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Low winter temperatures severely stress newly arriving insect species. Adaptive evolutionary changes in cold tolerance can facilitate their establishment in new environments. Ambrosia artemisiifolia, a noxious invasive plant, occurs throughout China. Ophraella communa, a biological control agent of A. artemisiifolia, mainly occurs in southern China. However, in 2012, it established populations in Beijing (39.98°N, 115.97°E) following introduction from Laibin (23.62°N, 109.37°E), implying cold adaptation. The mechanisms underlying its rapid evolution of cold tolerance remain unknown. We investigated the levels of cryoprotectants and energy reserves in adult O. communa from two latitudes. In high-latitude insects, we found high trehalose, proline, glycerol, total sugar, and lipid levels; five potential genes (Tret1a, Tret1b, Tret1-2, P5CS, and GST), responsible for regulating cold tolerance and involved in trehalose transport, proline biosynthesis, and glutathione S-transferase activation, were highly expressed. These hybridisation changes could facilitate cold temperature adaptation. We demonstrate the genetic basis underlying rapid adaptation of cold tolerance in O. communa, explaining its extension to higher latitudes. Thus, specialist herbivores can follow host plants by adapting to new temperature environments via rapid genetic evolution. [ABSTRACT FROM AUTHOR]

Soil erosion has been a major environmental issue in young citrus orchards in karst areas of Southwest China. Straw mulching is an effective measure to reduce soil erosion. However, few studies have considered this measure in soil and water conservation in citrus orchards in karst areas. In this study, the effects of straw mulching on runoff and sediment reduction in young citrus orchards were studied using the simulated rainfall method with two typical soils—red soil and lime soil—in karst areas. This study consisted of two rainfall intensities (60 and 120 mm/h) and four straw coverages (0, 20, 50, and 80%). The results showed that straw mulching can significantly reduce surface soil loss in both lime soil and red soil. The surface runoff reduction rate of lime soil with straw mulching was much higher than that of red soil. Under the condition of heavy rainfall (120 mm/h), the surface soil loss rate was reduced by more than 57.5% in lime soil with 20% straw mulching. In red soil, a similar reduction rate of soil loss can only be achieved when straw mulching is 50%. Straw mulching reduced the surface soil loss of lime soil in young citrus orchards, mainly because of limited runoff transport, while red soil was limited by soil stripping. The results can provide a scientific basis for soil and water conservation in young citrus orchards in karst areas. [ABSTRACT FROM AUTHOR]

Background: Although effective vaccines have been developed against coronavirus disease 2019 (COVID-19), the level of neutralizing antibodies (NAbs) induced after vaccination in the real world is still unknown. The aim of this work was to evaluate the level and persistence of NAbs induced by two inactivated COVID-19 vaccines in China. Methods: Serum samples were collected from 1,335 people aged 18 years and over who were vaccinated with an inactivated COVID-19 vaccine at Peking University People's Hospital from January 19 to June 23, 2021, for the detection of anti-severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibodies. Results: The positive rate for NAbs against SARS-CoV-2 was 79–91% from the first month to the second month after the second vaccine dose. The gradual decline in positivity rate for NAb response was observed from 78% at 3 months post-vaccination to 0% at 12 months post-vaccination. When there was a 21-day interval between the two doses of vaccine, the NAb positivity rate was 0% 6 months after the second dose. NAb levels were significantly higher when the interval between two doses were 3–8 weeks than when it was 0–3 weeks (χ2 = 14.04, p < 0.001). There was a linear correlation between NAbs and IgG antibodies in 1,335 vaccinated patients. NAb levels decreased in 31 patients (81.6%) and increased in 7 patients (18.4%) over time in the series of 38 patients after the second vaccination. The NAb positivity rate was significantly higher in 18- to 40-year-old subjects than in 41- to 60-year-old subjects (t = − 1. 959 , p < 0. 01 ; t = 0. 839 , p < 0. 01). Conclusion: The NAb positivity rate was the highest at the first and second month after the second dose of vaccine, and gradually decreased over time. With a 21-day interval between two doses of vaccine, neutralizing antibody levels persisted for only 6 months after the second dose of vaccine. Therefore, a third vaccine dose is recommended. Our results suggest that in cases in which NAbs cannot be detected, IgM/IgG antibodies can be detected instead. The level of NAbs produced after vaccination was affected by age but not by sex. Our results suggest that an interval of 21 to 56 days between shots is suitable for vaccination. [ABSTRACT FROM AUTHOR]

In February 2020, an inpatient in Peking University People's Hospital (PKUPH), China, was confirmed positive for the novel coronavirus. In this case, 143 hemodialysis patients were labeled as close contacts and required to be placed under the hospital-based group medical quarantine (HB-GMQ) for 2 weeks by the authorities. After the case was reported, false or misleading information about the case flourished on social media platforms, which led to infodemic. Under this context, PKUPH adopted patient-centered humanistic care to implement the HB-GMQ, through the synergy of administrative, healthcare, logistical, and other measures under the model of patient-centered care of the Massachusetts Medical Society (MMS). As a result, all the patients tided over the HB-GMQ with no COVID-19 infection and no unanticipated adverse events, and all met the criteria for lifting the HB-GMQ. According to the questionnaires taken during the HB-GMQ, a high level of satisfaction was found among the quarantined and no symptomatic increase of anxiety and depression in the patients before and during the HB-GMQ, by comparing the Zung self-rating anxiety scale (SAS) and self-rating depression scale (SDS) conducted in December 2019 and on the 12th day of the HB-GMQ. This article is to brief on PKUPH's experience in implementing patient-centered humanistic care tailored to hemodialysis patients under the HB-GMQ, and to validate the hypothesis that patient-centered humanistic care is effective and helpful to help them tide over the HB-GMQ, so as to shed light on how to implement the HB-GMQ and cope with the HB-GMQ-induced problems in other hospitals. [ABSTRACT FROM AUTHOR]

Purpose: Changes in soil organic carbon (SOC) stock have major impacts on global terrestrial carbon cycling. However, their responses to land use conversions are poorly characterized for karst areas with extremely fragile geology and intensive human disturbance. Methods: To investigate the effects of soil type and land use on SOC stock in a typical karst region of southwestern China, 0–15 cm topsoil samples were randomly collected in 2015. Furthermore, in the same locations as the sites in 1983, 0–100 cm stratified profile soil samples (0–10, 10–20, 20–30, 30–50, 50–70, and 70–100 cm) were collected to evaluate the changes in SOC stock as affected by land use conversions from 1983 to 2015. Results: The current SOC stock in 0–15 cm differed significantly between Calcisols and Ferralsols, and was highest in the secondary forest, followed by shrubland, grassland, plantation forest, and cropland. Changes in the stratified SOC stock (both recalculated to 0–20, 20–40, 40–60, 60–80, and 80–100 cm intervals in 1983 and 2015) varied among different land use conversions. Average stratified SOC stock decreased after forest degradation and reclamation, except in 80–100 cm. After reforestation, it had decreases in 0–20 and 20–40 cm, whereas it increased in subsoil (40–60, 60–80, and 80–100 cm). However, compared with the cropland in which soil was exposed to continuous conventional tillage, average stratified SOC stock increased in all soil layers after reforestation. Conclusion: The increases in SOC stock after reforestation and re-cultivation (short-term reuse in abandoned croplands) indicated the positive role of agricultural abandonment in increasing terrestrial SOC stock. [ABSTRACT FROM AUTHOR]

Coarse root systems provide a framework for water and nutrient absorption from the soil and play an important role in plant survival in harsh environments. However, the adaptions of plant roots in soil-limited environments with low water storage capacity and nutrient content needs to be better understood. The adaptation strategies of two common plant species (a deciduous tree Platycarya longipes and an evergreen shrub Tirpitzia ovoidea) from two contrasting habitats (a shallow rocky soil and a nearby deep soil) in a karst region of subtropical China were compared and analyzed. Foliar nutrient concentrations, stoichiometry, stable carbon, and oxygen isotopes were used to determine plant nutrient and water use status across these two habitats. Six indexes, including maximum root depth, maximum root radial extent, number of major roots and secondary roots, and tapering rate and curvature, were all investigated to characterize coarse root systems. Results show that both species exhibited similar nutrient and water use status in the two habitats that had contrasting water holding capacity and available nutrient content. On the other hand, although maximum root depths of the individual plants were not deeper than 33 cm, maximum radial extents were much larger when compared to rooting depths. Specifically, the ratio of radial extent to depth in the soil-limited habitat was approximately 6 and 1.5 times higher than that in the deep-soil habitat for the tree and shrub, respectively. Additionally, especially for the tree, a larger root radial extent was further accompanied by lower root tapering rate and bending levels. Our results provided evidence that plants growing in soil-limited environments maintain a stable resource use status along with large radially extended coarse root systems in humid karst regions like southwest China. [ABSTRACT FROM AUTHOR]

Context: The karst region of southwestern China, one of the largest continuous karsts in the world, is known for its unique landscapes and rich biodiversity. This region has suffered severe environmental degradation (e.g., vegetation cover loss, soil erosion and biodiversity loss). In recent decades, Chinese governments at different levels have initiated several ecological programs (e.g., Green for Grain, Mountain Closure) to restore the degraded environment and to alleviate poverty. Objectives: This study summarizes landscape studies of karst landscapes patterns, their dynamics and interactions among landscape pattern, hydrological processes and ecosystem services (ES). Methods: We conducted a systematic literature review of science and land use policy to identify knowledge gaps and recommend future research and policy directions. Results: Karst landscapes have experienced rapid turnover in recent decades due largely to the overlap of intense human activity on the fragile karst ecosystems. Many studies have comprehensively examined hydrology, soil processes and ecosystem services (ES) and their relationships with landscape pattern. Most of these studies have found that karst ecosystems recover with improved ES. However, the importance of epikarst in hydrological and soil processes, intense anthropogenic disturbance and landscape heterogeneity in landscape models remains elusive. Conclusions: Future research should focus on in-depth examination and modelling of karst specific hydrological and soil processes, investigating relationships between climatic change, landscape change, ecological processes, and region-specific ES assessments. Results from such research should provide the necessary scientific support for a comprehensive, national karst rocky desertification treatment project (Stage II) and poverty alleviation initiatives. [ABSTRACT FROM AUTHOR]

[Display omitted] • Runoff connectivity on a karst hillslope are identified by isotopic signals. • The proportion of young water and event water decreases from upslope to downslope. • Runoff from the upslope is connected to the downslope by the soil–bedrock interface. • Soil-epikarst structure controls the hydrological connectivity of karst hillslopes. Hydrologic connectivity along the hillslope critical zone is essential for the transmission of water, solutes, and nutrients to streams. However, the influences of critical zone structure on hydrological connectivity are not adequately understood, especially for hillslopes with complex topography. We investigated the hydrological connectivity along different topographical positions of two adjacent dolomite hillslope plots in southwest China: a deep soil plot (average value: 66 cm) and shallow soil plot (average value: 35 cm). We characterized the dynamics of multiple-interface runoff and soil water based on observations of stable isotopes (δ18O and δD) and hydrometric monitoring, and computed the lc -excess, young water fraction (y w), and hydrograph separation from June 2020 to July 2021. On both hillslopes, soil depth gradually increased from up-slope to down-slope, and the contribution of event water and y w to soil water gradually decreased (100 % to 69 %). In the vertical depth, a sudden decrease in the contribution of y w (98 % to 47 %) and event water (44 % to 11 %) in the down-slope of the soil-epikarst interface was observed. These results indicate that the infiltration of rainwater from up-slope to down-slope was altered by vertical flow to lateral flow, which was connected through the soil-epikarst interface and finally converged in the low-lying area. Contrary to expectations, the contribution of y w at the soil-epikarst interface was lower in the shallow soil plot (43 %) than in the deep soil plot (71 %). As a supplement, moisture at the soil-epikarst interface was significantly higher in the shallow soil plot. This indicates that the renewal cycle of groundwater was slower in shallow soil-covered hillslopes not only because almost all rainwater (∼98 %) entered the soil-epikarst to redistribute as well as the higher water storage area in the soil-epikarst interface. Accordingly, the soil-epikarst structure, which is differentiated by soil depth, controls hillslope hydrological connectivity and groundwater storage capacity in the karst region of southwest China. [ABSTRACT FROM AUTHOR]

Soil nitrogen (N) dynamics are crucial for ecosystem development and carbon sequestration. However, N dynamics during post-agriculture succession have not been well understood. Here soil N dynamics during post-agriculture succession were investigated in a subtropical karst area, southwest China. The succession sequence includes grassland (~10 years), shrubland (~29 years), secondary forest (~59 years) and primary forest with cropland as reference. The soil is calcareous lithosols. Soil N stock (0-15 cm) in the cropland (335.2 ± 55.1 g N m) was not significantly different from that in the grassland, but was elevated by 120 to 221 % in the later three succession stages. Across the sequence, soil N accumulated with an average rate of 12.4 g N m yr. Soil N stock recovered to the primary forest level in about 67 years following agricultural abandonment. NO concentrations increased while NH concentrations decreased with years following agricultural abandonment. High NO concentrations (66.5-120.9 mg N kg) may imply N saturation in the shrubland, secondary forest and primary forest. Rates of net N mineralization and nitrification increased with succession. δN of soil, leaves and litter was significantly elevated in the later three succession stages relative to the grassland, indicating that the N cycle became more open with succession. N release from bedrock weathering was likely a potential N source in addition to atmospheric N deposition and biological N fixation. Our study suggests that N would not be the limiting nutrient for secondary succession and ecological restoration in the karst region of southwest China. [ABSTRACT FROM AUTHOR]

The brown planthopper, Nilaparvata lugens (Stål), is a major rice pest in Asia. Acetamiprid is a widely used neonicotinoid insecticide for N. lugens control. Because of the frequent and excessive applications of chemical insecticides, moderate levels of resistance against acetamiprid have been found in field populations of N. lugens in China. To study the inheritance mode and fitness costs of acetamiprid resistance in N. lugens , an acetamiprid-resistant strain (AC-R) was selected from a susceptible strain (AC-S) in the laboratory. After 28 generations of selection, AC-R showed 26.15-fold resistance compared to AC-S. The LC 50 and degree of dominance (D) values of the F 1 RS and F 1 SR (progenies of reciprocal crosses) indicated that the acetamiprid resistance in N. lugens was inherited as autosomal and incompletely dominant. Significant differences between the expected and observed mortalities of the F 2 individuals suggested that acetamiprid resistance is controlled by multiple genes. The AC-R strain showed a relative fitness of 0.71 with a significantly decreased male adult longevity, fecundity, net reproductive rate (R 0), and finite rate of increase (λ), and a prolonged adult preoviposition period (APOP). However, the durations of the 1st, 2nd, and 4th instar nymphs of AC-R were significantly shorter than those of AC-S. The current study provides valuable information for understanding acetamiprid resistance and optimizing insecticide resistance management strategies of N. lugens in the field. • Acetamiprid resistance in N. lugens was inherited as autosomal and incompletely dominant trait. • Acetamiprid resistance in N. lugens was controlled by multiple genes. • The acetamiprid-resistant N. lugens showed a fitness cost apparent in a significantly reduced reproductive capacity. [ABSTRACT FROM AUTHOR]

The article examines the variations of surface soil moisture content in a karst depression area in southwest China during the dry and rainy seasons in 2005. It finds that the variability of surface soil moisture was relatively higher in the dry season than in the rainy season, while on the other hand, the mean soil moisture content was higher during the rainy season, especially after heavy rainfall. It also identifies land use types, bare-rock ratio, and soil organic matter as major factors affecting soil moisture variability in the karst ecosystem.

Vegetation restoration effectively prevents soil degradation. However, the changes in soil properties that occur in fragile ecosystems in response to vegetation restoration are unclear. The aim of this study was to investigate the effects of vegetation restoration on soil physicochemical properties and saturated hydraulic conductivity (Ks) at different elevations. Restoration strategies included natural shrubland (NR), managed plantation forest (PF), cropland (CR), and secondary forest (SF). Topsoil (0–15 cm) samples were collected from seven counties in the karst region of southwest China. The soil nutrients were significantly (p < 0.05) higher in both NR and PF than in CR but were lower in SF. Soil physical properties (bulk density, porosity, texture, and Ks) were significantly (p < 0.05) different between CR and SF but not significantly different between NR and PF. Hence, the short restoration period (~15 years) had a stronger influence on soil nutrients than on soil physical properties. The soil properties following different land-use types were affected by elevation. For SF and PF, soil Ca, total nitrogen, and sand content were significantly (p < 0.05) negatively correlated with elevation. For NR, only sand content was significantly (p < 0.05) negatively correlated with elevation. No soil parameters were significantly correlated with elevation in CR. Soil nutrients increased to a greater extent in the low-elevation area (150–500 m) than in the high-elevation (1000 to 1200 m) areas. This discrepancy could be explained by the relatively increased biomass after vegetation restoration. Clay content variation was the main factor controlling Ks variation. The change in clay content was greater in low-elevation areas than in higher-elevation areas, where higher weathering and erosion rates were caused by strong hydrothermal conditions. Accordingly, the present study showed that the variations in soil properties observed after vegetation restoration are influenced by both land-use types and elevation. • The influence of elevation & land use type on karst soil properties were assessed. • The short restoration period (~15 y) had a stronger influence on soil nutrients. • Soil nutrients increased greater in low-elevation than in high-elevation areas. • Clay content was the main factor controlling Ks variation under restoration. [ABSTRACT FROM AUTHOR]

Summary: Large-scale vegetation restoration has been helpful to prevent serious soil erosion, but also has aggravated water scarcity and resulted in soil desiccation below a depth of 200cm in the Loess Plateau of China. To understand the dynamic mechanism of soil desiccation formation is very important for sustainable development of agriculture in the Loess Plateau. Based on natural and simulated rainfall, the characteristics of soil water cycle and water balance in the 0–400cm soil layer on a steep grassland hillslope in Changwu County of Shaanxi Loess Plateau were investigated from June to November in 2002, a drought year with annual rainfall of 460mm. It was similarly considered to represent a rainy year with annual rainfall of 850mm under simulated rainfall conditions. The results showed that the temporal variability of water contents would decrease in the upper 0–200cm soil layer with the increase in rainfall. The depth of soil affected by rainfall infiltration was 0–200cm in the drought year and 0–300cm in the rainy year. During the period of water consumption under natural conditions, the deepest layer of soil influenced by evapotranspiration (ET) rapidly reached a depth of 200cm on July 21, 2002, and soil water storage decreased by 48mm from the whole 0–200cm soil layer. However, during the same investigation period under simulated rainfall conditions, soil water storage in the 0–400cm soil layer increased by only 71mm, although the corresponding rainfall was about 640mm. The extra-simulated rainfall of 458mm from May 29 to August 10 did not result in the disappearance of soil desiccation in the 200–400cm deep soil layer. Most infiltrated rainwater retained in the top 0–200cm soil layer, and it was subsequently depleted by ET in the rainy season. Because very little water moved below the 200cm depth, there was desiccation in the deep soil layer in drought and normal rainfall years. [Copyright &y& Elsevier]

Plantations, as a form of vegetation restoration, play a critical role in the recent greening of the earth. However, the sustainability of the restored vegetation under precipitation changes has rarely been estimated, largely because of a lack of knowledge about the related plant water adaptation. In the current study, six tree species, including evergreen and deciduous, were selected from a typical karst forest types in Southwest China, a hotspot of earth greening. Root water uptake depth and hydraulic-related traits of stem and leaf were studied. Our results showed that, in the wet season, the evergreen species mainly rely on soil water sources from a depth of 0–30 cm (49.74%), while the deciduous use deeper layers of 30–70 cm in depth (47.58%). In the dry season, the deciduous species shed their leaves while the evergreens utilized soil water at a depth of 0–10 cm with an average absorption of 66.96%. The evergreen species exhibit higher xylem-cavitation resistance (reflect by P 50) and leaf-turgor maintenance capacity (reflect by Ψ tlp) than the deciduous. The significant correlations between plant water uptake depth and water potential, and hydraulic traits and water uptake depth indicate the different water adaptation strategies of evergreen and deciduous. In detail, evergreen species that rely on shallower water sources exhibit a larger diurnal range of leaf water potential, more xylem-cavitation resistant and leaf-turgor maintenance capacity. In contrast, deciduous species, with deeper water uptake, show narrower diurnal range of leaf water potential with lower drought resistance of stem and leaves. Our results highlight the probable divergent response (such as growth restriction and hydraulic failure) of evergreen and deciduous plantation tree species to the changing precipitation patterns under climate change. • The sustainability of the restored vegetation has rarely been estimated due to the lack of plant water adaptation research. • Evergreens with shallower water sources show larger range of water potential, higher drought resistance of stem and leaves. • Deciduous species with deeper water uptake show narrower diurnal range of water potential and lower drought resistance. • There are divergent responses of evergreen and deciduous to the changing precipitation patterns under climate change. [ABSTRACT FROM AUTHOR]

Simple Summary: Cold hardiness is critical to the ability of insects to survive in cold climates and expand their geographical distribution. The molecular mechanisms underlying insect cold tolerance have been well-studied, but many potential genes that may impact these responses, including MRLC-sqh, have not been thoroughly evaluated. We first cloned and characterized the MRLC-sqh from Ophraella communa, an effective biological control agent of Ambrosia artemisiifolia, and found that the protein sequence was highly conserved across various Coleoptera insects. The relative expression of MRLC-sqh was tissue- and stage-specific, with high levels of expression in the gut and pupal stage of O. communa. In addition, the expression of MRLC-sqh was shown to decrease after cold shock between 10 and 0 °C and ascend between 0 and −10 °C, but these did not show a positive association between MRLC-sqh expression and cold stress. Silencing of MRLC-sqh prolonged the chill-coma recovery time in these beetles, suggesting their cold hardiness was reduced in the absence of this protein. Therefore, these results indicate that MRLC-sqh may be partly responsible for the regulation of cold-tolerance responses in insects. Ambrosia artemisiifolia is a noxious invasive alien weed, that is harmful to the environment and human health. Ophraella communa is a biocontrol agent for A. artemisiifolia, that was accidentally introduced to the Chinese mainland and has now spread throughout southern China. Recently, we found that upon artificial introduction, O. communa can survive in northern China as well. Therefore, it is necessary to study the cold hardiness of O. communa. Many genes have been identified to play a role in cold-tolerance regulation in insects, but the function of the gene encoding non-muscle myosin regulatory light chain (MRLC-sqh) remains unknown. To evaluate the role played by MRLC-sqh in the cold-tolerance response, we cloned and characterized MRLC-sqh from O. communa. Quantitative real-time PCR revealed that MRLC-sqh was expressed at high levels in the gut and pupae of O. communa. The expression of MRLC-sqh was shown to decrease after cold shock between 10 and 0 °C and ascend between 0 and −10 °C, but these did not show a positive association between MRLC-sqh expression and cold stress. Silencing of MRLC-sqh using dsMRLC-sqh increased the chill-coma recovery time of these beetles, suggesting that cold hardiness was reduced in its absence. These results suggest that the cold hardiness of O. communa may be partly regulated by MRLC-sqh. Our findings highlight the importance of motor proteins in mediating the cold response in insects. [ABSTRACT FROM AUTHOR]

Soil and epikarst play an important role in the hydrological cycle in karst regions. This paper focuses on investigating the seasonal recharge and mean residence time (MRT) of soil water and epikarst water in a small karst catchment of southwest China. The deuterium contents in precipitation, creek, soil baseflow (direct recharge of the saturated soil water to the stream), epikarst spring, and soil waters were monitored weekly for two years, and MRT was calculated by an exponential model (EM) and a dispersion model (DM). The obvious seasonal variation of deuterium in rainfall was buffered in epikarst water, indicating sufficient water mixing. Soil baseflow contained less rainy-season rainwater than epikarst spring discharge, reflecting the retarded effect of soil thickness on rainwater recharge. MRTs of all water bodies were 41-71 weeks, and soils in the depression extended those of shallow groundwater. This demonstrated that the deep soil layer played an important role in karst hydrological processes in the study catchment. The creek was recharged mostly by rainfall through epikarst, indicating its crucial role in water circulation. These results showed epikarst had a strong water-holding capacity and also delayed water contact time with dolomite. [ABSTRACT FROM AUTHOR]

• DOM molecular compositions in multi-interface runoffs were quantified by FT-ICR MS. • Soil-epikarst structures controlled the DOM quantity and molecular compositions. • High microbially-derived carbon was detected in epikarst flow. • Flow rate and discharge effected DOM quantity and quality during runoff process. • Soil thicknesses affected runoff DOM dynamics by impacting hydrological processes. Understanding the chemical composition, origin, and molecular structure of dissolved organic matter (DOM) in multi-interface runoff is essential for comprehending the fate of laterally transported DOM in complex soil-epikarst systems of karst hillslopes. Limited information, however, is available for the optical properties and molecular compositions of the transported OM in multiple runoff components on the karst hillslope in relation to land-uses and soil thicknesses. In this study, we conducted a study to observe the changes in the quantity and quality of DOM in multiple interface flow (surface, subsurface, and epikarst) during natural rainfall events in 2022 in karst hillslopes that are covered by different land uses (cropland and shrubland) and soil thicknesses (with mean depths of 66.0 cm for deeper soil and 35.4 cm for shallower soil) in the karst region of southwest China. chemcial compositions of runoff DOM were determined by optical analysis and microbial compositions in runoff were inferred with high-throughput sequencing. The results showed that the soil-epikarst structure was controlling the runoff DOM quantity and quality during rainfall events. A decrease in the aromaticity, humification, unsaturation, and oxidation degree and an increase in carbohydrate, aminosugars, protein, and lipid compounds were found from surface to epikarst flow, indicating that plant-and soil-derived carbon decreased, while the microbially-derived carbon increased. The results were further comfirmed by the higher bacterial richness and diversity, along with fungal diversity in the epikarst flow compared to other runoff components. The bio-labile protein materials (C2) were the most important component of runoff DOM output in karst hillslopes. In surface and subsurface flow, rainfall amount, runoff rate, and discharge significantly affected the DOM concentration and quality during rainfalls, indicating that the dynamics of DOM in runoff from karst hillslopes were predominantly influenced by hydrological processes. Furthermore, the runoff DOM quality in cropland was dominated by lower unsaturation and oxidation degrees and higher protein component, compared to those in shrubland. The compositions of DOM in runoff from hillslope plots with thicker soils were primarily characterized by microbially-derived materials. Our findings were conducive to understanding the mechanism governing the migration of DOM quality and quantity in discharge during multi-interface hydrological processes on karst hillslopes. [ABSTRACT FROM AUTHOR]

• Surface and bedrock topography are closely coupled in shallow soil-covered plot. • Soil moisture in thick soil plot is notably affected by the surface topography. • Runoff in thinner soil plot is remarkably affected by the bedrock topography. • Soil thickness is a critical factor in distinguishing hydrological processes. Topography plays a crucial role in predicting rainfall-runoff processes under climate change, as it affects the spatial distribution of water flow pathways. However, understanding the potential impact of high micro-topography heterogeneity on runoff generation remains challenging. We conducted high-resolution monitoring of soil moisture, instantaneous water table, and subsurface runoff in two 3D plots with different soil thicknesses (66 cm vs. 35 cm) in the karst region of southwest China. The topographic features were characterized by the soil thickness, relative elevation, and topographic wetness index obtained from a 1 × 1 m grid. The topography of the shallow-soil plot (SSP) exhibited a higher level of complexity, with a greater variability (approximately 80.0 %) in soil thickness compared to that of the deep-soil plot (DSP; approximately 61.5 %). Additionally, the SSP was prone to forming a micro-topography characterized by a combination of exposed bedrock and soil cover. In DSP, the variation in soil moisture was strongly controlled by surface topography, with elevation contributing to 52 % and 81 % of the explanation for the soil moisture at 30 cm and soil–bedrock interface, respectively. In SSP, the contribution of topography to the variation in soil moisture did not exceed 31 %. The controlling effect of topography on runoff is highlighted in SSP, with the contribution rates of surface and bedrock relative elevation reaching 79% and 97%, respectively.The weaker water storage capacity of the SSP resulted in a higher volume of subsurface runoff (161 t vs. 116 t) and frequency of runoff events (2248 vs. 1994) compared to the DSP. Accordingly, this study emphasizes that the soil–bedrock spatial heterogeneity will control the relationship between soil moisture, subsurface runoff, and terrain, which will contribute to providing a basis for flood prediction and model simulation in regions with complex topography. [ABSTRACT FROM AUTHOR]

Fatty liver disease associated with metabolic dysfunction is of increasing concern in mainland China, the world's most populous country. The incidence of fatty liver disease is highest in China, surpassing the incidence in European countries and the USA. An international consensus panel recently published an influential report recommending a novel definition of fatty liver disease associated with metabolic dysfunction. This recommendation includes a switch in name from non-alcoholic fatty liver disease (NAFLD) to metabolic (dysfunction)-associated fatty liver disease (MAFLD) and adoption of a set of positive criteria for disease diagnosis that are independent of alcohol intake or other liver diseases. Given the unique importance of this proposal, the Chinese Society of Hepatology (CSH) invited leading hepatologists and gastroenterologists representing their respective provinces and cities to reach consensus on alternative definitions for fatty liver disease from a national perspective. The CSH endorses the proposed change from NAFLD to MAFLD (supported by 95.45% of participants). We expect that the new definition will result in substantial improvements in health care for patients and advance disease awareness, public health policy, and political, scientific and funding outcomes for MAFLD in China. [ABSTRACT FROM AUTHOR]

• Soil-rock interfaces are identified by using electrical resistivity tomography. • Soil probe measurements are likely to underestimate soil thickness in karst areas. • Soil thickness/stock in karst forests decreases from high to low latitudes. • The rock outcrop coverage rate explains 52 % of the variation in soil thickness. Soils provide storage space for nutrients and water, which governs many hydrological processes and functions in the natural ecosystems. Due to the complex soil-rock structures and localized climate, soil thickness and stock vary distinctly in different karst areas in southwest China. The difficulties of soil detection and the non-transparent underground soil-rock structures limit a deeper understanding of the spatial distribution of soils and their ecological functions. In this study, we employed electrical resistivity tomography (ERT) combined with soil probes to detect the spatial distribution of soils on hillslopes in karst forests in southwest China. The ERT surveys were conducted at six sites with 19 plots (20 × 30 m2) along latitudinal gradients. The results show that the ERT method performs well in visualizing the complex soil–bedrock interfaces and patchy distribution of soils in karst hillslopes, with remarkable consistency with the observed soil thickness and rock outcrops. Soil probes often hit rocks in soils (which we call a "rock barrier effect"), resulting in an underestimation of the mean soil thickness within the one-meter exploration depth by ∼0.18 m. This indicates that soil stock estimates derived from soil probes may be obviously underestimated in karst areas where the rock barrier effects are widespread. Meanwhile, the concept of equivalent soil thickness is proposed to remove the impact of scattered bedrock on soil stock estimation. For the six selected sites, the ERT-inferred mean soil thickness, equivalent soil thickness, and stock are 0.86 m, 0.60 m, and 0.10 m3/m3 respectively, with a trend of decreasing from high to low latitudes. Moreover, the rock outcrop coverage rate explains 52 % (60 %) of the variation in soil thickness (stock), followed by the annual mean temperature. This study emphasizes the importance of considering bedrock topography and its distribution in improving the detection of soil distribution, and the implications of the findings in this study are perhaps most profound for soil thickness-related soil erosion, soil water storage, and carbon storage in karst critical zones. [ABSTRACT FROM AUTHOR]

Carbonate landscapes make up one-fifth of the terrestrial land area, a better understanding of the coupling relationship between the soil–epikarst form and hydrological function is imperative for hydrology and landscape evolution modeling. In this study, we monitored a total of 158 rainfall-runoff events on a karst slope between 2019/4 and 2022/5 in southwest China, while simultaneously examining the soil–epikarst architecture (924 pairs of soil thickness and epikarst weathering degree). The results indicated that soil thickness increased with the underlying epikarst weathering degree, and soil thickness was positively correlated with epikarst thickness (P < 0. 001). Additionally, a significant positive relationship (P < 0. 001) was observed between surface runoff (SR) and soil thickness, as well as a significant negative relationship (P = 0. 0018) between subsurface runoff (SSR) and soil thickness. These findings imply the dominance of SR and SSR (under normal rainfall conditions) in runoff plots with deep soil layers and thin soil layers, respectively. The soil thickness threshold at which the hillslope discharge shifted from being SSR-dominated to SR-dominated was approximately 50 c m. Nonetheless, a positive relationship was found between SR and SSR under extreme rainfall events, indicating the establishment of hydrological connectivity between the surface and subsurface. Moreover, the hillslope discharge when the rainfall depth is lower than 50 mm is primarily composed of either SR or SSR from different plots. In other words, the hillslope discharge is typically influenced by both SR and SSR when the rainfall depth exceeds 50 mm. We finally proposed a positive feedback loop among soil thickness, epikarst weathering degree, and the hydrological function of the soil–epikarst system (water storage and release). These findings enhance our understanding of the complex interactive relationships in hillslope hydrology by illuminating the physical links between critical zone structures and hydrological processes on the karst slope. [Display omitted] • Soil thickness increased with weathering degree of epikarst. • SR dominated deep soil sites under normal rainfall conditions. • SSR dominated thin soil sites under normal rainfall conditions. • SR had a positive relationship with SSR under extreme rainfall events. • Bedrock weathering degree, soil thickness, and SR form a positive feedback loop. [ABSTRACT FROM AUTHOR]

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. • Runoff with restoration strategies was lower than that of cropland. • Vegetation restoration weakens rainfall intensity's contribution to runoff. • Vegetation restoration reduced runoff generated by infiltration-excess mechanisms. • Soil depth contributes to 51% of the explained variability in runoff. [ABSTRACT FROM AUTHOR]

Accurate estimation of reference evapotranspiration (ET 0) is very important in hydrological cycle research, and is essential in agricultural water management and allocation. The application of the standard model (FAO-56 Penman-Monteith) to estimate ET 0 is restricted due to the absence of required meteorological data. Although many machine learning algorithms have been applied in modeling ET 0 with fewer meteorological variables, most of the models are trained and tested using data from the same station, their performances outside the training station are not evaluated. This study aims to investigate generalization ability of the random forest (RF) algorithm in modeling ET 0 with different input combinations (refer to different circumstances in missing data), and compares this algorithm with the gene-expression programming (GEP) method using the data from 24 weather stations in a karst region of southwest China. The ET 0 estimated by the FAO-56 Penman-Monteith model was used as a reference to evaluate the derived RF-based and GEP-based models, and the coefficient of determination (R 2), Nash-Sutcliffe coefficiency of efficiency (NSCE), root of mean squared error (RMSE), and percent bias (PBIAS) were used as evaluation criteria. The results revealed that the derived RF-based generalization ET 0 models are successfully applied in modeling ET 0 with complete and incomplete meteorological variables (R 2, NSCE, RMSE and PBIAS ranged from 0.637 to 0.987, 0.626 to 0.986, 0.107 to 0.563 mm day−1, and −2.916% to 1.571%, respectively), and seven RF-based models corresponding to different incomplete data circumstances are proposed. The GEP-based generalization ET 0 models are also proposed, and they produced promising results (R 2, NSCE, RMSE and PBIAS ranged from 0.639 to 0.944, 0.636 to 0.942, 0.222 to 0.555 mm day−1, and −1.98% to 0.248%, respectively). Although the RF-based ET 0 models performed slightly better than the GEP-based models, the GEP approach has the ability to give explicit expressions between the dependent and independent variables, which is more convenient for irrigators with minimal computer skills. Therefore, we recommend applying the RF-based models in water balance research, and the GEP-based models in agricultural irrigation practice. Moreover, the models performance decreased with periods due to climate change impact on ET 0. At last, both of the two methods have the ability to assess the importance of predictors, the order of the importance of meteorological variables on ET 0 in Guangxi is: sunshine duration, air temperature, relative humidity, and wind speed. [ABSTRACT FROM AUTHOR]

Temperature is an important near-surface microclimate parameter that plays a key role in hydrological, ecological, and biogeochemical functions. However, the spatio-temporal distribution of temperature on the invisible and inaccessible soil–weathered bedrock continuum, wherein hydrothermal processes are most active, remains poorly understood. Temperature dynamics were monitored at 5 min intervals in the air–soil–epikarst (∼3 m) system at different topographical positions of the karst peak-cluster depression in southwest China. The weathering intensity was characterized based on the physicochemical properties of samples collected through drilling. No significant difference was observed in air temperature across slope positions, which was related to the limited distance and elevation resulting in roughly consistent energy input. The control effect of air temperature on the soil–epikarst was weakened with the decrease in elevation (±0.36 to ±0.25 °C). It is attributed to the enhanced temperature regulation capacity of vegetation cover from the up slope (shrub dominant) to down slope (tree dominant) in a relatively uniform energy environment. Temperature stability is clearly distinguished in two adjacent hillslopes that were differentiated by weathering intensity. For every 1 °C change in the ambient temperature, the amplitude of soil-epikasrt temperature variation on the strongly and weakly weathered hillslopes were ±0.28 and ± 0.32 °C, respectively. The response of soil-epikarst temperature to ambient temperature was more sensitive in the wet season (±0.40 °C) than in the dry season (±0.20 °C), which was related to the cooling effect caused by abundant rainfall. The cooling effect was particularly prominent in the preferential flow development area composed of pipeline cracks, which appear in the hillslope with relatively weak weathering intensity. These demonstrate that soil–epikarst temperature responds more gently to the variability of rainfall and ambient temperature on a relatively strong weathered hillslope. Accordingly, this study highlights that the sensitivity of soil–epikarst temperature to climate change is regulated by vegetation and weathering intensity on karst hillslopes in southwest China. • Heterogeneity of epikarst temperature studied through direct in situ measurements. • The regulating effect on soil-epikarst temperature enhanced from up-to downslope. • Weathering intensity controls the spatial distribution of soil–epikarst temperature. • The cooling effect of rainfall is more prominent on weakly weathered hillslope. [ABSTRACT FROM AUTHOR]

• GPP and ET were positively and linearly correlated to Rn and VPD in a karst forest. • WUE was negatively correlated to meteorological factors but positively to Bowen ratio. • WUE was not proportional to 1/VPD or 1/VPD0.5 but interactively responded to drivers. Water-use efficiency (WUE) is a key parameter that measures the balance between carbon gain and water loss in an ecosystem. Achieving better understanding of how WUE responds to environmental drivers is critical for revealing ecohydrological processes and mechanisms, and for biophysical modelling to investigate the interactions between vegetation and the changing environment. Karst landforms cover ∼10 % of the Earth's land surface; however, to date few studies have focused on the behaviours of WUE in karstic ecosystems. To fill these knowledge gaps, a two-year experiment was conducted to investigate the WUE and its drivers in a climax karst forest in southwestern China. Results showed that both the GPP (Gross Primary Production) and ET (evapotranspiration) showed exponential relationships to Ta (air temperature, P < 0.05), but linear relationships to Rn (net radiation, R 2 = 0.38 (GPP) and 0.78 (ET), P < 0.05) and VPD (water vapour pressure deficit, R 2 = 0.36 (GPP) and 0.28 (ET), P < 0.05), being quite different from those in other ecosystems. The reasons would be the different habits of the karstic plants, and the facts that the root zone water availability rarely dropped to low levels due to the frequent precipitation. The WUE, with the mean of 8.0 ± 4.8 mg CO 2 g−1 H 2 O, exhibited negative relationships to VPD (R 2 = 0.23, P < 0.05), Rn (R 2 = 0.28, P < 0.05), and Ta (air temperature, R 2 = 0.42, P < 0.05), and a positive linear relationship to the Bowen ratio (R 2 = 0.17, P < 0.05). Besides these, results also showed that the effects of a specific driver (e.g., VPD) on WUE was affected obviously by other factors (e.g., Ta, Rn), indicating that whether a driver is important or not to WUE, depends strongly on the environmental conditions. As the WUE-response formulas are often used to investigate and model the interactions between vegetation and environment, these findings suggested that the modelers should caution the versatility of the WUE-response formulas. [ABSTRACT FROM AUTHOR]

[Display omitted] • Epikarst thickness in depression is markedly greater than that on hillslope. • Spherical model fits for the interpolation of spatial structure of epikarst thickness. • Soil thickness is identified as the primary control on epikarst thickness. • ANNs model is suitable for predicting epikarst thickness based on RFE for variable selection. Epikarst, as a distinct layer of karst critical zone, plays a crucial role in water storage-transfer functions and biogeochemical processes. The epikarst thickness, which shows high spatial variability, is an important parameter that controls the dynamic characteristics of the water cycle. Due to the time-cost constraints in conventional field surveys and coarse resolution of remote sensing interpretation, empirical statistical models based on epikarst forming factors are an alternative to quantify the epikarst thickness. In this study, we investigated the spatial variability of epikarst thickness in Huanjiang, Guangxi of southwest China, based on electrical resistivity tomography with 36 sampling lines (1,658 sampling points) in a dolomite catchment. The controlling factors of epikarst thickness were defined based on selecting terrain-vegetation-soil variables with GLM (generalized linear model), RFE (recursive feature elimination) and PLSR (partial least squares regression) methods. Then, the best method for predicting epikarst thickness was selected based on the model with the highest accuracy. Results showed that the mean epikarst thickness was 6.32 m; the epikarst was significantly thicker in the depression (7.2 m) than on the hill slope (5.8 m), whereas there were no significant differences among slope positions. Geostatistical analysis showed that the spherical model reflected the strong spatial autocorrelation of epikarst thickness. Based on the prediction performance of the models, the terrain-vegetation variables alone could not explain epikarst thickness satisfactorily (explanation rate, 32.9 %; testing accuracy, R2 <0.5). By contrast, the modeling accuracy significantly increased (64.7 %, 0.7) when soil properties were considered as predictors. Based on validation criteria (R2 and RMSE), RFE for selecting variables and ANNs for prediction (0.814, 2.137 m) were the optimal model set to predict the epikarst thickness. This study provides a reference method for predicting epikarst thickness at a hillslope scale and the information would be helpful for hydrological catchment modeling. [ABSTRACT FROM AUTHOR]

• The VIC model was improved by considering epikarst and reservoir characteristics. • Increase in ET was mainly caused by evaporation. • ET significantly increased in karst areas after vegetation restoration. • Driving factors of ET and T/ET were analyzed in karst areas and non-karst areas. Evapotranspiration (ET) is a vital factor in terrestrial water and energy cycles. Exploring the spatiotemporal variations in ET and transpiration (T) can improve our understanding of the role of vegetation restoration in the context of climate change. Karst ecosystems are particularly sensitive and vulnerable to environmental change. In this study, we investigated the spatiotemporal changes of ET, T, and the transpiration fraction (T/ET) in the Longjiang River Basin (LRB) of southwest China from 1987 to 2018 using the variable infiltration capacity (VIC) model. In karst areas, the original third soil layer in the VIC model was modified to an epikarst zone and a reservoir module was integrated with the model. Model validation and evaluation showed that the modified VIC model performed well in fitting the observations of runoff and ET. During the 32-year study period, ET, T, and T/ET increased by 2.30 mm·yr−1, 2.21 mm·yr−1, and 0.0006, respectively, with the significant increase concentrated in areas with increased forestland. High positive correlations between NDVI and ET, T, and T/ET were observed in areas where forestland and grassland increased. Temperature and wind speed were positively correlated with ET, T, and T/ET in areas with low altitude and abundant precipitation, where large areas of cropland are present. There was a positive correlation between precipitation and ET in karst areas, whereas the negative correlation between precipitation and T was mainly occurred in non-karst areas. The scenario analysis based on different land use data revealed that ET and T/ET exhibited significant differences in karst areas, but not in non-karst areas, indicating that karst areas were more affected by ecological restoration. Moreover, T did not show a significant increase after vegetation restoration, suggesting that increased ET was mainly caused by evaporation. This study provides insights into the effects of vegetation restoration and climate change on ET, T, and T/ET under different geological conditions and can help implement appropriate afforestation strategies in different geological settings. [ABSTRACT FROM AUTHOR]

• Subsurface runoff dominates the runoff components in karst hillslope. • Thinner soils decrease surface runoff and increase subsurface runoff. • Bedrock topography controlled subsurface runoff generation in the thinner soils. • Thinner soils had a higher contribution of new water than that in the thick soils. Hydrological processes in the critical zone are closely related to the soil–bedrock structures. However, the effect of soil thickness on the rainfall-runoff relationship on the hillslope with complex topography remains unclear. Surface runoff, lateral subsurface runoff from soil–epikarst interface, and epikarst runoff from the epikarst–bedrock interface were monitored on two adjacent plots with deep and shallow (66.0 vs. 35.4 cm) soil thicknesses from June 2019 to December 2020 in the karst region of southwest China. During the monitoring period, surface and subsurface runoff account for 20% and 37% of the total runoff in the deep-soil plot (DSP), and 3% and 43% in the shallow-soil plot (SSP). This demonstrates that runoff from the soil-epikarst system is predominant compared to the relatively small contribution of surface runoff. In the SSP, the surface topography wetness index (TWI) was highly coupled with bedrock TWI , and the bedrock TWI had a significant negative linear relationship (p < 0.01) with subsurface runoff. Moreover, isotope hydrogen-separation results showed that subsurface and epikarst runoff were dominated by pre-event water, but a higher contribution of event water was observed in the SSP than in the DSP. These findings supported the hypothesis that rainwater could infiltrate the epikarst more easily in shallow soil slopes. Rainfall and surface runoff exhibited a linear relationship in the dry season and a non-linear relationship in the rainy season, indicating the occurrence of threshold rainfall–runoff behavior. The rainfall amount threshold for surface runoff was higher in DSP (44.7 mm) than in SSP (39.5 mm), and the corresponding variation of rainfall intensity interpretation was greater (54% vs. 38%). For subsurface runoff, the rainfall amount threshold was higher in the DSP than in the SSP (91.0 vs 79.4 mm), and the corresponding variation of soil moisture interpretation was higher (56% vs. 20%). This demonstrated that runoff can be better predicted at deeper soil hillslopes by rainfall and antecedent soil moisture. Accordingly, this study emphasizes the importance of evaluating the spatial heterogeneity of soil thickness in hydrological process research. [ABSTRACT FROM AUTHOR]

• SR, SSR, and ESR coefficients were 2.2%, 3.8%, and 31.2%, respectively. • Epikarst zone exerted a critical role in partitioning, storage and release of water. • Soil depth was positively related to SR. • Rainfall depth thresholds for SR and SSR generation were 36 ± 2 mm and 43 ± 7 mm, respectively. Water balance characteristics and rainfall-runoff relationships of karst slope, are poorly understood worldwide, even though karst landscapes occupy 10–15% the planet's land surface. Dynamic hydrological responses were monitored for 43 rainfall events on a karst slope in southwest China over two years (2018–2019). The responses included surface, subsurface, and epikarst seepage runoff (abbreviated as SR, SSR, and ESR, respectively) and soil water content at different depths (10 cm, 30 cm, and the soil-epikarst interface) in twelve plots (5 m × 20 m , total 1200 m 2 ). Results showed that: (1) The hillslope-scale SR, SSR, and ESR coefficients were 2.2% (0.4%–5.2%), 3.8% (0.2%–12.4%), and 31.2% (0.6%–89.1), respectively. SR and SSR were relatively rare and of short duration, while ESR was a crucial component of the karst hillslope water balance and its duration was longer, demonstrating the critical role of epikarst zone in regulating flow functions such as water storage and release; (2) Soil depth exerted the greatest direct effect on SR, which increased as soil deepened. Factors controlling the rainfall-SSR response were difficult to identify. They require other geophysical exploration methods; (3) Threshold-like runoff responses to rainfall inputs were observed on karst slope, and the rainfall depth (P) runoff initiation thresholds for SR and SSR were 36 ± 2 mm and 43 ± 7 mm, respectively. The strength of the threshold-like input–output relationships was slightly greater when the P + ASI (antecedent soil water content index) was used as the hydrological input variable rather than without consideration of ASI. The differing shapes of nonlinear hydrological behaviours, such as the 'hockey stick', 'heaviside' function, or the sigmoid function were detected in karst slope. This suggests karst hydrological system complexity. Threshold values should be determined according to the shapes of nonlinear hydrological behaviours. These results extend the understanding of karst hydrological processes. [ABSTRACT FROM AUTHOR]

Vegetation restoration is an eco-friendly strategy for countering land degradation and biodiversity loss. Since 2000-2001, large-scale restoration projects have been performed in Southwest China, with the net primary productivity (NPP) increasing over the past two decades. However, negative ecohydrological impacts, including streamflow decline and soil moisture deficit, have been reported following afforestation. Current understanding of the permissible NPP capacity (NPP cap ) and NPP potential (NPP pot ) under karst and non-karst areas or planted and natural vegetations constrained by environmental factors remains unclear. Here multiple environmental drivers characterizing the heterogeneous landscape in the Xijiang River Basin (Southwest China) were employed to predict the NPP cap using a random forest model. Results showed that 85% of the area exhibited an increasing trend in NPP cap during 2001-2018. Overall, 3.50% of the area has exceeded the NPP cap , implying an excessive plantation and potential water deficit in these areas. Excluding agriculture activities, urban areas, and water bodies, we found there is room for an average extra 22.85% of NPP enhancement. The NPP pot was spatially imbalanced, with high NPP pot located in the northeast, indicating these areas as a target area for future vegetation restoration. Moreover, the NPP pot reduction in karst areas (1.12 g C m -2 a -1 ) was more pronounced than in non-karst areas (0.26 g C m -2 a -1 ), highlighting a stronger negative impact on NPP pot in karst areas. Furthermore, significant NPP pot differences were found between planted vegetation and natural vegetation for both karst and non-karst areas. According to the findings, we identified four separate restoration sub-zones and proposed tailored strategies to guide the implementation of future restoration efforts. Our study highlights restoration potential and where land is available for reforestation but also the urgent need for future restoration activities towards ecosystem sustainability., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

In an experiment with alternating dry and wet conditions of soil in cultivated land, orchards and forest lands with limestone and dolomite in karst peak depression, combined with digital image processing technology, we investigated the development law of soil surface cracks under alternating dry and wet condition. The results showed that with the alternation of wet and dry, the average width of cracks decreased at a fast-slow-slower rate, with an order of limestone > dolomite under the same land use, and orchard > cultivated land > forest soil under the same soil-forming parent rock. In the first four dry and wet alternations, the degrees of soil fragmentation and connectivity were higher in dolomite development than in limestone, with significant differences in fracture development rose diagrams. In the subsequent cycles, soil fragmentation of most samples increased, the difference dominated by parent rock gradually decreased, the crack development rose diagram converged, and the connectivity showed the pattern of forest land > orchard > cultivated land. After the fourth cycle, the alternations of dry and wet seriously damaged soil structure. The physical and chemical properties of capillary porosity and non-capillary tube porosity were dominant in the development of cracks before that, but it was more dependent on the organic matter content and the sand composition after that.

We selected a typical dolomite slope and set up three micro-plots (projection length was 2 m, width was 1.2 m) on the upper, middle, and lower slopes to analyze the variations of soil losses and the key influencing factors during two hydrological years (2020-2021). The results showed that soil losses at different slope positions on dolomite slopes followed an order of semi-alfisol in lower slopes (386 g·m -2 ·a -1 ) > inceptisol in middle slopes (77 g·m -2 ·a -1 ) > entisol in upper slopes (48 g·m -2 ·a -1 ). Downward along the slope, the positive correlation gradually increased between soil losses and surface soil water content, as well as rainfall, while it gradually decreased with the maximum 30 min rainfall intensity. The meteorological factors affecting soil erosion on the upper, middle and lower slopes were the maximum 30 min rainfall intensity, precipitation, average rainfall intensity and surface soil water content, respectively. Soil erosion processes on upper slopes were mainly driven by raindrop splash erosion and infiltration-excess runoff, while that on lower slopes were mainly driven by saturation-excess runoff. The volume ratio of fine soil in the soil profile was the key factor of soil losses on dolomite slopes, with an explanation rate of 93.7%. The lower slope was the key site of soil erosion in the dolomite slopes. Subsequent rock desertification management should be based on the erosion mechanism of different slope positions, while control measures should be arranged according to local conditions.

Background: Soil carbon management at landscape scale requires reliable information on the spatial distribution of soil organic carbon (SOC). However, how to improve the accuracy of spatial prediction is not well addressed in the karst region of southwestern China. This study evaluates the performance of univariate kriging (ordinary kriging (OK)) and hybrid kriging (co-kriging (CK), regression kriging (RK) and residual maximum likelihood (REML)) in mapping the spatial distribution of SOC at a depth of 0-15 cm. Terrain attributes and the normalised difference vegetation index (NDVI) were used as ancillary variables., Results: The distribution of SOC was significantly related to NDVI and terrain attributes. Furthermore, geostatistical analyses reflected a moderately structured spatial correlation of SOC. Regression analyses identified the NDVI and slope as the best predictors for describing the spatial pattern of SOC. Combined with NDVI and slope gradient, REML and RK performed better in increasing map prediction accuracy and decreasing the soothing effect of kriging., Conclusion: The spatial pattern of SOC was controlled by topography and cultivation activity. The predictive abilities of OK and CK were limited. Combined with the auxiliary variables, REML and RK can improve the prediction accuracy. This study is beneficial for the further research of precise SOC management in the typical karst landscape., (Copyright © 2012 Society of Chemical Industry.)

Remote sensing of local environmental conditions is not accessible if substrates are covered with vegetation. This study explored the relationship between vegetation spectra and karst eco-geo-environmental conditions. Hyperspectral remote sensing techniques showed that there were significant differences between spectral features of vegetation mainly distributed in karst and non-karst regions, and combination of 1,300- to 2,500-nm reflectance and 400- to 680-nm first-derivative spectra could delineate karst and non-karst vegetation groups. Canonical correspondence analysis (CCA) successfully assessed to what extent the variation of vegetation spectral features can be explained by associated eco-geo-environmental variables, and it was found that soil moisture and calcium carbonate contents had the most significant effects on vegetation spectral features in karst region. Our study indicates that vegetation spectra is tightly linked to eco-geo-environmental conditions and CCA is an effective means of studying the relationship between vegetation spectral features and eco-geo-environmental variables. Employing a combination of spectral and spatial analysis, it is anticipated that hyperspectral imagery can be used in interpreting or mapping eco-geo-environmental conditions covered with vegetation in karst region.