Karst Region Research Articles

Study of path recognition and parameter identification of groundwater runoff channels in karst areas

ABSTRACT The location and water conductivity characteristics of groundwater runoff channels in karst areas significantly influence the spatial distribution of groundwater. Currently, few studies have utilized mathematical algorithms to analyse the locations of these channels and their conductivity characteristics, particularly with groundwater level distribution as the objective function. This paper fully leverages the principle of water flowing to lower elevations and employs an optimized gradient descent method to identify the flowpaths. Additionally, a hybrid population optimization algorithm is used to determine the water conductivity parameters of the identified channels. The accuracy and applicability of the proposed path identification and parameter identification methods are validated through five preset cases. Finally, the proposed methods are applied in the Pingnan mining area, yielding results that align with on-site geophysical explorations and pumping tests. In conclusion, the proposed methods can provide valuable guidance for groundwater resource management and disaster mitigation in karst regions.

Karst water quality, source of pollution, and health risk assessment in China.

Karst water quality, source of pollution, and health risk assessment in China.

Isotopic variability of δ13C and δ15N signals in cave systems: insights from the blind tetra Astyanax mexicanus

Stable isotope analysis allows the study of element cycles in ecosystems and trophic ecology. δ13C reflects the diversity of primary productivity, while δ15N is a good indicator of trophic levels of organisms. Caves have limited resources due to the absence of light, reducing the trophic chains in these ecosystems. These extreme conditions impose strong selection pressures on cave-dwelling organisms, known as troglobites, which exhibit specific adaptations such as vision and pigment loss, and metabolic and physiological differences with their surface counterparts. The species Astyanax mexicanus corresponds to a model organism in the study of regressive evolution, which presents two different ecotypes, a widely distributed surface morph, and a cave-dwelling morph present in at least 34 caves in three karst regions of San Luis Potosí and Tamaulipas, Mexico. In the present study, we characterized the δ13C and δ15N of seven cave populations of A. mexicanus, corresponding to two karst regions: Sierra de El Abra and Sierra de Guatemala, representing distinct genetic cavefish lineages. We also developed a Nutrient Input Index (NI), to assess whether cave geomorphology influences resource availability. We found isotopic differences between caves and regions analyzed. Caves in the Sierra de El Abra showed higher δ15N values and wider trophic niche ranges compared with those in the Sierra de Guatemala, reflecting a more complex trophic network tentatively associated also with its geological history. In addition, a relationship was observed between the proximity of pools to the surface and the δ13C values, which could suggest differences in NI directly associated with cave geomorphology, impacting selective forces across the different cave systems.

The coupled effect of climate change and LUCC on meteorological drought in a karst drainage basin, Southwest China

With global warming and the acceleration of the water cycle, the frequency and severity of droughts have progressively increased. Although Southwest China is located inland, the combined effects of global climate change, regional climate anomalies, and human activities have led to a diversified set of driving mechanisms for meteorological droughts. Based on monthly global and regional meteorological factors (10 global factors and 8 regional factors) and land use/land cover data from 1948 to 2023, this study employs classical correlation analysis, wavelet analysis, and Bayesian principles to explore the temporal and spatial evolution characteristics of meteorological droughts in Southwest China, as well as their driving mechanisms. The results show that: (1) between 1948 and 2023, meteorological droughts in Southwest China exhibited a north-south (annual average, spring, and winter) or east-west decreasing trend (autumn) and alternating east-west intensity in summer. The drought frequency ranged from 0.35 to 0.39, generally showing a decreasing trend from southwest to northeast. (2) Global atmospheric circulation significantly influences meteorological droughts in Southwest China, especially during El Niño years, when global atmospheric circulation factors such as Nino 3.4 and SOI have a more prominent impact on drought, particularly in the summer and autumn. In contrast, during La Niña years, drought intensity and frequency are more pronounced in spring and autumn. Regional climate factors, particularly temperature and evapotranspiration, also have a significant effect on drought across different seasons, especially in winter and spring, when higher temperatures and evapotranspiration exacerbate droughts, and precipitation has a relatively weaker effect. (3) Land use changes significantly affect meteorological droughts in Southwest China, with a driving probability ranging from 0.39 to 0.42. Under different climate conditions, the driving probabilities of land use changes are ranked as follows: El Niño years (0.32–0.52) > Normal years (0.31–0.51) > La Niña years (0.27–0.50). In particular, land use changes such as the expansion of built-up areas and the reduction of farmland could intensify the frequency and severity of meteorological droughts in drought-prone areas. Additionally, the reduction of green spaces or forests may also exacerbate droughts, especially during the urbanization process. Notably, during El Niño years, the driving effect of various landforms on drought shows different skewed distributions. Therefore, this study clarifies, to some extent, the evolution and mechanisms of meteorological droughts in Southwest China and provides technical guidance and theoretical support for drought prevention and disaster relief efforts in the Karst region.

Assembly and comparative analysis of the complete mitochondrial genome of Echinacanthus longipes (Acanthaceae), endemic to the Sino-Vietnamese karst flora

BackgroundEchinacanthus longipes is an endemic species in the Sino-Vietnamese karst flora in the family Acanthaceae. It displays distinctive environmental adaptation characteristics in karst regions. Although it provides an important model for understanding the role of limestone karst in speciation and endemism, the mitochondrial genome (mtDNA) of E. longipes has not been fully characterized.ResultsHere, the mtDNA of E. longipes was successfully assembled as a complex structure in the form of two small circular and three linear molecules with a total length of 810,200 bp. The annotated results revealed 36 protein-coding genes (PCGs), 22 tRNA genes, and three rRNA genes in this mtDNA. Notably, substantial sequence repeats and more tRNAs translocations from the chloroplast to the mtDNA were identified. Among the PCGs of E. longipes, the majority of 401 RNA editing sites were involved in amino acid transitions to hydrophobic sites. The current phylogenetic analysis based on PCGs revealed the evolution of Lamiales and a close relationship between E. longipes and Avicennia marina. However, comparative analyses, including size, structure, GC contents, and genes, reflected the variation in the mitogenomes within Acanthaceae, and the collinearity analysis confirmed the low level of conservation in the genomes of related species in Lamiales. Moreover, the Ka/Ks analysis revealed that negative selection occurred on most PCGs, with the notable exception of ccmB, which underwent positive selection. Interestingly, the ccmB gene had the most protein editing sites.ConclusionsThis study will be invaluable for the mitochondrial study of Acanthaceae. It also provides extensive information for functional genetic and adaptive studies of Echinacanthus in karst regions in the future.

Increased soil multifunctionality is determined by altered bacterial–fungal–protistan compositions and co‐occurrence network complexity during vegetation restoration in a Karst region, southwest China

Increased soil multifunctionality is determined by altered bacterial–fungal–protistan compositions and co‐occurrence network complexity during vegetation restoration in a Karst region, southwest China

Research on Human Needs and the Valorization of Supply–Need Relationships in Ecosystem Services—A Case Study of the Southwest Karst Region

Human needs alter ecosystem services (ESs), which then affect human needs. Based on the human needs theory, human needs in ESs are classified into four major categories of needs. A monetization method was used to quantify the ecosystem service need value (ESNV), the ES value equivalent method was used to calculate the ES supply value (ESSV), and the correlation coefficient method was used to understand the relationships and mutual influences among human needs. Finally, the supply and demand relationships were compared to obtain the gap between the supply of and demand for ESs. Taking Hechi City, a city with a predominantly karst landscape, as an example, we found that: (1) the total area of high-value areas and generally high-value areas in Hechi City increased by 10,935.15 km2, whereas the total area of low-value areas decreased by 11,094.07 km2. (2) A positive correlation exists between the various demands. Spiritual needs and material needs are moderately significantly positively correlated, with a correlation coefficient of 0.54. Security needs are positively correlated with material needs, with a correlation coefficient of 0.6. (3) The ESNV and ESSV in Hechi City are slightly imbalanced. Du’an requires an external ecosystem supply of CNY 21.9192 million for living material, while Jinchengjiang has the potential to export a water supply value of CNY 22.9934 million to external ecosystems. (4) The centers of gravity of various types of supply and demand are distributed primarily within Jinchengjiang District, only the center of gravity of production material needs is in the northern part of Du’an County. The distance between the centers of gravity of the demand and supply for living materials increased by 2100.44 m, the distance between the centers of gravity of the demand and supply for oxygen security increased by 639.15 m. The results are complementary to current research on ESs from the perspective of ES demand. These findings can thus provide scientific foundational information to help decision makers understand the balance between the supply and demand of ESs in a region and promote the construction of a human-harmonious ecosystem.

C, N, P, and K Ecological Stoichiometry Characteristics of Different Organs of Tree Species in Dolomite and Limestone Karst Areas of Southwestern China

To explore environmental differentiation in the stoichiometric characteristics of carbon (C), nitrogen (N), phosphorus (P), potassium (K), and their ratios among tree species organs in different lithological karst regions of Guizhou, six common species were selected from the limestone karst area of Liping and the dolomite karst area of Shibing. The analysis focused on the differences in the contents of C, N, P, and K, as well as the ratios of C/N, C/P, C/K, and N/P, and the correlations among these elements in branches, leaves, and roots, with the aim of investigating the allocation distribution patterns of nutrient elements among organs in tree species under different lithological karst conditions. The results showed the following: In both dolomite and limestone karst regions, the tree species exhibited a distinct characteristic: their leaves exhibited high C levels, but relatively low N and P levels. Tree species in both karst regions showed high C/N, C/P, and C/K ratios, indicative of rapid C assimilation rates and efficient utilization of N, P, and K. Plant growth in the dolomite region was N-limited, while plant growth in the limestone region was P-limited. However, plant growth in neither region was K-limited. The nutrient characteristics and adaptation strategies of plants in dolomite and limestone karst regions were the result of multiple factors, such as lithology, plant organs, and interactions among elements. In conclusion, considering the differences in lithology during vegetation restoration and management in karst regions, targeted application of nitrogen or phosphorus fertilizers is expected to promote plant growth and further enhance the carbon sequestration capacity of both karst plants and soils.

Analyzing the Source of Sulfate in Karst Groundwater Based on a Bayesian Stable Isotope Mixing Model: A Case Study of Xujiagou Spring Area, Northern China

The source of sulfate in the groundwater of karst springs in the northern Taihang Mountains remains unclear due to the influence of multiple factors. To investigate this, 33 sampling points were selected in August 2022 across the exposed, covered, and buried areas of the spring basin, and water samples were collected. Hydrochemistry and sulfur–oxygen dual isotope methods were employed to examine the distribution characteristics of sulfate, δ18OSO4, and δ34SSO4. Based on the distinct characteristics of sulfur isotopes from different sources, the sources of sulfate in various environments were qualitatively analyzed. Additionally, the contribution rates of each source were quantitatively determined using a Bayesian stable isotope mixing model. The results showed that the sulfate content in karst groundwater ranged from 16.68 to 156.84 mg/L, with an average of 62.22 mg/L, and indicated an increasing trend from exposed to covered to buried areas. The δ34SSO4 values in karst groundwater ranged from 3.1‰ to 13.5‰, with an average of 6.49‰, while the δ18OSO4 values ranged from 2.9‰ to 10.3‰, with an average of 5.49‰. The δ34SSO4 values showed a general increasing trend across the exposed, covered, and buried areas, whereas the δ18OSO4 values remained relatively stable across these areas. The analysis revealed that the primary sulfate sources in the exposed area were atmospheric precipitation, soil sulfate, chemical fertilizer, and sewage, contributing 19.6%, 63.5%, 9.4%, and 7.5%, respectively. In the covered area, the main sources were atmospheric precipitation, sulfide oxidation, soil sulfate, and gypsum dissolution, with contributions of 16.5%, 58.7%, 15.9%, and 8.9%, respectively. In the buried area, the sulfate primary originated from atmospheric precipitation, sulfide oxidation, and gypsum dissolution, contributing 11.6%, 78.5%, and 9.9%, respectively. This study provides critical insights into the sulfate sources in different environments, enhancing the understanding of groundwater sulfate pollution in the study area. These findings provide a scientific foundation for managing groundwater pollutants and resources in the karst regions of northern China.

Distributions and Driving Factors of Hydrochemical Compositions in Different Types of Karst Groundwater in Qingjiang River Basin

The karst groundwater resource is the key water supply for native residents and industrial and agricultural production in karst regions of southwest China and is even the only water supply for rural regions. Understanding the formation mechanism of hydrochemical compositions is practically imperative to the sustainable development and utilization of karst groundwater resources. The hydrochemical ions of 34 karst spring samples and 12 underground river water samples from the Qingjiang River Basin were measured and analyzed in this study. On the basis of investigating the distribution characteristics of hydrochemical components, methods such as hierarchical clustering analysis, Gibbs model, and relationships between hydrochemical components were used to comprehensively reveal the chemical genesis mechanism of karst groundwater from the perspectives of water-rock interaction and anthropogenic activities, especially in the disturbance mechanism of acidic pollutants on the natural dissolution of carbonate rocks. The results showed that the karst groundwater in the Qingjiang River Basin was weakly alkaline （7.12 ≤pH ≤ 8.69）, and the overall water quality was good. Only the maximum concentration of NO3- in the karst spring （80.2 mg·L-1） exceeded the maximum acceptable limit for drinking purposes （10 mg·L-1 as N）. The Ca2+ and HCO3- were identified as the dominant ions, associated with the main water phrase of HCO3-Ca·Mg in approximately 97.1% of karst spring samples and all underground river water samples. The dominant ions were derived from the strong dissolution of calcite, whereas Mg2+、SO42-, and F- were controlled by the weak dissolution of dolomite, gypsum, and fluorite, respectively. Karst groundwater NO3- was derived from the agricultural fertilizers and rainwater input, whereas the H2SO4 acid rain input was identified as another important source of karst groundwater SO42-. In addition, the carbonate rocks in the study area were mainly naturally dissolved； however, the input of exogenous acid by humans has changed the original karst hydrogeochemical evolution process and further decreased the carbonate sink flux of karst aquifers, accelerated the decrease rate of karst groundwater table, and increased the pollution risks of karst groundwater.

Spatial diversity and distribution of fern and lycophyte species in karst and non-karst landscapes towards conservation needs.

Karst formations are distinguished by their high levels of species diversity and endemism, including ferns and lycophytes. However, the existing data on plant community composition in karst formations remains deficient. Addressing these knowledge gaps is imperative, given the current accelerated rates of species loss, to enhance efforts to conserve biodiversity in these habitats. This study documents and explains patterns of fern and lycophyte species diversity within karst landscapes (KL) and non-karst landscapes (NKL) in the Philippines. Our comprehensive analysis involved aggregating 19,529 occurrence points encompassing 1,024 fern and lycophyte species sourced from field expeditions, voucher records from local herbaria, and online databases. Indices for species richness, weighted endemism, and corrected weighted endemism were then computed across KL and NKL areas to describe spatial diversity and identify fern and lycophyte hotspot areas. Gap analyses were also performed to determine if established protected areas (PAs) were sufficient to cover the identified fern and lycophyte diversity hotspots. Principal Component Analysis (PCA) was conducted to determine potential ecological drivers of distribution between KL and NKL areas. The findings reveal that most fern and lycophyte species were recorded to occur in NKL areas, with 995 (97.16%) species identified, while 676 (66.02%) species were documented to occur in KLs, including 29 (2.83%) exclusive to karsts. Identified hotspots for NKL are within mountain ecosystems, which are already under existing legal protection. In contrast, KLs have five areas identified as congruent hotspots but considered gap areas due to their exclusion from current PA boundaries. Existing PAs thus provide less protection to karst habitats and their associated floras. PCA did not reveal any significant environmental predictors, suggesting separation of KL and NKL species distributions, possibly due to lack of high-resolution environment data available for karsts. To facilitate the conservation of fern and lycophyte species in karsts, we propose installing and expanding existing PA boundaries, along with conducting more focused surveys in karst regions to better understand their ecological dynamics.

Response of starch molecular structures to temperature and light during rice grain-filling stage in karst region.

Response of starch molecular structures to temperature and light during rice grain-filling stage in karst region.

Carbon transfer from land to fluvial networks in a typical karst river-reservoir system

Carbon transfer from land to fluvial networks in a typical karst river-reservoir system

Early-warning ecological risk assessments of multi-element pollution in the surface soil of karst basins in southwest China based on the delayed geochemical hazard model.

Early-warning ecological risk assessments of multi-element pollution in the surface soil of karst basins in southwest China based on the delayed geochemical hazard model.

Integrated quantitative tracing for Karst groundwater contamination: A case study of landfill in Zunyi, Guizhou Province, China.

Integrated quantitative tracing for Karst groundwater contamination: A case study of landfill in Zunyi, Guizhou Province, China.

Fire and clipping drive microbial fixation pathways in soil phosphorus and sulfur cycling in China's key karst region

Fire and clipping drive microbial fixation pathways in soil phosphorus and sulfur cycling in China's key karst region

Notes on the genus Draconarius Ovtchinnikov, 1999 (Araneae: Agelenidae) with description of two new species from Laos

Two new species of the Draconarius venustus group are described from the Vang Vieng karst region of Laos: D. laosensis spec. nov. (♂♀) from various caves, and D. externus spec. nov. (♂) from the leaf litter. Detailed descriptions, illustrations and photographs of copulatory organs along with somatic features of the new species are provided. Additionally, the male palp of D. joshimath from India is illustrated in detail and the species is assigned to the D. venustus group. Distribution maps for all known records of the genus Draconarius s.l. are given along with an analysis of cave-dwelling species and its elevational distribution.

Spiradiclis hechiensis (Rubiaceae), a new cave-dwelling species from Northwest Guangxi, China

A new species of Rubiaceae, Spiradiclis hechiensis, is described and illustrated from a cave in the Karst region of Northwest Guangxi, China. Morphologically, it is related to S. pauciflora in the shape and color of the corolla. It can be easily distinguished by the shape of leaf blades, bracts, and calyx lobes, the number of secondary veins and flowers, as well as the size of capsules and seeds. At present, only one population has been confirmed to have approximately 50–100 mature individuals from the type locality. According to the IUCN Red List Categories and Criteria, it is provisionally assessed as Critically Endangered [CR B1+2ab (iii)].

Characteristics of spatial and temporal evolution and coupling relationships between urbanization and atmospheric particulate matter in the Qianzhong urban agglomeration

The summary has been revised as follows: In karst regions, the relationship between urbanization and atmospheric particulate matter is crucial for mitigating air pollution. Previous studies often focused on single-perspective discussions, lacking comprehensive multi-perspective analyses. Based on multi-source remote sensing data from 2000 to 2022 for the Qianzhong urban agglomeration (QUA)), we constructed the normalized principal component urbanization index (NPCUI) and normalized principal component atmospheric particulate matter index (NPCAIPM) to delve into the spatiotemporal coupling relationship between the urbanization and atmospheric particulate matter. The results demonstrate that NPCUI and NPCAIPM offer a more comprehensive and precise representation of urbanization processes and particulate matter concentrations compared to traditional single indicators. Since the implementation of the Western Development Strategy in 2011, urbanization indicators in Guizhou have shown significant growth, with PM2.5 and PM10 levels increasing by 75.78% and 55.87%, respectively. These findings illustrate industrialization's and urban expansion's effects on air quality. Integrating perspectives from geography, systematics, and physics, we discovered complex spatiotemporal coupling dynamics between urbanization and atmospheric particulates. Coordination has improved over time, but regional differences remain evident. This study provides critical insights and a scientific basis for addressing atmospheric particulate pollution during the urbanization process in karst regions, emphasizing the importance of high-quality coordinated development.

Bioavailability and Speciation of Potentially Toxic Trace Metals in Limestone-Derived Soils in a Karst Region, Southwestern China

Bioavailability and Speciation of Potentially Toxic Trace Metals in Limestone-Derived Soils in a Karst Region, Southwestern China