Subjects: Geosciences >> Geology submitted time 2024-06-21 Cooperative journals: 《干旱区科学》
Abstract： Quantifying surface cracks in alpine meadows is a prerequisite and a key aspect in the study of grassland crack development. Crack characterization indices are crucial for the quantitative characterization of complex cracks, serving as vital factors in assessing the degree of cracking and the development morphology. So far, research on evaluating the degree of grassland degradation through crack characterization indices is rare, especially the quantitative analysis of the development of surface cracks in alpine meadows is relatively scarce. Therefore, based on the phenomenon of surface cracking during the degradation of alpine meadows in some regions of the Qinghai-Tibet Plateau, we selected the alpine meadow in the Huangcheng Mongolian Township, Menyuan Hui Autonomous County, Qinghai Province, China as the study area, used unmanned aerial vehicle (UAV) sensing technology to acquire low-altitude images of alpine meadow surface cracks at different degrees of degradation (light, medium, and heavy degradation), and analyzed the representative metrics characterizing the degree of crack development by interpreting the crack length, length density, branch angle, and burrow (rat hole) distribution density and combining them with in situ crack width and depth measurements. Finally, the correlations between the crack characterization indices and the soil and root parameters of sample plots at different degrees of degradation in the study area were analyzed using the grey relation analysis. The results revealed that with the increase of degradation, the physical and chemical properties of soil and the mechanical properties of root-soil composite changed significantly, the vegetation coverage reduced, and the root system aggregated in the surface layer of alpine meadow. As the degree of degradation increased, the fracture morphology developed from "linear" to "dendritic", and eventually to a complex and irregular "polygonal" pattern. The crack length, width, depth, and length density were identified as the crack characterization indices via analysis of variance. The results of grey relation analysis also revealed that the crack length, width, depth, and length density were all highly correlated with root length density, and as the degradation of alpine meadows intensified, the underground biomass increased dramatically, forming a dense layer of grass felt, which has a significant impact on the formation and expansion of cracks.
Subjects: Geosciences >> Hydrology submitted time 2024-06-21 Cooperative journals: 《干旱区科学》
Abstract： 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.
Subjects: Geosciences >> Atmospheric Sciences submitted time 2024-06-21 Cooperative journals: 《干旱区科学》
Abstract： Vapor pressure deficit (VPD) plays a crucial role in determining plant physiological functions and exerts a substantial influence on vegetation, second only to carbon dioxide (CO2). As a robust indicator of atmospheric water demand, VPD has implications for global water resources, and its significance extends to the structure and functioning of ecosystems. However, the influence of VPD on vegetation growth under climate change remains unclear in China. This study employed empirical equations to estimate the VPD in China from 2000 to 2020 based on meteorological reanalysis data of the Climatic Research Unit (CRU) Time-Series version 4.06 (TS4.06) and European Centre for Medium-Range Weather Forecasts (ECMWF) Reanalysis 5 (ERA-5). Vegetation growth status was characterized using three vegetation indices, namely gross primary productivity (GPP), leaf area index (LAI), and near-infrared reflectance of vegetation (NIRv). The spatiotemporal dynamics of VPD and vegetation indices were analyzed using the Theil-Sen median trend analysis and Mann-Kendall test. Furthermore, the influence of VPD on vegetation growth and its relative contribution were assessed using a multiple linear regression model. The results indicated an overall negative correlation between VPD and vegetation indices. Three VPD intervals for the correlations between VPD and vegetation indices were identified: a significant positive correlation at VPD below 4.820 hPa, a significant negative correlation at VPD within 4.820–9.000 hPa, and a notable weakening of negative correlation at VPD above 9.000 hPa. VPD exhibited a pronounced negative impact on vegetation growth, surpassing those of temperature, precipitation, and solar radiation in absolute magnitude. CO2 contributed most positively to vegetation growth, with VPD offsetting approximately 30.00% of the positive effect of CO2. As the rise of VPD decelerated, its relative contribution to vegetation growth diminished. Additionally, the intensification of spatial variations in temperature and precipitation accentuated the spatial heterogeneity in the impact of VPD on vegetation growth in China. This research provides a theoretical foundation for addressing climate change in China, especially regarding the challenges posed by increasing VPD
Subjects: Geosciences >> Atmospheric Sciences submitted time 2024-06-21 Cooperative journals: 《干旱区科学》
Abstract： Methane (CH4) is a potent greenhouse gas that has a substantial impact on global warming due to its substantial influence on the greenhouse effect. Increasing extreme precipitation events, such as drought, attributable to global warming that caused by greenhouse gases, exert a profound impact on the intricate biological processes associated with CH4 uptake. Notably, the timing of extreme drought occurrence emerges as a pivotal factor influencing CH4 uptake, even when the degree of drought remains constant. However, it is still unclear how the growing season regulates the response of CH4 uptake to extreme drought. In an effort to bridge this knowledge gap, we conducted a field manipulative experiment to evaluate the impact of extreme drought on CH4 uptake during early, middle, and late growing stages in a temperate steppe of Inner Mongolia Autonomous Region, China. The result showed that all extreme drought consistently exerted positive effects on CH4 uptake regardless of seasonal timing. However, the magnitude of this effect varied depending on the timing of season, as evidenced by a stronger effect in early growing stage than in middle and late growing stages. Besides, the pathways of CH4 uptake were different from seasonal timing. Extreme drought affected soil physical-chemical properties and aboveground biomass (AGB), consequently leading to changes in CH4 uptake. The structural equation model showed that drought both in the early and middle growing stages enhanced CH4 uptake due to reduced soil water content (SWC), leading to a decrease in NO3–-N and an increase in pmoA abundance. However, drought in late growing stage primarily enhanced CH4 uptake only by decreasing SWC. Our results suggested that seasonal timing significantly contributed to regulate the impacts of extreme drought pathways and magnitudes on CH4 uptake. The findings can provide substantial implications for understanding how extreme droughts affect CH4 uptake and improve the prediction of potential ecological consequence under future climate change.
Subjects: Geosciences >> Hydrology submitted time 2024-06-21 Cooperative journals: 《干旱区科学》
Abstract： Over the last three decades, more than half of the world's large lakes and wetlands have experienced significant shrinkage, primarily due to climate change and extensive water consumption for agriculture and other human needs. The desiccation of lakes leads to severe environmental, economic, and social repercussions. Urmia Lake, located in northwestern Iran and representing a vital natural ecosystem, has experienced a volume reduction of over 90.0%. Our research evaluated diverse water management strategies within the Urmia Lake basin and prospects of inter-basin water transfers. This study focused on strategies to safeguard the environmental water rights of the Urmia Lake by utilizing the modeling and simulating (MODSIM) model. The model simulated changes in the lake's water volume under various scenarios. These included diverting water from incoming rivers, cutting agricultural water use by 40.0%, releasing dam water in non-agricultural seasons, treated wastewater utilization, and inter-basin transfers. Analytical hierarchy process (AHP) was utilized to analyze the simulation results. Expert opinions with AHP analysis, acted as a multi-criteria decision-making tool to evaluate the simulation and determine the optimal water supply source priority for the Urmia Lake. Our findings underscore the critical importance of reducing agricultural water consumption as the foremost step in preserving the lake. Following this, inter-basin water transfers are suggested, with a detailed consideration of the inherent challenges and limitations faced by the source watersheds. It is imperative to conduct assessments on the impacts of these transfers on the downstream users and the potential environmental risks, advocating for a diplomatic and cooperative approach with adjacent country. This study also aims to forecast the volumes of water that can be transferred under different climatic conditions—drought, normal, and wet years—to inform strategic water management planning for the Urmia Lake. According to our projection, implementing the strategic scenarios outlined could significantly augment the lake's level and volume, potentially by 3.57×109–9.38×109 m3 over the coming 10 a and 3.57×109–10.70×109 m3 in the subsequent 15 a.
Subjects: Geosciences >> Atmospheric Sciences submitted time 2024-06-21 Cooperative journals: 《干旱区科学》
Abstract： Stable water isotopes are natural tracers quantifying the contribution of moisture recycling to local precipitation, i.e., the moisture recycling ratio, but various isotope-based models usually lead to different results, which affects the accuracy of local moisture recycling. In this study, a total of 18 stations from four typical areas in China were selected to compare the performance of isotope-based linear and Bayesian mixing models and to determine local moisture recycling ratio. Among the three vapor sources including advection, transpiration, and surface evaporation, the advection vapor usually played a dominant role, and the contribution of surface evaporation was less than that of transpiration. When the abnormal values were ignored, the arithmetic averages of differences between isotope-based linear and the Bayesian mixing models were 0.9% for transpiration, 0.2% for surface evaporation, and –1.1% for advection, respectively, and the medians were 0.5%, 0.2%, and –0.8%, respectively. The importance of transpiration was slightly less for most cases when the Bayesian mixing model was applied, and the contribution of advection was relatively larger. The Bayesian mixing model was found to perform better in determining an efficient solution since linear model sometimes resulted in negative contribution ratios. Sensitivity test with two isotope scenarios indicated that the Bayesian model had a relatively low sensitivity to the changes in isotope input, and it was important to accurately estimate the isotopes in precipitation vapor. Generally, the Bayesian mixing model should be recommended instead of a linear model. The findings are useful for understanding the performance of isotope-based linear and Bayesian mixing models under various climate backgrounds.
Subjects: Geosciences >> Geography Subjects: Biology >> Ecology Subjects: Law >> Civil and Commercial Law Subjects: Management Science >> Business Management of Department Subjects: Other Disciplines >> Synthetic discipline submitted time 2024-06-19
Abstract： Purpose/significance South Africa is a world famous tourist paradise . A thematic study on how South Africa is developing its tourism industry can provide a useful reference for China. Method/process This paper summarizes South Africa’s experience in tourism development, based mainly on foreign research data and using literature review methods. Result/conclusion In the development of tourism, South Africa has five major successful experiences: first, it has attached great importance to tourism and taken a number of initiatives, including the enactment of the Tourism Act, the introduction of a number of tourism development strategies and plans, and the establishment of the Department of Tourism of South Africa and the South African Tourism; second, it has actively upgraded its hardware and software facilities; third, it has endeavored to diversify its tourism products; fourth, it has put the concept of responsible tourism into practice; and fifth, it has made great efforts to develop its domestic tourism industry.
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.
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