint, whereas that of temperate savanna grasslands first decreased and then increased insignificantly. Additionally, the desert grassland area was significantly negatively correlated with annual precipitation (AP), whereas the sandy grassland area was negatively correlated with annual mean wind speed (AMWS). The dynamics of typical grasslands were jointly influenced by climate and human factors, with temperate savannas mainly driven by the AP and AMWS. Moreover, high-cover grasslands were more sensitive to human activities than low-cover grasslands, and the most significant driving factors changed before and after the breakpoint in the area dynamics. These findings provide valuable insights into the monitoring and conservation of sandy land ecosystems.

Spatio-Temporal Evolution of Ecological Sensitivity in the Desert of China from 1981 to 2022

The northern desert of China plays an important strategic role in land resource security and national economic development. Research on the spatio-temporal changes of ecological sensitivity can provide a scientific reference for desert management and ecological restoration in arid and semi-arid areas in northern China. This paper takes the northern desert of China as the research area, uses the spatial distance model to build a comprehensive ecological sensitivity evaluation index system, and discusses the spatio-temporal evolution characteristics of ecological sensitivity in the area from 1981 to 2022. The results show the following: (1) The land use types in the northern desert of China are mainly sandy land, grassland and other lands. The changing areas of grassland and other lands are 74,353.14 km2 and 50,807.97 km2, which is an important factor affecting the ecological sensitivity in the northern desert of China. (2) Five aspects, including terrain, climate, hydrology, soil and vegetation, influence and restrict each other, and jointly create the background conditions for the distribution and change of ecological sensitivity in the northern desert of China. Climate and terrain are the most important influencing factors affecting the ecological sensitivity of northern desert of China. Vegetation is the most active and basic factor affecting the ecological sensitivity of northern desert of China. Hydrology and soil have a certain limiting effect on the ecological sensitivity of northern desert of China. (3) The spatial heterogeneity of ecological sensitivity in the northern desert of China is significant, showing the characteristics of high volatility in the west, low volatility in the central region and low volatility in the east. (4) For nearly 42 years, ecological sensitivity of the northern desert of China shows first increasing and then decreasing characteristics. The area of the fluctuation reduction zone accounts for 26.34% of the total research area, of which the area of extreme sensitivity and mild sensitivity varies by 11.84% and 65.28%, respectively. (5) The spatial aggregation characteristics of ecological sensitivity have changed significantly, and the area of high–high and low–low agglomeration areas has also been decreasing, indicating that the environment is obviously improving. In the future, we should pay attention to the efficient use of natural resources in the northern desert of China and strengthen the protection of all kinds of land to achieve the sustainable development of the regional environment.

Ammoniated straw incorporation coupled with N management synergistically enhanced soil structure and crop productivity in a desert oasis farmland

AbstractStraw return is the simplest and the most economic method to improve soil structure. Slow decomposition rate limits straw return in sandy fields, which has becoming one of the obstacles in sandy land reclamation. Ammonification of straw before return accelerates straw decomposition, but it requires the use of extra N fertilizer, however, little is known about N fertilizer management in fields with ammoniated straw incorporation. So, a 3‐year field experiment was conducted with different proportions of N fertilizer aimed to maize straw ammonification and field broadcasting, and evaluated straw decomposition proportion, straw N release, soil organic carbon content, soil aggregates, soil water and N availability, and grain yield. Total N application rate was 300 kg per hectare, with five N input amounts for straw per hectare ammonification: 0 (SN0), 40 (SN40), 80 (SN80), 120 (SN120), and 160 (SN160) kg, and the rest of N broadcasted in soil during maize growing season. Ammonification accelerated straw decomposition and N release, and these effects showed no significant difference between SN80, SN120, and SN160. After straw decomposition for 150 days, the decomposition proportion was 62.1%, 53.0%, and 39.2% in SN80, SN40, and SN0, respectively. After 3 years of straw return, SN80 exhibited a significantly higher mean weight diameter of soil aggregates (35.6% higher), organic carbon content (18.4% higher), water‐holding capacity (17.4% higher), and soil water storage (17.2% higher) than SN0. Additionally, SN80 and SN120 showed the most significant effect on “N slow‐release” in soil. The above effects resulted with more available soil water and N used for crop growth, and increased grain yields (18.1% higher) and water use efficiency (18.6% higher) in SN80, compared with SN0. Hence, we conclude that a proper N allocation between straw and soil can synergistically enhance soil structure and crop productivity in sandy farmlands. This founding would provide scientific and technological support for straw return in sandy fields and is beneficial to sustainable development of oasis.

Response of Wheat Productivity to the Addition of Nitrogen Fertilizer Rates on Several Doses in the New Sandy Lands in Luxor Governorate

Response of Wheat Productivity to the Addition of Nitrogen Fertilizer Rates on Several Doses in the New Sandy Lands in Luxor Governorate

A nature-based solution to reduce soil water vertical leakage in arid sandy land

Quick water seepage in sandy soils results in a serious restriction for ecological restoration, becoming a worldwide urgent research issue in arid areas. Search for practical solutions are focused on reserving the limited rainfall into topsoil layer to meet plant water demand. Based on fieldwork, this study evaluates the blocking effects of Pisha sandstone on soil water leakage, by inserting sandstone layers in the different soil depths (10–15 cm, 20–25 cm, 30–35 cm), which act as isolation layers within the sandy soil. Results showed that the inserted Pisha sandstone layers significantly decreased the soil water infiltration rates at the different stages and cumulative infiltration. The inserted sandstone layer at the depth of 10–15 cm presented the highest permeability resistance, and its initial infiltration rate, stable infiltration rate and average infiltration rate decreased by 102.42 mm h−1, 144.30 mm h−1 and 132.79 mm h−1, respectively. Meanwhile, the soil water content in the 5–10, 20–25, and 30–35 cm soil layers increased by 2.17%, 2.20%, and 1.37%, respectively, due to the inserted Pisha sandstones. This experimental study proves that the insertion of Pisha sandstones effectively hinders the downward penetration of soil water in sandy soil. These findings provide a new alternative for an effective solution of the fast water leakage problem of sandy land.

The continuing decrease of sandy desert and sandy land in northern China in the latest 10 years

Timely monitoring of the sandy desert and sandy land (SDSL) dynamics and their driving factors is vital for ecological restoration policy-making to combat the expansion of the SDSL. Northern China, being the principal implementation area of ecological restoration projects, is ecologically fragile and encompasses almost all of the SDSL regions in China. To explore and compare the dominant driving factors for SDSL changes by extracting both aeolian activity information and vegetation indices, the SDSL datasets in northern China from 2010 to 2020 were first constructed in this study by the human–computer interactive interpretation method based on the series Landsat image data. The spatiotemporal dynamic characteristics of SDSL were subsequently analyzed, and the dominant driving factors of SDSL changes were further explored via the geodetector model by the fractional vegetation cover trend and the difference of aeolian activity index. The results showed a net decrease of 3,780.25 km2 in the total SDSL area between 2010 and 2020, and the decrease rate was 2.44 times higher in the shorter period of 2015–2020 compared to 2010–2015. The spatial differentiation between the western and eastern parts of the Helan Mountains was prominently exhibited by the relatively higher changed SDSL area in the eastern part (62.74% for aeolian activity weakened and 83.32% for aeolian activity intensified) and the increasingly changed SDSL area in the western part (from 33.09% to 39.60% in aeolian activity weakened and from 13.02% to 19.60% in aeolian activity intensified). Especially, the increased aeolian activity intensified SDSL area has happened on the southern edge of the Gurbantunggut Desert and along both sides of the Tarim River from 2015 to 2020 deserve attention. The co-driving of the multiple driving factors dominated the change of SDSL from 2010 to 2020, with the county mean value of the difference in aeolian activity index (MDAAI) and the county mean value of the trend in fractional vegetation cover (MFVCT) as dependent variables, respectively. Climatic factors of the mean annual average temperature, the mean annual cumulative precipitation, and the mean annual aridity index have a relatively larger explanatory power for the change of SDSL in both MDAAI and MFVCT. Anthropogenic factors of the mean annual afforestation area and the mean annual number of large livestock and sheep and goats (year-end) have a greater explanatory power in MDAAI, while the mean annual number of large livestock and sheep and goats (year-end) and the mean annual population density in MFVCT. In particular, the dependent variable MDAAI is better at identifing the dominant drivers of aeolian activity intensified SDSL area compared to MFVCT, with anthropogenic factors playing a stronger dominant role.

High-northern-latitude forcing modulated fluvial‒aeolian interplay during the Last Glacial Period in the Mu Us Desert, northern central China

Substantial stratigraphic evidence from the Late Quaternary at orbital- and millennial‒scales indicates that the formation and evolution of aeolian‒sand landscapes results from the interaction between regional aeolian and fluvial‒lacustrine activity. In many deserts (sandy lands) across the planet, fluvial‒aeolian interplay at the glacial‒interglacial scale since the Late Quaternary has been responsive to monsoonal precipitation, and linked to atmospheric CO2 and periodic variations in insolation. However, the patterns of fluvial‒aeolian interplay and their relationship with climate change are not always consistent over a given timescale during the Late Pleistocene. The paucity of studies on fluvial‒aeolian interplay in the Mu Us Desert (MUD) during the Last Glacial Period (LGP) hinders our understanding of the relationships between the dynamics of aeolian and fluvial‒lacustrine landscapes and their drivers. Here, based on a comprehensive field survey and stratigraphic dating of a typical fluvial‒aeolian sequence in the MUD, we synthesized the chronology of fluvial‒lacustrine and aeolian strata during the LGP. Our results show that extensive development of a fluvial‒lacustrine environment in the MUD during the LG mainly occurred during the late Last Glacial Maximum (LGMa, 20.1–18.4 ka BP) and Bølling/Allerød interstadial (14.8–12.6 ka BP), while thicker aeolian sands extensively accumulated during the Heinrich Stadial 2, Heinrich Stadial 1, and Younger Dryas periods. However, the development of fluvial‒lacustrine environments showed considerable spatial heterogeneity, mainly occurring on the southern and eastern margins of the desert, while they were extremely rare in the central and western parts of the desert owing to strong wind erosion. Comparisons with other high-resolution geological records from the Asian monsoon region reveal that the fluvial‒aeolian interplay in the MUD during the LGP was highly consistent with the evolution pattern of the East Asian summer monsoon (EASM) on the millennial‒centennial scale, and indicate that the development of fluvial‒lacustrine environments was mainly controlled by an increase in monsoonal precipitation during strengthening of the EASM. Consistency with other broad changes at high latitudes in the Northern Hemisphere suggests that fluvial‒aeolian interplay during the LGP in northern Chinese deserts, as represented by the MUD, was mainly controlled by changes in high-northern-latitude ice volume and the Atlantic Meridional Overturning Circulation.

Instantaneous sap flow velocity simulation of Euonymus bungeanus based on neural network optimization model.

The sap flow of trees is complex and difficult to express with multivariate linear or empirical models. A simple and feasible method on the basis of understanding sap flow variation to simulate its variation with environmental factors is of special importance for quantitatively analyzing forest ecohydrological processes and regional water demand. In this study, with one of the shelter forest species Euonymus bungeanus in the east sandy land of Yellow River in Ningxia as the research object, we continuously measured the trunk sap flow velocity by thermal diffusion sap flow meter, and analyzed the effects of environmental factors on stem sap flow. We used the particle swarm optimization (PSO) and sparrow search algorithm (SSA) optimized neural network model to predict sap flow velocity of E. bungeanus. Results showed that the main environmental factors influencing sap flow were solar radiation, vapor pressure deficit, air temperature, and relative humidity, with the influencing importance of 32.5%, 25.3%, 22.0% and 16.1%, respectively. The response process between sap flow and environmental factors presented a hysteresis loop relationship. The optimized BP, Elman and ELM neural network models improved the comprehensive evaluation index (GPI) by 1.5%, 30.0% and 5.3%, respectively. Compared with the PSO-Elman and SSA-ELM optimization models, the SSA-BP optimization model had the best prediction results with an improvement of 1.0% and 23.2% in GPI, respectively. Therefore, the prediction results of the BP neural network model based on the sparrow search algorithm could be used as an optimal model for predicting instantaneous sap flow velocity of E. bungeanus.