Areas Of Southwest China Research Articles

Spatio-temporal dynamics of vegetation over cloudy areas in Southwest China retrieved from four NDVI products

The Normalized Difference Vegetation Index (NDVI) is the most commonly used index for assessing vegetation. However, significant differences among various satellite datasets, complex terrain, and the impact of clouds on optical sensors limit vegetation change assessment based on NDVI. To address these issues, this study utilizes multi-source satellite data (GIMMS3g NDVI, CDR AVHRR NDVI, SPOT NDVI, and MODIS NDVI) to monitor vegetation dynamics at different time scales from 1990 to 2020 in Sichuan Province, China. The results indicate that over time, NDVI values from the four NDVI products in Sichuan Province have shown an upward trend. There are certain differences in the spatial distribution and spatial heterogeneity of the change rate of NDVI values among the four NDVI products at different time scales, and the differences are mainly concentrated in the Sichuan Basin (SB) and the Western Sichuan alpine plateau region (WS). Compared with the other three NDVI products, GIMMS NDVI has the highest value but the smallest increase during the study period. The SPOT NDVI value is the smallest, but the increase is relatively large. However, within the overlapping period of the four NDVI datasets, only the annual average of CDR AVHRR NDVI showed a downward trend (slope2000–2013 = −0.0001·a−1). The annual fluctuation of CDR AVHRR NDVI is the smallest, and compared to other NDVI datasets, its correlation with climate factors shows significantly weaker spatial variability. Moreover, the ability of CDR AVHRR NDVI to distinguish different vegetation land cover types is significantly poor (STD = 0.045). The findings of this study will provide a reference for further research on vegetation changes in Sichuan Province and NDVI reconstruction in cloudy areas.

Teaching Methods of Spoken English — Taking Rural Areas in Southwest China for Example

Based on the theoretical knowledge of educational psychology and language specialization, and under the guidance of “Positive Psychology Theory”, this project develops a set of innovative spoken English programs for secondary school students that combines Wittgenstein’s “Language Game Theory” with positive psychology theory and the “Positive Psychology Theory”. The program is based on a new model of student-student interaction and teacher-led guidance to improve secondary school students’ English speaking ability through small group classes and a differentiated game program for the students. The program breaks the traditional spoken English teaching model, combines students’ physiological and psychological characteristics, and strives to promote students’ personalized development, help students achieve from passive reception to active participation, and effectively improve students’ English language skills; in addition, the program also provides assistance and reference for solving the uneven distribution of educational resources between urban and rural areas and promoting the revitalization of rural education.

Breaking the poverty trap in an ecologically fragile region through ecological engineering: A close-up look at long-term changes in ecosystem services

Ecological vulnerability and poverty are interrelated and must be addressed together. The resolution of this issue will help us to meet the challenges during the process of implementing concrete actions for realizing the 2030 UN sustainable development goals (SDGs). Ecological restoration projects (ERPs) can enhance ecosystem services (ESs) while providing policy support for improving people's livelihoods. However, processes and mechanisms of ERPs on the ecological environment and socioeconomic development in poverty-stricken and ecologically fragile areas have rarely been studied. To address these issues, we conducted a comparative analysis on the changes of land use and land cover (LULC), ecosystem services (ESs), and socioeconomic development in Bijie City, a karst rocky desertification area in southwest China, before and after the implementation of ERPs in 2000, as well as the complex relationship between these factors. ERPs have affected LULCs, ESs, socioeconomics, and poverty reduction significantly since 2000. Specifically, the total ecosystem service value (ESV) in the study area has increased by more than 3 times in the past 30 years, with the ESV of tourism services and carbon storage increasing the most, from CNY 0.001 and 337.07 billion in 1990 to CNY 11.07 and 108.97 billion in 2019, respectively. The correlation between ESs is mainly synergistic, while the tradeoff between carbon storage and water yield is in a fluctuating upward trend. LULC conversion of cropland to green, and cropland to water, wetland and shrubs has positive effects on carbon storage and water yield, respectively. During study period, GDP, urbanization increased by over 70 times, 5 times, respectively, whereas poverty population, poverty incidence, and employment rate of various sectors (i.e., agriculture, forest, animal, and fishery, or AFAF) decreased by 96.4%, 97.7%, and 18.24%, respectively. Our findings emphasized that ERPs can effectively help poor and ecologically fragile areas to get out of the poverty trap and achieve the “win-win” goals of ecological and socio-economic sustainable development. These results have profound environmental management references to China and other developing countries around the world in realizing ecological restoration, poverty reduction, and the SDGs.

Soil organic nitrogen variation shaped by diverse agroecosystems in a typical karst area: evidence from isotopic geochemistry.

Soil organic nitrogen (SON) levels can respond effectively to crop metabolism and are directly related to soil productivity. However, simultaneous comparisons of SON dynamics using isotopic tracing in diverse agroecosystems are lacking, especially in karst areas with fragile ecology. To better understand the response of SON dynamics to environmental changes under the coupling of natural and anthropogenic disturbances, SON contents and their stable N isotope (δ15NSON) compositions were determined in abandoned cropland (AC, n = 16), grazing shrubland (GS, n = 11), and secondary forest land (SF, n = 20) from a typical karst area in southwest China. The SON contents in the SF (mean: 0.09%) and AC (mean: 0.10%) profiles were obviously lower than those in the GS profile (mean: 0.31%). The δ15NSON values ranged from 4.35‰-7.59‰, 3.79‰-7.23‰, and 1.87‰-7.08‰ for the SF, AC, and GS profiles, respectively. Decomposition of organic matter controlled the SON variations in the secondary forest land by the covered vegetation, and that in the grazing shrubland by goat excreta. δ15NSON ranges were controlled by the covered vegetation, and the δ15NSON fractionations during SON transformation were influenced by microorganisms in all surface soil. The excreta of goats that contained 15N-enriched SON induced a heavier δ15NSON composition in the grazed shrubland. Long-term cultivation consumes SON, whereas moderate grazing increases SON content to reduce the risk of soil degradation. This study suggests that optimized crop-livestock production may benefit the sustainable development of agroecosystems in karst regions.

Karst rocky desertification restoration increases soil inorganic N supply to reduce plant N limitation

Nitrogen (N) limitation of plant growth following vegetation restoration is widespread in global terrestrial ecosystems, especially in karst rocky desertification areas. However, neither the temporal changes in plant N limitation during the restoration of those areas nor the mechanisms underlying N availability are well understood. In this study, several indicators reflecting soil N availability, N transformation rates, and plant communities were investigated in four areas in southwest China differing in their grade of rocky desertification. Our results showed that plant growth was severely N limited in the intense rocky desertification areas. The plant community-level foliar N content, 15N values, and N:P ratio increased significantly as the rocky desertification grade decreased, indicating a decrease in plant N limitation. This was attributed to increased soil N availability, evidenced by the higher soil δ15N values as well as total N and inorganic N contents along the rocky desertification grade. With the decreasing rocky desertification grade, the rates of organic N conversion to ammonium (NH4+) and nitrate (NO3–), the adsorption of NH4+ on cation-exchange sites, and the release of adsorbed NH4+ increased significantly, which could enhance soil inorganic N supply capacity and accelerate NH4+ turnover to increase N availability. Noticeably, the sharp decrease in the rate of NH4+ oxidation to NO3– with the decrease in the rocky desertification grade led to a shift in inorganic N from NO3–-dominated to NH4+-dominated. The increased contents of soil organic matter, calcium, iron-aluminum oxides, and sand, the proportion of aggregates > 2 mm, as well as the greater abundances of fungi and bacteria were the primary drivers of the N transformation rates along the rocky desertification grade. Overall, our study highlights the importance of N cycling in controlling N availability and thus in determining plant N limitation in karst rocky desertification areas. The results of the study provide a scientific basis for the ecological restoration of rocky desertification in karst ecosystems.

Coupling effect of key factors on ecosystem services in border areas: a study of the Pu'er region, Southwestern China.

The coupling effects created by transboundary and local factors on ecosystem services are often difficult to determine. This poses great challenges for ecosystem protection and management in border areas. To decrease uncertainty, it is crucial to quantify and spatialize the impact multiple factors have on ecosystem services within different scenarios. In this study, we identified key transboundary and local factors from a set of 15 sorted factors related to four main ecosystem services. We employed a Bayesian Network-Geographic Information System (BN-GIS) model to simulate 90 scenarios with multiple factors combinations, quantifying and spatializing the coupling effects on the main ecosystem services. These simulations were conducted in the Pu'er region, which is situated alongside three countries, and serves as a representative border area in southwest China. The results showed that: (1) The coupling effects of multiple factors yield significant variations when combined in different scenarios. Managers can optimize ecosystem services by strategically regulating factors within specific areas through the acquisition of various probabilistic distributions and combinations of key factors in positive coupling effect scenarios. The outcome is a positive coupling effect. (2) Among the four main ecosystem services in the Pu'er region, food availability and biodiversity were affected by key transboundary and local factors. This suggests that the coupling of transboundary and local factors is more likely to have a significant impact on these two ecosystem services. Of the 45 combination scenarios on food availability, the majority exhibit a negative coupling effect. In contrast, among the 45 combination scenarios on biodiversity, most scenarios have a positive coupling effect. This indicates that food availability is at a higher risk of being influenced by the coupling effects of multiple factors, while biodiversity faces a lower risk. (3) Transboundary pests & diseases, application of pesticides, fertilizer & filming , population density, and land use were the key factors affecting food availability. Bio-invasion, the normalized differential vegetation index, precipitation, and the landscape contagion index were the key factors affecting biodiversity. In this case, focusing on preventing transboundary factors such as transboundary pests & disease and bio-invasion should be the goal. (4) Attention should also be paid to the conditions under which these transboundary factors combine with local factors. In the areas where these negative coupling effects occur, enhanced monitoring of both transboundary and local factors is essential to prevent adverse effects.

Effects of foliar application of Zn combined with organic matters on Cd accumulation and its chemical forms in rice.

Rice consumption is a key Cd exposure pathway, which poses a health risk to humans. Reducing cadmium (Cd) concentrations in rice remains challenging. In this study, a pot experiment was conducted to examine the effects of foliar spray of Zn combined with organic matters (including Zn-lysine (Zn-Lys), Zn-fulvic acid (Zn-FA), Zn-amino acid (Zn-AA), and Zn combined with glutathione (Zn + GSH)) on Cd accumulation in rice grains. Compared with the control group, all treatment groups exhibited reduced Cd concentration in rice grains, while improving plant growth, and reducing Cd transport from other tissues to the grains. Zn-FA was found to be the most effective fertilizer, which considerably reduced Cd concentrations in grains from 0.77 ± 0.068 to 0.14 ± 0.021mg/kg and yielded reductions of up to 81%, which is within the Chinese food maximum tolerable limit of 0.2mg/kg. Furthermore, the analysis of the chemical forms of Cd of rice tissues indicated that the treatment groups had increased proportions of integrated with pectates and protein in the stems. Except for the group treated with Zn-Lys spray, the percentages of undissolved Cd phosphate in the leaves were increased in all treatment groups, which reduced Cd toxicity to rice plants. The foliar application of Zn combined with organic matters may be a promising strategy to decrease Cd concentration in rice grains cultivated in severely Cd-contaminated agricultural soil, particularly in the karst area in southwest China with limited available cultivable agricultural land.

Characteristics of Cd Fluxe in Topsoil Around Typical Mining Area in Hezhou, Guangxi

Guangxi is a typical geological high background area in southwest China, where carbonates, black rock series, basic-ultrabasic rock mass, and metal deposits (mineralized bodies) exhibit strong weathering into loam, resulting in higher cadmium (Cd) content in the soil than that in other areas of China. In order to investigate the degree of influence of mining activities on topsoil environmental quality in the area with high geological background, we chose a mining area and control area in Hezhou for this research and systematically carried out a comparative study on Cd transport routes and transport flux density in topsoil. The results showed that the average atmospheric dry and wet deposition flux densities of Cd in the soil of the mining area and control area were 1.87 g·(hm2·a)-1 and 1.52 g·(hm2·a)-1, accounting for 61.5% and 60.3% of the total input flux density, respectively. The flux density of Cd in the soil by fertilization and irrigation was lower. Surface water infiltration was the main avenue of soil Cd output in both the mining area and control area, accounting for 75.4% and 86.6% of the total output flux density, respectively. The harvest output flux density in the mining area was higher than that in the control area, and the Cd content of rice planted in the mining area was higher than the standard, whereas that of maize was safe. On the whole, the net transport flux densities of soil Cd in the mining area and control area were -3.05 g·(hm2·a)-1 and -4.05 g·(hm2·a)-1, both of which showed Cd leaching in the soil. However, the points of high atmospheric deposition flux density and exceeding Cd content in rice were mainly distributed around the mining area, which may have posed a potential threat to the health of local residents. Therefore, it is suggested to control the soil Cd pollution through monitoring and planting structure adjustment.

Heavy metal contamination in duck eggs from a mercury mining area, southwestern China.

Mercury (Hg) contamination in the environment around mercury mines is often accompanied by heavy metal contamination. Here, we determined concentrations of chromium (Cr), zinc (Zn), strontium (Sr), barium (Ba), and lead (Pb) in duck eggs from a Hg mining area in Southwest China to assess the contamination and health risk. Duck eggs obtained from the mining area exhibit higher concentrations of Cr, Zn, Sr, Ba, and Pb compared to those from the background area, with egg yolks containing higher metal levels than egg whites. Specifically, the mean Cr, Zn, Sr, Ba, and Pb concentrations of duck eggs from the Hg mining area are 0.38, 63.06, 4.86, 10.08, and 0.05 μg/g, respectively, while those from the background area are only 0.21, 24.65, 1.43, 1.05, and 0.01 μg/g. Based on the single-factor contamination index and health risk assessment, heavy metal contamination in duck eggs poses an ecological risk and health risk. This study provides important insight into heavy metal contamination in duck eggs from Hg mining areas.

Quantifying Spatiotemporal Characteristics and Identifying Influential Factors of Ecosystem Fragmentation in Karst Landscapes: A Comprehensive Analytical Framework

Guanling-Zhenfeng County, a microcosm of the ecologically fragile karst area in southwest China, experiences rapid population growth and urban expansion which intensifies land use transformation and ecological landscape fragmentation. Exploring the spatiotemporal characteristics of landscape fragmentation and its causes in Guanling-Zhenfeng County is of great significance in maintaining the stability of the ecosystem and ecological protection in karst areas. In this study, a comprehensive landscape fragmentation index (FI), geographic probe, multi-scale geographically weighted regression (MGWR), and PLUS model were used to quantitatively explore the spatiotemporal characteristic heterogeneity, causes, and future scenario projections of landscape fragmentation in Guanling-Zhenfeng County from 2000 to 2020. The results showed that: (1) the distribution of each landscape index was characterized by obvious spatial differentiation. Among them, the spatial distribution trends of patch density (PD) and largest patch index (LPI) were opposite and the distribution trends of Shannon diversity index (SHDI) and Shannon evenness index (SHEI) were similar. There were fewer heterogeneous patches in the study area from 2000 to 2020, and the landscape shape was more regular and less fragmented. (2) The overall landscape fragmentation in Guanling-Zhenfeng County from 2000 to 2020 was dominated by moderate fragmentation, with the smallest percentage of extreme fragmentation, and heavy fragmentation was mainly distributed in the north-central part of the study area. (3) Natural and social factors jointly affect the landscape fragmentation in Guanling-Zhenfeng County, and there is a significant interactive enhancement effect among the factors, with population density being the most important influence factor. In addition, the effects of the factors on landscape fragmentation showed significant spatial non-stationarity. (4) The characteristics of landscape fragmentation changes in Guanling-Zhenfeng County under different scenarios varied significantly, with the largest percentage of increase in heavy landscape fragmentation under the business-as-usual scenario (BAU), the next under the land use planning scenario (LUP), and the smallest under the ecological protection scenario (ESP).

Tin (Sn) Geochemical Mapping Based on a Fixed-Value Method: A Case Illustration in Gejiu Area, Southwest China

Geochemical maps play an important role in mineral resource exploration. There are three traditional methods for creating geochemical maps: the cumulative frequency method, the logarithmic interval method, and the Avg±k∗Std (where Avg and Std are the abbreviations of average and standard deviation, and k is a multiple of Std) method. However, with the increasing scope of the study area and cumulative data, the limitations of traditional methods, which depend on the amount of data, are exposed. A fixed-value method for Sn geological mapping is proposed to overcome the limitations of traditional methods. In the fixed-value method, Sn concentrations are divided into 19 levels on 18 fixed values ranging from 1 μg/g (corresponding to the detection limit) to 1000 μg/g (corresponding to the cut-off grade of Sn in hard rocks). The 19 levels are mapped in six color tones. The first to fifth levels are the lowest background areas in blue tones, which correspond to Sn concentrations ranging from the minimum to 3.4 μg/g. The sixth to ninth levels are high background areas in yellow tones corresponding to concentrations less than 10 μg/g, the 10th to 12th are low anomaly areas in pink tones less than 28 μg/g, the 13th to 15th are high anomaly areas in red tones less than 200 μg/g (corresponding to the placer cut-off grade), the 16th to 18th in gray tones less than 1000 μg/g, and the 19th level is in black corresponding to Sn ores with Sn concentration not less than 1000 μg/g. The fixed-value method along with three traditional methods was used to contour the Sn geochemical maps in the Gejiu area in Southwest China. The illustration results of the presented fixed-value method and three traditional methods for geochemical mapping of Sn are all feasible for Sn deposit exploration in the Gejiu area, Southwest China. Compared to traditional methods, the presented fixed-value method overcomes the flaws of traditional methods and is also more meaningful in geochemistry.

Low frequency of SLC26A4 c.919-2A > G variant among patients with nonsyndromic hearing loss in Yunnan of Southwest China

BackgroundGene variants are responsible for more than half of hearing loss, particularly in nonsyndromic hearing loss (NSHL). The most common pathogenic variant in SLC26A4 gene found in East Asian populations is c.919-2A > G followed by c.2168A > G (p.H723R). This study was to evaluate their variant frequencies in patients with NSHL from special education schools in nine different areas of Southwest China’s Yunnan.MethodsWe performed molecular characterization by PCR-products directly Sanger sequencing of the SLC26A4 c.919-2AG and c.2168 A > G variants in 1167 patients with NSHL including 533 Han Chinese and 634 ethnic minorities.ResultsThe SLC26A4 c.919-2A > G variant was discovered in 8 patients with a homozygous state (0.69%) and twenty-five heterozygous (2.14%) in 1167 patients with NSHL. The total carrier rate of the c.919-2A > G variant was found in Han Chinese patients with 4.50% and ethnic minority patients with 1.42%. A significant difference existed between the two groups (P < 0.05). The c.919-2A > G allele variant frequency was ranged from 3.93% in Kunming to zero in Lincang and Nvjiang areas of Yunnan. We further detected the SLC26A4 c.2168 A > G variant in this cohort with one homozygotes (0.09%) and seven heterozygotes (0.60%), which was detected in Baoshan, Honghe, Licang and Pu`er areas. Between Han Chinese group (0.94%) and ethnic minority group (0.47%), there was no statistical significance (P > 0.05). Three Han Chinese patients (0.26%) carried compound heterozygosity for c.919-2A > G and c.2168 A > G.ConclusionThese data suggest that the variants in both SLC26A4 c.919-2A > G and c.2168 A > G were relatively less frequencies in this cohort compared to the average levels in most regions of China, as well as significantly lower than that in Han-Chinese patients. These results broadened Chinese population genetic information resources and provided more detailed information for regional genetic counselling for Yunnan.

Healthcare-seeking behaviours of patients with acute respiratory infection: a cross-sectional survey in a rural area of southwest China

ObjectivesThis study aimed to assess the healthcare-seeking behaviour and related factors of people with acute respiratory symptoms in the rural areas of central and western China to estimate the disease...

The Impact of Large-Scale Water Diversion Projects on the Water Supply Network: A Case Study in Southwest China

The uneven spatial and temporal distribution of water resources has consistently been one of the most significant limiting factors for social development in many regions. Furthermore, with the intensification of climate change, this inequality is progressively widening, posing a critical challenge to the sustainable development of human societies. The construction of large-scale water projects has become one of the crucial means to address the contradictions between water supply and demand. Thus, evaluating the functional aspects of water source network structures and systematically planning the layout of engineering measures in a scientifically reasonable manner are pressing issues that require urgent attention in current research efforts. Addressing this, our study takes the Erhai Lake basin and the surrounding areas in southwest China as the study area and combines landscape ecology and network analysis theory methods to propose a water supply network analysis method that takes into account both structure and node characteristics. Based on this methodology, we analyze the connectivity characteristics of water supply networks in the Erhai region under current (2020) and future (2035) planning scenarios. The results show that there were 215 nodes and 216 links in the water supply network of the Erhai Lake basin in 2020; with the implementation of a series of water conservancy projects, the planned 2035 water supply network will increase by 122 nodes and 163 links, and the connectivity of the regional water network will be significantly improved. Also, we identify some key nodes in the network, and the results show that the water supply network in 2035 will have obvious decentralization characteristics compared with that in 2020. And, based on the network degradation analysis, we find that with the implementation of engineering measures, the resilience of the water supply network will be significantly strengthened by 2035, with stronger risk tolerance. This study extends the quantitative representation of water source network characteristics, which can provide a useful reference for water network structure planning and optimization.

Water quality and microecosystem of water tanks in karst mountainous area, Southwest China.

Karst mountainous areas in Southwest China, the world's largest bare karst area, are faced with growing water shortages. Rainwater harvesting plays an important role in alleviating water shortage. However, there remains a substantial gap in the research regarding the water quality of tanks. Water samples were seasonally collected from ten tanks to investigate the physicochemical properties, microbial communities, and their key influencing factors. The result showed that pH, turbidity, chroma, DOC, and CODMn exceeded drinking water guidelines. The alkaline pH value and the deterioration of sensory properties was the main feature of tank water, from which the over-standard rate of the uncleaned water tanks was higher. Moreover, principal component analyses suggested that tank water quality was influenced by human activities, catchment areas, and material cycling processes within the tanks, of which in-tank microbial activities were the most important driving factors in water quality variation. Proteobacteria, Actinobacteria, Bacteroidetes, Cyanobacteria, Firmicutes, and Verrucomicrobia were the predominant bacterial phyla in water tanks. Acinetobacter, Cyanobium-PCC-6307, CL500-29-marine-group, Candidatus-Aquiluna, and Exiguobacterium were the most abundant genera. The bacterial communities were significantly affected by the management practices. Higher relative abundance of Cyanobacteria and lower relative abundance of Proteobacteria was detected in the uncleaned tanks, which was a sign of tank water quality deterioration. The microbial community structure was closely related to the environmental factors. There was evidence that the water quality was affected by the existence of a microecosystem dominated by photosynthetic microorganisms in the water tanks. In addition, Acinetobacter, Enterobacter, Pseudomonas, and Legionella identified as the potential opportunistic pathogenic genera were frequently detected but the relative abundances except Acinetobacter were low in the tanks. Overall, our findings indicated that management style influences water quality and bacterial communities of tank water.

Risk assessment and source identification of soil heavy metals: a case study of farmland soil along a river in the southeast of a mining area in Southwest China.

To investigate the heavy metals (HMs) contamination of surface farmland soil along the river in the southeast of a mining area in southwest China and identify the contamination sources, 54 topsoil samples were collected and the concentrations of seven elements (Zn, Ni, Pb, Cu, Hg, Cr, and Co) were determined by inductively coupled plasma optical emission spectrometry (ICP-OES) and atomic fluorescence spectrometry (AFS). The geo-accumulation index ([Formula: see text]) and comprehensive potential ecological risk index ([Formula: see text]) were used for analysis to determine the pollution degree of HMs and the risk level of the study area. Meanwhile, the Positive Matrix Factorization (PMF) model was combined with a variety of statistical methods to determine the sources of HMs. To explore the influence of the river flowing through the mining area on the concentrations of HMs in the farmland soil, 15 water samples were collected and the concentrations of the above seven elements were determined. The results showed that the concentrations of Pb, Cu, and Zn in soil all exceeded the risk screening value, and Pb in soil of some sampling sites exceeded control value of "Agricultural Land Soil Pollution Risk Control Standard".[Formula: see text] showed that Pb was heavily contaminated, while Cu and Zn were moderately contaminated. RI showed that the study area was at moderate risk. PMF and various statistical methods showed that the main source of HMs was the industrial source. In the short term, the river flowing through the mine has no significant influence on the concentration of HMs in the soil. The results provide a reference for the local government to control contamination and identify the sources of HMs.

Study on the Impact of Flow Dynamic Allocation Mechanism on the Balanced Propagation of Multicluster Fractures in Horizontal Wells

Abstract The implementation of the multicluster fracturing technique in horizontal wells is crucial to the economic development of shale gas reservoirs. The stress shadow area generated by them suppresses the effective expansion of fractures, leading to lower construction quality. Numerous well logging and production data indicate that dynamic flow allocation is also an important mechanism restricting oil and gas production. To reveal the mechanism of multifracture synchronous competitive expansion, a multifracture expansion finite element model considering fluid-solid coupling in porous media was established. A wellbore model was built to characterize the fluid pressure drop, incorporating pipe flow and fluid connection elements to emulate fluid flow within the wellbore, and the influence of various factors on the balanced expansion of fractures was investigated. The results show that high porosity, uniform perforation, and high elastic modulus of sweet spots are favorable for the balanced expansion of multiple fractures when using high-volume and low-viscosity fracturing fluids. When the spacing is small and the porosity is low with nonuniform perforation, the threshold generated by perforation friction will dominate the balanced fluid injection and expansion of each fracture. The horizontal well fracturing plan in a certain area of southwest China was optimized using this model. After optimization, when the spacing is less than 15 m, the total number of perforations is 32, and the average injection rate per cluster will be increased by 0.125 m3/min, with a coefficient of variation of 3.9% among clusters. When the perforations are nonuniformly distributed, the average injection rate per cluster will be increased by 0.101 m3/min, the fluid inflow difference coefficient of each cluster is 4.1%, and multiclusters will have a uniformly developed fracture network. This study has certain guiding significance and reference value for the balanced expansion of multifractures in horizontal wells.

Voices Behind Images: Exploring Left-Behind Children’s Lives with Grandparents through Photovoice

Abstract Today, many children are living with their grandparents in rural hometowns whilst their parents migrate to work in cities. This qualitative study explores these left-behind children’s perspectives of grandparental involvement in their lives through Photovoice. Thirty left-behind children (63% female, mean age = 12 years) in a major labour-sending rural area in southwest China joined five-session Photovoice groups, during which they took photos that best represented their lives with their grandparents. Visual data of eighty-four photos were analysed with thematic analysis. The most prominent themes were living environments and daily routines with grandparents, followed by grandparents’ material support, time spent together, reciprocal support and perceived cultural traditions from the grandparents. Boys highlighted more material support from their grandparents in their shared photos, whereas girls focused more on their perceptions of cultural traditions being passed from their grandparents. This study illustrates the multifaceted nature of intergenerational solidarity and highlights the protective roles grandparents play in left-behind families in the labour migration context. The findings suggest the importance of using strength-based, culturally sensitive social work research (e.g. Photovoice techniques) and practices (e.g. community empowerment) to foster quality grandparental companionship and intergenerational bonding in left-behind families.

Evolution and Transformation Analysis of Land-use in Mountainous “Granary”—Evidence from Typical Basin in Karst Mountainous Areas of Southwest China

Intermountain basins are the granaries of the karst mountains of southwest China. Revealing the process and trend of land-use transformation in typical mountainous “granaries” is of great significance to optimizing land-use, food security, and rural revitalization in the karst mountains of southwest China. Lianjiang basin in Huishui County is the largest in Guizhou Province of southwest China, and a typical mountainous “granary” is used as a case study area. Based on seven periods of high-definition remote sensing images from 1966 to 2020 and on-the-spot investigation, we adopt the analysis methods of landscape pattern, moving window, and buffer zone and conduct an in-depth study on the spatial evolution of land-use and the land-use transformation law of the typical “granaries” of karst mountainous areas in southwest China from the perspectives of changes in the quantity of land-use, changes in the types of land-use, and changes in the landscape pattern. The results showed that the transformation of land-use in the basin was mainly manifested in the transformation of the function of cultivated land and the diversification of the function of cultivated land. The landscape pattern of the basin was gradually transformed from traditional rural landscape to modern agricultural landscape. The gradient effect of land-use evolution and transformation in the study basin was obvious. Traffic, location, and land resources significantly affect land-use transformation in the basin. Based on the above analysis, this paper proposes that the “granary” basins in karst mountainous areas should optimize the land-use of the basin by the trade-off between regional socio-economic development, ecological protection, and food security. The results of this paper provide a reference for land-use optimization and rural development in the granary-type basins and other similar areas in the karst mountains of southwest China.

Improving soil thickness estimations and its spatial pattern on hillslopes in karst forests along latitudinal gradients

Soils provide storage space for nutrients and water, which governs many hydrological processes and functions in the natural ecosystems. Due to the complex soil-rock structures and localized climate, soil thickness and stock vary distinctly in different karst areas in southwest China. The difficulties of soil detection and the non-transparent underground soil-rock structures limit a deeper understanding of the spatial distribution of soils and their ecological functions. In this study, we employed electrical resistivity tomography (ERT) combined with soil probes to detect the spatial distribution of soils on hillslopes in karst forests in southwest China. The ERT surveys were conducted at six sites with 19 plots (20 × 30 m2) along latitudinal gradients. The results show that the ERT method performs well in visualizing the complex soil–bedrock interfaces and patchy distribution of soils in karst hillslopes, with remarkable consistency with the observed soil thickness and rock outcrops. Soil probes often hit rocks in soils (which we call a “rock barrier effect”), resulting in an underestimation of the mean soil thickness within the one-meter exploration depth by ∼0.18 m. This indicates that soil stock estimates derived from soil probes may be obviously underestimated in karst areas where the rock barrier effects are widespread. Meanwhile, the concept of equivalent soil thickness is proposed to remove the impact of scattered bedrock on soil stock estimation. For the six selected sites, the ERT-inferred mean soil thickness, equivalent soil thickness, and stock are 0.86 m, 0.60 m, and 0.10 m3/m3 respectively, with a trend of decreasing from high to low latitudes. Moreover, the rock outcrop coverage rate explains 52 % (60 %) of the variation in soil thickness (stock), followed by the annual mean temperature. This study emphasizes the importance of considering bedrock topography and its distribution in improving the detection of soil distribution, and the implications of the findings in this study are perhaps most profound for soil thickness-related soil erosion, soil water storage, and carbon storage in karst critical zones.