Search Results (92)

To study hydrogeological characteristics after the occurrence of abnormal water bursts from the weak water-rich (permeable) aquifer of the Changxing Formation limestone overlying deep working faces during production in Guizhou karst landform mining areas, hydrogeological data covering the exploration and production periods of the Xinhua mining region in Jinsha County, Guizhou Province, were collected. On the basis of surface and underground drilling, geophysical exploration techniques, empirical equations, and indoor material simulation methods, the hydrogeological evolution characteristics of the Changxing Formation limestone in the mining region after mining damage to coalbed 9 were studied. The research results indicated that the ratio of the height of the roof failure fracture zone (as obtained via numerical simulation and ground borehole detection) to the mining height exceeded 25.78, which is far greater than the empirical model calculation values (from 13.0 to 15.8). After mining the underlying coalbed 9, an abnormal water-rich area developed in the Changxing Formation limestone, and mining damage fractures led to the connection of the original dissolution fissures and karst caves within the limestone, resulting in the weak water-rich (permeable) aquifer of the Changxing Formation limestone becoming a strong water-rich (permeable) aquifer, which served as the water source for mine water bursts. Over time, after mining damage occurrence, the voids in the Changxing Formation limestone were gradually filled with various substances, yielding water storage space and connectivity decreases. The specific yield decreased with an increasing water burst time and interval after the cessation of mining in the supply area, and the correlation coefficient R was 0.964, indicating a high degree of correlation between the two parameters. Full article

A deep interaction between groundwater and surface hydrology characterizes karst environments. These settings feature closed depressions, whose hydrological role varies depending on whether they have genetic and hydraulic relationships with overland–subsurface flow (epigenic) or deep groundwater circulation (hypogenic). Epigenic dolines and poljes are among the diagnostic landforms of karst terrains. In this study, we applied a hydrological criterion to map closed depressions—including dolines—across the Alburni karst massif, in southern Italy. A GIS-based, semi-automatic approach was employed, combining the sink-filling method (applied to a 5 m DEM) with the visual interpretation of various informative layers. This process produced a raster representing the location and depth of karst closed depressions. This raster was then used to automatically delineate endorheic areas using classic GIS tools. The resulting map reveals a thousand dolines and hundreds of adjacent endorheic areas. Endorheic areas form a complex mosaic across the massif, a feature that had been poorly emphasized in previous works. The main morphometric features of the dolines and endorheic areas were statistically analyzed and compared with the structural characteristics of the massif. The results of the proposed mapping approach provide valuable insights for groundwater management, karst area protection, recharge modeling, and tracer test planning. Full article

Natural and planted forests differentially regulate soil quality through vegetation–soil interactions. The effects of four types of planting covers on soil nutrients, enzyme activities, and microbial communities in the Guangxi Camellia nitidissima National Nature Reserve were studied, revealing the multi-dimensional influences of natural (broadleaf, shrubland) and planted forests (bamboo, pine) on soil quality. Surface soils (0–10 cm depth) were characterized for physicochemical properties (pH, TC, TN, NO₃⁻-N, AP), enzyme activities (α-amylase, urease, phosphatase, β-glucosidase), and microbial composition (using 16S rRNA and ITS region sequencing). Mantel tests and PLS–PM modeling were employed to investigate interactions among vegetation, soil variables, and microbes. Natural forests exhibited higher pH, nitrate nitrogen, and enzymatic activities (urease, phosphatase, β-glucosidase) alongside enhanced carbon–nitrogen accumulation and reduced acidification. Planted forests showed elevated available phosphorus and nutrient supply but lower organic matter retention. Microbial communities displayed higher similarity within natural forests, with fungal composition strongly linked to total carbon/nitrogen (p < 0.05). Vegetation type positively influenced bacterial diversity but negatively affected fungal communities. Natural forests maintained critical soil–microbe–plant interactions supporting ecosystem resilience through carbon–nitrogen cycling, while planted forests fostered divergent microbial functionality despite short-term nutrient benefits. These findings underscore natural forests’ unique role in preserving ecological stability and reveal fundamental limitations of artificial systems in mimicking microbially-mediated biogeochemical processes. Conservation policy should prioritize the protection of natural forests while simultaneously integrating microbial community management with vegetation restoration efforts to enhance long-term ecosystem functionality and nutrient cycling efficiency. Full article

As a typical karst landform region, the Lijiang River Basin, located in Southwest China, is characterized by both soil erosion and ecological fragility. The transformation of land use, driven by long-term intensive human activities, has exacerbated the degradation of ecosystem services, threatening the region’s carbon sink function. To clarify the coupling mechanism between land use and land cover change (LUCC) and carbon storage, this paper integrates complex network theory with the PLUS-InVEST model framework. Based on land use data from five periods, i.e., 2001, 2006, 2011, 2016, and 2021, the key transformation types are identified, and the evolution of carbon storage from 2021 to 2041 is simulated under three scenarios, namely, inertial scenario, ecological protection scenario, and urban development scenario. The paper finds that (1) land use transformation in the basin exhibits spatial heterogeneity and network complexity, as evidenced by a significant negative correlation between the node clustering coefficient and the average path length, revealing that land type transitions possess small-world network characteristics. (2) The forested land experienced a net decrease of 196.73 km² from 2001 to 2021, driving a 3.03% decline in carbon storage. This highlights the inhibitory effect of unregulated urban expansion on carbon sink capacity. (3) Scenario simulations indicate that the carbon storage under the ecological protection scenario will be 1.0% higher than under the inertial scenario and 1.5% higher than under the urban development scenario. These suggest that restricting impervious land expansion and promoting forest and grassland restoration can enhance carbon sink capacity. Therefore, this paper provides a quantitative basis for optimizing territorial spatial planning and coordinating the “dual carbon” goals in karst regions. Full article

Guizhou Province is one of the regions in China where macadamia is cultivated. The area is characterized by prominent karst landforms, with uneven distribution of precipitation and utilizable water resources, which poses significant challenges to macadamia production. To explore the effects of different drought levels on the anatomical structure and physiological characteristics of macadamia seedlings, and to reveal their adaptation mechanisms and regulatory responses to drought stress, this study established a drought stress experiment on O.C (Own Choice) macadamia seedlings. The seedlings were subjected to stress in a 25% PEG-6000 solution for 0 h (CK), 24 h, 36 h, 48 h, and 72 h, and cellular structural features of stems and leaves were measured, as well as physiological and biochemical indices. The results indicated that macadamia seedlings gradually exhibited dehydration and chlorosis with prolonged drought stress. At 72 h of drought stress, root water potential, leaf water potential, chlorophyll content, relative water content, and root activity decreased by 353%, 98%, 44%, 72%, and 79%, respectively. Leaf thickness, palisade tissue thickness, and spongy tissue thickness were reduced by 19%, 33%, and 29%, respectively. Stomatal density increased by 50%, while stomatal aperture, vessel diameter, and cell wall thickness significantly decreased. Photosynthesis was markedly impaired: Pn, Tr, Gs, WUE, Fv/Fm, qP, and ΦPSII declined by 73%, 25%, 67%, 64%, 0.23, 60%, and 84%, respectively, whereas Ci and qN increased by 107% and 11%, respectively. Cell membranes began to sustain damage after 24 h of drought stress, with electrolyte leakage and MDA content rising by 266% and 672%, respectively, at 72 h. Prolonged drought stress reduced IAA, CTK, and GA levels by 37%, 33%, and 16%, respectively, while ABA content increased by 48%. To counteract drought stress, seedlings activated osmotic adjustment and reactive oxygen species (ROS) scavenging mechanisms. Osmolyte content significantly increased with stress duration, reaching 61%, 73%, 697%, and 107% increments in SS, SP, Pro, and betaine at 72 h. Antioxidant enzyme activities initially rose, peaking at 24 h (SOD, POD, CAT, and APX increased by 132%, 288%, 110%, and 46%, respectively), then gradually declined. By 72 h, SOD and APX activities fell below control levels, while POD and CAT remained elevated. These findings demonstrate that under PEG-6000-simulated drought stress, macadamia seedlings alleviate damage by modifying leaf and stem cellular structures and activating antioxidant and osmotic adjustment mechanisms. This study provides a theoretical basis for understanding the physiological mechanisms of macadamia drought stress response. Full article

Karst geology creates a complex environment with diverse landforms, blurred boundaries, and multi-factor interactions. This paper presents a new drilling pile installation method: drill to a set depth, clean the hole, insert prefabricated piles, and drive or vibrate them to the target elevation. It suits tough geological conditions well. Pile foundations bear both axial and lateral eccentric loads. To explore prestressed high-strength concrete (PHC) pile foundations under eccentric vertical loads in karst areas, on-site bearing capacity tests were conducted. The results show that as load eccentricity increases, PHC pile foundation-bearing capacity drops notably. A finite element model was developed to analyze the stress and strain behavior of PHC pile foundations under eccentric loading in complex geological conditions, aiming to assess their bearing capacity and stability. Key findings include: (1) Under constant external load, the maximum displacement of the PHC pile foundation increases with greater load eccentricity. (2) Enhanced concrete strength reduces the maximum displacement of the pile foundation, while the peak stress remains stable. (3) The height of karst caves has a minimal impact on the bearing capacity and deformation of PHC pile foundations. These results highlight the importance of considering load eccentricity, concrete strength, and cave height in optimizing the design of PHC pile foundations for safety in complex geological settings. Full article

The semi-automated extraction of landforms using GIS analysis is one of the main topics in computer analyses. The use of digital elevation models (DEMs) in GIS applications makes the extraction and classification procedure of landforms easier and faster. In the present paper, we assess the accuracy of semi-automated landform maps by means of a comparison with hand-made landform maps realized in the Pleistocene Agri intermontane basin (southern Italy). In this study, landform maps at three different scales of 1:50,000, 1:25,000, and 1:10,000 were used to ensure a good level of detail in the spatial distribution of landforms. The semi-automated extraction and classification of landforms was performed using a GIS-related toolbox, which identified ~48 different landform types. Conversely, the hand-made landform map identified ~57 landforms pertaining to various morphogenetic groups, such as structural, fluvial, karst landforms, etc. An overlap of the two landform maps was produced using GIS applications, and a 3D block diagram visualization was realized. A visual inspection of the overlapping maps was conducted using different spatial scales of patch frames and then analyzed to provide information on the accuracy of landform extraction using the implemented tools. Full article

Horsfieldia hainanensis is China’s second-class key protected wild plant with high scientific research, timber, and medicinal values. In this study, the SNP molecular marker technology was used to determine the genetic diversity, genetic structure, genetic differentiation, genetic relationship, and its influencing factors of H. hainanensis populations. It provided a scientific basis for the formulation of its protection strategy. The results showed that (1) the genetic diversity of H. hainanensis populations exhibited a very low level (π = 0.0011). (2) The overall genetic differentiation of H. hainanensis populations was relatively large. There was a significant genetic differentiation between Hainan populations and Guangxi and Yunnan populations on the mainland (FST = 0.556); the genetic differentiation between Guangxi and Yunnan populations was relatively smaller (FST = 0.242). There is a natural water barrier around Hainan Island that reduces the gene exchange between island populations and mainland populations. Therefore, geographical isolation is one of the main factors affecting the genetic differentiation of H. hainanensis populations (p = 0.0103 < 0.05). (3) The genetic relationship between Hainan populations and Yunnan and Guangxi populations was relatively distant, while the genetic relationship between Yunnan and Guangxi populations was relatively closer. In conclusion, it is recommended that during in situ protection, the Guangxi population with higher genetic diversity should be preferentially protected, especially the populations in NG and SL should be regarded as the key protected populations of wild populations. The gene exchange between Yunnan population (MLP) and Guangxi populations (NG, SL, DX1, and DX2) should be enhanced by means of artificial pollination in different localities. During ex situ protection, the germplasm resource collection work of the population (NG, SL) with higher genetic diversity should be carried out preferentially. The technical research on tissue culture and rapid propagation should be actively carried out. A germplasm resource nursery should be established. The individuals should be planted according to provenance and family, but the planting distance between individuals can be appropriately reduced to increase the gene exchange between individuals and make up for the defects during in situ protection. Full article

The unique Karst landforms in Southwest China led to fragile soil structures and erosion, compounded by the large-scale non-agricultural transfer of the rural labor force. This study employed a two-way fixed effects model to analyze the impact of rural labor mobility on the green utilization efficiency of cultivated land, controlling for unobservable individual and time-specific factors. Mediation analysis examined how changes in planting structure influenced this relationship, considering labor force structure heterogeneity. Results revealed a U-shaped relationship, with rural labor mobility initially causing a short-term decline in efficiency but leading to a long-term increase. The mechanism of action showed that rural labor mobility indirectly affected efficiency by altering planting structures; specifically, increased replanting frequency had a partial mediating effect (0.158), while a “grain-oriented” focus masked the effect (0.067). Additionally, an aging workforce and low education levels negatively impacted green utilization efficiency, complicating the situation in the Karst region. To enhance green utilization of cultivated land, it is essential to protect migrant farmers’ rights, improve agricultural labor quality, promote industrial upgrades, and adjust planting structures. These strategies will guide regional agriculture and ensure sustainable land resource use. Full article

The Soil and Water Assessment Tool (SWAT) model is extensively used globally for hydrological and water quality assessments but encounters challenges in karst regions due to their complex surface and groundwater hydrological environments. This study aims to refine the delineation of hydrological response units within the SWAT model by combining geomorphological classification and to enhance the model with an epikarst zone hydrological process module, exploring the accuracy improvement of SWAT model simulations in karst regions of Southwest China. Compared with the simulation results of the original SWAT model, we simulated runoff and nutrient concentrations in the Mudong watershed from January 2017 to December 2021 using the improved SWAT model. The simulation results indicated that the modified SWAT model responded more rapidly to precipitation events, particularly in bare karst landform, aligning more closely with the actual hydrological processes in Southwest China’s karst regions. In terms of the predictive accuracy for monthly loads of total nitrogen (TN) and total phosphorus (TP), the coefficient of determination (R²) value of the modified model increased by 10.3% and 9.7%, respectively, and the Nash–Sutcliffe efficiency coefficient (NSE) increased by 11.3% and 9.9%, respectively. The modified SWAT model improves prediction accuracy in karst areas and holds significant practical value for guiding non-point source pollution control in agricultural watersheds. Full article

Hydraulic dissolution, driven by carbon dioxide-rich precipitation and runoff, leads to the gradual breakdown and removal of soluble rock materials, creating unique surface and subsurface features. Dissolution is a complex process that is related to numerous factors, and the complete simulation of its process is a challenging problem. On the basis of deep investigation of the theories of geology and rock geomorphology, this paper puts forward a method for simulating the dissolution phenomenon on a rock surface. Around the movement of water, this method carries out dissolution calculations, including processes such as droplet dissolution, water flow, dissolution, deposition, and evaporation. It also considers the lateral dissolution effect of centrifugal force when water flows through bends, achieving a comprehensive simulation of the dissolution process. This method can realistically simulate various typical karst landforms such as karst pits, karst ditches, and stone forests, with interactive simulation efficiency. Full article

The karst landform in Yunnan Province, China, represents one of the most biodiverse regions for Hemiphyllodactylus. Previous research has revealed that the karst forests in this province host a greater diversity of Hemiphyllodactylus than previously acknowledged. However, substantial fundamental data essential for taxonomic and biogeographical studies are lacking. We conducted extensive surveys for Hemiphyllodactylus in the Yunnan Province that led to the discovery of three new species from Menglian Dai, Lahu, and Wa Autonomous County and Jinghong City based on morphological and genetic data. A phylogenetic reconstruction based on the ND2 gene (1038 bp) placed the three new species into clade 3 and clade 4 of Agung et al. The uncorrected genetic pairwise distance of the Menglian specimens were greater than 5.7%, and those of the Jinghong City specimens were greater than 5.2% and 8.5%, respectively. They could be distinguished from their congeners by body size, chin scales, internasal scales, ventral scales, dorsal scales, and the total number of femoral and precloacal pores. Furthermore, we update the distributional knowledge of the known species. Full article

As a vital indicator for measuring the coupled carbon–water cycle of an ecosystem, water use efficiency (WUE) can also reflect the adaptive capacity of plants in different ecosystems. Located in Southwest China, the Li River Basin has a representative karst landform, and the uneven rainfall in the region leads to severe water shortage. In this study, we analyzed the spatial–temporal transformation characteristics of the WUE of the basin and its relationship with different influencing factors from 2001 to 2020 based on a correlation analysis and trend analysis. The main conclusions are as follows: (1) The average value of WUE in the Li River Basin was 1.8251 gC· mm⁻¹·m⁻², and it kept decreasing at a rate of 0.0072 gC· mm⁻¹·m⁻²·a⁻¹ in the past 20 years. With respect to the spatial distribution of the multi-year average of WUE, it exhibits a gradual increasing trend from west to east. (2) Between gross primary productivity (GPP) and evapotranspiration (ET), it was found that ET was the primary influencing factor of WUE. Precipitation was positively correlated with WUE in the Li River Basin, accounting for 67.22% of the total area of the basin. The air temperature was negatively correlated with WUE, and the area was negatively correlated with WUE, accounting for 92.67% of the basin area. (3) The normalized difference vegetation index (NDVI) and leaf area index (LAI) were negatively correlated with WUE, and the proportions of negatively correlated areas to the total area of the basin were similar; both were between 60 and 70%. The growth of vegetation inhibited the increase in WUE in the basin to a certain extent. Regarding Vapor Pressure Deficit (VPD), the proportions of positive and negative correlation areas with WUE were similar, accounting for 49.58% and 50.42%, respectively. (4) The occurrence of drought events and the enhancement in its degree led to a continuous increase in WUE in the basin; for different land cover types, the correlation of the standardized precipitation evapotranspiration index (SPEI) was in the following order from strongest to weakest: grassland > cropland > forest > shrubland. Full article

The Huixian Wetland is a natural ecosystem of immense ecological value, providing crucial ecosystem services such as water purification, water regulation, and a habitat for the region’s flora and fauna. Its karst peak forest landforms and surrounding environment also possess unique ecological and landscape value. However, with the ongoing socioeconomic development, including the rise of industrial, agricultural, and aquaculture activities in the wetland area, the nutrient composition of the Huixian Wetland has been altered. This paper reviews the current status of nitrogen, phosphorus, heavy metals, emerging pollutants, and biodiversity in various environmental media of the Huixian Wetland. It synthesizes the literature to identify the factors influencing these changes and projects future research directions for the wetland. This work is of significant practical importance, providing scientific foundations for the restoration and protection of the Huixian Wetland. Full article

Groundwater quality and availability in coastal aquifers have become a serious concern in recent times due to increased abstraction for domestic, agricultural and industrial purposes. (1) Background: Zhuhai city is selected as a representative coastal aquifer in Southern China to comprehensively evaluate the hydrochemical characteristics, spatial distribution and controlling mechanisms of groundwater. (2) Methods: A detailed study utilizing statistical analyses, a Piper diagram, Gibbs plots, and ion ratios was conducted on 114 surface water samples and 211 groundwater samples. (3) Results: The findings indicate that the pH of most groundwater is from 6.06 to 6.52, indicating a weakly acidic environment. The pH of surface water ranges from 5.35 to 9.86, with most values being weakly alkaline. The acidity in the groundwater may be related to the acidic atmospheric precipitation, an acidic unsaturated zone, oxidation of sulphide minerals and tidal action. The groundwater chemical types are predominantly mixed, followed by Ca-Mg-HCO₃ type. Surface water samples are predominantly Na-Cl-SO₄ type. The NO₃⁻ concentration in groundwater is relatively high, with a mean value of 17.46 mg/L. The NO₂⁻ and NH₄⁺ concentrations in groundwater are relatively low, with mean values of 0.46 mg/L and 7.58 mg/L. (4) Conclusions: The spatial distribution of the principal chemical constituents in the groundwater is related to the landform. The chemical characteristics of groundwater in the study area are mainly controlled by the weathering and dissolution of silicate and sulfate minerals, evaporation, seawater mixing and cation exchange. Nitrate in clastic fissure groundwater, granite fissure groundwater and unconfined pore groundwater primarily originates from atmospheric precipitation, agricultural activities of slope farmland and forest land. Nitrate in confined pore groundwater and karst groundwater primarily originates from domestic sewage and mariculture wastewater. Our findings elucidate the processes characterizing the hydrogeology and surface water interactions in Zhuhai City’s coastal system, which are relevant to other catchments with similar geological characteristics. Full article