Karst Region Research Articles

Integrating Automated Drip Irrigation and Organic Matter to Improve Enzymatic Performance and Yield of Water Efficient Chilli in Karst Region

Integrating Automated Drip Irrigation and Organic Matter to Improve Enzymatic Performance and Yield of Water Efficient Chilli in Karst Region

Research on Spatial Morphological Characteristics and Influencing Factors of Industrial Heritage: A Case Study of Nine Industrial Heritages in Guizhou Province

Industrial heritage, recognized as a significant aspect of historical and cultural heritage, has garnered considerable attention from scholars globally. To elucidate the spatial morphological characteristics and the underlying influencing factors of industrial heritage within karst regions, this study employs methods such as the interstice index, fractal dimension analysis, and spatial syntax. It conducts research on the spatial morphological characteristics of nine typical industrial heritages in Guizhou Province. The primary factors contributing to the variations in layout forms are the intricate karst topography and the functional requirements of production. The functional zoning of industrial heritage aligns with its layout, characterized by straightforward functional zones that have not developed into composite spaces. The overall connectivity of industrial heritage is relatively low, exhibiting weak integration, significant disparities in control values, low average depth values, and a deficiency in comprehensibility and diversity of options. This indicates that the internal connectivity of industrial heritage spaces is generally inadequate, with low accessibility, strong interrelations, average convenience, limited connectivity, and generally acceptable passage. The overall spatial, architectural, and roadway configurations of industrial heritage predominantly exhibit a uniform pattern. Importantly, industrial heritage reveals a highly variable overall spatial form, with an average fractal dimension of 1.57, complex architectural layouts (average fractal dimension of 1.50), and simplistic road network designs (average fractal dimension of 1.43), which collectively suggest high spatial complexity and irregular characteristics. This study can provide a reference for the analysis of spatial characteristics and influencing factors of other material cultural heritages, and it is of great significance for the systematic protection and revitalization of industrial heritage.

Inversion Model for Permeability Coefficient Based on Random Forest–Secretary Bird Optimization Algorithm: Case Study of Lower Reservoir of C-Pumped Storage Power Station

The geological complexity of the karst regions presents significant challenges, with the permeability coefficient being a critical parameter for accurately analyzing seepage behavior in hydraulic engineering projects. To overcome the limitations of traditional inversion methods, which often exhibit low computational efficiency, poor accuracy, and instability, this study utilizes a finite-element forward model and orthogonal experimental design to establish a sample set for permeability-coefficient inversion. A surrogate model for seepage calculation based on the Random Forest (RF) algorithm is subsequently developed. Furthermore, the Secretary Bird Optimization Algorithm (SBOA) is incorporated to propose an intelligent RF–SBOA inversion method for permeability-coefficient estimation, which is validated through a case study of the C-pumped storage power station. The results demonstrate that the RF model’s predictions for water levels at four boreholes closely align with the measured data, outperforming models such as CART, BP, and SVR. The SBOA effectively identifies the optimal geological permeability coefficient, with the borehole water-level inversion achieving a maximum relative error of only 0.128%, which meets the accuracy requirements for engineering applications. Additionally, the computed distribution of the natural seepage field is consistent with the typical distribution patterns observed in mountain seepage systems. During the normal water-storage phase, both the calculated seepage flow and gradient comply with engineering standards, while the seepage-field distribution aligns with empirical observations. This inversion model provides a rapid and accurate method for estimating the permeability coefficient of strata in the project area, with potential applicability to permeability inversion in other engineering geology contexts, thus demonstrating considerable practical value for engineering applications.

Evaluation of stormwater runoff pollutant distributions combined with land-use information in a regional karst aquifer in Texas, USA.

Fast urbanization can result in significant stormwater runoff pollution due to changes in land use. A 3-year study on the distribution and temporal variations of urban water pollutants in stormwater runoff was conducted, with a specific focus on the influence of land-use patterns in the recharge zone of a regional karst aquifer in Texas (Edwards Aquifer). The presence and concentration of various water pollutants including total suspended solids (TSS), total dissolved solids (TDS), nutrients (nitrite, nitrate, ammonia and phosphate), total carbon (TC) and total organic carbon (TOC), oil and grease (O&G), and eight heavy metals (Fe, Mg, Cu, Pb, Zn, Ni, Cr, Cd) were measured in stormwater samples collected from three bioswales. Results show that average TSS in site S1 (598.87mg/L) and S2 (628.69mg/L), COD in site S1 (103.97mg/L), phosphate in sites S1 (1.44mg/L) and S3 (0.65mg/L), and O&G (ranging from 50.63 to 84.32mg/L) in all three sites surpassed the national average (NSQD). While residential areas were identified as the main sources of nutrients, roads and parking lots were associated with heavy metals. Temporal variations indicated the effect of antecedent dry days on the concentrations of TSS and phosphate. Growing seasons as well as pet feces were associated with elevated nitrate concentrations in residential areas. Organic carbon was found overall higher during warmer months, while heavy metals during cooler months. The study also identified specific land-use practices that can be enhanced to mitigate stormwater pollution, such as the implementation of permeable pavements, rain gardens, and stricter waste disposal regulations. The results of this study offer valuable insights for enhancing stormwater management strategies to better mitigate stormwater pollution in urban regions.

A vulnerable soil environment study in karst areas: a bibliometric analysis

Karst landforms are widely distributed around the world, and karst rocky desertification has occurred on a large scale in many countries and regions, causing significant adverse impacts on local natural environments and societies. The improvement and rational use of karst soil is a key aspect of rocky desertification governance. Karst soil science studies are of great value in karst regions and are essential for controlling karst rocky desertification and ecological restoration. In order to understand the research hotspots and the development directions in the field of vulnerable karst soil environment, we undertook bibliometrics citation analysis on 1913 contributions to the literature written in the range from 2001 to 2019 based on the “Web of Science” core collection citation index database. Hopefully, this work will help to set up a scientific foundation for further studies. Using CiteSpace visualization software, we analyzed the distribution of disciplinary categories, reference co-citation clusters, and keyword clusters in the literature. The results show the basic characteristics and evolution of the literature related to karst pedology. We then recognized the main intellectual bases in the domain of karst soil science. This study also revealed the research hotspots and trends in this field. Through a bibliometrics citation analysis of research on karst vulnerable soil environment, the present study provides a quantitative and objective understanding of development directions that have emerged in this field over the past 19 years, offering a reference for future research.

A Paleoenvironmental Reconstruction of Lake Vrana on the Island of Cres (Croatia) Based on the Geochemistry and Mineralogy of the Late Pleistocene and Holocene Sediments

A 7.4 m long sediment core has been retrieved from the central part of Lake Vrana on the island of Cres to reconstruct the paleoenvironmental conditions. Lake Vrana is the deepest freshwater lake in Croatia, located in the karst region of the eastern Adriatic coast. A dated sediment sequence in Lake Vrana of 4.4 m has spanned the past 16.4 kyr, and it featured a dynamic sediment deposition until the beginning of the Holocene, including strong sediment input and supply to the lake by runoff sediments of dolomitic origin from the catchment in the period 16.4–14.4 cal kyr BP. High organic carbon content, which originates from mixed terrestrial and aquatic origins in the periods 14.4–13.3 cal kyr BP and 12.7–11.7 cal kyr BP, indicates fluctuating lake levels in shallow water environments during the Late Glacial to Holocene transition. The Holocene sequence indicates the development of more stable conditions and continuous sediment deposition, characterized by an increasing trend of siliciclastic sediments delivered into the lake during the early Holocene (11.7–10 cal kyr BP) and dominantly from 8 to 4.4 cal kyr BP, indicating enhanced input and erosion, which coincides with the humid and pluvial period recorded in the central Mediterranean region. It is followed by sediments with high organic carbon content between 4.4 and 1.6 cal kyr BP, which points to higher lake productivity. Calcite sedimentation prevailed between 1.6 to 0.4 cal kyr BP, indicating stable deeper-lake conditions. Predominantly, siliciclastic sediments from 0.4 to 0.1 cal kyr BP pointed to erosion during the Little Ice Age (LIA), with enhanced precipitation and sediment discharge from the catchment. The re-establishment of calcite sedimentation has been observed over the last 100 years.

Soil Properties Regulate Soil Microbial Communities During Forest Succession in a Karst Region of Southwest China

Natural vegetation restoration has emerged as an effective and rapid approach for ecological restoration in fragile areas. However, the response of soil microorganisms to natural succession remains unclear. To address this, we utilized high-throughput sequencing methods to assess the dynamics of soil bacterial and fungal communities during forest succession (shrubland, secondary forest, and primary forest) in a karst region of Southwest China. Our study revealed that bacterial α-diversity was significantly higher in secondary forest compared to both shrubland and primary forest. Intriguingly, the soil bacterial community in primary forest exhibited a closer resemblance to that in shrubland yet diverged from the community in secondary forest. Conversely, the soil fungal community underwent notable variations across the different forest stages. Furthermore, analysis of the microbial co-occurrence network revealed that, within these karst forests, the relationships among soil fungi were characterized by fewer but stronger interactions compared to those among bacteria. Additionally, soil properties (including pH, soil organic carbon, total nitrogen, moisture, and available potassium), soil microbial biomass (specifically phosphorus and nitrogen), and plant diversity were the drivers of soil bacterial community dynamics. Notably, soil pH accounted for the majority of the variations observed in the soil fungal community during karst forest succession. Our findings provide valuable insights that can inform the formulation of strategies for ecological restoration and biodiversity conservation in karst regions, particularly from a microbial perspective.

The Contribution of Moisture Sources of Precipitation to Water Resources Recharge in Semi-Arid Regions

This study investigates the isotopic composition of precipitation in Iran and its moisture sources, offering insights crucial for addressing water recharge and management in semi-arid regions. This study analyzes 150 precipitation events collected from 11 stations across Iran over multiple years. The HYSPLIT model was used to trace air mass trajectories contributing to these events. The isotopic composition of precipitation from each moisture source was examined to identify their distinct characteristics. Furthermore, the contribution of each air mass to groundwater and surface water recharge was quantified using the Simmr mixing model in R programming language, combining stable isotope data from precipitation and surface/groundwater samples. Precipitation in northern Iran is associated with low d-excess values, indicating moisture from high-latitude sources, particularly the Caspian Sea, while higher d-excess values in the west and south point to moisture mainly from the Persian Gulf and the Mediterranean Sea. Air mass trajectory analysis via the HYSPLIT model identified the dominant pathways of Continental Tropical (CT), Continental Polar (CP), and Mediterranean (MedT) air masses across Iran. Quantitative analysis using the Simmr mixing model revealed that the CT air mass contributes up to 33.6% to groundwater recharge in southern Iran’s karstic regions, while the CP air mass dominates in the north, with up to 46.8% contribution. The MedT air mass, although significant in the west, decreases in influence towards the east. Isotope data from groundwater and surface water sites showed more depleted values than local precipitation, likely due to larger catchment areas. These findings contribute to water management strategies by identifying the variations in moisture sources that influence groundwater and surface water recharge in Iran. Understanding these variations enables the development of targeted strategies for managing water resources in semi-arid regions facing increasing water scarcity. The methodologies applied in this study can be adapted to other regions, providing a valuable framework for sustainable water management in areas where identifying moisture sources is critical.

Ecological Suitability Evaluation of City Construction Based on Landscape Ecological Analysis

Ecological suitability evaluation is a critical component of regional sustainable development and construction, serving as a foundation for optimizing spatial patterns of regional growth. This is particularly pertinent in karst mountainous regions characterized by limited land resources and heightened ecosystem vulnerability, where a quantitative assessment of ecological suitability for land development is both crucial and urgent. Based on the fundamental principles of structural and functional dynamics in landscape ecology, this study focuses on Gui’an New Area, a designated urban development zone situated in the karst landscape of Guizhou Province. An index system was established encompassing three dimensions: ecological elements, ecological significance, and ecological resilience, utilizing the integrated ecological resistance (IER) model to evaluate the suitability of regional development and construction. The results reveal that the eastern region exhibits higher suitability compared to the central and western regions, with the northwest region demonstrating the lowest suitability overall. Relatively speaking, the evaluation of geological environment suitability and the comprehensive ecological constraints associated with development and construction indicates that the areas currently planned and ongoing reflect flat terrain and low ecological risk. Furthermore, within the scope of ecosystem dynamic adaptation, developmental activities in these regions exert minimal impact on the natural ecosystem, thereby demonstrating a high suitability for development and construction. In terms of future key development zones, areas with gentle slopes ranging from 8 to 15 degrees are recommended, aligning with the actual requirements for cultivated land protection. The total area designated as prohibited development zones constitutes the smallest proportion, representing only 9.45%, which is significantly lower than that of priority development zones (38.75%) and moderate development zones (22.45%). From the perspective of landscape ecology, this paper provides a comprehensive investigation into the ecological suitability evaluation system for development and construction in the karst regions of Southwest China, offering valuable insights for assessing ecological suitability in similar areas.

Caves’ environmental stability shaping subterranean biodiversity in the neotropics

Caves, once thought to be isolated ecosystems", are now understood to have intricate connections with surface environments, particularly evident at their entrances. These connections can significantly affect the microclimate within caves, leading to varying degrees of environmental stability. Our research explores the impact of microclimate conditions, specifically related to cave environmental stability, on biodiversity changes. We surveyed subterranean invertebrates during two different seasonal periods in 17 limestone caves in three karst regions in southeastern Brazil. Our analysis aimed to understand how environmental stability influences the overall richness of cave invertebrates and troglobitic species richness (restricted to subterranean habitats). We hypothesized that more stable caves would experience less fluctuation in relative species richness and lower turnover between seasons. Additionally, we anticipated that caves with greater environmental stability would harbor a higher richness of cave-restricted species in the function of their length. Our findings support these hypotheses, revealing a significant positive correlation between cave environmental stability and species richness. Caves with higher environmental stability demonstrated lower species turnover rates between seasons, indicating enhanced community stability. While environmental stability significantly affected species richness, its influence on cave-restricted species was comparatively less pronounced. This suggests a complex interplay of factors shaping the unique fauna of caves. Nonetheless, the implications of climate change underscore the importance of preserving the environmental stability of these ecosystems. Using environmental stability as a guide can help protect cave biodiversity from the adverse effects of climate change, contributing to broader conservation efforts for these unique habitats.

Stoichiometric and bacterial eco-physiological insights into microbial resource availability in karst regions affected by clipping-and-burning

Despite growing interest in soil microbial resource limitation (MRL), the impacts of clipping-and-burning on bacterial resource acquisition and its soil carbon, nitrogen, and phosphorous stoichiometry (C:N:P) remain unclear, yet are critical for nutrient cycling and SOC accumulation in vegetation restoration. We examined the soil C:N:P and eco-enzymatic stoichiometry, bacterial life-history strategies, and bacterial resource limitation under the influence of clipping-and-burning management practices: high-intensity fire (HIF), low-intensity fire (LIF), clipping-and-fire (CF), clipping (CP), and an undisturbed control (CK) in a Karst site in southwest China. The results showed that SOC, TN, and TP in HIF and LIF were significantly (p < 0.05) reduced (by 64%, 97%, and 99%) compared to CK. However, soil C:N, C:P, and N:P ratios were surprisingly higher (18.1, 56, and 3.08) in CF than in CK. The ratios of soil microbial biomass carbon (MBC) and nitrogen (MBN) were higher (4.8) under clipping. In contrast, their ratios with microbial biomass phosphorus (MBP) were observed to be higher (22.3 and 6.4) under high-intensity fire compared to CK. Moreover, results show that there is a higher percentage of species linked with oligotroph bacteria of Rickettsiales in CF treatments than CK. Soil bacterial communities in CF treatments exhibited co-limitation by C and P, whereas N limitation was more pronounced under low-intensity fire conditions. In conclusion, the evidence links MRL to soil C:N:P stoichiometry, underscoring the critical role of oligotrophic bacteria in mediating soil nutrient dynamics under clipping-and-burning disturbances. These findings improve our understanding of MRL over the Karst region under clipping-and-burning treatments, shedding light on its relationship with soil C:N:P, eco-enzymatic stoichiometry, and bacterial life-history strategies.

The conversion of biomass to biochar decreases soil organic and inorganic carbon-derived CO2 emissions under different water conditions in karst regions

Due to the unique geological background and climatic condition, karst soils in southwest China are mainly developed on carbonate rocks and accompanied by frequent dry-wet alternations. Therefore, the effects of biomass (BS) and biochar (BC) on the soil carbon pools (especially inorganic carbon) in karst regions are different from those in non-karst regions. In order to understand the responses of soil organic carbon (SOC) and soil inorganic carbon (SIC)-derived CO2 emissions to BS and BC amendments under different water conditions in karst regions, a microscopic study under dry-wet alternate (DW) and constant moisture (CM) conditions was established to investigate the stability of BC, BS, and their effects on SOC and SIC pools by isotope double-labeling methods. Results showed that the contribution rates of SOC and SIC to soil CO2 emissions were 51.55 %–99.52 %, 0.48 %–48.45 % and 60.55 %–97.72 %, 2.28 %–39.45 % under DW and CM conditions, respectively. Compared with the control, BS application under different water conditions increased SOC and SIC-derived CO2 emissions by 929.78˗1443.39 % and 169.69˗335.71 %, respectively. However, BC amendment significantly decreased SOC and SIC-derived CO2 emissions, especially in the DW condition. The mean residence time (the inverse of the decomposition rate) of BC in karst soils under different conditions ranged from 657 to 3105 years, which was much higher than those of BS (7˗18 years). Therefore, the conversion of BS to BC in karst regions enhances carbon sequestration due to its stability of recalcitrant carbon, the decrease of SOC and SIC- derived CO2 emissions. This study is helpful to understand the quantification of CO2 sources from calcareous soils and elucidate the environmental behaviors and carbon sequestration potentials of BC or BS amendments in karst regions.

Coupled iron and heavy metal accumulation in karst soils in Southwestern China: Iron isotope perspective

Heavy metals (HMs) are abundant in the karst soils of Southwest China, posing significant health risks to millions of people. Iron (Fe) (hyr)oxides serve as critical carriers of HMs in these soils; however, the processes governing Fe oxide formation and transformation associated with HM accumulation during carbonate weathering in karst region is less understood. In this study, we present Fe isotope compositions from a carbonate–derived profile to investigate the major factors controlling Fe migration. In the saprolite layer, strong correlations between δ56Febulk and the proportions of extracted FeNH2OH.HCl or Feresidue fractions suggest that the formation of goethite and phyllosilicate may be responsible for variations in δ56Febulk. The positive correlations between δ56FeNH2OH.HCl values and HM concentrations in this layer suggest an enhanced capacity for HM fixation by goethite in these soils. In contrast, the fractionation of Fe isotopes in the soil layer appears to be influenced by vegetation, as indicated by the correlation between total organic carbon and δ56Febulk. The negative correlations between δ56Febulk values and HM concentrations in the soil layer likely indicate that vegetation litter enhances the retention capacity of Fe oxides for HMs. This study highlights the trajectory of Fe and its connection to HM accumulation in karst soil with high geological background levels.

Genetic Diversity Analysis and Fingerprint Construction for 87 Passionfruit (Passiflora spp.) Germplasm Accessions on the Basis of SSR Fluorescence Markers

A comprehensive genetic diversity analysis of 87 Passiflora germplasm accessions domesticated and cultivated for several years in the karst region of Guizhou, China, was conducted utilizing simple sequence repeat (SSR) fluorescent markers. These Passiflora species, renowned for their culinary and medicinal value, could bring significant economic and ecological benefits to the region. This study aimed to assess the genetic resources of these species and facilitate the selection of superior cultivars adapted to the karst environment. Our analysis revealed an abundance of SSR loci within the Passiflora transcriptome, with single-base repeats being the most prevalent type. Through rigorous primer screening and amplification, we successfully identified 27 SSR primer pairs exhibiting robust polymorphisms. Further interrogation at eight microsatellite loci revealed 68 alleles, underscoring the high level of genetic diversity present in the cultivated accessions. The average expected heterozygosity was 0.202, with the ssr18 locus exhibiting the highest value of 0.768, indicating significant genetic variation. The mean polymorphic information content (PIC) of 0.657 indicates the informativeness of these SSR markers. Comparative analyses of the cultivated and potential wild progenitors revealed distinct genetic variations among the different Passiflora types. Genetic structure and clustering analyses of the 87 accessions revealed seven distinct groups, suggesting gene flow and similarities among the resources. Notably, a DNA fingerprinting system was established using eight SSR primer pairs, effectively distinguishing the selected cultivars that had adapted to the karst mountainous region. This study not only deepens our understanding of Passiflora genetic resources in the karst environment but also provides a valuable reference for conservation, genetic improvement, and cultivar selection. The rich genetic diversity of the Passiflora germplasm underscores their potential for sustainable utilization in breeding programs aimed at enhancing the economic and ecological viability of these valuable plant species.

Pollution and Carbon Sequestration of Highway Runoff in Karst Regions: A Case Study from Guangxi, China

Pollution and Carbon Sequestration of Highway Runoff in Karst Regions: A Case Study from Guangxi, China

Matching and driving mechanism analysis of the supply and demand relationships of soil conservation services in karst peak-cluster depression basin in Southwest Guangxi, China

The karst peak-cluster depression basin in southwestern Guangxi, characterized by a fragile ecological environment and intensive human activities, is characterized by rocky desertification and ecological function degradation. This degradation not only impairs the region’s ecological integrity but also limits its ecological and welfare benefits. Traditionally, the estimation of soil conservation service supply and demand in karst areas relies on internationally recognized models, which often exclude the critical factor of karst desertification. This omission introduces significant uncertainty in the assessment of soil supply and demand in karst terrains. To address this gap, our study employs an adapted revised universal soil loss equation model tailored for karst regions to conduct a quantitative analysis of the soil supply–demand relationship in southwestern Guangxi. We explore its spatiotemporal evolution and spatial matching characteristics utilizing geographic detectors to identify the driving factors influencing the ecological supply-to-demand ratio (ESDR). Our findings revealed the following: (1) From 2000 to 2020, the soil conservation supply–demand ratio in the study area showed a fluctuating upward trend, with an overall increase of approximately 63.29%. Specifically, there was a fluctuating increase from 2000 to 2008 and from 2013 to 2020, while a downward trend was observed from 2009 to 2012. (2) The predominant matching pattern of the soil conservation services in the research area was “low supply, low demand”, which was primarily located in the southeastern part of southwestern Guangxi. (3) The supply–demand relationship of soil conservation services is significantly influenced by factors such as vegetation coverage, slope, soil type, and lithology, with each factor exhibiting a marked interactive effect on the ESDR. This study evaluates and reveals the supply–demand relationship and driving mechanisms of soil conservation services in the karst region of southwestern Guangxi, which contributes to the precise formulation of strategies for rocky desertification prevention and ecological restoration.

Collecting empires: Dominik Bilimek and early subterranean zoology between politics and field research

The Moravian Cistercian monk and collector Dominik Bilimek (1813–1884) is considered one of the earliest European naturalists to conduct zoological research on subterranean fauna in Latin America. During the second French invasion of Mexico, from 1861 to 1867, he accompanied Maximilian of Habsburg, the newly enthroned emperor of Mexico, to the region. There, he explored the Grutas de Cacahuamilpa near Taxco de Alarcón, comparing its fauna to his earlier discoveries in Postojnska jama in Carniola (Slovenia). After the victory of the Mexican republican forces and Maximilian’s execution, Bilimek retained his role as curator of the emperor’s collections, which he took back with him to Europe and exhibited at Miramare Castle near Trieste. Prior to his Mexican venture, Bilimek had embraced the imperial goals and intellectual agendas of the Viennese central administration while teaching at the monarchy’s military institutes. Following the revolutions of 1848/49, extensive research undertakings—including geoscientific, biological, and archaeological surveys—were initiated to preserve the Habsburg monarchy as a supranational entity amidst internal and external crises, and to legitimize its territorial framework as both a natural and cultural unit. These developments coincided with the initial surge of zoological interest in Carniolan caves, which spurred efforts to gather similar findings in other karst regions of the monarchy. Drawing on historical sources, this article explores the intersection of political concepts and fieldwork practices in the early study of cave biology. Special attention is given to the sites, networks, and modes of collecting during this transformative period.

Rainfall water collection and irrigation via stone bud and karren on karst rocky desertification slopes: Application and benefit analysis

Lack of surface water is a key factor leading to agricultural drought in karst regions and exacerbates the karst rocky desertification, which is characterized by high rate of exposed bedrock. With the characteristics of impermeability, runoff collection, and wide distribution, stone bud and karren (SBK), a unique karst landscape type composed of exposed bedrock and gullies, has a great potential to solve water shortage in agricultural irrigation, especially in the rain-rich karst regions of Guizhou Province, China. Using unmanned aerial vehicle images to identify SBK and measured rainfall–runoff data for validation, we applied SBK as a basic unit to harvest rainfall water on rocky desertification slopes and analyzed the benefits of rainfall water collection and irrigation via SBK. The results showed the following: (1) Karrens on rocky desertification slopes could be identified using a method coupling terrain opening difference and depression filling, and the simulated runoff on SBK could achieved the average NSE and R2 of 0.82 and 0.86, with RMSE and RSR less than 0.03 m3 and 0.51, respectively. (2) The exposed bedrock utilization rate and rainfall water collection coefficient of SBK were 0.62 and 0.55, respectively, such that the area ratio of exposed bedrock to the cultivated land meeting irrigation water demand reached 1:3.1, 1:3.7 and 1:7.0 under 90 %, 80 % and 50 % possibilities of irrigation. (3) Implementing SBK for rainfall water harvesting and irrigation could efficiently avoid crop failure in the karst regions where crops faced drought within only one week after rainfall, and was at an affordable cost to local farmers with limited environmental damage. The use of SBK to harvest rainfall water could also alleviate surface water shortages in karst regions caused by problems such as uneven temporal distribution of rainfall and engineering water shortages. Consequently, SBK demonstrate a strong application potential to alleviate agricultural drought in karst rocky desertification regions.

Leveraging machine learning for sustainable cultivation of Zn-enriched crops in Cd-contaminated karst regions

Karst soils often exhibit elevated zinc (Zn) levels, providing an opportunity to cultivate Zn-enriched crops. (meanwhile) However, these soils also frequently contain high background levels of toxic metals, particularly cadmium (Cd), posing potential health risks. Understanding the bioaccumulation of Cd and Zn and the related drivers in a high geochemical background area can provide important insights for the safe development of Zn-enriched crops. Traditional models often struggle to accurately predict metal levels in crop systems grown on soils with high geochemical background. This study employed machine learning models, including Random Forest (RF), Support Vector Machine (SVM), and Extreme Gradient Boosting (XGBoost), to explore effective strategies for sustainable cultivation of Zn-enriched crops in karst regions, focusing on bioaccumulation factors (BAF). A total of 10,986 topsoil samples and 181 paired rhizosphere soil-crop samples, including early rice, late rice, and maize, were collected from a karst region in Guangxi. The SVM and XGBoost models demonstrated superior performance, achieving R2 values of 0.84 and 0.60 for estimating the BAFs of Zn and Cd, respectively. Key determinants of the BAFs were identified, including soil iron and manganese contents, pH level, and the interaction between Zn and Cd. By integrating these soil properties with machine learning, a framework for the safe cultivation of Zn-enriched crops was developed. This research contributes to the development of strategies for mitigating Zn deficiency in crops grown on Cd-contaminated soils.

Source apportionment of Cd in karst soil based on the delayed geochemical hazard model.

Soil Cd contamination has become increasingly prominent in karst regions. Studies have generally elucidated the natural sources of Cd in high-background areas and analyzed their migration and enrichment mechanisms. This study comprehensively analyzed the total content and speciation of Cd in high-background areas using the delayed geochemical hazard (DGH) model to identify the sources of Cd in the region. The results indicated that Cd in the research area followed a pattern of gradual geochemical disasters. In Quaternary soil, brick-red soil, and submergenic paddy soil with hydromorphic characteristics, 32%, 7.69%, and 30% of soil Cd samples exceeded the critical threshold of the releasable total amount, respectively. Based on the DGH model, it was concluded that Cd in this region was mainly influenced by human activities. Field investigations corroborated this conclusion and aligned with the findings. Compared with the traditional source apportionment receptor models (mainly PCA and PMF), the DGH model not only saved considerable time and cost, but also avoided uncertainty associated with the results and complex and varied data processing and computational analysis processes. Moreover, the DGH model was able to identify the factors having the greatest impact on the ecological risk of Cd in the research area, thus facilitating targeted prevention and management planning based on the characteristics or chemical properties of their elements.