Utilizing sediment grain size characteristics to assess the effectiveness of clay–sand barriers in reducing aeolian erosion in Minqin desert area,China

The clay–sand barriers in Minqin desert area,China,represent a pioneering windbreak and sand fixation project with a venerable history of 60 a.However,studies on evaluating the long-term effectiveness of clay–sand barriers against aeolian erosion,particularly from the perspective of surface sediment grain size,are limited and thus insufficient to ascertain the protective impact of these barriers on regional aeolian activities.This study focused on the surface sediments(topsoil of 0–3 cm depth)of clay–sand barriers in Minqin desert area to explain their erosion resistance from the perspective of surface sediment grain size.In March 2023,six clay–sand barrier sampling plots with clay–sand barriers of different deployment durations(1,5,10,20,40,and 60 a)were selected as experimental plots,and one control sampling plot was set in an adjacent mobile sandy area without sand barriers.Surface sediment samples were collected from the topsoil of each sampling plot in the study area in April 2023 and sediment grain size characteristics were analyzed.Results indicated a predominance of fine and medium sands in the surface sediments of the study area.The deployment of clay–sand barriers cultivated a fine quality in grain size composition of the regional surface sediments,increasing the average contents of very fine sand,silt,and clay by 30.82%,417.38%,and 381.52%,respectively.This trend became markedly pronounced a decade after the deployment of clay–sand barriers.The effectiveness of clay–sand barriers in erosion resistance was manifested through reduced wind velocity,the interception of sand flow,and the promotion of fine surface sediment particles.Coarser particles such as medium,coarse,and very coarse sands predominantly accumulated on the external side of the barriers,while finer particles such as fine and very fine sands concentrated in the upwind(northwest)region of the barriers.By contrast,the contents of finest particles such as silt and clay were higher in the downwind(southeast)region of the sampling plots.For the study area,the deployment of clay–sand barriers remains one of the most cost-effective engineering solutions for aeolian erosion control,with sediment grain size parameters serving as quantitative indicators for the assessment of these barriers in combating desertification.The results of this study provide a theoretical foundation for the construction of windbreak and sand fixation systems and the optimization of artificial sand control projects in arid desert areas.

Distribution Characteristics of Soil Total Nitrogen in Low-efficiency Forest Land in the Northern Windy Desert Area of Jingbian County

[Objectives]The paper was to investigate the distribution characteristics of soil total nitrogen in low-efficiency forest land in the northern windy desert area of Jingbian County.[Methods]The distribution of soil total nitrogen in the 0-40 cm soil layer of 5 towns in the northern windy desert area of Jingbian County was studied through field sampling and laboratory detection.[Results]The average soil total nitrogen contents of Hongdunjie Town,Haizetan Town,Huanghaojie Town,Ningtiaoliang Town,Dongkeng Town and windy desert area in the 0-20 cm soil layer were 0.259,0.224,0.242,0.248,0.431 and 0.275 g/kg,respectively.The soil total nitrogen content in Dongkeng Town was higher than those in other towns,while there was little difference among other regions.The average total nitrogen contents in the 20-40 cm soil layer were 0.239,0.285,0.113,0.262,0.349 and 0.241 g/kg,respectively.The soil total nitrogen content in Huanghaojie Town was slightly lower than those in other towns,while that in Dongkeng town was higher.The variation coefficient of soil total nitrogen content in the survey area was greater than 30%,and there was great difference in spatial distribution.With the increase of soil depth,there was little change in soil total nitrogen content,namely the soil total nitrogen contents in 5 towns and windy desert area were not statistically different in the 0-40 cm soil layer.According to the nutrient grading standard of the second national soil survey,the soil total nitrogen content in the survey area was in the deficiency grade.[Conclusions]The research will provide a scientific guidance for the healthy and sustainable development of vegetation in arid regions.

Impact of climate change and human activities on the spatiotemporal dynamics of surface water area in Gansu Province, China

Understanding the dynamics of surface water area and their drivers is crucial for human survival and ecosystem stability in inland arid and semi-arid areas.This study took Gansu Province,China,a typical area with complex terrain and variable climate,as the research subject.Based on Google Earth Engine,we used Landsat data and the Open-surface Water Detection Method with Enhanced Impurity Control method to monitor the spatiotemporal dynamics of surface water area in Gansu Province from 1985 to 2022,and quantitatively analyzed the main causes of regional differences in surface water area.The findings revealed that surface water area in Gansu Province expanded by 406.88 km2 from 1985 to 2022.Seasonal surface water area exhibited significant fluctuations,while permanent surface water area showed a steady increase.Notably,terrestrial water storage exhibited a trend of first decreasing and then increasing,correlated with the dynamics of surface water area.Climate change and human activities jointly affected surface hydrological processes,with the impact of climate change being slightly higher than that of human activities.Spatially,climate change affected the'source'of surface water to a greater extent,while human activities tended to affect the'destination'of surface water.Challenges of surface water resources faced by inland arid and semi-arid areas like Gansu Province are multifaceted.Therefore,we summarized the surface hydrology patterns typical in inland arid and semi-arid areas and tailored surface water'supply-demand'balance strategies.The study not only sheds light on the dynamics of surface water area in Gansu Province,but also offers valuable insights for ecological protection and surface water resource management in inland arid and semi-arid areas facing water scarcity.

Three-year Variations of Water, Energy and CO_2 Fluxes of Cropland and Degraded Grassland Surfaces in a Semi-arid Area of Northeastern China

Based on 3 years （2003-05） of the eddy covariance （EC） observations on degraded grassland and cropland surfaces in a semi-arid area of Tongyu （44°25′N, 122°52′E, 184 m a.s.1.）, Northeast China, seasonal and annual variations of water, energy and CO2 fluxes have been investigated. The soil moisture in the thin soil layer （at 0.05, 0.10 and 0.20 m） clearly indicates the pronounced annual wet-dry cycle; the annual cycle is divided into the wet （growing season） and dry seasons （non-growing season）. During the growing season （from May to September）, the sensible and latent heat fluxes showed a linear dependence on the global solar radiation. However, in the non-growing season, the latent heat flux was always less than 50 W m^-2, while the available energy was dissipated as sensible, rather than latent heat flux. During the growing season in 2003-05, the daily average sensible and latent heat fluxes were larger on the cropland surface than on the degraded grassland surface. The cropland ecosystem absorbed more CO2 than the degraded grassland ecosystem in the growing season in 2003-05. The total evapotranspiration on the cropland was more than the total precipitation, while the total evapotranspiration on the degraded grassland was almost the same as the total annual precipitation in the growing season. The soil moisture had a good correlation with the rainfall in the growing season. Precipitation in the growing season is an important factor on the water and carbon budget in the semi-arid area.

Land-Air Interaction over Arid/Semi-arid Areas in China and Its Impact on the East Asian Summer Monsoon. Part I:Calibration of the Land Surface Model (BATS)Using Multicriteria Methods

To improve the land surface simulation in the arid and semi-arid areas of northern China, the observational data from two field experiments in Dunhuang and Tongyu are used to optimize the parameters in the land surface model, BATS, through calibration with the multicriteria method. Sensitivity analysis to the parameters in Dunhuang and Tongyu indicates that different parameters need to be calibrated in two sites with different environmental and climate regimes. Comparison of observed sensible heat flux, latent heat flux, and ground surface temperature with the simulated ones shows the simulations with the optimized parameters have been substantially improved. Especially, the holistic simulations with the calibration of the parameter values are much closer to the observations in the arid region （Dunhuang）, and the energy partition with the calibrated parameters can also be simulated well in the semi-arid region （Tongyu）. Whole results demonstrate that the parameter calibration of the land surface model is important when the model is to be used to investigate the land-air interaction.

The causes of land landscape changes in semi-arid area of Northwest China: a case study of Yulin city

Rapid land landscape change has taken place in many arid and semi-arid regions such as the vulnerable ecological area over the last decade. In this paper, we quantified land landscape change of Yulin in this area between 1985 and 2000 using remote sensing and GIS. It was found that fallow landscape decreased by 125,148 hm^2 while grassland and woodland increased by 107,975 hm^2 and 17,157 hm^2, respectively. The major factors responsible for these changes are identified as the change in the government policy on preserving the environment, continued growth in mining, and urbanization. The efforts in restoring the deteriorated ecosystem have reaped certain benefits in reducing the spatial extent of sandy land through replacement by non-irrigated farmland, woodland and grassland. On the other hand, continued expansion of mining industry and urbanization has exerted adverse impacts on the land landscape. At present regional economic development conflicts directly with the protection of the natural environment. Such a conflict has caused the destruction to the land resources and fragmentation of the landscape accompanied by land desertification, the case is even serious in some localities.

Lake Area Changes and the main causes in the hinterland of Badain Jaran Desert during 1973–2010,China

Lake area information in the Badain Jaran Desert in 1973, 1990, 2000, and 2010 was obtained by visual interpretation and water index analysis of remote sensing images, based on the spatial and temporal characteristics of lake area changes during 37 years. Results indicated that the nttmber of lakes declined from 94 to 82 and the total surface area was reduced by 3.69 km2 during 1973-2010. The desert lake area reduced by different degrees in different periods, but this occurred most rapidly during 1973-1990. According to the statistics of lake area changes, lake area decreases mainly occurred in the lakes with areas less than 0.2 km2, while the areas of lakes greater than 0.9 km2 only fluctuated. The changes of lake areas were probably due to changes in the quantity of underground water supplies rather than the effects of local climate change or human factors.

Geochemical Stream Sediment Survey in the Wadi Umm Rilan Area,South Eastern Desert,Egypt:A New Occurrence for Gold Mineralization

The present paper investigates the stream sediment geochemistry, behavior of gold and associated elements, delineates Au-anomalous sites and defines related sources in the Wadi Umm Rilan area. Fifty three major and trace elements were analyzed using ICP-MS and treated applying various statistical and mapping techniques. The results showed a significant difference of mean and median Au and most chemical elements in the three portions of the area, and higher values were recorded in the western portion. Furthermore, Au-anomalous sites appeared in upper and lower parts of the Wadi Umm Rilan, along the tributaries of metavolcanic unit and near granitoid contacts. This indicates the main source of Au mineralization is related to emplacement of granitoid plutons and accompanying hydrothermal solutions. There are significant indications for the presence of more than one mineralization event forming a probable single major episode of mineralization in the area, involving Au, Pb and U mineralizations. Geology, geomorphologic aspects and weathering processes could control stream sediment geochemistry, anomalies of Au and associated elements, elemental association and their dispersion patterns. Therefore, the area is fruitful and regarded as a promising target for Au exploration, using Ag, As, Sb, Cd, Cs, and TI as pathfinder elements.

Remote Sensing Parameterization of Land Surface Heat Fluxes over Arid and Semi-arid Areas

Dealing with the regional land surfaces heat fluxes over inhomogeneous land surfaces in arid and semi-arid areas is an important but not an easy issue. In this study, one parameterization method based on satellite remote sensing and field observations is proposed and tested for deriving the regional land surface heat fluxes over inhomogeneous landscapes. As a case study, the method is applied to the Dunhuang experimental area and the HEIFE (Heihe River Field Experiment, 1988-1994) area. The Dunhuang area is selected as a basic experimental area for the Chinese National Key Programme for Developing Basic Sciences: Research on the Formation Mechanism and Prediction Theory of Severe Climate Disaster in China (G1998040900, 1999-2003). The four scenes of Landsat TM data used in this study are 3 June 2000, 22 August 2000, and 29 January 2001 for the Dunhuang area and 9 July 1991 for the HEIFE area. The regional distributions of land surface variables, vegetation variables, and heat fluxes over inhomogeneous landscapes in arid and semi-arid areas are obtained in this study.

Rehabilitation and Sustainable Use Pattern of Rocky-desertified Land in Southwest China’s Poverty-stricken Karst Mountainous Areas——A Case Study in Benggu Township, Xichou County, Yunnan, China

The rocky desert in a karst area directly causes the lack of soil, water and forest, hence leading to the poverty there. In 1990, the villagers from the Muzhe Village in Benggu Township, Xichou County, Yunnan declared a war against rocky desert in an attempt to ask the fields for more yields. They invented a distinctive land rehabilitation and sustainable use pattern called “transforming heavenand earth” that had been practiced in Southwest China’s karst areas. The key mechanism of the pattern was to develop terraced fields with well conserved soil, water and fertility by exploding rocks in the fields, building stone walls, gathering more soil, and improving soil quality and productivity for the fields in combination with building of irrigation facilities and roads, as well as with forestation and agriculture structure adjustment. The purpose of the pattern was to alleviate poverty in the karst areas by improving soil productivity and promoting agriculturaldevelopment. A typical area was studied with the help of Participatory Rural Appraisal (PRA) and the pattern was carried out there for fifteen years, have produced excellent ecological benefits and good economic benefits. Its application in the area approved that it was a sustainable land use pattern for rocky desert areas.

Artificial woodland degradation in semi-arid agro-pastoral transitional area： conceptual model and status assessment

Planting trees was used as one of cost-effective measures for desertification control in add and semi-add areas of China. Woodland degradation, however, is becoming an inevitable issue in these areas. In this paper, a typical county, Ejin Holo County, Inner Mongolia, China was selected for its assessment of artificial woodland degradation. A conceptual model for woodland degradation was delineated qualitatively based on field sampling survey, and four model-based indicators as humidity index （HI）, vegetation index （NDVI）, soil type （ST） and soil erosion modulus （EM） were screened out and used to a GIS-based method for artificial woodland degradation assessment in this semi-add agro-pastoral transitional area. All the indicator layers were overlaid and desertification assessed using simplified equation with equal weights for each indicators. The assessment results showed that in 336. 09 km^2 of total woodland area, 311.35 km^2 woodland were under degradation, and the area for slight, medium, severe degradation was 78.97, 119.73 and 112.65 km^2, respectively. It was suggested that much attention should be paid on woodland improvement and plant species selection, especially shrub species, before revegetation in similar areas.

Properties of Solar Radiation over Chinese Arid and Semi-Arid Areas

Climatic characteristics of broadband solarradiation (Rs) in Chinese arid and semi-arid areas are reported in this study. The annual average daily Rs in thearid and semi-arid areas is 16.3 ± 5.77 and 15.3 ± 5.16 MJm-2 d-1, respectively. The highest value (17.2 ± 5.84 MJm-2 d-1) appears in an arid area at Linze. The lowest valueappears in the semi-arid area of Ansai. Pronounced seasonal variation of Rs is observed with the highest value insummer and the lowest in winter. The clearness indexshowed similar seasonal pattern at most sites, with theminimum observed in the summer and the highest valuesin winter at both arid and semi-arid areas. The seasonalvariation of the ratio of Rs to its extraterrestrial value Kt inthe arid area is more significant than that observed in thesemi-arid region, and it is caused by the different range ofvariation of water vapor between arid and semi-arid areasThe seasonal fluctuations in Rs and Kt are mainly controlled by the water vapor content in these areas. Theaerosol particles have significant influence on Rs and Kt atstations with higher aerosol burden.

Probabilistic modeling of soil moisture dynamics in a revegetated desert area

Soil moisture is the key link between land hydrological and ecological processes which plays an important role in the terrestrial water cycle. As extreme weather events have increased in recent years, the stochastic simulation of soil moisture has gradually become the focus of ecohydrology research. Based on continuous monitoring of soil moisture data from 2008 to 2011, and histor- ical precipitation data from 199l to 2011, combined with the Rodriguez-Iturbe soil moisture dynamic stochastic model, soil mois- ture dynamics and its probability density fimction in a revegetated desert area was simulated. Results show that annual soil mois- ture dynamic changes of the revegetated desert area during the growing season complied with rainfall distribution; soil moisture probability presents a single-peak distribution in the plant rhizosphere layer （0-60 cm）. The peak width in the 20 cm topsoil was wider than in other soils, and the distribution presented the strong fluctuations and multiple aggregates. The peak widths of 40 cm and 60 cm soil moisture probability distribution were small, which are in accordance with simulated results of the Rodri- guez-lturbe model. This confrms that the Rodriguez-Imrbe model has good applicability and can well simulate the statistical characteristics of soil moisture in an arid revegetated desert area.

Environmental Conditions of Barchan Dune and Barchan Chain-A Case Study from the Hexi Desert Area of Gansu

[Objective] The paper was to discuss why the top of tall barchan dunes and barchan chains widespread in single prevailing wind area had not been leveled by wind erosion. [Method] Based on the preliminary survey of distribution status,the morphological characteristics and environmental conditions of barchan dunes and barchan chains in Hexi desert area of Gansu were investigated in details. The significance of difference between samples and significance of correlation between indicators were examined via variance test. [Result] Barchan dunes and barchan chains in Hexi desert area of Gansu distributed at the leeward direction of desert fringe,generally in patch distribution. The distribution area was gravelly beach or cohesive gravel beach,with broader dune slack; winds in distribution area of barchan dunes and barchan chains blew obviously from one direction,while winds at other directions were light or occasionally strong but with low frequency;the barchan dune in the desert fringe of Hexi desert area of Gansu was relatively tall,while barchan chain was even more taller and larger. Coincidence or separation of the dune peak and the sand ridge might be related to distribution frequency of dominant prevailing wind or wind at opposite direction and the observation seasons.[Conclusion]Studying top stability of barchan dune has an important academic value in revealing blowing sand movement rule at desert fringe,invasion of sand flow,and expansion of desert.

Comparisons between Movement Speed of Main Types of Dunes:A Case Study of Desert Areas in Hexi Region of Gansu Province

In desert areas in Hexi region,11 barchan dunes,6 chains of barchan dunes,6 pyramid dunes,6 parabolic dunes and 6 accumulated sand-belts were chosen to study their movement speed based on images obtained by Google Earth in various periods.The results show that among the dunes,the movement of the barchan dunes was the fastest,followed by the chains of barchan dunes,and only the tops of the pyramid dunes swayed,while the parabolic dunes and accumulated sand-belts hardly moved forward.The higher the barchan dunes(or the chains of barchan dunes) were,the slower the movement was.On the contrary,the higher the pyramid dunes were,the faster the swing was.There was a positive correlation between the movement speed of the barchan dunes and the average wind speed of sandstorms.

Study on the Resistance Indexes of Four Kinds of Desert Plants in Qinghai Lake Area

[Objective] The research aimed to study the resistance of four kinds of desert plants in Qinhai Lake area.[Method] By contrasting the resistance indexes of four kinds of plants which included Ephedra intermedia,Stellera chamaejasme,Achnatherum splendens and Xanthopappus subacaulis,the resistance of four kinds of plants in Qinghai Lake area was analyzed.The resistance indexes included the soluble protein,MDA,free Pro content and the activities of SOD,POD,CAT.Moreover,the resistance of four kinds of plants was evaluated comprehensively by using Fuzzy membership function method.[Result] Under the low-temperature and arid adversity in Qinghai Lake area,SOD activity presented as Stellera chamaejasme>Xanthopappus subacaulis>Ephedra intermedia>Achnatherum splendens,and CAT activity presented as Stellera chamaejasme>Xanthopappus subacaulis>Achnatherum splendens>Ephedra intermedia.Under the same high-salt environment,CAT activity of Stellera chamaejasme was eight times higher than that of Ephedra intermedia.It illustrated that the salt resistance of Stellera chamaejasme was stronger than that of Ephedra intermedia.The free Pro content showed as Xanthopappus subacaulis>Ephedra intermedia>Stellera chamaejasme>Achnatherum splendens.Under the same adversity,Pro content of Ephedra intermedia was 2.83 times of Stellera chamaejasme.It was because that MDA content in Stellera chamaejasme was the lowest,and the membranous peroxide harm was the smallest.It caused that Pro content (stress penetration material) was low.It also illustrated that the resistance of Stellera chamaejasme was stronger than that of Ephedra intermedia.The comprehensive evaluation of Fuzzy membership function showed that the resistance presented as Xanthopappus subacaulis>Stellera chamaejasme>Ephedra intermedia>Achnatherum splendens.[Conclusion] The research provided the theory basis for the breeding of drought-resistance new variety and the development of good germ plasm resource in Qinghai Lake area.

Effects of vibration in desert area caused by moving trains

The ballast layer, filled with fine particles like blown sand, is one of the important problems of ballasted railway tracks in desert areas. Blown sand, as a contaminator of ballast layer, increases track stiffness and may cause serious damage to sleepers, pads, rails, and vehicles. In this paper, the effects of increasing track stiffness due to windy sands in the ballast layer and the train induced vibrations due to this phenomenon were studied. Based on field studies in a desert area in Iran, a two-dimensional finite/infinite element model for a railway track with plane strain condition was analyzed using the software ABAQUS, and the track vibrations were examined by changing the values of stiffness of ballast layer. Vibrations caused by the load of train at different distances from the cross-section of track were inves- tigated, and the values of vertical vibration displacement, velocity, and acceleration were calculated. Results show that acceleration values of vertical vibration increase with the increasing of ballast layer stiffness caused by the filling of sand, while the vertical vibration velocity of track and the induced ground displacement decrease. The farther the distance from the source of vibration, the less the displacement, velocity, and acceleration. In addition, the methods for reducing train-induced vibrations were introduced.

Studying surface structure in desert areas using multiple kinds of surface wave data

Shallow surface wave methods are mostly used for investigation of the surface velocity structure in environmental and engineering geophysics in non-desert areas. For the special geological features of the Takelamagan Desert area, we use the multi-channel analysis of surface wave （MASW） method to process multi-channel shallow surface wave records to determine the near surface velocity structure in the desert area. We also process, analyze, and compare the surface waves in many-trace records extracted from the oil exploration shot gathers in the area. We show that the MASW method can determine detailed shallow velocity structure in desert areas and the many-trace records can be used to get detailed deep geological structure. The combination of the two different datasets can obtain the exact velocity structure upper 60 m depth in the survey area.

A Study of Siliceous Pneumoconiosis in a Desert Area of Sunan County,Gansu Province,China

Three hundred and ninety five residents in a desert area were examined with chest radiographs and 28 cases with siliceous pneumoconiosis were found. The prevalence of siliceous pneumoconiosis was 7.09%, and that over 40 years of age was 21%. The histological findings of lungs from a camel living in that area for 20 years also confirmed to have siliceous pneumoconiosis.

Spatiotemporal change of beneficiary area from wind erosion prevention service in the Ulan Buh Desert in 2008 and 2018

The Ulan Buh Desert is one of the eight deserts in China that provides wind erosion prevention service(i.e.,the ecosystem;vegetation,production,and construction activities that promote sand fixation).It is significant for the construction of the national ecological barrier,and the protection of the ecological security in the Yellow River and North China.In this study,we selected two representative years(2008 and 2018)and quantified wind erosion prevention service from the Ulan Buh Desert using the RWEQ model.Meanwhile,the HYSPLIT model was used to simulate the spatial flow process from the service supply area to the beneficiary area and to determine its scope.The specific dust reduction amount in the beneficiary area was then calculated.The energy and the time-space relation of wind erosion prevention service in the areas that receive benefits from Ulan Buh Desert were compared before and after implementing environmental restoration measures.The results showed that:(1)the total amount of wind erosion prevention in the Ulan Buh Desert in 2018 was 2.12×10^(10)kg,which was 5.17 times higher than that in 2008;(2)in 2018,the distribution density of the flow path of wind erosion prevention service was lower than that in 2008,and the flow paths in each year were concentrated in the beneficiary areas with the path distribution frequency of less than 10%;(3)the total dust reduction in the downwind area of the Ulan Buh Desert in 2018 was higher than that in 2008,totaling 15.54 million tons.Inner Mongolia Autonomous Region and Shanxi Province had the most significant amount of dust reduction.