Subjects: Geosciences >> Geography submitted time 2024-06-12 Cooperative journals: 《干旱区研究》
Abstract： Landscape ecological risk evaluation is an essential tool for measuring the safety of ecosystems within a certain range. Taking the Yarkant River Basin as the study area, we synthesized the Markov-PLUS model and the landscape ecological risk assessment index to analyze and predict the evolution characteristics of land use and landscape ecological risk and the change trends under multiple future scenarios and to delineate the risk focus management regions. The results were as follows: (1) Cultivated land, water, and impervious surface in the Yar-kant River Basin increased, and woodland, grassland, and unused land decreased from 2005 to 2020. In 2035, land use under Scenario I followed the historical development pattern of change. In comparison with Scenario I, cultivated land increased and other land types decreased in Scenario II; woodland, grassland, and water increased and cultivated land, impervious surface, and unused land decreased in Scenario III. (2) From 2005 to 2035, the landscape ecological risk of the Yarkant River Basin as a whole showed an upward trend, and the spatial distribution was characterized by "low in the southwest and high in the northeast." The risk deterioration area was mainly concentrated in the alluvial plains at lower altitudes, and the risk maintenance area was mainly distributed in the mountains and glaciers at higher altitudes. (3) In comparison with Scenarios I and II, Scenario III had a smaller average value of the landscape ecological risk index, and it was the optimal future scenario to achieve a win-win situation for both ecological protection and economic development in the Yarkant River Basin. (4) The alluvial plain in the northeastern part of the Yarkant River Basin was a stable high-risk region, the edges of the alluvial plain and the mountains in the west were risk-prone regions, and the mountains and glaciers in the south were in-creasing-risk lagging regions. The results of this study can provide a reference for the optimization of local landscape ecological security patterns and ecological risk prevention or reduction.
Subjects: Geosciences >> Geography submitted time 2024-06-12 Cooperative journals: 《干旱区研究》
Abstract： There are a large number of rodent mounds in the alpine grassland rodent activity area of the Yellow River source, and soil wind erosion is easy to occur under the influence of dry and windy climate. In order to clarify the characteristics and laws of soil wind erosion in rodent mounds, this study took the Ochotona curzoniae and Myospalax baileyi mounds in 14 test areas at different altitudes and vegetation coverage in the Yellow River source basin as the research objects. The field simulated wind erosion test device was used to analyze and discuss the soil loss and nutrient loss law of rodent mounds in different regions under different wind speeds. results showed: (1)There was a significant difference in the amount of soil wind erosion between different regions ( P<0.05 ). When the wind speed is small, there is no significant difference in soil loss between the two different mounds. When the wind speed increased to 12 m·s-1, the soil loss of plateau pika mound was greater than that of plateau zokor mound ( P<0.05 ). When the wind speed increased from 3 m·s-1 to 12 m·s-1, the average increase of soil loss in the two kinds of mounds was 238.16% and 146.31%, respectively. (2) The wind erosion rate of the mound soil in each test area generally showed a decreasing trend from fast to slow. Vegetation coverage was a significant factor affecting the soil loss of the mound under low wind speed and was related to altitude. (3)With the aggravation of grassland degradation, soil total nitrogen content, available nitrogen, available potassium and organic matter content decreased significantly, while total phosphorus, total potassium and available phosphorus showed an upward trend. This study shows that the difference of soil wind erosion in different regions of the Yellow River source is closely related to soil moisture content, particle size and wind speed.
Subjects: Geosciences >> Geography submitted time 2024-06-12 Cooperative journals: 《干旱区研究》
Abstract： This study analyzed the land use structure, dynamics, intensity, and land use conversion of the agro-pastoral ecotone of Gansu Province from 2000 to 2020 using remote sensing (RS), geographic information system (GIS), and Geodetector in combination with social and economic data. (1) From 2000 to 2020, cultivated land, forest land, and grassland were the main land use types in the agro-pastoral ecotone of Gansu Province, and the total proportion of the three was more than 95%. The difference degree of land use structure was less than 0.01, and the structure was generally stable. The overall land use change initially increased and subsequently slowed down over time. (2) The conversion of cultivated land, forest land, and grassland accounted for more than 96% of the total conversion area in the agro-pastoral ecotone of Gansu Province. Land use conversion was observed among all land use types. Converted cultivated lands were mainly converted to forest land and grassland, whereas other land use types were converted to construction land. Land use type changes were mainly concentrated in the Loess hills in central Gansu and the Loess Plateau gully region in eastern Gansu. (3) In the context of l ong term land use changes, Geodetector demonstrated good applicability. The driving factors for land use changes in the farming–pastoral ecotone of Gansu varied during different periods. These changes were driven by a combination of socioeconomic factors and natural geographic factors, with the former having stronger explanatory power for land use change. Interactions among these factors exhibited either two-factor enhancement or nonlinear enhancement. Two-factor interactions had stronger explanatory power for land use changes than single-factor explanations.
Subjects: Geosciences >> Geography submitted time 2024-06-12 Cooperative journals: 《干旱区研究》
Abstract： In the present study, clay sand barrier–artificial Haloxylon ammodendron plantations and a mobile sand site (control) in the Minqin desert area were used to investigate the plant species composition, species importance value, dominan t species characteristics, species diversity, and soil moisture content. This study explored the long term effects of clay sand barrier–artificial Haloxylon ammodendron plantation construction on regional plant community structure, species diversity, and soil moisture. In total, 12 species belonging to 12 genera and 6 families were recorded in the c lay sand barrier–artificial Haloxylon ammodendron plantations in the Minqin desert area, with Chenopodiaceae and Zygophyllaceae being the dominant families. The construction of the artificial sand control system significantly increased the number of plant species in the region (from 4 species to 5–8 species). With an increase in the installation period, the vegetation structure gradually evolved from Agriophyllum squarrosum and Haloxylon ammodendrine (dominant species) to Grubovia dasyphylla, Kali collinum,Limonium aureum, and Haloxylon ammodendrine (dominant species). The life forms also shifted from a single type dominated by annual herbaceous plants to a composite type consisting of annual herbaceous plants, perennial herbaceous plants, and shrubs. Regarding alpha diversity, species richness index, Shannon–Wiener index, Simpson index, Pielou index, and Alatalo index showed an overall unimodal trend, with the highest species number and most even species distribution observed in the 20-year installation site and the lowest species number and most uneven species distribution observed in the control sand site. The Jaccard index of plant community similarity between neighboring sites with various installation periods showed the following order: control sand site > 1-year installation site > 20-year and 40-year installation sites > 1-year and 5-year installation sites > 10-year and 20-year installation sites > 40-year and 60-year installation sites > 5-year and 10-year installation sites. The dissimilarity index and Cody index showed the opposite trend. The fluctuation pattern of the regional soil moisture content was consistent with the trend of plant community succession. Compared with deeper soil layers (40 –60 cm), the role of shallow soil layers (10–30 cm) in the natural succession process of regional plants was more pronounced.
Subjects: Geosciences >> Geography submitted time 2024-06-12 Cooperative journals: 《干旱区研究》
Abstract： In the context of global climate change, the spatiotemporal characteristics of fractional vegetation coverage (FVC)serve as a crucial indicator for assessing ecological environment quality in various regions. However, the specific spatiotemporal variations, change trends, and underlying echanisms of FVC response to human activities in Inner Mongolia remain undefined. Bridging this knowledge gap is essential for understanding ecological management outcomes and providing a scientific basis for local ecological policies and spatial planning. Using MOD13A1 NDVI data, land cover data, and nighttime light data spanning from 2000 to 2022, we calculated the annual maximum fractional vegetation coverage in Inner Mongolia and explored its spatiotemporal variations. Additionally, we illustrated the change trends in FVC. We conducted pixel-by-pixel correlation analysis to examine the response modes of FVC to human activities. Our findings reveal the following: (1) FVC distribution in Inner Mongolia demonstrated a decreasing trend from northeast to southwest, consistent with the overall precipitation changes in China. Notably, areas along the Yellow River, such as the Houtao Plain and the Qiantao Plain, exhibit relatively higher FVC due to abundant water resources and well-developed agriculture. Overall, FVC showed improvement with a growth rate of 0.0039·a-1, remaining relatively stable in most areas (64.02%) and significantly increasing in 31.64% of the region, all prefecture-level cities showing a positive average annual growth. (2) Changing trends in FVC were predominantly nonsignificant (65.62%), followed by a significant increase (17.36%), an extremely significant increase (13.43%), a significant decrease (3.27%), and an extremely significant decrease (0.32%). Regions experiencing significant and highly significant reductions displayed a strong spatial correlation with newly developed construction land. (3) Regarding human activities in Inner Mongolia, most regions (79.67%) showed no significant influence on FVC changes. In 12.80% of the regions, human activities positively impacted FVC, primarily in grassland and arable land areas surrounding urban zones. Conversely, 7.53% of the regions demonstrated a negative impact of human activities on FVC, chiefly in areas undergoing land cover transitions from arable land to construction land and newly added industrial and mining zones. While most regions showed no significant correlation between FVC variation and human activities, this does undermine the impact of ecological protection policies implemented in China like the “Ecological Protection Red Line” and “Arable Land Red Line.” The effectiveness of these measures lies in preventing land type conversion, such as grassland and arable land to othe r categories. This not only maintains the stability of FVC within protected areas but also regulates the intensity of human activities. However, the outcomes of these measures are not adequately reflected in nighttime light data. Therefore, while nighttime light data partially reflect the influence of human activity intensity on FVC, its limitations must be fully recogn ized in the comprehensive evaluation of ecological protection policies.
Subjects: Geosciences >> Geography submitted time 2024-06-12 Cooperative journals: 《干旱区研究》
Abstract： Inrecentyears,drasticandextremeformsofsoilerosion,suchaslandslides,mudflows,andsiltdam outbursts,triggeredbyextremerainstormsontheLoessPlateauhaveattractedwidespreadattention.FromOcto- ber3to6,2021,alargeshallowlandslidedisasterwastriggeredbyheavyrainfallalongtheCaijiachuanwater- shedinJixianCounty,ShanxiProvince.Inthisstudy,therainfallprocess,landslideinitiationconditions,andero- sioncharacteristicswereanalyzedusingpredisasterandpostdisasterunmannedaerialvehicleimagery,historical remotesensingimages,andrainfalldataprovidedbytheNationalFieldScientificObservatoryforForestEcosys- temsinJixianCounty,ShanxiProvince.Theresultsshowthatitwasatypical “long-duration,low-intensity” rain- fall,withatotalprecipitationof121.8mminthefirst72hoftheinitiationofthemassive,shallowlandslidesand arainfallintensityof33.2mm·(6h) -1duringtheinitiationofthelandslides.Thelandslidetriggeredbythisrain- stormrequiredaslightlysmallercatchmentareaandexhibitedhigherlandslidemobilitythanthelandslidetrig- geredbyatypicalshort-duration,high-intensityrainstormin2003;however,theslopeofthelandslidewasnot significantlydifferent.Thus,thecumulativerainfallintheearlystagewasthemainfactorinfluencingtheoccur- renceandflexibilityofthemassivelandslidedisaster.Themagnitudeoflandslidenumberprobability,areaproba- bility,anderosionintensityincatchmentswithdifferentlandusetypesdecreasedinthefollowingorder:farmland catchment>plantationforestcatchment>closedcatchment.Thisfindingindicatedthatthelandusetypeandvege- tationcoveraffectthedegreeoflandslideerosiontoacertainextentandthatanarboreal-dominatedwatershedis moreunfavorabletolandslideinitiation.
Subjects: Geosciences >> Geography submitted time 2024-06-12 Cooperative journals: 《干旱区研究》
Abstract： Drought prediction has always been a major challenge in the field of drought research. Improving the accuracy of drought prediction is the key to solve the drought problem. Based on the monthly Precipitation and average temperature data of 34 meteorological stations in Xinjiang from 1961 to 2019, the Standardized Precipitation Evapotranspiration Index (SPEI) was calculated. The dry and wet changes of meteorology in Xinjiang were analyzed. An empirical mode decomposition (EMD) -Grey wolf optimizer (GWO) -Long short-term memory network is proposed. The drought combination prediction model based on data decomposition of LSTM was used to forecast the drought, and the performance of the model was evaluated. The results show that: (1) the drought periodicity is stable and the periodicity is long; (2) EMD can effectively optimize the stationarity of data, GWO can optimize the parameters of the prediction model, and the prediction accuracy of the combined model is significantly improved compared with that of the single prediction model; (3) The accuracy of the results of the four prediction models in descending order is as follows: EMD-GWO-LSTM, GWO-LSTM, GWO-Support Vactor Regression (SVR), LSTM (goodness of fit: 0.972, 0.939, 0.862, 0.830, respectively), The prediction accuracy of EMD-GGO-LSTM combined prediction model is better than the other three prediction models. The EMD-GWO-LSTM combined model can effectively improve the prediction accuracy of meteorological drought, and provide a new method for meteorological drought forecast and drought mitigation in Xinjiang.
Subjects: Geosciences >> Geography submitted time 2024-06-12 Cooperative journals: 《干旱区研究》
Abstract： Soil moisture is indispensable for the growth and development of plants in arid zones and determines the dynamics and direction of the succession of arid plant communities. It is particularly important to investigate the dynamic characteri stics of soil moisture in different landscape types at the edge of the oasis in the middle reaches of the Heihe River and to develop effective, scientific, and reasonable measures to prevent wind and fix sand to prevent desertification. This study focused on three landscape types—protected forest landscapes, desert–oasis transition zone landscapes, and desert landscapes—at the edge of the oasis in the middle reaches of the Heihe River. HYDRUS-2D model simulation, LSD analysis, and Pearson correlation analysis were used to study the characteristics of soil moisture dynamics and the influencing factors of the three landscape types. The results were as follows: (1) the RMSE of soil volumetric water content ranged from 0.002 to 0.006 cm3·cm -3, MRE ranged from 4.22% to 5.20%, and R2 ranged from 0.72 to 0.97. The simulation results showed a high degree of agreement with the measured data, and the HYDRUS-2D model can be used for simulation studies of soil moisture in this study area. (2) The soil volumetric water content of protected forest landscapes and desert–oasis transition zone landscapes showed a trend of initial increase and subsequent decrease with increasing soil depth, whereas desert landscapes showed a trend of initial decrease and subsequent increase with increasing soil depth. (3) Effective precipitation plays a decisive role in the dynamics of the soil volumetric water content, and precipitation above 9.5 mm significantly increases the soil moisture content and infiltration depth over a short period. The depth of soil moisture infiltration in all periods after precipitation in desert landscapes was higher than that in protected forest landscapes and desert–oasis transition zone landscapes. (4) The soil volumetric water content of the three landscape types was related to factors such as precipitation, evapotranspiration, bulkiness, soil granular composition, and soil water-holding properties. The soil water-holding properties were significantly correlated with factors such as precipitation and evapotranspiration (P < 0.01). Of these, precipitation and clay-powder grain content were significantly positively correlated with soil volumetric water content, whereas bulk weight and sand grain content were significantly negatively correlated with soil volumetric water content. Thus, planting windbreak shrubs in the study area can increase the content of soil sticky powder particles, improve the ability of the soil to collect and utilize rainwater, and slow the process of infiltration, thus positively affecting the soil water-holding properties.
Subjects: Geosciences >> Geography submitted time 2024-06-12 Cooperative journals: 《干旱区研究》
Abstract： Water use efficiency (WUE) is an important measure of the tradeoff between photosynthetic carbon sequestration and water consumption in ecosystems. Estimation of vegetation’WUE and analysis of the spatiotemporal distribution of vegetation WUE are crucial for ecosystem preservation as well as the wise use and development of water resources in this area. In this study, we assessed the spatial and temporal characteristics of vegetation WUE and its main influencing factors in Salt Lake County from 2000 to 2019 on the basis of GPP and ET data from MODIS. The results were as follows: (1) Both ET and GPP increased significantly from 2000 to 2019 (P< 0.01), and the rates of increase were 7.61 mm·a-1 and 7.23 g C·m-2 ·a-1 , respectively. ET and GPP showed obvious heterogeneity in space. (2) Between 2000 and 2019, the vegetation WUE in Yanchi County fluctuated between 0.80 and 1.11 g C·kg-1 ·H2O, and the multiyear average value was 0.91 g C·kg-1 ·H2O. The rate of increase was 0.0013 g C·kg- 1 ·H2O·a- 1 , but it was not significant. The vegetation WUE showed high heterogeneity in space, with high values mainly distributed in the northeast and low values in the southwest. (3) From 2000 to 2019, WUE mainly increased and decreased in 54.70% and in 45.30% of the area, respectively, in Yanchi County. In the future, 61.48% of the area in Yanchi County will show the same change trends in WUE as in the past, and 38.52% of the area will show reversed trends in WUE. (4) The WUE of each land use type in different study periods decreased in the following order: forest land > cultivated land > grassland. (5) There was a significant correlation between WUE and GPP in Yanchi County (P<0.05), whereas variations in GPP were mainly driven by changes in ET, NDVI, and precipitation, indicating that GPP is the main reason for the changes in WUE in Yanchi County. The Yanchi County Ecological Restoration Project not only enhances vegetation productivity but also increases regional water consumption, resulting in fluctuations in the WUE of the regional ecosystem. This suggests that vegetation restoration in Yanchi County has intensified regional water depletion while enhancing vegetation productivity, which provides a theoretical basis for future ecological revegetation and codevelopment of water resources in Yanchi County.
Subjects: Geosciences >> Geography submitted time 2024-06-12 Cooperative journals: 《干旱区研究》
Abstract： The topographic conditions of the bell in the upper reaches of the Ili River lead to an extremely uneven spatial distribution of precipitation, and it is difficult for limited observation stations to truly determine the spatial and temporal changes in daily precipitation. Therefore, it is necessary to assess the applicability of different precipitation products in the upper reaches of the Ili River. On the basis of seven statistical indicators and the generalized three- cornered hat method, we determined the accuracy and uncertainty of three precipitation products (GPM, ERA5, and CHIRPS) in the upper reaches of the Ili River. The results show that : (1) ERA5 showed the highest correlation between POD and FAR, and its moderate and heavy rain precipitation estimates were the most accurate. The root mean square error of GPM was the smallest, and POD and FAR were the lowest. CHIRPS showed the smallest relative bias and mean error, its POD and FAR values were between those of GPM and ERA5, and its light rain precipitation estimates were the most accurate. The accuracy of rainstorm precipitation estimated by the three precipitation products was not high, but ERA5 was better than GPM and CHIRPS. (2) The uncertainty of daily precipitation of ERA5 was between that of GPM and CHIRPS, and the signal-to-noise ratio was the largest. GPM showed the lowest uncertainty of daily precipitation, and the signal-to-noise ratio was between that of ERA5 and CHIRPS. CHIRPS had the largest uncertainty of daily precipitation and the smallest signal-to-noise ratio. (3) The daily precipitation quality of ERA5 was better than that of GPM and CHIRPS, and itcan be used to analyze the precipitation characteristics in the upper reaches of the Ili River. GPM had the lowest uncertainty of daily precipitation and is most likely to improve its quality through system calibration. The present findings provide support for hydrological simulation and water resource change analysis in the upper reaches of the Ili River
Subjects: Geosciences >> Geography submitted time 2024-06-12 Cooperative journals: 《干旱区研究》
Abstract： Based on the Landsat imagery data from 2001 to 2021, the NDVI and the image dichotomous model were used to estimate vegetation cover and explore the spatial and temporal trends and driving forces of vegetation cover in Ulan Buhe Desert along the Yellow River, in the hope of providing a theoretical basis for the restoration of vegetation in Ulan Buhe Desert along the Yellow River and the selection of key areas for future ecological construction. The results show that: (1) the overall vegetation cover in the study area showed a fluctuating upward trend, and the vegetation restoration status was good. The average vegetation cover increasing from 0.294 to 0.526, and the increase was most obvious from 2007 to 2017. (2) From 2001 to 2021, the transfer of vegetation cover between different levels in Ulan Buhe Desert along the Yellow River is more frequent, in which low vegetation cover and lower vegetation cover were transferred out to medium vegetation cover and higher vegetation cover in a large area of 102.00 km2 and 128.82 km2, respectively. In addition, 42.1% of the area in the study area tends to increase significantly, mainly in the near Dengkou section, and 4.90% of the area tends to decrease significantly, mostly in the near Wuhai section, which should be the key area of concern in future ecological restoration. (3) The spatial variability of vegetation cover in this area is mainly driven by human activities and climate factors, and the interaction between the driving factors is mainly enhanced by two factors, among which, the key interaction factors with the highest degree of influence are land use type and annual average temperature . In this study, the dynamic change characteristics and driving forces of vegetation coverage in Ulan Buhe Desert along the Yellow Rive were studied in an orderly and piecemeal manner, providing theoretical and data support for desertification control, land rational use and high-quality development in the study area.
Subjects: Geosciences >> Geography submitted time 2024-06-12 Cooperative journals: 《干旱区研究》
Abstract： The Yellow River Basin in Inner Mongolia is an important ecological region in China, and exploring changes in habitat quality and its driving factors is of great significance for regional desertification prevention and biodiversity conservation. Based on land use/cover data from 1990 to 2020, GIS technology and InVEST model were used to evaluate the habitat quality of the region, and the driving factors of spatial heterogeneity of habitat quality were analyzed through geographic detectors. The results indicate that: (1) The overall spatial distribution pattern of habitat quality in the study area is low in the north and high in the south, with a positive spatial correlation and significant spatial clustering. The area with low habitat quality level accounts for 23.50%, mainly distributed in the Kubuqi Desert and the southeastern part of the study area; (2) From 1990 to 2020, the habitat quality in the Yellow River Basin of Inner Mongolia showed a trend of first decreasing and then slightly rebounding. Over the past 30 years, the area of degraded habitat quality accounted for 11.97%, mainly concentrated in the northern part of the study area and near the banks of the Yellow River. It is a region of cultivated land expansion and sandy land distribution, with significant human activity interference. Future ecological governance and restoration work should focus on this area; (3) Natural factors such as DEM, NDVI, and soil type are the main driving factors for the spatial differentiation of habitat quality. Any two interactive detection factors have a greater explanatory power for the spatial differentiation of habitat quality than their single factor. The research results can provide reference and guidance for the ecological environment protection and restoration work in the Yellow River Basin of Inner Mongolia.
Subjects: Geosciences >> Geography submitted time 2024-06-12 Cooperative journals: 《干旱区研究》
Abstract： Exploring the dynamic change characteristics of soil moisture and vegetation water demand in the Northwest Arid Zone can provide scientific basis for the amount of water required at different stages of ecological recovery and the optimal allocation of water resources. Based on this, the Perpendicular Drought Index (PDI), Modified Perpendicular Drought Index (MPDI), and Vegetation-adjusted Perpendicular Drought Index (VAPDI) were constructed by using the Sentinel-2 L2A and Landsat8 OLI remote sensing images, combined with the 111 data from 0-10 cm of the measured soil in the north and south mountains of Lanzhou City as the study area. Perpendicular Drought Index (PDI), Modified Perpendicular Drought Index (MPDI) and Vegetation-adjusted Perpendicular Drought Index (VAPDI) were constructed respectively, and the quantitative coefficients of determination (R2), Mean absolute Arrors (MAE), Mean Relative Errors (MRE), and average relative errors of the four model indicators were used. (MAE), mean relative error (MRE), and root mean square error (RMSE) to evaluate the accuracy of the model inversion, select the optimal soil moisture inversion model and combine the soil moisture limiting coefficients with the spatial data of forest, grassland, and cropland vegetation area in the study area in 2019, and the evapotranspiration of the reference crop within the growing season at each site, and finally construct the ecological water demand model of the vegetation, to clarify the soil moisture and vegetation ecological water demand in the study area. The results showed that: (1) there were different degrees of linear negative correlations between PDI, MPDI, VAPDI and measured data under the two data sources, of which the R2 was 0.37, 0.64 and 0.59, respectively, and from the results of the evaluation indexes, the fit coefficient of determination of the soil moisture regression model of MPDI was the highest, and the spatial soil moisture regression model of the two remote sensing data inversions had the highest coefficient of determination. data inversion of soil moisture spatial distribution pattern had consistency. (2) The soil moisture inversion of Sentinel-2 L2A with high resolution is more refined, and the overall soil moisture shows a fluctuating growth trend, with the average value of soil moisture for multiple time periods being 23.27%, showing a decrease and then an increase and then a decrease, with an overall increase of 74.07%. (3) The monthly average value of vegetation water demand in April-October in the north and south mountains of Lanzhou City showed an increase and then a decrease, which was consistent with the change of soil moisture content, and the value of vegetation water demand was the largest in April-October, 3.98×107 m3 in July, and the smallest vegetation ecological water demand was 0.97×107 m3 in October, which appeared in October. month. With the implementation of the environmental greening project, the north and south hills of Lanzhou City have gradually formed a community structure with a combination of multiple species from only drought-tolerant herbs and low shrubs. This study can provide a reference for the rational use of soil and water resources and vegetation restoration in the north and south mountains of Lanzhou City.
Subjects: Geosciences >> Geography submitted time 2024-06-12 Cooperative journals: 《干旱区研究》
Abstract： In this study, to further restore and reconstruct the historical process of land use change before and after the construction of a water storage project and better grasp and forecast the direction of land use transfer, adaptive research on land use type interpretation was performed using the support vector machine theory. The adaptive adjustment ability and evolution direction of the land use structure before and after the construction of a water storage project were analyzed by examining the dynamic change in land use. The main conclusions were as follows: (l) The overall classification accuracy of the support vector machine for land use type interpretation is as high as 91.7%, and the Kappa coefficient is 0.90, depending on the advantages of self-learning and self-adaptation. In contrast with the relatively low accuracy observed for cultivated land producers, higher classification and recognition ability was observed other land types such as water bodies and forest land. (2) The Google Earth Engine (GEE) platform was used to examine the evolution process of land use types; it was found that the implementation of the second stage of the “Three-North Shelterbelt” project (2001-2020) significantly increased the area of construction land and forest land and increased the area of forest land by nearly five times compared with the initial stage of implementation in 2000. (3) Since the construction and operation of the project, nearly two-thirds of the area of forest land and construction land have maintained their original appearance, water bodies and unused land have been affected by water conservancy and urban construction projects, and more than 65% of the area has transformed from the original appearance type to other types. The “Three-North Shelterbelt” project accelerated the increase in forest area and improvement in grassland vegetation cover, and the net increase in the transformation of low-cover grassland to medium and high-cover grassland was 48.0% and 50.2%, respectively.
Subjects: Geosciences >> Geography submitted time 2024-06-12 Cooperative journals: 《干旱区研究》
Abstract： The movement characteristics of barchan dunes along the southern edge of the Taklamakan Desert reveal wind-sand transport features and geomorphological evolution processes, which are of great significance for the systematic prevention of sand and dust disasters in the region. This study used satellite remote sensing images and meteorological reanalysis data to analyze the morphological changes and moving features of six barchan dune groups along the southern edge of the Taklamakan Desert from 2012 to 2022. The results showed that (1) the average moving speed of barchan dunes within the study area was 6.86 m·a−1, and the moving direction was consistent with the prevailing wind direction in the corresponding region; (2) the association between the morphological parameters of barchan dunes within the area was complex; (3) the movement of barchan dunes is jointly influenced by the wind energy environment, topography, climatic conditions, and vegetation coverage, of which the dune height, underlying surface vegetation coverage, average annual rainfall, and surface temperature were negatively correlated with dune moving speed, and these negative correlations were significantly optimized after regional classification; (4) the average sand transport rate in the study area was 77120.5 kg·m−1·a−1, and it was influenced by the underlying surface conditions and the wind energy environment within the region, which provides an important reference for optimizing sand prevention and control measures. The study results reflect the complexity of the moving pattern of the barchan dunes, and the degree of impact varied with the presence of different geographical environmental factors, which necessitates field-specific analysis. Moreover, the dynamic changes in morphological parameters during the evolution of dunes reveal the internal mechanism of dune migration, providing substantial data for studying the evolution characteristics of dunes and a scientific basis for wind prevention and solidifying work and land planning.
Subjects: Geosciences >> Geography submitted time 2024-06-12 Cooperative journals: 《干旱区研究》
Abstract： This study examined the vegetation characteristics and species diversity of mixed herb communities in different years on the slope of expressway in the Loess Plateau, and explored the relationship between herb community characteristics, species diversity, and soil physical and chemical properties. The characteristics of herb communities, α species diversity, and their correlation with soil physical and chemical properties were studied using the Mantel test after 15 a, 12 a, 8 a, 4 a, and 2 a of restoration of herb communities on the highway slope of the Loess Plateau by space instead of time. In total, 13 species of 13 genera in 8 families were investigated in 15 a of slope restoration, 10 species of 10 genera in 7 families were investigated in 12 a of restoration, 5 species of 5 genera in 3 families were investigated in 8 years of restoration, 5 species of 5 genera in 3 families were investigated in 4 a of restoration, and 6 species of 6 genera in 4 families were investigated in 2 a of restoration. Patric species richness recovered in the order 15 a>12 a>8 a>2 a>4 a, the Shannon-Wiener and Simpson indices recovered in the order 15 a>12 a>2 a>8 a>4 a, and the Pielou evenness index recovered in the order 15 a>2 a>8 a>12 a>4 a.Patric species richness was significantly positively correlated with total porosity and capillary porosity, organic matter, total nitrogen, and total phosphorus (P<0.05), and the Shannon-Wiener index was significantly positively correlated with organic matter and total phosphorus (P<0.05). After spraying mixed grass species in different years on the slope, the herb communities mostly contained perennials, but there were differences in species composition and quantity of the community. The species richness, Shannon-Wiener index, and Simpson index of patric species showed an upward trend as the number of restoration years increased. Soil total porosity, capillary porosity,organic matter, total nitrogen, and total phosphorus were the key environmental factors affecting patric species richness and the Shannon-Wiener index.
Subjects: Geosciences >> Geography submitted time 2024-06-12 Cooperative journals: 《干旱区研究》
Abstract： Reservoirs play a pivotal role in regional economic development and societal well-being. In recent years, Xinjiang has experienced frequent extreme precipitation events, posing significant challenges to reservoir safety. However, research on precipitation characteristics specific to Xinjiang's reservoirs remains limited, impeding scientific guidance for water resource utilization and reservoir management. Utilizing daily precipitation data from 1961 to 2022 and hourly precipitation data from 2009 to 2022 in the Xiagou Reservoir watershed of Yiwu County, Hami City, this study analyzed long-term variations in different time scales and precipitation levels. The findings indicate: (1) During the rainy season from 1961 to 2022, the average precipitation in the Xiagou Reservoir catchment area showed a weak increasing trend, and the number of days with no continuous precipitation showed a significant increasing trend. The total number of precipitation days and the maximum continuous precipitation days both show a significant decreasing trend. The increase in precipitation and the significant decrease in precipitation days may lead to further enhancement of precipitation intensity in the region. (2) The rainy season is mainly characterized by light rain, yet over the past 62 years, the number of light rain and moderate rain days has decreased while heavy rain and torrential rain days have increased. The highest proportion of rainstorm rainfall to the total rainfall in rainy season is close to 50.0%, and the increase of rainstorm rainfall is the main reason for the increase of rainfall in rainy season in Xiagou reservoir catchment area. (3) Daily precipitation displays a pattern of advancing high values as precipitation intensity strengthens. For instance, high values for light rain occur in the afternoon, moderate rain at midday, heavy rain in the morning, and torrential rain in the early morning. Except for torrential rain, high values for other precipitation levels are predominantly during the daytime. The daily variation curves for average precipitation intensity exhibit multiple peaks with significant differences. The relationship between cumulative precipitation frequency and cumulative precipitation amount is more closely associated with light and moderate rain than with precipitation intensity. Conversely, the relationship between average precipitation intensity and cumulative precipitation amount is more closely related to heavy and torrential rain than to cumulative precipitation frequency.
Subjects: Geosciences >> Geography submitted time 2024-06-12 Cooperative journals: 《干旱区研究》
Abstract： From observational data of scattering coefficients, the mass concentrations of aerosols and pollutants, and meteorological elements, collected from July 9, 2020 to July 8, 2023 in Xilinhot, the characteristics of aerosol scattering coefficients—including the variation over time, probability density distribution, and correlation with different types of aerosols and meteorological impact factors—are studied. Consequently, the scattering coefficient levels are classified. The results show that: (1) the overall level of aerosol scattering is relatively low, but the transport of dust aerosol in spring and the high frequency of temperature inversions in winter and at night may increase aerosol scattering. (2) The smaller the aerosol, the higher the correlation between aerosols and scattering coefficients, with the correlation coefficients following the order BC>PM2.5>PM10, although seasonal differences are observed. In addition, NO2 is an important factor in increasing scattering in autumn, whereas SO2 contributes to scattering in summer, autumn, and winter. (3) The increases in correlation coefficients are considered as the contribution rates of current meteorological factors to scattering coefficients, with contribution rates of between 1% and 2%.
Subjects: Geosciences >> Geography submitted time 2024-06-12 Cooperative journals: 《干旱区研究》
Abstract： Abstract: Given the difficulties in the field measurement of soil salinization in Xinjiang and the difficulty in quickly and broadly evaluating the potential hazards of soil salinization, this study considers cotton fields in the Aral Reclamation area of Xinjiang as the research object, and uses multispectral remote sensing image data from Sentinel-2 SR and Landsat-9 OLI to construct a high-dimensional data set by comprehensively integrating 20 spectral indices and combining spectral indices. The optimal feature subset is screened using the method of exhaustive feature combination and cross-validation, and the inversion accuracy of soil salinization is compared for four machine learning algorithms (i.e., XGBoost, random forest, deep neural network, and K-nearest neighbor) under different feature combinations. Simultaneously, the difference in accuracy between Sentinel-2 SR and Landsat-9 OLI remote sensing images in soil salinization inversion is analyzed. The results show that: (1) The model constructed based on XGBoost algorithm can achieve high-precision prediction of cotton field salinization, with R2 higher than 0.7359, MSE lower than 0.0415, and MAPE lower than 0.1285. (2) For both Sentinel-2 SR and Landsat-9 OLI image data, the prediction accuracy of the XGBoost model is significantly better than other three algorithms. (3) There is a specific feature combination that enables the XGBoost algorithm to achieve the highest prediction accuracy. (4) The KNN algorithm underestimates the degree of cotton field salinization as a whole, and the accuracy of Sentinel-2 SR image data in cotton field salinization prediction (R2 = 0.7282–0.8838) is better than that of Landsat-9 OLI image data. This study realizes the precise monitoring of soil salinization in cotton fields in the Aral Reclamation area of Xinjiang, which should provide an effective and timely technical reference for soil salinization control and prevention in cotton fields in reclamation areas.
Subjects: Geosciences >> Geography submitted time 2024-06-12 Cooperative journals: 《干旱区研究》
LEI Feiya
LI Xiaoshuang
TAO Ye
YIN Benfeng
RONG Xiaoying
ZHANG Jing
LU Yongxing
GUO Xing
ZHOU Xiaobing
ZHANG Yuanming。
Abstract： Biological soil crusts (BSCs) are the main active groundcover community in arid regions. BSCs can significantly affect the material cycle and energy exchange, improve the physical, chemical, and biological properties of surface soil, and influence the soil multifunctionality (SMF). Moss crust is an important type of BSCs. This study investigates the SMF variability of moss crust-covered and bare sand in the deserts of northwestern arid regions, and explored the main drivers of the variability. We analyzed eight crucial ecosystem function indicators. SMF was calculated by applying the mean method and factor analysis approach. We used the ordinary least square and structural equation modeling to explore the drivers of SMF changes. The results show that: (1) soil monofunctionality and SMF under moss crust cover were higher than those in bare sand (P<0.05). (2) The drivers of the SMF change in bare sand and under moss crust cover were very different. The main drivers of SMF in bare sand were aridity and soil water content, whereas the driver of SMF under moss crust cover was soil sand content(Sand). (3) The mean annual temperature had the largest indirect effect on changes in SMF for both soil in bare sand and under moss crust cover. Therefore, the development of moss crust significantly increased SMF and, in addition, modulated the relevant drivers of SMF. Our results are important for a deep understanding of the differences and drivers of SMF in desert soil with bare sand and under moss crust cover
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