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.
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•The spread time of four droughts in southwest China was evaluated.•Karst area impacted the spread time of drought (mainly in agricultural drought).•Forests mainly rely on 10-200 cm of soil water during the drought.•Grassland and cropland mainly rely on 0-10 cm of soil water during the drought.•SIF is more sensitive to precipitation and groundwater than NDVI and NIRv.
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•Afforestation increases > 2 mm aggregate proportion and associated SOC and TN contents.•Afforestation stimulates C and N transformations within aggregates.•Afforestation changes soil ...C flow pathways from < 0.053 mm to 4–8 mm progressively.•Afforestation exerts the positive effect on SOC and TN stocks.
Vegetation restoration can significantly increase soil organic carbon (SOC) and total nitrogen (TN) stocks, however, the response of SOC and TN stocks, as well as their distribution, transformation, and stability within aggregates, to afforestation in fragile karst ecosystems remains unclear. In this study, soil samples were collected from orchards, 10-, 20-, and 40-year Dodonaea viscosa plantations after afforestation following orchard abandonment in a karst rocky desertification area. A natural succession shrubland soil served as the control. Aggregate size distribution, SOC and TN contents, and δ13C and δ15N values in bulk soils and aggregate fractions were determined. The results showed that 0.25–2 mm aggregates were the main contributors to SOC and TN stocks, amounting to 47.7 %-55.6 % and 43.0 %-51.7 %, respectively. Compared to orchards, D. viscosa afforestation significantly increased SOC and TN stocks by 160 %-393 % and 184 %-416 %, respectively, more obviously with prolonged afforestation. This effect was mainly attributed to the increases in > 2 mm aggregate fractions and their associated SOC and TN contents. In addition, δ13C and δ15N values decreased with decreasing aggregate size in afforested and shrubland soils. The C flow pathways followed the trend from < 0.053 mm to 4–8 mm following afforestation, but this was not the case for orchard soils exhibiting pathways from 2-4 mm to < 0.053 mm progressively. These results indicated that large aggregates showed a faster turnover rate and contributed to higher SOC and TN contents following afforestation. The significant and positive relationships between SOC and TN contents and magnesium, aluminium and iron oxides suggested the stimulatory effect on SOC and TN accumulation. Noticeably, although SOC and TN stocks in bulk soils following 40-year afforestation reached the level of shrubland, the proportion of > 2 mm aggregates and the geometric mean diameter remained significantly lower than those of shrubland soils. Soil aggregate stability following D. viscosa afforestation may take longer to reach natural restoration levels.
•We found the ESV increased by US$ 23.42 billion from 1992 to 2015 in karst areas.•The contribution rate of regulating service function was 69%.•The implementation of ecological project has a ...positive impact on ESV in karst areas.•The ESV appeared to be more sensitive to bidirectional land transfer.
Karst ecosystem services (ESs), the key components of global terrestrial ESs, play a crucial role in human welfare and livelihood. However, the spatiotemporal changes of ecosystem service values (ESVs) in the karst areas of China remain unclear. In this paper, land use/land cover (LULC) data were used to estimate the ESVs changes during 1992–2015 by the benefit transfer method, to reveal its spatial heterogeneity and to explain the sensitivity of ESVs to land use change. The results indicated that the ESVs were increased by US$ 23.42 billion at 0.10%·yr−1 due to the LULC changes in over 15% of the total karst areas in China, while those in the non-karst areas were reduced by US$ 32.87 billion at 0.14%·yr−1. In particular, the value of the regulation services contributed 69.05% to the total ESVs in the karst area, followed by support services (18.23%), provision services (8.54%), and cultural services (4.15%). The net change of ESVs showed a spatial heterogeneity, i.e. ESVs in the Northwest and North part of southwest increased, but that in the northeast and eastern part of southwest decreased. The ESVs were more sensitive to the bidirectional land conversion than the unidirectional conversion. These results provide an important scientific basis for ecological restoration and reconstruction of karst areas.
•Tunnel excavation-induced karst groundwater drawdown changed hydrological processes.•Tunnel excavation changed the distribution patterns of karst water resources.•Tunnel excavation altered the ...physical and chemical properties of karst soils.•Tunnel excavation changed physiological processes and growth rates of karst plants.•Tunnel excavation induced karst geological hazards.
Due to a lack of awareness of environmental protection at the beginning of tunnel excavation and the unique ecological vulnerability of karst areas, tunnel excavation is beginning to have increasingly serious negative effects on the ecological environments in karst areas, leading to challenges related to regional water resources and ecological security. The groundwater drawdown caused by tunnel drainage has had far-reaching impacts on the hydrology, ecology and environment in karst areas. The most prominent effects of the recent advances in drainage techniques include the destruction of aquifer structures, changes in the distribution patterns of water resources and the groundwater flow field and even the initiation of geological disasters (i.e., collapses) in karst areas. In addition, karst water circulation and hydrogeochemical processes have also been affected. However, due to the complex geological conditions and limited observational data in karst areas, the impacts of tunnel drainage on ecological systems remain poorly understood. With increased understanding, researchers have found that the physical and chemical properties of the soil, the speed of soil erosion, the physiological processes and growth rates of plants, and even the compositions of plant communities are gradually changing in tunnel-affected karst areas, although the understanding of these processes and mechanisms remains far from sufficient. Based on the progress made regarding the understanding of water resource and hydrological process issues resulting from tunnel excavation in karst areas, we expect to experience a worldwide increase in investigations of the eco-hydrogeological effects of tunnel excavation in the future.
The southwest karst area is considered to have the most vulnerable groundwater environment in China. Groundwater quality is an important factor restricting sustainable economic development. In this ...study, traditional water chemistry method, water quality index (WQI), and hazard index (HI) were applied to comparatively analyze the hydrochemical characteristics of groundwater and the water quality in the exposed karst region (EKR) and buried karst region (BKR) in Bama, a typical karst area in southwest China. Generally, the main water type was Ca/Mg–HCO3. Due to the predominance of dissolution of carbonate rocks in EKR and silicate rocks in BKR, higher total dissolved solids (TDS), Ca and HCO3− concentrations, and lower H2SiO3 content were detected in groundwater in EKR compared with BKR. As affected by weathering of rocks such as lead-zinc ore, the maximum concentrations of Zn and Sr were 11.23 mg/L and 13.30 mg/L, showing that mineral water resources are widely distributed in Bama. The ion ratios and isotope abundances (δD and δ18O) in groundwater samples indicated stronger evaporation and rock-water interaction in EKR than BKR. Human activities exerted a more significant influence on the water quality in EKR compared to BKR. The mean WQI value also suggested that the groundwater quality was better in BKR (9.56) than EKR (12.17). Although 95.7% of the water samples in the study area were classified as excellent based on their WQI values, 4.3% of the water samples still had significant health risks (HI > 1) due to the high Sb, Zn, As, and Sr concentrations. It is recommended to reduce anthropogenic pollution in EKR and develop a plan for clean production of mineral water industry according to local conditions, which will help the sustainable development of the local economy.
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•Groundwater hydrochemistry in exposed and buried karst regions is totally different.•Aquatic environment in exposed karst regions is more sensitive than buried ones.•Sb, As, and Zn are the main trace elements which may pose non-carcinogenic risks.•Groundwater quality assessment contributes to sustainable water management.
Heavy metal pollution poses a serious hazard to the soil bacterial community. The purpose of this study is to understand the characteristics of soil heavy metal pollution in lead-zinc mines in karst ...areas and the response of Pb, Zn, Cd, and As-induced composite pollution to soil microorganisms. This paper selected soil samples from the lead-zinc mining area of Xiangrong Mining Co., Ltd., Puding County, Guizhou Province, China. The soil in the mining area is contaminated by multiple heavy metals such as Pb, Zn, Cd and As. The average levels of Pb, Zn, Cd and As in the Pb-Zn mining soil were 14.5, 7.8, 5.5 and 4.4 times higher than the soil background in this area, respectively. Bacterial community structures and functions were analyzed using 16 S rRNA high-throughput sequencing technology and the PICRUSt method. A total of 19 bacterial phyla, 34 classes and 76 orders were detected in the tested soil. At the phylum level, the Proteobacteria are the dominant flora of the soil in the tailings reservoir area of the lead-zinc mine, respectively GWK1 (49.64%), GWK2 (81.89%), GWK3 (95.16%); and for the surrounding farmland soil, the Proteobacteria, Actinobacteriota, Acidobacteriota, Chloroflexi and Firmicutes are the most abundant in five bacterial groups. RDA analyses revealed that the heavy metal pollution of the lead-zinc mining area has a significant impact on the diversity of soil microorganisms. As the distance from the mining area increased, the heavy metal comprehensive pollution and potential risk value decreased, and the bacterial diversity increased. Additionally, various types of heavy metals have different effects on bacterial communities, and soil heavy metal content will also change the bacterial community structure. Proteobacteria positively related to Pb, Cd, and Zn, therefore, Proteobacteria were highly resistant to heavy metals. PICRUSt analysis suggested that heavy metals significantly affect the metabolic function of microorganisms. Microorganisms might generate resistance and enable themselves to survive by increasing the transport of metal ions and excreting metal ions. These results can be used as a basis for the microbial remediation of heavy metal-contaminated farmland in mining areas.
•Heavy metal pollution of the karst mining area has a significant impact on the diversity of soil microorganisms.•Different types of heavy metals have different effects on bacterial communities.•Heavy metal content will change the bacterial community structure.•Heavy metals significantly affect the metabolic function of microorganisms.
•A coupled conceptual hydrological model (K-XAJ) for simulating the rainfall-runoff processes in karst-dominated areas.•The proposed K-XAJ model satisfactorily simulated the rainfall-runoff ...processes.•The peak flow predicted by the K-XAJ model was larger than that by the Xinanjiang (XAJ) model.•The interflow routed by the K-XAJ model was significantly smaller than that by the XAJ model.•The magnitude of groundwater predicted by the K-XAJ model was greater.
Rainfall-runoff processes in the karst dominated regions are of great importance. However, not all areas in a karst-dominated river basin are covered by typical limestone and both limestone and soil cover may exist. This study proposes a coupled conceptual hydrological model for simulating the rainfall-runoff processes in karst-dominated areas. The model, named as K-XAJ, couples the traditional Xinanjiang (XAJ) model and a two reservoir-based karst model for simulating runoff in both the karst area and the non-karst area in the Lijiang River basin. Simulated results demonstrated that the proposed K-XAJ model satisfactorily simulated the rainfall-runoff processes. Compared with the traditional XAJ model, the K-XAJ model produced better forecasts. The peak flow predicted by the K-XAJ model was larger than that by the XAJ model, but the interflow routed by the K-XAJ model was significantly smaller than that by the XAJ model. The magnitude of groundwater predicted by the K-XAJ model was greater. This study thus provides a new way to simulate rainfall-runoff processes in karst areas.
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•Propose optimization method for territorial spatial functional areas under double evaluations.•Construct sustainable development patterns of territorial space in karst areas to ...improve ecological quality.•Analyze different functions of territorial spatial functional areas for environmental governance.•Discuss control approaches for territorial space in karst areas.
Optimizing and controlling territorial space have become national strategic issues for China. However, urban-agricultural-ecological functions have serious conflicts in karst areas, causing differences in regional development and leading to severe problems related to the ecological environment and poverty. In this study, based on evaluations of urban-agricultural-ecological suitability and resource and environment carrying capacity, we explored an optimization method for territorial spatial functional areas and amendment rules for unsuitable areas in karst areas, identified different territorial spatial function areas, and proposed territorial spatial control approaches taking the functional area control and rock desertification space control as cores. On the one hand, the results showed that the optimization of the territorial space was divided into three single functional areas (i.e., urban space, agricultural space, and ecological space) and four multifunctional areas (i.e., urban-agricultural space, urban-ecological space, agricultural-ecological space, and urban-agricultural-ecological space). Among those different functional areas, the largest was ecological space, which was primarily distributed in the northwest, southwest, and northeast with good ecological environments and the south and southeast with severe rocky desertification. The second was agricultural-ecological space, which was primarily distributed in the north with better ecology and the south and southeast with severe rocky desertification. This region was the most important multifunctional area of the karst areas. The smallest type was urban-ecological space, which was primarily distributed in the central and northeastern regions with higher ecological and residential values. On the other hand, in terms of territorial spatial control, the region formed control patterns of functional areas of the “trinity”, which centered on classified protection, comprehensive improvement, and cluster development. Additionally, from the three aspects of control of deteriorating rocky desertification area, control of severe rocky desertification area, and control of corresponding policies, we explored new approaches and methods for the development and protection of rocky desertification space. The results of this research provide references for territorial spatial planning and management in karst areas.
•A method was provided to reveal the mechanism of human disturbance change on ESs.•The implementation of ECRLs will significantly reduce the HDI and increase the TES.•ELP lessens the trade-off ...between water yield and carbon storage and habitat quality.•Ecological restoration policies were proposed to promote regional development.
Exploring the impacts of human disturbance on ecosystem services (ESs) in karst areas is crucial for regional sustainable management, and China’s ecological conservation red lines (ECRLs) could provide innovative solutions for global biodiversity conservation. However, it remains unclear how the implementation of ECRLs policies will change the mechanism of human disturbance on ESs. Based on the Conversion of Land Use and its Effects at Small Region Extent (CLUE-S) model, we projected land use changes in 2035 under a Business as Usual (BAU) scenario, Ecological Protection (ELP) scenario, and Future City Plan (FCP) scenario in Weining County, China. The Integrated Valuation of Ecosystem Services and Trade-off (InVEST) model was used to quantify six ESs—crop production, water yield, soil conservation, carbon storage, nitrogen export, habitat quality—and total ecosystem services (TES). Then, we analyzed the impacts of human disturbance changes on ESs. Our research showed that under the ELP scenario, the human disturbance index would decrease by 6.18% and increase in soil conservation (0.34%), carbon storage (21.27%), and habitat quality (9.14%) compared with 2015. A greater area of forest and grassland would lead to a reduction in cropland area, which would lower crop production by 20.76%, with water yield and nitrogen export decreasing by 6.63% and 19.91%, respectively, from 2015 to 2035. The ELP scenario would lessen trade-offs between water yield and carbon storage and habitat quality, such that water yield and nitrogen export would be similar. Meanwhile, to ensure future crop production, more attention should be given to the increase in water yield and nitrogen export caused by cropland expansion, especially in its non-karst areas. TES would increase by 9.27%, which is higher than that obtained under either the BAU or FCP scenario. Eco-environmental conservation and restoration policies were proposed to help its regional high-quality development. Our research provides a decision-making basis to evaluate the implementation effects of ECRLs policies in karst areas and inform the directed management of ecosystems by the government.
Although data exist about the impact of karst soil restoration in some regions and climates, this information is lacking in the sub-humid Brazilian savannah. Runoff plots with distinct soil covers ...(bare soil, and ecologically restored areas with native species) were installed over a Lithic entisol on a karst slope of the Brazilian savanna (Cerrado), where runoff, erosion, and soil water balance were monitored during 3 hydrologic years. Mean runoff and erosion in the ecologically restored areas decreased from 546 mm yr−1 to 360 mm yr−1, and from 34 Mg ha-1yr−1 to 5 Mg ha-1yr−1, respectively. Soil loss tolerance was exceeded the bare plot of the Lithic entisol in all three hydrologic years. In the third year, erosion fell below soil loss tolerance in the restored plots, indicating that soil degradation could be effectively reduced with ecological restoration. The runoff and erosion data of the present study was fitted by an exponential relationship developed for non-karst soils of the Cerrado. Soil water balance was improved in the restored plots, increasing infiltration and evapotranspiration, and reducing runoff. The results fill an important information gap in tropical karst science, and could be utilized in similar settings.
