Sandy Land Research Articles

[Spatio-temporal Variation in NEP in Ecological Zoning on the Loess Plateau and Its Driving Factors from 2000 to 2021].

Net ecosystem productivity (NEP) is an important index for the quantitative evaluation of carbon sources and sinks in terrestrial ecosystems. Based on MOD17A3 and meteorological data, the vegetation NEP was estimated from 2000 to 2021 in the Loess Plateau (LP) and its six ecological subregions of the LP (loess sorghum gully subregions:A1, A2; loess hilly and gully subregions:B1, B2; sandy land and agricultural irrigation subregion:C; and earth-rock mountain and river valley plain subregion:D). Combined with the terrain, remote sensing, and human activity data, Theil-Sen Median trend analysis, correlation analysis, multiple regression residual analysis, and geographic detector were used, respectively, to explore the spatio-temporal characteristics of NEP and its response mechanism to climate, terrain, and human activity. The results showed that:① On the temporal scale, from 2000 to 2021 the annual mean NEP of the LP region (in terms of C) was 104.62 g·(m2·a)-1. The annual mean NEP for both the whole LP and each of the ecological subregions showed a significant increase trend, and the NEP of the LP increased by 6.10 g·(m2·a)-1 during the study period. The highest growth rate of the NEP was 9.04 g·(m2·a)-1, occurring in the A2 subregion of the loess sorghum gully subregions. The subregion C had the lowest growth rate of 2.74 g·(m2·a)-1. Except for the C subregion, all other ecological subregions (A1, A2, B1, B2, and D) were carbon sinks. ② On the spatial scale, the spatial distribution of annual NEP on the LP was significantly different, with the higher NEP distribution in the southeast of the LP and the lower in the northwest of the LP. The high carbon sink area was mainly distributed in the southern part of the loess sorghum gully subregions, and the carbon source area was mainly distributed in the northern part of the loess sorghum gully subregions and most of the C subregion. The high growth rate was mainly distributed in the central and the southern part of the A2 subregion and the southwest part of the B2 subregion. ③ Human activities had the greatest influence on the temporal variation in NEP in the LP and all the ecological subregions, with the correlation coefficient between human activity data and NEP being above 0.80, and the relative contribution rates of human factors was greater than 50%. The spatial distribution was greatly affected by meteorological factors, among which the precipitation and solar radiation were the main factors affecting the spatial changes in the NEP of the LP. The temporal and spatial variations in the NEP in the LP were influenced by natural and human social factors. To some extent, these results can provide a reference for the terrestrial ecosystem in the LP to reduce emissions and increase sinks and to achieve the goal of double carbon.

Quantification of Holocene temperatures in the eastern Hunshandake Sandy Land using δ13C of loess organic matter

The soil organic carbon isotope indicator (δ13Corg) is widely used in paleoecology and paleoclimate reconstruction due to its ability to record the history of paleovegetation change. Although it has been used as a proxy for precipitation reconstruction, increasing evidence suggests that temperature has played a crucial role in influencing the relative abundance of C3/C4 plants in the mid-latitudes during the interglacial period. This opens up the possibility of reconstructing Holocene temperature using δ13Corg. In this study, the variation of δ13Corg values in a Holocene loess profile (GLH profile), located in the eastern Hunshandake Sandy Land, China, was investigated. And we analyzed the correlation between δ13Corg values and modern temperature for a total of 792 topsoil samples from mid-latitudes of the Northern Hemisphere, which had thermal conditions comparable to the GLH profile. Strong positive correlations were found between δ13Corg values of topsoil samples and both summer temperatures (r = 0.672, p < 0.001) and growing season temperatures (r = 0.669, p < 0.001). Additionally, δ13Corg values showed significant positive correlations with accumulated temperatures above 10 °C (r = 0.641, p < 0.001) and above 0 °C (r = 0.527, p < 0.001). However, the correlation with mean annual temperature was weak (r = 0.280, p < 0.001). The δ13Corg variation in the GLH profile recorded a mixed C3/C4 vegetation composition, with C4 plants comprising between 23.40% and 1.70% of the total abundance during the Holocene. The combined evidence from modern processes and profile variations confirms that warm-season temperature was the main factor driving variations in the δ13Corg values in the GLH profile. Therefore, we used δ13Corg–temperature conversion equations to quantify Holocene seasonal and accumulated temperatures based on the GLH profile. The reconstructed summer temperature peaked at 9.3 ka, followed by a fluctuating downward trend during the mid- and late-Holocene, which is consistent with variations in summer solar insolation. Mean summer temperatures were relatively high at 23.3 °C and 22.5 °C in the early and mid-Holocene, respectively, while the lowest mean summer temperature of 20.5 °C occurred in the late Holocene. Accumulated temperatures above 10 °C and above 0 °C in the early Holocene were 3722 °C·d and 4641 °C·d, respectively, similar to modern observations in the Beijing area, indicating a southward shift of the temperature zone by nearly three degrees of latitude since the early Holocene. These reconstruction results are supported by modern observations, TraCE21 simulations, and other studies. This study is significant for extending the application of the organic carbon isotope indicator for quantitative paleoclimate reconstructions. It verifies its effectiveness in quantifying Holocene temperatures in the marginal zone of the East Asian summer monsoon.

Integrating spatial patterns and driving factors of cultural ecosystem services into territorial spatial governance: A case study of the Horqin Sandy Land with multi-ethnic settlements

Although the spatial patterns of cultural ecosystem services (CES) are often considered in land use management, there is a noticeable disparity in research coverage compared to biophysical ecosystem services (BES). Moreover, there is a lack of research focusing on human perceptions of CES. To address this gap, this study proposed a CES-BES framework that integrates spatial patterns, driving factors of CES, and their interactions with BES, based on the general framework of social and ecological systems. To alleviate the dual pressures of ecological degradation and cultural preservation, this study utilized the constructed CES-BES framework to offer land use recommendations aimed at promoting sustainable development in the Horqin Sandy Land. CES and BES were quantified through a combination of questionnaire surveys, SolVES model and process modeling, including aesthetic, biodiversity, cultural, economic, future, and historical values, as well as net primary productivity, crop production, wind protection, and sand fixation. The results revealed that CES in the Horqin Sandy Land exhibited a discernible pattern of "high in the west and low in the east." Notably, the factors perceived by respondents exerted a more substantial influence on CES than non-perceptual factors. Female respondents showed relatively lower sensitivity to CES overall, but higher sensitivity to biodiversity. Han respondents tended to prioritize biodiversity, while Mongolian respondents were more sensitive to cultural and historical values. Herders exhibited higher sensitivity to biodiversity, while respondents from other occupations showed higher sensitivity to cultural and future values. The influence of land use, topography, and accessibility on different CES was generally similar. All CES showed a positive correlation with elevation, slope, and distance to water, while they showed a negative correlation with distance to roads. Based on the results, the Horqin Sandy Land has been divided into five regions, with development recommendations provided for each region to ensure sustainable development. This study provides a novel perspective and methodological framework for CES supporting territorial spatial governance and land use management, contributing to a more comprehensive understanding of CES.

Fingerprinting aeolian sediment sources in the Mu Us Sandy Land using the MixSIAR model

Understanding and quantifying aeolian sediment sources in sand seas is imperative to elucidate their formation mechanism and promote ecological restoration, particularly in transitional zones between agricultural farming and animal grazing. Despite considerable efforts to identify the provenance of the Mu Us Sandy Land (Mu Us), a clear boundary demarcating the provenance differences between its western and eastern regions remains elusive. Furthermore, the quantitative contributions of its potential source areas are yet to be determined. This study elucidated these aspects using robust source indicators and the MixSIAR fingerprinting model, underpinned by geochemical data. Utilizing provenance indicators such as the K/Ba, K/Rb, Ba/Sr, and Rb/Sr ratios, this study identified the line connecting Angsu and Huanghaojie Town as the clear boundary demarcating the provenance differences between the western and eastern Mu Us. The eastern Mu Us's coarse sand primarily derives from underlying sandstones (70.5%) and local fluvio-lacustrine deposits (29.5%), while the western region's coarse sand predominantly originates from Yellow River (YR) sediments in the Yinchuan Basin, transported from the Northeastern Tibetan Plateau (NTP) (82.2%), and local fluvio-lacustrine deposits (17.8%). Similarly, the Mu Us's fine sand mainly originates from local fluvio-lacustrine deposits, contributing 66.5% and 67.6% to the fine sand in the eastern and western regions, respectively. Under strong westerly winds, Gobi deposits from upwind areas contribute 33.5% and 32.4% of fine sediments to the eastern and western Mu Us, respectively. The spatial heterogeneity of material sources in the Mu Us highlights the combined influence of fluvial and wind processes. Lacustrine deposits play a crucial role in the sediment provenance of the Mu Us. This study demonstrates that the MixSIAR model constitutes an effective approach for quantitative provenance research in deserts located in climatic transitional zones worldwide.

Physiological responses of Bassia dasyphylla to drought during seed germination from different provenances

Bassia dasyphylla is a prevalent herbaceous plant that exhibits enhanced resilience to dryness and elevated temperatures. It is frequently found in dispersed or grouped formation on sandy soil within steppe, semi-desert, and desert regions. Herein, we conducted experiments to examine the growth and physiological traits of B. dasyphylla seeds originated from various regions in response to water scarcity. The study seeks to investigate the ability of these seeds to germinate under drought conditions and offer valuable insights for the development and breeding of high-quality germplasm resources in Inner Mongolia. The results demonstrated that B. dasyphylla originating from desert steppe (DS) exhibited a greater capacity to endure drought conditions in comparison to its counterparts from sandy land (SL). At a water potential of -0.30 MPa, the Seed germination rate from DS was 33.3%, while from SL it was 22.7%. With the increase in drought duration and intensity, germination rate, plumule length, both single-seed weight (SSW) and seed water content (SWC) of B. dasyphylla declined. The protective enzyme activity exhibited an initial increase, followed by a subsequent decline as the duration of the drought increased. Notably, we found that the protective enzyme activity from DS was higher than that from SL. During the initial and intermediate stages of dryness, the soluble sugar and protein of the plant from DS effectively inhibited the peroxidation of membrane lipids, whereas the osmoregulatory properties from SL did not have a significant impact. The findings suggest that the ability of B. dasyphylla to withstand drought conditions in DS can be attributed to its elevated amounts of protective enzymes and osmoregulatory factors, which serve to safeguard the cell membrane during periods of drought.

Coupled hydraulics and carbon economy underlie age-related growth decline and revitalisation of sand-fixing shrubs after crown removal.

Crown removal revitalises sand-fixing shrubs that show declining vigour with age in drought-prone environments; however, the underlying mechanisms are poorly understood. Here, we addressed this knowledge gap by comparing the growth performance, xylem hydraulics and plant carbon economy across different plant ages (10, 21 and 33 years) and treatments (control and crown removal) using a representative sand-fixing shrub (Caragana microphylla Lam.) in northern China. We found that growth decline with plant age was accompanied by simultaneous decreases in soil moisture, plant hydraulic efficiency and photosynthetic capacity, suggesting that these interconnected changes in plant water relations and carbon economy were responsible for this decline. Following crown removal, quick resprouting, involving remobilisation of root nonstructural carbohydrate reserves, contributed to the reconstruction of an efficient hydraulic system and improved plant carbon status, but this became less effective in older shrubs. These age-dependent effects of carbon economy and hydraulics on plant growth vigour provide a mechanistic explanation for the age-related decline and revitalisation of sand-fixing shrubs. This understanding is crucial for the development of suitable management strategies for shrub plantations constructed with species having the resprouting ability and contributes to the sustainability of ecological restoration projects in water-limited sandy lands.

Vegetation–Lake–Sand Landscape of Northeast China Sandy Land between 1980 and 2022: Pattern, Evolution, and Driving Forces

Vegetation–Lake–Sand Landscape of Northeast China Sandy Land between 1980 and 2022: Pattern, Evolution, and Driving Forces

An improvement of the Revised Wind Erosion Equation by considering the effect of non-photosynthetic vegetation

Non-photosynthetic vegetation (NPV) can significantly impact the magnitude of wind erosion. However, most wind erosion models did not take NPV into account, which led to large uncertainties in wind erosion simulation. To reduce these uncertainties, the effects of NPV on wind erosion should be considered in wind erosion simulations. Herein, we collected the hyperspectral and fractional coverage (fNPV) data of NPV from the Mu Us Sandy Land (MUSL). Through constructing a model between the normalized difference tillage index (NDTI) and fNPV, the fNPV values in the MUSL from 2014 to 2017 were estimated by Landsat 8-OLI images and were used to improve the combined vegetation factor (COG) in the Revised Wind Erosion Equation (RWEQ) model to improve this model. Then, the improved RWEQ model was employed to simulate the wind erosion process of the MUSL during these years. The results showed that the mean values of the fNPV in the MUSL from 2014 to 2017 were approximately 2.71 times higher than those estimated by NDVI data (MOD13Q1). The improved RWEQ that considering the NPV significantly improved the precision of the simulation results, as validated by measured data. Compared with the wind erosion modulus (WEM) without NPV, the decreased values caused by NPV were 130.48 t/km2/a (annum), 91.79 t/km2/a, 85.51 t/km2/a and 93.76 t/km2/a from 2014 to 2017, respectively, and the rates of decrease in wind erosion in the corresponding year were 26.52 %, 16.9 %, 21.47 % and 31.33 %, respectively. We believe that integrating NPV monitoring technology into wind erosion models could significantly improve the accuracy of wind erosion simulation, and this study provides new insight into wind erosion modelling, which would be of interest to scholars in the fields of wind erosion and dust emission.

Effects of freeze–thaw cycles on soil nutrients by soft rock and sand remodeling

Abstract To explore the mechanism of freeze–thaw cycles on the nutrient release of soft rock and sand-remodeled soils in Mu Us Sandy land of China, and to clarify the adaptation potential of remodeled soils with different proportions to extreme environment, indoor freezer simulation freeze–thaw experiments were carried out. The research results show that during the 2 cycles of freeze–thaw, the remodeled soil organic matter content and total nitrogen content (TNC) of the three treatments reached their peaks. Compared with that before freezing, T1, T2, and T3 treatments increased TNC by 40.9, 90.2, and 118.9%. The freeze–thaw cycle has a significant impact on the emergence rate of maize (P &lt; 0.05). In the soil during the 2 freeze–thaw cycles, the seedling emergence rate of maize is the highest. Compared with non-freeze–thaw treatment, the maize emergence rate of T1, T2, and T3 treatments was increased by 2, 3, and 3 times, and the emergence rate of T2 and T3 treatments was higher than that of T1 treatments under different freeze–thaw cycles. In conclusion, short-term freeze–thaw cycles can promote soil carbon and nitrogen mineralization and improve nutrient availability in Mu Us Sandy land, and T2 and T3 treatments have better adaptability to the environment.

Improving Tuber Yield of Tiger Nut (Cyperus esculentus L.) through Nitrogen Fertilization in Sandy Farmland.

The cultivation of tiger nut (Cyperus esculentus L.) on marginal lands is a feasible and effective way to increase food production in Northern China. However, the specific influence of nitrogen fertilizer application on the growth dynamics, tuber expansion, overall yield, and nitrogen use efficiency (NUE) of tiger nuts cultivated on these sandy lands is yet to be fully elucidated. From 2021 to 2022, we conducted a study to determine the effect of N fertilizers on the leaf function morphology, canopy apparent photosynthesis (CAP), tuber yield, and NUE of tiger nut. The results indicate that the tuber yield and NUE are closely related to the specific leaf area (SLA), leaf area index (LAI), leaf nitrogen concentration per area (NA), CAP, and tuber expansion characteristics. Notably, significant enhancements in the SLA, LAI, NA, and CAP during the tuber expansion phase ranging from the 15th to the 45th day under the 300 kg N ha-1 treatment were observed, subsequently leading to increases in both the tuber yield and NUE. Moreover, a maximum average tuber filling rate was obtained under the N300 treatment. These improvements led to substantial increases in the tuber yield (32.1-35.5%), nitrogen agronomic efficiency (NAE, 2.1-5.3%), nitrogen partial factor productivity (NPP, 4.8-8.1%), and nitrogen recovery efficiency (NRE, 3.4-5.7%). Consequently, 300 kg N ha-1 of N fertilizers is the most effective dose for optimizing both the yield of tiger nut tubers and the NUE of tiger nut plants in marginal soils. Structural equation modeling reveals that N application affects the yield and NUE through its effects on leaf functional traits, the CAP, and the tuber filling characteristics. Modeling indicates that tuber expansion characteristics primarily impact the yield, while CAP predominantly governs the NUE. Above all, this study highlights the crucial role of N fertilizer in maximizing the tiger nut tuber yield potential on marginal lands, providing valuable insights into sustainable farming in dry areas.

Spatial-temporal Evolution and Driving Factors of Desertification Based on Computer Interpretation in Tarim River Basin

The Tarim River Basin is an important life hinge in Xinjiang, which plays a vital role in maintaining ecological stability. In recent years, it is faced with challenges such as the expansion of sandy land, the decrease of precipitation and sand-dust storm, which lead to the aggravation of desertification and the contradiction between man and land. This study used remote sensing images from 2000 to 2020 to analyze desertification trends through automatic interpretation by computer, combined with NDVI(Normalized Difference Vegetation Index) and FVC(Fractional Vegetation Cover) indicators. The results showed that the total area of desertification land decreased, but the area of serious desertification land increased. Precipitation, Sunshine, wind speed, air temperature, cultivated land area change, urbanization and other factors affect desertification, of which cultivated land area change, temperature change and precipitation change are the most important factors. Policies focused on preventing wind erosion have been inadequate as the economy has developed and conflicts between people and land have intensified.

Spatial and temporal characteristics of drought in the Mu Us Sandy Land based on the Standardized Precipitation Index

The environment of the Mu Us Sandy Land, northern Shaanxi, is fragile, so the temporal and spatial evolution of drought can provide a reference for ecological construction and agricultural production. Based on the daily precipitation data of five meteorological stations from 1967 to 2020, the spatial and temporal evolution characteristics of drought in the Mu Us Sandy Land of northern Shaanxi were analyzed using the methods Standardized Precipitation Index (SPI) and run-length theory. The results show that 1) the smaller the time scale, the higher the sensitivity of the SPI to primary precipitation. 2) The annual, summer, autumn, and winter SPI showed an upward and a wetting trend, and the fastest wetting speed is observed in summer, while spring showed an increasing trend of drought. 3) In the past 54 years, the duration, degree, and intensity of drought events at SPI-3 and SPI-12 scales in the Mu Us Sandy Land of northern Shaanxi showed an insignificant decreasing trend, but the decreasing rate at the SPI-12 scale was faster than that at the SPI-3 scale. The serious periods of drought are November 2018 to May 2019 and April 1999 to July 2021. 4) The duration of drought events at two timescales in each region showed a decreasing trend. The longest durations of drought were in Yulin and Jingbian; Shenmu and Dingbian are the regions with the fastest reduction rate of drought degree at the two scales. Hengshan shows rapid reduction of drought intensity at the two scales and also the region with large average drought intensity. These results are helpful in understanding and describing drought events for drought risk management under the condition of global warming.

Analysis of Spatiotemporal Dynamics of Land Desertification in Qilian Mountain National Park Based on Google Earth Engine

Notwithstanding the overall improvement in the ecological condition of the Qilian Mountains, there are localized occurrences of grassland degradation, desertification, and salinization. Moreover, timely and accurate acquisition of desertification information is a fundamental prerequisite for effective monitoring and prevention of desertification. Leveraging the Google Earth Engine (GEE) platform in conjunction with machine learning techniques, this study aims to identify and extract the spatiotemporal dynamics of desertification in the Qilian Mountain National Park (QMNP) and its surroundings (QMNPs) spanning from 1988 to 2023. Results show that based on the random forest algorithm, the multi-index inversion methodology achieves a commendable overall accuracy of 91.9% in desertification extraction. From 1988 to 2023, the gravity center of light desertification shifts southeastward, while centers characterized by moderate, severe, and extremely severe desertification display a westward retreat with fluctuations. The area of sandy land shows an expansion trend in the medium term, but after 2018, desertification in QMNPs reversed. As of 2023, the sandy land area measured 16,897.35 km2, accounting for 18.29% of the total area of QMNPs. The insights garnered from this study provide a valuable reference for regional desertification prevention and control in the future.

Preliminary Phytochemistry and Anatomy of Grangea Maderaspatana L. from family Asteraceae

Grangea maderaspatana L. is a popular Indian medicinal plant belonging to the Asteraceae family. This plant is commonly known as Madras Carpet growing in sandy lands and waste places. It is reported to contain flavonoids, diterpenes, sesquiterpenoids, steroid, and essential oil. The herb is good for pain in the eyes and ears. The root is an appetizer; astringent to the bowels, diuretic, anthelmintic, Emmenagogue, galactagogue, stimulant; useful in griping, in troubles of the chest and lungs, headache, Paralysis, rheumatism in the knee joint, piles, pain in the muscles, diseases of the spleen and the liver, the troubles of the ear, the mouth and the nose; lessens perspiration (Unani).

Effects of Different Ecological Restoration Pattern on Soil Organic Nitrogen Components in Alpine Sandy Land

Ecological restoration can improve soil fertility and have a significant impact on the soil nitrogen cycle. Nitrogen (N) is an essential nutrient element for plant growth and development, and also an important factor limiting soil productivity. As an important part of soil nitrogen, the composition and proportion of soil organic nitrogen components can directly or indirectly affect the difficulty of soil organic nitrogen mineralization and nitrogen availability, and then affect soil fertility. However, the current studies on soil nitrogen under ecological restoration mainly focus on nitrogen accumulation and nitrogen mineralization, while there are relatively few studies on changes in soil organic nitrogen components, especially in alpine regions. Therefore, in this study, three restoration pattern of mixed forage (MG), single shrub (SA) and shrub combination (SG) that have been restored continuously for 15 years in northwest Sichuan, China, were taken as the research object, and natural sandy land (CK) without manual intervention was taken as the control. Through field sampling and laboratory analysis, the characteristics of the soil nitrogen content and its proportion to soil total nitrogen (TN) under ecological restoration in alpine sandy land in northwest Sichuan, China, were investigated, and the correlation between the nitrogen content and soil physicochemical properties was analyzed. The results showed that the three ecological restoration patterns significantly increased the contents of acylated ammonium nitrogen (AMMN), acid-lyzed amino sugar nitrogen (ASN), acid-lyzed amino acid nitrogen (AAN), acid-lyzed unknown nitrogen (HUN), acid-lyzed total nitrogen (AHN) and non-acid-lyzed nitrogen (NHN) in soil, and the change trend was consistent with that of soil TN. Ecological restoration improved soil nitrogen mineralization and storage capacity by increasing the proportion of AAN, HUN and NHN to soil TN, and the effect was most obvious in the MG pattern 20–40 cm and SG pattern 40–60 cm soil layers. In general, except ASN, the soil nitrogen content was positively correlated with the soil TN, soil water content (SWC) and soil organic carbon (SOC), and negatively correlated with the soil bulk density (BD) and pH. The results of this study will help us to understand the supply capacity of soil nitrogen under ecological restoration and provide a scientific basis for the selection of an ecological restoration mode and the improvement of the restoration effect and efficiency in alpine sandy land.

Probability density distributions of morphological parameters of barchan dunes and their responses to the climate environment

Barchan dunes are a common aeolian geomorphology in sand seas on Earth and Mars. They occur primarily as barchan dune groups. Obvious regional differences occur in the size distribution of dune swarms in different dune fields because of sediment grain size, regional airflow, sand flux, and surface conditions. To explore dune size distributions in different barchan dune fields and clarify the effects of climate on barchan dune morphometry, we used high-resolution remote sensing images and extended time-series meteorological data. Barchan dune fields were located in the southeast edge of the Taklimakan Desert, the western and southern parts of the Qaidam Basin Desert, the Gonghe Basin Sandy Land, and the sand belt connecting the Badain Jaran Desert and the Tengger Desert. Our results revealed the probability density distribution of morphological parameters of barchan dunes, correlations among parameters, and responses to wind regime. The main conclusions are: (1) Probability density distributions of the lengths of windward and lee slopes, the lengths of the two horns, and the dune width, height, and spacing in different deserts followed a log-normal distribution function. (2) Good correlations were found among the dune morphological parameters; width and height, windward slope length and width, and height and spacing showed positive proportionality, and the basal area and the product of width and height were linearly correlated in a double logarithmic coordinate system. (3) Good correspondence was found between dune asymmetry and regional wind conditions, which can be explained by Tsoar's model. Morphological parameters of barchan dunes were linearly and positively correlated with the drift potential. These results provide essential data for further study of the morphological thresholds for dune-dune interactions and elucidation of the mechanisms of interaction among barchan dunes.

Change pattern and stability of oasisization land in Mu Us Sandy Land.

Understanding land structure change and stability in the process of oasisization is particularly important for the desertification control in sandy land. Based on land use data of eight periods from 1980 to 2020, we extracted the spatial distribution information of oasis land in Mu Us Sandy Land, and analyzed the spatio-temporal variations of land transformation patterns and stability of oasis land with overlay analysis and grid analysis. The results showed that desertification in the Mu Us Sandy Land had reversed, with a significant process of oasis. The area of forest and grassland increased from 10.2% in 1980 to 73.7% in 2020, while the area of oasisization land increased from 32500 km2 in 1980 to 33900 km2 in 2020. The area of extremely severe, severe, and moderate desertification significantly decreased, while the area of non-desertification and mild desertification obviously increased. The four patterns of oasisization land transformation, including stability, fluctuation, expansion, and retreat, which accounted for 78.7%, 12.2%, 6.2%, and 2.9% of the oasisization land area in 2020, respectively. The oasisization land with low change intensity (the cumulative change intensity less than 0.12) in the Mu Us Sandy Land accounted for 82.7% of the total oasisization area, and the oasisization land in the sandy land was generally stable. Zoning management strategies should be applied according to the stability of sand belt and transformation pattern of oasisization land to achieve the goal of efficient system management and improvement, including eliminating sand hazards at desertification expansion areas with strong wind and sand activities, consolidating sand resources at oasisization areas where ecologically fragile desertification was frequent, and sustainably managing and utilizing sand resources at stable expansion of oases in forest- and grass-rich oasisization areas.

Characteristics of spatial and temporal variability in the distribution of biological soil crusts on the Loess Plateau, China.

Biological soil crust (biocrust) is widely distributed on the Loess Plateau and plays multiple roles in regulating ecosystem stability and multifunctionality. Few reports are available on the distribution characteristics of biocrust in this region, which limits the assessment of its ecological functions. Based on 388 sampling points in different precipitation zones on the Loess Plateau from 2009 to 2020, we analyzed the coverage, composition, and influencing factors of biocrust across different durations since land abandonment, precipitation levels, topography (slope aspect and position), and utilization of abandoned slopelands (shrubland, forest, and grassland). On this base, with the assistance of machine learning and spatial modeling methods, we generated a distribution map of biocrust and its composition at a resolution of 250 m × 250 m, and analyzed the spatial distribution of biocrust on the Loess Plateau. The results showed that the average biocrust coverage in the woodlands and grasslands was 47.3%, of which cyanobacterial crust accounted for 25.5%, moss crust 19.7%, and lichen crust 2.1%. There were significant temporal and spatial variations. Temporally, the coverage of biocrust in specific regions fluctuated with the extension of the abandoned durations and coverage of cyanobacterial crust, while moss crust showed a reverse pattern. In addition, the coverage of biocrust in the wet season was slightly higher than that in the dry season within a year. Spatially, the coverage of biocrusts on the sandy lands area on the Loess Plateau was higher and dominated by cyanobacterial crusts, while the coverage was lower in the hilly and gully area. Precipitation and utilization of abandoned land were the major factors driving biocrust coverage and composition, while slope direction and position did not show obvious effect. In addition, soil organic carbon content, pH, and texture were related to the distribution of biocrust. This study uncovered the spatial and temporal variability of biocrust distribution, which might provide important data support for the research and management of biocrust in the Loess Plateau region.

Evolution of vegetation cover and impacts of climate change and human activities in arid regions of Northwest China: a Mu Us Sandy Land case

Evolution of vegetation cover and impacts of climate change and human activities in arid regions of Northwest China: a Mu Us Sandy Land case

The vegetation–topography heterogeneity coupling in the Loess Plateau, China

As a result of adaptation to the environment, the great environmental spatial heterogeneity leads to the high spatial heterogeneity of vegetation status. This coupling may be more apparent in water-limited drylands, where topography is the main determinant of small-scale variation in water availability and energy. Metrics describing this coupling may contribute to the detection of the extension of vegetation reshaped by human intervention and other driven forces. In this study, the heterogeneity index of coupling (HIC) was developed to indicate the coupling between spatial heterogeneity of vegetation status (Hv) and the spatial heterogeneity of topography (HT) in the Loess Plateau in northern China. The 16-day composed MODIS normalized vegetation index (NDVI) with a resolution of 250 m and SRTM DEM were employed to quantify the heterogeneity of vegetation status and the topographical heterogeneity. The results show that HIC varies among geomorphic zones, land cover types, and land cover change categories. Among all land cover types, HIC of sandy areas was the largest, followed by the HIC of the forest, shrub, farmland, and grassland. Among geomorphic zones, the highest HIC value appeared in plains with dense residential areas, followed by sandy land that is frequently reshaped by wind, rocky mountainous areas, hilly and gully loess plateaus, and loess tableland. It was revealed that the alternation of vegetation by human activities and natural disturbances shaped greater HIC. Results of this study approved the effectiveness of the HIC in reflecting the coupling of the vegetation status with topography at regional scale.