Karst Area Of Southwest China Research Articles

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.

Estimating fracture characteristics and hydraulic conductivity from slug tests in epikarst of southwest China

Study regionGuizhou Province, Southwest China Study focusThis study aims to estimate the hydraulic conductivity (Kh) of the weathered rock fractures (epikarst) based on the best fitting of observed water head in 105 slug tests in the study sites. Specifically, comparisons of the estimated results from the analytical and numerical methods reveal the effects of changes in fracture flow conditions (e.g., steady and non-steady) on Kh for various fracture apertures and soil fillings. New hydrological insights for the regionThe results comparatively show that Kh from the analytical solution of steady flow was significantly underestimated, and the numerical modeling of the non-linear and unsteady flow can improve the water head fitting when the Reynolds number (Re) > 17.27. The optimized Kh ranges 0.014–2673 m/d and the mean value of Kh is about 100 times the median value, suggesting that epikarst flow might be controlled by a limited number of larger fractures. Moreover, the soil filling in large fractures (>10 mm) creates a turning point of the exponential increase of Kh with d. Comparatively, the naturally full-filling fractures resemble the soil matrix with a low Kh, and the partial-filling fractures can create preferential flow around the soil-rock interfaces with a high Kh. These results fundamentally improve our understanding of water infiltration, retention, and availability for plant uses in the karst areas of southwest China.

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.

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).

Exploring the geological structure of a large-scale landslide using semi-airborne TEM in the Karst area of southwest China

Abstract The karst strata in the southwestern mountainous areas of China are extensively developed, creating a fragile geological environment. Landslide geological disasters occur frequently in these areas due to high annual rainfall, concentrated time periods, and frequent human engineering activities. Conventional ground geophysical methods face challenges in complex terrains, making it difficult to quickly and reliably obtain underground structures in landslide-prone areas. The semi-airborne transient electromagnetic method (SATEM) combines ground-based transmission and airborne reception of electromagnetic responses. This method, characterized by large emission magnetic moment and rapid data collection in the air, offers advantages in detecting deep geological structures in complex terrain areas. This article presents the application of a newly developed loop source SATEM system, integrated with multi-rotor unmanned aerial vehicles (UAVs), to conduct deep geological structure detection experiments on a large-scale landslide. The inversion results clearly depict the spatial distribution of the Feixianguan Formation and Longtan Formation, as well as vertical fractures developed in the strata due to underground coal mining. The detection test demonstrates the applicability of the SATEM method in detecting underground structures in Karst Plateau special landform areas, providing a new detection approach for similar regions.

Assessment of Huixian Karst Wetland for Local Water Augmentation in Guilin, China

Due to the rapid exploitation of water resources in the Huixian karst wetland in the southwest of China in the past decades, the wetland has suffered from shrinkage in size and serious degradation of ecological functioning. To assess how much water within the wetland could still be taken out for local supply purposes while the wetland can still be kept in its normal ecological functioning. Through the use of multi-methods, including field surveys by a multi-disciplinary team, water balance, Remote Sensing, GIS and numerical simulation, this paper characterizes the wetland regime of the study area and finally determines scenarios of water resource utilization for local water supply within acceptable parameters of wetland ecological health. Through the analysis of the methods, it was found that the hydrological characteristics of the study area were conditioned by not only the karst water but also the regional precipitation fluctuations. A zone of mobile watersheds for Lake Mudong was established as opposed to a conventional single watershed. If the wetland ecosystem is kept at the current status of class III, a scenario of withdrawal of up to 20% of lake inflows could be accommodated. The results and their approaches would provide much-needed information for the protection of the wetland and its sustainable water utilization per se. It would offer a basic reference for similar problems in karst areas of southwest China and other areas alike.

Monitoring the evolution process of karst desertification and quantifying its drivers in the karst area of Southwest China.

Karst desertification (KD) is a unique desert ecological phenomenon occurring in the karst region of Southwest China (KRSC). Studying the KD evolution process and distinguishing the influences of human activities and climate factors on KD are essential for restoring KD areas. This article is based on MODIS remote sensing data and ERA5-Land data. Additionally, multiple linear regression models, correlation analysis, and residual analysis are utilized to analyze the spatiotemporal evolution characteristics of KD in the southwest region of China from 2000 to 2020. This study aims to differentiate the impacts of human activities and climate change on the desertification process in karst areas. (1) In the southwest region of China, the overall KD shows an intensifying trend at both ends of the study area and an ameliorating distribution pattern in the central region. In particular, Guizhou province, which is located in the center of the study area, demonstrated significant suppression in the KD process from 2000 to 2020. (2) In the southwest karst region, there are significant spatial differences in the correlation between the KD process and precipitation, temperature, and radiation. Temperature is significantly negatively correlated in most parts of Yunnan. (3) According to the residual analysis, approximately 89.62% of the karst areas in the southwest are influenced by climate, while 10.38% are influenced by human activities. Climate change has a relatively small impact on the ability to improve KD compared to the disruptive influence of human activities. Some human activities, such as afforestation, in which grassland and cultivated land are converted to forest, play a substantial role in inhibiting the KD process. Conversely, the rapid expansion of urban areas tends to exacerbate KD in adjacent regions. Therefore, this study of the evolution process of KD in Southwest China can provide a scientific basis for monitoring and controlling KD and provide theoretical support for coping with the challenges posed by KD to China's ecological environment.

Hydrological modelling of large-scale karst-dominated basin using a grid-based distributed karst hydrological model

Hydrological modelling is important to flood hazard prevention in the flood-prone karst area of Southwest China. Due to the special hydrogeological features with strong spatial heterogeneities and whose information is rarely obtained in large-scale karst-dominated basins; thus, it’s still a challenge to conduct accurate sub-daily distributed precipitation-streamflow simulation in these regions. To reveal the characteristics of hydrological response and the inertia of karst systems that are influenced by the spatial heterogeneity of the degree of karstification, a new Grid-based Distributed Karst Hydrological Model (GDKHM) is developed by this study to simulate streamflow in Li River Basin (LRB), which is a typical large-scale karst-dominated basin of Southwest China. The GDKHM considers the duality of hydrological behavior and the spatial heterogeneities of land uses types and karstification of each grid and river channels routing characteristics between different sub-basins. The results show the GDKHM using calibrated parameters could reflect the spatial distribution characteristics of hydrological response in the LRB. The mean NSE, KGE, R2 and RRE of the streamflow of all the sub-basin outlets during validation period reached 0.82, 0.84, 0.83 and 4.64%, respectively. The hydrograph simulation result of nested interior grid without recalibration was also satisfied. Furthermore, the GDKHM was able to reproduce the Auto-correlation function (ACF) shapes of simulated lateral inflow time series in sub-basins with different percentage of karst terrain areas (PKTAs) during validation period, and the ACF characteristics information including memory effect, slopes of rapid-conduit and slow-matrix flow phases could be captured, which indicates the model can characterize the spatial variability of karst system inertia in large karst basin. Due to the better performance in hydrograph and ACF of streamflow, GDKHM has the potential to successfully support flood forecasting in large-scale karst-dominated basins.

Spatial variations in soil erodibility induced by rock outcropping on sloping cropland in the karst region of Southwest China

Sloping croplands in karst areas of Southwest China usually contain a multitude of rock outcrops with diameters larger than 25 cm. Rock outcrops and spatial location have substantial effects on soil properties and thus likely affect soil erodibility. Moreover, rock outcropping is a indicator of rocky desertification and has an important impact on soil erosion and soil formation processes. However, the potential effects of spatial location and rock outcrops on the soil erodibility of sloping cropland in karst areas are still unclear. This study was performed to explore the variations in soil erodibility reflected by saturated hydraulic conductivity (KS), mean weight diameter (MWD), soil structural stability (SSI), soil erodibility factor (K) and soil organic carbon content (SOC) at three spatial locations in sloping cropland with rock outcrops on the karst hillside. The results showed that the soil erodibility indicators KS, MWD, SSI and SOC declined with increasing soil depth for all tested sites. SSI and SOC were predominant factors contributing to the variation in soil erodibility, which were 34.9 % and 35.1 % at the upper spatial location, 31.4 % and 30.9 % at the middle spatial location, and 32.1 % and 32.6 % at the lower spatial location, respectively. There were significant variations in the K factor between the sloping cropland with rock outcrops and the control group. The variations in soil erodibility indicators with rock outcrops and spatial locations were attributed to the changes in soil particle distribution, soil bulk density and SOC. There was a significant linear correlation between the K factor and spatial location, slope gradient, coverage and height of rock outcrops. These results indicated that rock outcrops and their characteristics can reduce soil erosion intensity by redistributing precipitation and runoff, thus further affecting infiltration and soil erodibility. These findings are helpful to comprehend the processes and mechanisms of the spatial variation in soil erosion on sloping cropland with rock outcrops.

Spatiotemporal variations of drought and driving factors based on multiple remote sensing drought indices: A case study in karst areas of southwest China

Spatiotemporal variations of drought and driving factors based on multiple remote sensing drought indices: A case study in karst areas of southwest China

Carbon Sink Trends in the Karst Regions of Southwest China: Impacts of Ecological Restoration and Climate Change

Southwest China (SWC) holds the distinction of being the world’s largest rock desertification area. Nevertheless, the impacts of climate change and ecological restoration projects on the carbon sinks in the karst area of Southwest China have not been systematically evaluated. In this study, we calculated carbon sinks by utilizing the Carnegie–Ames–Stanford Approach (CASA) model, and the actual measurements, including the net primary productivity (NPP) data and soil respiration (Rs,) were calculated to obtain carbon sink data. Our findings suggest that the carbon sinks in the karst areas are displaying increasing trends or positive reversals, accounting for 58.47% of the area, which is larger than the overall average of 45.08% for Southwest China. This suggests that the karst areas have a greater carbon sequestration potential. However, approximately 10.42% of carbon sinks experience negative reversals. The regions with increasing and positive reversals are primarily located in the western parts of Guizhou and Guangxi, while negative reversals are observed in the eastern parts of Chongqing, Guangxi, and Guizhou. Ecological restoration projects are the main driving factors for the carbon sinks with increasing trends. Increased humidity and ecological restoration management are the main reasons for the positive reversals of carbon sinks. However, warming and drought shift the carbon sinks from increasing to decreasing in Chongqing, east of Guangxi and Guizhou. The findings of this study highlight the significant role of ecological restoration projects and reexamine the impact of climate change on carbon sequestration.

Postharvest Quality Exploration of “Crystal” Grapes in Karst Mountainous Area: Regulatory Effect of High Concentration 1-MCP Fumigation

The comprehensive exploration and thorough understanding of the physicochemical characteristics of “Crystal” grapes in the Karst area of Southwest China can not only produce edible table grapes, but also offer significant theoretical backing for the management of rocky desertification in the Karst area and consequently generate enhanced social and ecological benefits. This study explored the regulatory effect of 1-MCP fumigation on the postharvest storage quality of "Crystal” grapes, aiming to provide some technical support for the development of the grape industry in the Karst mountainous areas. The results indicate that compared with the control group, both the 10.0 and 50.0 μL/L 1-MCP treatment groups effectively inhibited the increase in decay rate, browning rate, shedding rate, and color change of the grapes, significantly inhibited the enhancement of polyphenol oxidase (PPO), peroxidase (POD), and lipoxygenases (LOX) browning-related enzyme activities, improved the superoxide dismutase (SOD) activity of the fruits, hindered the decrease of ascorbic acid (AsA) and polyphenols, delayed the accumulation of malondialdehyde (MDA) content, and significantly postponed the peak period of polygalacturonase (PG) activity in the fruits and the degradation of protopectin to soluble pectin, thereby maintaining desirable texture characteristics. The utilization of 1-MCP for fruit fumigation yielded a heightened overall fragrance, thereby facilitating the emission of terpenes, alcohols, aldehydes, ketone aromatic compounds, and methyl aromatic substances within the fruit. Overall, both the M10 and M50 treatments are equally effective in preserving the storage quality of “Crystal” grapes. Under the condition of ensuring the excellent edible quality of crystal grapes, M2 can extend the shelf life of crystal grapes by about 5 days, and M10 and M50 can extend the storage period of crystal grapes by 10~15 days. Considering the cost, it is recommended that the industry employs a concentration of 10.0 μL/L of 1-MCP for “Crystal” grapes. Simultaneously, this study also provides theoretical support for the ecologically high-quality development of cultivated land in the Karst mountainous area of Guizhou and tree selection.

Effects of rock lithology and soil nutrients on nitrogen and phosphorus mobility in trees in non-karst and karst forests of southwest China

The primary productivity of terrestrial plants is widely limited by nitrogen (N) and phosphorus (P), and the mobility of N and P in plants is the key to predicting plant growth and development. Non-karst and karst forests soil have different nutrient supply capacities due to the difference in soil parent material, but the effect mechanism of the two soil nutrient conditions on the N and P mobility process of trees remains unclear. In this study, forests dominated by three typical tree species, Eucalyptus maideni, Pinus yunnanensis, and Quercus franchetii were selected as the research objects in non-karst and karst areas of southwest China to investigate the effects of soil nutrient conditions on plants’ N and P foraging, transportation and resorption. The results showed that the rock lithology had significant effects on the soil nutrients, plants’ N and P foraging, transportation, and resorption. The soil total N and P concentrations, soil organic carbon concentration, and pH were higher in karst forests than those in the non-karst forests, but the green leaves N and P concentrations exhibited opposite characteristics. The root foraging potential for N and P in non-karst forests was significantly higher than that in karst forests. The N resorption efficiency of trees in karst forests was higher than that in non-karst forests, but the P resorption efficiency was lower than that in non-karst forests. The trade-offs of foraging, transportation and resorption of trees were adjusted according to changes in nutrient conditions, but the trade-offs of the three processes were not continuous in non-karst and karst forests. Compared with non-karst forests, the decreased degree of root nutrient foraging potential in karst forests was greater than the transportation factor and resorption efficiency. The slow-growing Quercus franchetii among the three typical forests showed better adaptability to foraging, transportation, and resorption of N and P in karst areas. The results revealed the response of different forests’ N and P mobility patterns of trees to different nutrient conditions in non-karst and karst areas, which was helpful to improve the prediction and mechanistic understanding of nutrient cycling in local forest ecosystems.

Dominant influence of plants on soil microbial carbon cycling functions during natural restoration of degraded karst vegetation

The impacts of natural restoration projects on soil microbial carbon (C) cycling functions have not been well recognized despite their wide implementation in the degraded karst areas of southwest China. In this study, metagenomic sequencing assays were conducted on functional genes and microorganisms related to soil C-cycling at three natural restoration stages (shrubbery, TG; secondary forest, SG; old-growth forest, OG) in the southeast of Guizhou Province, China. The aims were to investigate the changes in microbial potentials responsible for soil C cycling and the underlying driving forces. The natural restoration resulted in vegetation establishment at all three restoration stages, rendering alterations of soil microbial C cycle functions as indicated by metagenomic gene assays. When TG was restored into OG, the number and diversity of genes and microorganisms involved in soil C cycling remained unchanged, but their composition underwent significant shifts. Specifically, microbial potentials for soil C decomposition exhibited an increase driven by the collaborative efforts of plants and soils, while microbial potentials for soil C biosynthesis displayed an initial upswing followed by a subsequent decline which was primarily influenced by plants alone. In comparison to soil nutrients, it was determined that plant diversities served as the primary driving factor for the alterations in microbial carbon cycle potentials. Soil microbial communities involved in C cycling were predominantly attributed to Proteobacteria (31.87%–40.25%) and Actinobacteria (11.29%–26.07%), although their contributions varied across the three restoration stages. The natural restoration of degraded karst vegetation thus influences soil microbial C cycle functions by enhancing C decomposition potentials and displaying a nuanced pattern of biosynthesis potentials, primarily influenced by above-ground plants. These results provide valuable new insights into the regulation of soil C cycling during the restoration of degraded karst vegetation from genetic and microbial perspectives.

Spatial heterogeneity of human activities and its driving factors in karst areas of Southwest China over the past 20 years

Guizhou Province is located in the karst mountain regions of Southwest China, where the ecological environment is extremely fragile and particularly sensitive to human activities. Therefore, understanding the changing characteristics and driving factors of human activity in recent decades is urgent. In this study, least squares, correlation analysis, spatial autocorrelation analysis, and GeoDetector model were used. Based on a large collection of nightlight, topography, and meteorological data, combined with geographical information technology, we investigated the spatial distribution, intensity change, and degree of impact of human activity from 2000 to 2020. The results showed that during the study period, human activities intensity and range were expanding. The human activity areas expanded from 15,963 to 86,923 km2 at an increasing rate of 4,279.2 km2/a, which was 1,118.4 km2/a from 2000 to 2010 and 6,375.3 km2/a from 2010 to 2020. The human activity intensity increased from 0.009 to 0.018, with an increasing rate of 0.0006/a, which was 0.00028/a from 2000 to 2010 and 0.00073/a from 2010 to 2020. The rate of increase in the human activity intensity and the rate of expansion in the human activity range from 2010–2020 were significantly higher than that from 2000–2010, becoming more notable (p ≤ 0.01), especially after 2012. With the expansion of human activities, the center of gravity of human activity moved towards the northeast by 20.71 km. The human activities were primarily distributed in areas with the gentlest slopes (6–15°), middle and low altitudes (489–1,982 m), suitable temperatures (12.36–17.74°C), and abundant precipitation (1,001.99–1,276.99 mm). The research results using the GeoDetector model indicate that slope had the greatest impact on human activities with a q value of 0.1338; precipitation, elevation, and temperature had q values of 0.0626, 0.0253, and 0.0136, respectively. The combined impact between the precipitation and slope was the greatest with a q value of 0.1803. In Guizhou Province, under policy guidance, human activities that promoted vegetation change accounted for 79.60%. This study attempts to enhance sustainable development and provides valuable information on the environmental protection of karst mountain regions.

Evaluating the hydrological function of vegetation restoration in fragile karst area: Insights from the continuous surface and subsurface runoff monitoring

Satellite remote sensing of vegetation has indicated that vegetation greenness has increased globally. However, the feedback mechanisms of vegetation restoration on eco-hydrological functions remain unclear, especially in fragile ecosystems. In this study, twelve three-dimensional hillslope plots with different vegetation restoration strategies were selected and their surface and subsurface runoff (SR and SSR, respectively) were monitored in the karst region of southwest China. These strategies were classified as either natural restoration (NR) or artificial management methods (PF, planted forest; GL, grassland), using cropland (CL) as a reference. The results showed that vegetation restoration effectively reduced both SR and SSR. Runoff from the three restoration strategies (59–66 mm) was significantly lower than that from the CL (119 mm). All the strategies had lower runoff than that of CL, except for PF, which exhibited higher SR because of its sparse canopy. Vegetation restoration reduced SR by increasing vegetation cover, which can intercept rainwater and weak the contribution (2.9–12.9%) of rainfall intensity to runoff, thereby reducing runoff generated by “infiltration-excess” mechanisms. This decrease in SSR may be due to an increased water storage capacity in the soil-root zone, causing the soil-bedrock interface to require more rainwater to “fill” and then “spill” to form lateral SSR during the rainfall events. These findings demonstrate that both canopy interception and root-soil interactions contribute to the improvement in hydrological function after vegetation restoration. Among the environmental factors contributing to runoff variation, soil depth was identified as the most crucial (51% of the variance) and showed a positive and negative correlations with SR and SSR, respectively. Consequently, restoration strategies with higher rainwater retention capacity can be selected to reduce SR losses, especially in areas with deeper soil layers. Accordingly, this study reveals that vegetation restoration reduces runoff and highlights the influence of soil depth in karst areas of southwest China.

Types of vegetables shape composition, diversity, and co-occurrence networks of soil bacteria and fungi in karst areas of southwest China

BackgroundMicroorganisms are of significant importance in soil. Yet their association with specific vegetable types remains poorly comprehended. This study investigates the composition of bacterial and fungal communities in soil by employing high-throughput sequencing of 16 S rRNA genes and ITS rRNA genes while considering the cultivation of diverse vegetable varieties.ResultsThe findings indicate that the presence of cultivated vegetables influenced the bacterial and fungal communities leading to discernible alterations when compared to uncultivated soil. In particular, the soil of leafy vegetables (such as cabbage and kale) exhibited higher bacterial α-diversity than melon and fruit vegetable (such as cucumber and tomato), while fungal α-diversity showed an inverse pattern. The prevailing bacterial phyla in both leafy vegetable and melon and fruit vegetable soils were Proteobacteria, Acidobacteriota, Actinobacteriota, and Chloroflexi. In leafy vegetable soil, dominant fungal phyla included Ascomycota, Olpidiomycota, Mortierellomycota, and Basidiomycota whereas in melon and fruit vegetable soil. Ascomycota, Mortierellomycota, Basidiomycota, and Rozellomycota held prominence. Notably, the relative abundance of Ascomycota was lower in leafy vegetable soil compared to melon and fruit vegetable soil. Moreover, leafy vegetable soil exhibited a more complex and stable co-occurrence network in comparison to melon and fruit vegetable soil.ConclusionThe findings enhance our understanding of how cultivated soil bacteria and fungi respond to human disturbance, thereby providing a valuable theoretical basis for soil health in degraded karst areas of southwest China.

Identification of priority areas for soil erosion control based on minimum administrative units and karst landforms in karst areas of Guizhou

Soil erosion is one of the most serious ecological threats in karst areas of Southwest China. The identification of priority areas for remediation and its driving factors is essential to improving the efficiency of prevention and control. The present study systematically considered natural and socio-economic factors not involved in the revised universal soil loss equation (RUSLE) model, and determined priority areas for soil erosion management based on minimum administrative units and karst landforms. Then, the driving factors were identified by using geographic detector. The results showed that the priority areas were mainly concentrated in the southwest, southeast and northeast, overlapping with the severely eroded areas (Erosion rate=45.79 t·ha−1·a−1). Gradient risk zones had geomorphological differences, but the most eroded zones were all controlled by bedrock exposure rates, elevation, or slope position. The spatial correlation and high erosion rate of priority areas provided opportunities to optimize the efficiency and cost of control. Driving factors were affected by karst landforms. The explanation power of slope position on soil erosion was higher in the peak cluster depressions and karst basins with small undulations ([Formula: see text]), while the karst gorges, trough valleys and plateaus with large undulations gradually decreased ([Formula: see text]). The interaction of driving factors will enhance the explanatory power for soil erosion. Among them, the repetition rate of elevation was 60%, and the repetition rate of lithology and development index was 40%. This study provides useful information for identifying and managing priority areas for soil erosion control, and enriches the theory of soil and water conservation in karst areas.

Ameliorative Effects of Vermicompost Application on Yield, Fertilizer Utilization, and Economic Benefits of Continuous Cropping Pepper in Karst Areas of Southwest China

In recent years, vermicompost (V) has been widely used as an amendment for improving crop productivity and soil quality. However, the ameliorative effect of vermicompost on the continuous cropping pepper remains unclear, particularly in the karst areas of southwestern China. A field experiment was conducted to study the effect of vermicompost application on the yield, quality, nutrient accumulation, fertilizer utilization, and economic benefits of continuous cropping pepper from 2021 to 2022. The experiment included six treatments: CK (no fertilizer), FP (the fertilization practice of local farmers), and FPV (FP combined with vermicompost of 1500, 2250, 3000, and 3750 kg·ha−1). The results show that vermicompost application increased the yield of fresh pod pepper by 28.34–51.36% (2021) and 47.13–68.82% (2022), whereas the yield of dry pod pepper increased by 16.97–35.14% (2021) and 34.48–62.61% (2022), respectively, compared with the FP treatment. The application of vermicompost reduced the nitrate content and increased the vitamin C (VC) and soluble sugar content of the fruits, which is beneficial for improving their quality. Vermicompost application not only increased nutrient uptake but also significantly improved agronomic efficiency (AE) and recovery efficiency (RE). In addition, although the application of vermicompost increased production costs, the increase in yield improved net incomes (16.02–31.83% in 2021 and 35.83–62.85% in 2022), especially in the FPV4 treatment. In conclusion, the use of vermicompost amendment had a positive effect on the productivity and economic benefits of continuous cropping pepper, which may be an effective nutrient management strategy for the continuous cropping pepper in the karst mountain areas of southwest China.

Characteristics of drought propagation and effects of water resources on vegetation in the karst area of Southwest China

The topography is complex in the southwest karst region of China, with severe surface water scarcity but abundant groundwater resources. Studying drought propagation and vegetation demand for water is important to effectively protect the ecological environment and improve the management of water resources. We employed CRU precipitation data, GLDAS, and GRACE data to calculate SPI (Standardized precipitation index), SSI (Standardized soil moisture index), SRI (Standardized runoff index), and GDI (Groundwater drought index), characterizing meteorological, agricultural, surface water and groundwater droughts, respectively. The Pearson correlation coefficient was adopted to study the propagation time of these four types of droughts. The random forest method was used to identify the importance of precipitation, 0–10 cm soil water, 10–200 cm soil water, surface runoff, and groundwater for NDVI (Normalized difference vegetation index), SIF (Solar-induced chlorophyll fluorescence), and NIRV (Near-infrared reflectance index of vegetation) at the pixel scale. The propagation time of meteorological drought to agricultural drought and agricultural drought to groundwater drought in the karst area of southwest China was significantly reduced by 1.25 months compared with the non-karst area. The response of SIF to meteorological drought was faster than that of NDVI and NIRV. The importance of water resources for vegetation in the whole study period (2003−2020) was ranked as precipitation, soil water, groundwater, and surface runoff. The contribution of soil water and groundwater in forest was 38.66 %, while 31.66 % and 21.67 % for grassland and cropland, respectively, which indicated that the demands of soil water and groundwater in forest were greater than that of grassland and cropland. When drought occurred (2009–2010), soil water, precipitation, runoff, and groundwater were ranked in order of importance. The importance of 0-200 cm soil water was 48.67 %, 57 %, and 41 % in forest, grassland, and cropland, respectively, higher than precipitation, runoff, and groundwater, indicating that soil water was the main water resource for vegetation to cope with drought. Since the cumulative effect of drought on SIF was more obvious, SIF showed a more serious negative anomaly than NDVI and NIRV from March to July 2010. The correlation coefficients between SIF, NDVI, NIRV, and precipitation were 0.94, 0.79, and 0.89 (P < 0.001), and the correlation coefficients with groundwater were −0.27 (P < 0.001), −0.02 (P > 0.05) and −0.15 (P < 0.05), respectively. Compared to NDVI and NIRV, SIF was more sensitive to meteorological drought and groundwater drought and had great potential in drought monitoring.