Subjects: Geosciences >> Geography submitted time 2024-06-12 Cooperative journals: 《干旱区研究》
Abstract： Farmland use intensity is an important factor to improve food production, alleviate the conflict between humans and land, and achieve sustainable agricultural development. Based on the farmland data obtained from high spatial resolution remote sensing images, this paper explores the farmland use intensity and its driving mechanism in the Yarlung Zangbo-Lhasa-Nyangqu River (YLN) region in 2000 and 2020 through a comprehensive evaluation index model. The results show that: (1) the degree of farmland use intensity in the YLN region has increased in the past 20 years, but the overall level is low. The farmland use intensity in 2020 was 38.2% higher than in 2000, which is mainly attributable to the increase in agricultural input, technological input, and the exploitation and utilization level. (2) There is a large difference in the change in farmland use intensity among different districts and counties; the high intensity areas migrated from east to west and increased in scope. The difference in farmland use intensity between east and west regions narrowed, and the number of low intensity districts and counties decreased. (3) The irrigation index, proportion of farmland area, and farmland quality have the most significant independent effects on the degree of farmland use intensity in the YLN, whereas socioeconomic factors, agricultural science and technology factors, and policy and environment factors interact with farmland resource endowment to increase the degree of impact on the farmland use intensity. Based on the above results, the following policy recommendations are proposed: the continuous promotion of agricultural science and technology innovation in the YLN region with a focus on regional differences, to realize sustainable development in high intensity areas and total factor inputs in low intensity areas, and facilitate the synergistic effects of agricultural policy and economy to coordinate and promote enhanced farmland use intensity in the YLN region.
Subjects: Geosciences >> Geography submitted time 2024-06-12 Cooperative journals: 《干旱区研究》
Abstract： This study aimed to reveal the effects of different habitats and substrates on seed germination and seedling growth of Malus sieversii after passing through digestive tract of cattle. A controlled experiment was set up in field based on the different habitats and substrates in which seeds were deposited after passing through the digestive tract of cattle. The three habitats were as follows: forest edges, gaps, and understory. The four treatments were as follows: W (seeds through digestive tract + intact feces), P (seeds through digestive tract + broken feces), T (seeds through digestive tract + soil), and control C (seeds not through digestive tract + soil). The results showed that: The seed germination rates, seedling survival rate, and seedling biomass of M. sieversii were significantly different (P<0.05) in different habitats and treatments. In the forest edge habitat, seeds germinated rate was higher in soil substrate compared to fecal substrate, while the gaps and understory habitats showed the opposite trend. Seedling survival rate was significantly higher in the forest edge and gaps habitats compared to the understory habitat. Under the same treatment, seedling biomass was higher in the forest edge compared to the gaps, and higher in the gaps compared to the understory. Within the same habitat, seedling biomass from fecal substrate in forest edge and gap habitats surpassed that of soil substrate. The study revealed that the heterogeneity of habitat and substrate is the main reason that affects the seed germination and seedling establishment of M. sieversii after passing through digestive tract of cattle.
Subjects: Geosciences >> Geography submitted time 2024-06-12 Cooperative journals: 《干旱区研究》
Abstract： Seed germination and the seedling growth of sand-fixing plants are decisive aspects of land desertifica- tion management, and soil moisture is the main limiting factor affecting these aspects. In this study, we compared and analyzed the seed germination of three sand-fixing plants under different moisture gradients (4%, 6%, 8%, 10%, 15%, 20%, and 25%) in an indoor potting experiment using Hedysarum scoparium, Caragana korshinskii, and Artemisia desertorum to investigate the response of seed germination and seedling growth of sand- fixing plants to changes soil in moisture. The results showed that: (1) significant differences (P<0.05) were observed in the seed germination characteristics of the three sand-fixing plants as the soil moisture increased. The germina- tion rates tended to increase and then decrease as the soil moisture increased. C. scoparium had the highest germi- nation rate at 15% and 20% soil moisture (83.00% in both); C. korshinskii had the highest germination rate at 10% soil moisture (73.00% ); and the seed germination rate of A. desertorum reached the maximum value of 77.50% at 15% soil moisture, and then slowly decreased, although the change was not significant. (2) The leaf ar- ea and root length of the three plants showed tended to first increase and then decrease as the soil moisture in- creased, and the specific leaf area and root:crown ratio tended to decrease and then increase. (3) The highest bio- mass of C. scoparium, C. korshinski, and A. desertorum seedlings was 0.0733 g, 0.1142 g, and 0.0363 g at 10%, 8%, and 20% soil moisture, respectively, and the aboveground biomass was significantly higher than the below- ground biomass (P<0.05), although the allocation of belowground biomass by C. korshinski seedlings was higher than that of C. scoparium and A. desertorum. (4) The SOD activity, POD activity, CAT activity, Pro content, SS content, and Chl content of the three sand-fixing plants tended to increase and then decrease as the soil moisture increased, whereas the MDA content, membrane permeability, and relative water content tended to decrease and then increase. Based on the above results, it was concluded that the three sand-fixing plants of C. scoparium, C. korshinski, and A. desertorum had the best seedling growth at 15% , 8% and 8% soil moisture, respectively, through the analysis of the affiliation function method. Therefore, when these three sand-fixing plants are used for vegetation restoration, the changes in soil moisture caused by rainfall conditions should be fully considered in addition to the seeds’own traits to improve the seedling emergence rate and the success of seedling growth.
Subjects: Geosciences >> Geography submitted time 2024-06-12 Cooperative journals: 《干旱区研究》
Abstract： The effects of water, salt, and nitrogen (N) regulation on changes in the soil water, transport of salt nutrients, and growth indices and yield of cotton (Gossypium hirsutum) were analyzed under drip irrigation covered by film. A two-year three-factor full-combination field experiment was conducted to study the effects of three levels of irrigation (W1: 2700 m3·hm−2, W2: 3600 m3·hm−2, and W3: 4500 m3·hm−2), salinity (S1: 3 dS·m−1, S2: 6dS·m−1, and S3: 9 dS·m−1), and N (F1: 105 kg·hm−2, F2: 210 kg·hm−2, and F3: 315 kg·hm−2). The effects of different combinations of water-salt-nitrogen on soil moisture, salinity, N distribution, plant growth, and yield were investigated. The results showed the following: the soil moisture was mainly located in the 30-40 cm soil layer, and the water content of different soil depths essentially first increased and then decreased. The average water content of the 0-40 cm soil layer in the bud and boll stages of S3F3W1 and S2F3W1 increased by 1.3%-21.8% compared with that of S1F3W1, and the average water content of the combination of S1F3 increased by 1.39%-13.83% compared with those of S1F2 and S1F1 under the same amount of irrigation. The soil salinity tended to decrease and then increase during the fertile period. The S1 treatment increased and then decreased the soil salinity as N application increased, and the soil salinity in S2 and S3 decreased as the N application increased. The N content was significantly higher with the F3 treatment than F1 or F2. In the W2 and W3 treatments, N slowly accumulated in the 40-60 cm soil layer, and the N content was significantly higher with the S1 treatment than S2 or S3. The soil moisture, salinity, and N content interacted; under appropriate soil moisture and N conditions, lower soil salinity enabled the plants to utilize nutrients more efficiently, which facilitated their growth, and thus enhanced yield. To obtain high economic benefit, the recommended rate of irrigation for low and medium saline soils is 3600 m3·hm−2 and the rate of N is 210 kg·hm−2. For highly saline soils, the recommended rate of irrigation is 4500 m3·hm−2 and the rate of N is 315 kg·hm−2. This study provides a theoretical basis to explore the mechanism of water and salt nutrient transport and the efficient use of water and fertilizer in cotton farmland ecosystems under multiyear drip irrigation under a membrane in arid areas.
Subjects: Geosciences >> Geography submitted time 2024-06-12 Cooperative journals: 《干旱区研究》
Abstract： The construction and optimization of an ecological network is an effective way to prevent landscape fragmentation and ensure regional ecological security. In this study, the Lanzhou-Xining urban agglomeration was selected as the research area. Using the adaptive cycle as the theoretical basis, coupled with the granularity inverse method and morphological spatial pattern analysis, the ecological sources were identified, and the comprehensive“ potential-connectivity-resilience ”ecological resistance surface was established. The circuit theory was applied to determine the vital ecological nodes and corridors. On this basis, an ecological network was constructed and optimization strategies were proposed. The results showed that the spatial distribution of ecological sources was uneven and fragmented, covering a total area of 4147.84 km2. As a whole, the resistance of the study area was characterized by a “high in the west and low in the east” trend, decreasing from the main city to surrounding areas. In total, 40 ecological corridors with a total length of 2278.59 km were extracted and distributed in the central part of the study area. Similarly, 24 ecological pinch points were extracted, primarily distributed in major river corridors and ecological sources; 25 ecological barrier points were identified, mostly located in ecological corridors. The structural indices of the ecological network α, β, and γ were 0.60, 2.00, and 0.74, respectively. By adding 12 stepping-stone patches, these indices increased by 18.33%, 14.00%, and 9.46%, respectively. These results can provide a references point for land space development and ecological security maintenance in the Lanzhou Xining urban agglomeration.
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： Based on the daily minimum temperature measured at 42 meteorological stations in Qinghai Province from 1961 to 2019, the spatial and temporal evolution of different grades of cold days (extreme cold, extremely cold, severe cold, major cold, minor cold, light cold, slightly cold, cool) were analyzed. The results showed that: (1) From 1961 to 2019, the number of cold days in Qinghai Province gradually increased with decreasing levels, mainly dominated by slightly cold days. The total number of cold days showed an overall decreasing trend, with a significant rapid decrease occurring in 1995. The decrease in total cold days was mainly caused by the reduction in extremely cold days. After the climate abrupt change in 1997, the trends of severe cold, major cold, minor cold, light cold, slightly cold, and total cold days decreased, while the trend of extremely cold days increased. The trends of extreme cold and cool days decreased and increased respectively, with a distribution roughly equal. (2) Qinghai Province exhibits significant spatial differences in cold days, with the total number of cold days grad-ually increasing with altitude, and the trends of higher-level cold days are more pronounced. As the level of cold- ness decreases, the trends of increase and decrease develop towards lower latitudes and areas with relatively low-er altitudes. (3) The numbers of extreme cold, extremely cold, severe cold, light cold, slightly cold, and total cold days gradually decrease with increasing annual mean temperature, while the numbers of major cold, minor cold, and cool days gradually increase with increasing annual mean temperature. (4) Except for severe cold days, the numbers of other levels of cold days in Qinghai Province show persistence, and the downward trend will continue in the future, but the strength of persistence varies.
Subjects: Geosciences >> Geography submitted time 2024-06-12 Cooperative journals: 《干旱区研究》
Abstract： Based on data from 152 meteorological stations in Northwest China and 16 climate models of CMIP6,the CMIP6 model data were bias- corrected using the RoMBC method. The Standardized Precipitation Evapotranspiration Index (SPEI) was then constructed to analyze the spatial and temporal distribution and variation of drought in Northwest China under the historical and future scenarios (SSP1-2.6, SSP2-4.5, SSP3-7.0, SSP5-8.5). The results are as follows: (1) Under the historical scenario, the northwest area experienced a notable increase in both the temperature and precipitation. The temperature and precipitation have been rising at a rate of 0.15 ℃-0.74 ℃ and 2.71-14.83 mm per decade, respectively, and the same is expected for future scenarios. (2)From 1975 to 2014, the annual and seasonal SPEI in Northwest China decreased overall. The maximum decline rate in spring was 0.19 per decade. Droughts in most areas were increasingly intense throughout the year, particularly in spring and winter. In terms of drought frequency in Northwest China, mild and moderate droughts appeared more than severe and extreme droughts, and this type of natural disaster was more frequent in the east of the country than in the west. (3) From 2020 to 2100, Northwest China is likely to suffer from droughts, but there are no distinct drought characteristics identified in the research under the SSP1-2.6 scenario. The northwest region is expected to experience an increase in the number of droughts, trends in drought, and drought frequency under the other three scenarios. The most severe drought conditions were observed under the SSP5-8.5 scenario.This study provides insights into the spatial and temporal development of drought in Northwest China using meteorological and model data. The findings can serve as a basis for drought risk assessment, scientific water resources management, and agricultural production in the region.
Subjects: Geosciences >> Geography submitted time 2024-06-12 Cooperative journals: 《干旱区研究》
Abstract： Using the InVEST model, the carbon storage in the Tarim River Basin was estimated over a long period, and the spatial--temporal variation characteristic were described using trend analysis, correlation coefficients, and band set statistics to explore the overall spatial--temporal correlation between climate change and carbon storage in the study area; in addition, quantitative analysis of was performed the attribution of carbon storage in different topographic locations with the help of partial least square method. The results showed that: (1) From 2002 to 2020, the overall carbon storage level in the Tarim River Basin was low, following a horseshoe-shaped distribution characteristic (“low in the middle and high in the periphery”), and overall followed an increasing trend. (2) Carbon storage and average annual temperature, potential evapotranspiration, and average annual precipitation in the study area had the characteristics of opposite spatial distribution rather than the same spatial distribution, and the spatial differentiation was obvious. (3) The overall influence of climate factors on carbon storage followed the order: potential evapotranspiration>average annual temperature>average annual precipitation. (4) The potential evapotranspiration is the most significant variable for the levels I, III, and IV topography in the Tarim River Basin, whereas the average temperature and average precipitation are the most significant variables for the levels II and Vtopography in the Tarim River Basin.
Subjects: Geosciences >> Geography submitted time 2024-06-12 Cooperative journals: 《干旱区研究》
Abstract： For this study of the physical and chemical properties and mechanical characteristics of soil in the distribution area of Xiazangtan super large scale landslide of the upper Yellow River, plants and soil samples at different positions of the landslide were collected, and the plant growth index, soil density, water content, root content, shear strength index, and nutrient element content were measured. Spearman’s correlation analysis was used to explore the vegetation types, physical and chemical properties of soil, and the shear strength characteristics of the root–soil composite system in different positions of the landslide. The number of plant species tended to increase as the altitude decreased, and the dominant herbaceous herbs were Stipa aliena, Oxytropis ochrocephala, and Artemisia desertorum. The pH of the soil in the distribution area of the landslide was neutral to alkaline. The contents of organic matter, total nitrogen, and total phosphorus change greatly at the trailing edge of the landslide, whereas the contents of total potassium, alkali-hydrolyzed nitrogen, and four other nutrients change greatly but do not show obvious variation. The water content of soil first increases and then decreases with the decrease in altitude, while the density of soil increases as the altitude decreases, increasing by 7.05% and 5.88%, respectively. The cohesion c value and root content of the root-soil composite system first increased and then decreased as the altitude decreased. In addition, Spearman correlation analysis showed that the cohesion c value of the root-soil composite system was negatively correlated with altitude, but positively correlated with root content, organic matter, and water content. The results of this study have practical significance for guiding the prevention and control of geological disasters such as soil erosion, and shallow landslide in the upper reaches of the Yellow River, from Longyang Gorge to Jishi Gorge.
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 >> Space Physics Subjects: Other Disciplines submitted time 2024-06-08
Abstract： 469219 Kamo`oalewa is selected as one of the primary targets of Tianwen-2 mission, which is currently believed to be the most stable quasi-satellite of Earth. Here we derive a weak detection of the Yarkovsky effect for Kamo`oalewa, giving $A_2 = -1.075 pm0.447 times 10^{-13} rm{au/d}^2$, with the available ground-based optical observations from Minor Planet Center and a relatively conservative weighting scheme. Due to the quasi-satellite resonance with Earth, we show that the detection of Yarkovsky effect by orbital fitting with astrometric observations becomes difficult as its orbital drift shows a slow oscillatory growth resulting from the Yarkovsky effect. In addition, we extensively explore the characteristics of orbital uncertainty propagation and find that the positional uncertainty mainly arises from the geocentric radial direction in 2010-2020, and then concentrates in the heliocentric transverse direction in 2020-2030. Furthermore, the heliocentric transverse uncertainty is clearly monthly dependent, which can arrive at a minimum around January and a maximum around July as the orbit moves towards the leading and trailing edges, respectively, in 2025-2027. Finally, we investigate a long-term uncertainty propagation in the quasi-satellite regime, implying that the quasi-satellite resonance with Earth may play a crucial role in constraining the increase of uncertainty over time. Such interesting feature further implies that the orbital precision of Kamo`oalewa is relatively stable at its quasi-satellite phase, which may also be true for other quasi-satellites of Earth.
Peer Review Status:
Awaiting Review
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： 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： 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： The Lower Malian River Basin are typical loess plateau gully areas in eastern Gansu. They are of great significance for the sustainable development of regional ecosystems and for studying the temporal and spatial characteristics and response of water yield under the background of climate and land use change. Based on the InVEST (Integrated Valuation of Ecosystem Services and Trade-offs) model, the spatial and temporal patterns and change in water yield of the Lower Malian River Basin in 1990, 2000, 2010, and 2020 were quantitatively evaluated. The degree of influencing factors on the spatial differentiation of water yield function was analyzed using geographic detection. The results show that: (1) From 1990 to 2020, the total water yield of the Lower Malian River Basin first decreased, then increased, and then decreased again. Compared with 1990, the total water production in 2020 was reduced by 5.9 × 107 m3, which was a reduction of 25.43%. The water yield in different periods was higher in the southern and marginal areas and lower in the northern and central areas. (2) The water yield capacity of each land use type followed the order: construction land > bare land > agricultural land > low-coverage grassland > high-coverage grassland > shrub land > forest land > open water. (3) There was a significant positive correlation between water yield and precipitation, and a negative correlation between actual evapotranspiration and altitude. Precipitation and actual evapotranspiration were the main factors determining the spatial distribution and change in water yield, with q values of 0.616–0.735 and 0.517–0.653, respectively. The research results provide scientific evidence to support the development, utilization, and management of soil and water resources in the gully areas of the Loess Plateau in eastern Gansu.
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： This study aimed to spatially and temporally characterize not only land surface temperature (LST) in the complex mountainous terrain of Daqingshan, Inner Mongolia but also the environmental factors affecting it.We used the Weather Research and Forecasting Mode (WRF) used to obtain LST data with high temporal and spatial resolution and analyze the variation of mountain influencing factors. The accuracy of the WRF simulated LST(WRF LST) was verified by the observation values of meteorological stations and MODIS LST values, and the relationship between LST and environmental factors was analyzed by the method of comprehensive impact factor analysis and the method of single impact factor analysis. The comprehensive impact factor analysis is based on regional WRF LST and regional environmental factors. Single impact factor analysis achieves the relationship between WRF LST and single environmental factors by fixing other environmental factors. The results revealed that the correlation coefficients between the simulated and observed values were >0.97 (P<0.001) and the spatial correlation with MODIS LST was 73% (P<0.05), indicating that WRF has good practicability in mountainous areas. After comprehensive impact factor analysis, it was found the annual WRF LST had the greatest correlation with elevation (R>0.97), followed by temperature at 2 m and water/air mixing ratio at 2 m (R>0.8), vegetation coverage and slope (R>0.3), and other factors. By single impact factor analysis, LST decrease rate with elevation was 0.83 K·(100 m)-1, 0.79 K·(100 m)-1, 0.80 K·(100 m)-1 and 0.32 K·(100 m)-1 in spring, summer, autumn and winter, and it increased by -0.05, 0.17 K, -0.14 K, and 0.02 K for every 10° increase in slope in spring, summer fall winter, respectively. LST also increased for every 10% increase in vegetation cover by 0.31 K, 1.41 K in summer and winter, and was not correlated with fall. The slope direction and average LST for the four seasons were south>southwest>southeast>west>east>northwest>northeast>north. The 2 m water-air mixing ratio increased logarithmically with LST, while the 2 m air temperature increased exponentially with LST. This study demonstrated that the WRF model can be used to simulate the spatial and temporal distribution of LST in mountainous terrain and analyze the LST relationship in complex mountain environments.
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： 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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