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The southwestern region of China is the largest exposed karst area in the world and serves as an important ecological security barrier for the upstream of Yangtze River and Pearl River. Different from the critical zone of non-karst areas, the epikarst, formed by an interwoven network of denudation pores, is the core area of karst critical zone. Water is the most active component that participates in internal material cycle and energy flow within the critical zone. We reviewed relevant research conducted in the southwestern region from three aspects: the characterization of critical zone structure, the hydrological processes of soil-epikarst system, and their model simulations. We further proposed potential research hotpots. The main approach involved multi-scale and multi-method integrated observations, as well as interdisciplinary collaboration. Precisely characterizing the eco-hydrological processes of the vegetation-soil-epikarst coupling system was a new trend in the future research. This review would provide scientific reference for further studies on hydrological processes in critical zones and regional hydrological water resource management in karst areas. [ABSTRACT FROM AUTHOR]

In order to solve the problem of low tear strength of wool worsted plain weave fabrics, the effects of fabric tightness, yarn breaking strength, yarn breaking elongation, yarn twist coefficient and finishing process on the tear strength index were analyzed and studied through 14 groups of comparative experiments. The results show that the breaking strength of the yarn in the stress triangle, the frictional resistance between the transverse and longitudinal yarns, and the stretchability of the stressed yarn are the fundamental factors that affect the tear strength of the fabric. The warp and weft tightness of wool worsted plain weave fabric are about 46% and 40% respectively, and the yarn breaking strength is not less than 170 cN and the breaking elongation is not less than 18% or the breaking strength is not less than 160 cN and the breaking elongation is not less than 40%, which can ensure that the tearing strength index of the fabric· can meet the requirements of GB/T 3917.2-2009. [ABSTRACT FROM AUTHOR]

Well Qing-92 is a sidetracked well with diameter of 139.7 mm in Zhongyuan Oilfield. During the drilling process, difficulties were encountered, such as large displacement, long openhole section, hard trajectory control, difficult drilling fluid property adjustment, difficult completion logging and cementing operation, etc. Through optimizing large displacement sidetracking profile, enhancing trajectory control, bit selection, promptly adjusting drilling fluid property, and decently preparing completion logging and cementing operation, the well drilling favorable conditions are guaranteed. The successful drilling of the well plays a referencing role to similar type of well drilling in the future. [ABSTRACT FROM AUTHOR]

Copyright of Tropical Geography is the property of Tropical Geography Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Mountain Research (10082786) is the property of Mountain Research Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Environmental Science & Technology (10036504) is the property of Editorial Board of Environmental Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Irrigation & Drainage is the property of Journal of Irrigation & Drainage Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Natural Gas Industry is the property of Natural Gas Industry Journal Agency and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Carsologica Sinica is the property of Institute of Karst Geology, CAGS and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Carsologica Sinica is the property of Institute of Karst Geology, CAGS and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Natural Gas Industry is the property of Natural Gas Industry Journal Agency and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Hydrogeology & Engineering Geology / Shuiwendizhi Gongchengdizhi is the property of Hydrogeology & Engineering Geology Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Ecological Science is the property of Ecological Science Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Exploring the effectiveness of the pilot project on comprehensive control of rock desertification since its launch by China's government is of great significance for regional sustainable development. Jointly affected by the karst surface-underground geological structure and human activities, the natural ecological environment is fragile in southwest Guangxi, with frequent droughts and floods, severe soil erosion and rock desertification. Consequently, the socio-economic development in this region is relatively lagging behind. With the support of national policies, southwest Guangxi has been comprehensively carrying out projects of controlling rocky desertification, promoting the control of rocky desertification and poverty alleviation in a coordinated manner. According to "Thirteenth Five-Year Plan for Comprehensive Control of Rocky Desertification in Karst Areas of Guangxi Zhuang Autonomous Region", southwest Guangxi is designated as an area for the control of cluster-peak depression, in which comprehensive control of rocky desertification has been carried out in terms of building ecological barriers, protecting biodiversity, and promoting the protection and the comprehensive utilization of water and soil resources. In order to further investigate the effectiveness of controlling rocky desertification in cluster-peak depression of southwest Guangxi, this study the physical exploration. Based on the correction of the data from the borehole, the parameter of geological radar, V, is taken to be 0.060 m•ns -1 which is applicable to the study area. The study results indicate that Biyun lake belongs to the oblique tectonic basin, where leakage points and underground river pipes are mainly developed close to the axis of the Babu compound oblique, along the lithological interface of three sections of greystone and the second section of the mudstone of Jialingjiang Group. The mudstone constitutes a water separating plate of the karst leakage zone. After lake water seeps along the zone, it flows northwest, and is discharged in the end at the outlet of the Babu underground river. In addition, the leakage of Biyun lake is mainly of the karst pipeline type. The karst leakage zone is located at the measuring point of 540 m, with a 40-meter- deep of karst pipeline; therefore, the leakage section is relatively narrow, and it is feasible to plug the leakage by grouting. The drilling test results confirm the reliability of the technical method used in karst areas, which is combined by hydrogeological investigation, tracer test and physical exploration, because this method can well determine the direction of the leakage channel and the location of the leakage zone, and thus providing guidance on the leakage control of lakes or reservoirs in karst areas. [ABSTRACT FROM AUTHOR]

Yunnan is located in the center of the east-Asian karst area, one of the three largest karst areas in the world. Rocky desertification is widespread in the area, which seriously restricts the sustainable development of local social economy. In this study, we summarize the research status and achievements of rocky desertification in Yunnan mainly from three aspects, rocky desertification zoning, governance model and vegetation restoration in rocky desertification areas. The results show that rocky desertification areas in Yunnan are divided into 2 large areas and 5 small ones. After years of exploration, 23 kinds in 4 categories of rocky desertification control models have been formed, and 435 kinds of plant species can be used for ecological restoration in rocky desertification areas, including 376 species of shrubs and 59 species of herbs. Finally, combined with geographical location, climate and altitude, this paper preliminarily summarizes the suitable restoration vegetation, and points out the shortcomings in the studies on the control of rocky desertification, so as to provide an important theoretical reference for the subsequent research on the restoration and control of rocky desertification vegetation. [ABSTRACT FROM AUTHOR]

The karst area in Southwest China is an important region for the implementation of sustainable development strategies in China, as well as an area with extremely fragile ecological environment and concentrated distribution of rocky desertification. As a "National Pilot Zone for Sustainable Development" and "National Pilot Demonstration Zone for the Innovative Sustainable Development Agenda", Gongcheng Yao autonomous county of Guangxi is an important demonstration area for the coordinated development of karst landscape resource conservation and special ecological agriculture. Therefore, exploring the spatiotemporal evolution and the driving mechanism of rocky desertification in this area can provide an important scientific basis for the comprehensive management of rocky desertification, and the protection and restoration of karst ecosystem in China's pilot zones for sustainable development. Based on remote sensing images of Landsat series satellite from 2000, 2005, 2010, 2015, and 2021, this study extracted information on rocky desertification by the interpretation of human-computer interaction, and quantitatively analyzed the spatiotemporal evolution law of rocky desertification in Gongcheng county. Meanwhile, by combining data of carbonate rock and land use, this study revealed the inherent driving mechanisms of geological conditions and land use changes about the evolution of rocky desertification in Gongcheng county. The study results show that the rocky desertification in Gongcheng county experienced three stages: accelerated deterioration from 2000 to 2005, rapid improvement from 2005 to 2015 and slow deterioration from 2015 to 2021. The total area of rocky desertification ranged from 88.96--229.55 km2. From 2000 to 2005, the rocky desertification in Gongcheng county shifted from no rocky desertification to mild and intermediate rock desertification, and reversely, it showed improvement from 2005 to 2021. The rocky desertification presented a spatial pattern of development from north to south in Gongcheng county. Xiling town, Lianhua town and Ping'an town were the main areas where rocky desertification occurred, accounting for 55.47%--61.31% of the total rocky desertification area of the county. In 2005 and 2010, when the rocky desertification was relatively severe, it was mainly at a moderate level in Xiling town, while it was mainly at a mild level in other years. In addition, the rocky desertification of Gongcheng county mainly occurred in the limestone area, accounted for 71.42%--75.85% of the total rocky desertification area of this county. But the rocky desertification area in orchards and shrub land accounted for 35.92%--39.21% and 31.77%--31.86% of the county's total area, respectively. The study results indicate that there exist strong karstification, severe soil erosion/leakage, and insufficient materials and slow rates of soil forming due to the wide distribution of pure limestone in Gongcheng county. Besides, the long-term cultivation of single economic fruit forests such as peaches and plums in orchards has led to a decline in fruit tree quality, and a large number of fruit trees have been cut down in recent years, resulting in an exacerbation of rocky desertification. Therefore, the local authority in Gongcheng county should consider constructing three-dimensional ecological planting model in the karst areas such as Xiling town, Lianhua town and Ping'an town during the comprehensive treatment of rocky desertification, so as to promote the coordinated and sustainable development of ecological industry, rocky desertification control and social economy. [ABSTRACT FROM AUTHOR]

Southwest China is one of the three largest continuous karst clusters in the world; therefore, studies on karst rocky desertification in this area are very important. For more than 20 years' control, the decreasing area and risk of karst rocky desertification has contributed to the continuous ecological improvement. Nowadays, studies on rocky desertification mainly focus on the eight provinces in Southwest China, which have been designated as rocky desertification monitoring areas by the Chinese government. After the first phase of the comprehensive control project for karst rocky desertification in 2016, the expansion trend of rocky desertification in the southwest region was effectively curbed. Subsequent articles published tend to focus on analyzing the current situation, comprehensive management, or species adaptability of rocky desertification monitoring areas. However, the Qinba region in Shaanxi Province is located outside the monitoring area. In the process of studying the karst geological relics of the Zhenba Sanyuan Tiankeng Group, signs of rocky desertification have been found, but there still exists a research gap in the investigation and research on karst rocky desertification in this area which is one of the areas with the richest biodiversity in China, known as "ecological lung", "central water tower" and "biological gene bank". Unfortunately, this area is burdened with poverty, so the investigation and study of karst rocky desertification in the Qinba region of Shaanxi Province is of great significance to ensure green and high-quality development and ecological civilization construction. In this paper, by analyzing the current situation of karst rocky desertification in Southwest China, we summarized its harm to the ecological environment and social economy, clarify natural and human factors resulting in rocky desertification, and integrate the typical treatment experience in Southwest China. We also introduce three technical methods, including remote sensing interpretation, UAV remote sensing survey and analysis of carbonate dissolution rate, to provide a scientific basis for studies on karst rocky desertification in the Qinba region of Shaanxi Province. Study results show that the area of karst rocky desertification in the Qinba region covers 63.37 km², and the areas of severe, moderate and mild rocky desertification cover 17.97 km², 21.60 km² and 23.80 km², respectively. Based on the survey results, there are both regional differences and some similarities in distribution patterns in the areas of rocky desertification development. Specifically, the degree of rocky desertification in the limestone area is more severe than that in the dolomite area. It is also more severe in the area with developed water system than that in the arid and semi-arid area, and the more active the new structure is, the more severe the rocky desertification is. Compared to the Southwest China, the degree of karst rocky desertification in the Qinba region of Shaanxi Province is relatively light, with a smaller distribution area, mainly due to the less rainfall in the study area. The karst rocky desertification in Beiyang mountain of Zhen'an county is the most severe, with an area of 7.28 km². In the 1960s, a large-scale free-range of livestock severely damaged vegetation. The indiscriminate deforestation by humans further exacerbated the process of rocky desertification. The rocky desertification in Hailuogong village of Shanyang county is also severe, covering an area of 5.83 km², because the landform in this area is a typical peak-cluster depression, which is likely developed into rocky desertification. The contradiction between people and land needs to be solved urgently. In conclusion, more monitoring and research efforts are needed in Beiyang mountain and Hailuogong where the rocky desertification is severe. Firstly, we should clarify the causes of rocky desertification in the Qinba region and compare them with the causes in Southwest China to determine whether the rocky desertification is mainly resulted from natural factors or human factors. Secondly, we should know how to clarify the causes of karst rocky desertification in the Qinba region; for example, we can dynamically monitor the change of rock desertification by field verification, remote sensing interpretation, climate change analysis, etc. We can also calculate the contribution rate of each influence factor by geographical detector model. Thirdly, we should further study influence factors of karst dissolution rate. We can monitor physical and chemical properties of soil (soil moisture, carbon dioxide concentration, pH, organic matter content and porosity) in areas with moderate to severe rocky desertification, and analyze the relationship between dissolution rate and physical and chemical properties of soil in rocky desertification areas. Finally, in order to provide basic data for carbon neutrality research in Shaanxi, we should conduct studies on the carbon sink of rocky desertification areas in the Qinba region, with the methods such as dissolution test pieces and hydrochemical runoff. [ABSTRACT FROM AUTHOR]

If the tunnel construction work is done in the karst area, the tunnel shall keep a certain distance from the karst cave to ensure the stability of the surrounding rock and support. If the distance between the tunnel and the filled karst cave with high water pressure is short, it is easy to cause the instability and damage of tunnel face or the circumferential surrounding rock, thus resulting in karst water inrush, mud inrush, collapse and other disasters. Especially, the karst cave concealing around the tunnel is often difficult to be accurately predicted. Therefore, the study of the critical safety distance between the karst cave and the tunnel plays a vital role in the evaluation and prevention of disasters caused by concealing filled karst cave. Studies on the critical safety distance between tunnel and karst cave can be divided into qualitative research, semi-quantitative research and quantitative research. Qualitative research, such as judging the influence degree of karst cave on tunnel through numerical analysis, is generally conducted to comprehensively analyze the factors affecting the stability of structure for water burst prevention and obtain the empirical critical safety value. Semi-quantitative research mainly focuses on theoretical calculation, which can be roughly sub-divided into three types: simplified beam slab model based on strength theory, catastrophe theory model and the model of crack tension-compression shear based on fracture mechanics. Mainly focusing on numerical simulation, quantitative research is conducted to set up multiple groups of numerical tests for calculation, and to obtain the calculation model of safety distance through linear regression. The safety distance between the tunnel and the filled karst cave can be explored by theoretical calculation and numerical simulation test. Based on the bending and shear strength theory, the mechanical calculation models of the filled karst cave at the top, bottom and side of the tunnel are established by using the fixed beam model at both ends. Meanwhile, the self-weight of the internal filler and the pore water pressure are taken into account. Given the influence of the surrounding rock pressure above the karst cave on the waterproof rock stratum, the critical safety distance between the tunnel and the karst cave can be explored, and the calculation formula of the distance in different circumferential positions can be deduced. However, this formula does not consider the excavation effect of the tunnel and the process of support, nor can it reflect the changes of the displacement, stress and plastic zone of the surrounding rock. Therefore, it is difficult to obtain a universal formula to express relationship. It is necessary to supplement the predicted safety distance with the help of numerical simulation. In this study, the numerical model of the critical safety distance between the filled karst cave and the tunnel at different circumferential positions was established by FLAC 3D software. Based on the method of orthogonal experimental design (a total of 48 numerical test schemes), the stability of surrounding rock has been evaluated by the distribution range of plastic zone of surrounding rock caused by tunnel excavation. If the plastic zone connects the tunnel with the karst cave, the distance between these two indicates that the surrounding rock is unstable, and thereby the critical safety distance can be calculated. The results of critical safety distance under different working conditions were also analyzed by range analysis and variance analysis. Besides, the law and significance of three influencing factors--the level of surrounding rock, the water pressure in karst cave and the karst cave size--on the critical safety distance were explored. Through the nonlinear multiple regression analysis of the orthogonal test results, the prediction formula of the critical safety distance between the filled karst cave and the tunnel at different circumferential positions was established respectively. The results show that the critical safety distance increases with the increase of surrounding rock level, pressure of karst cave water and the karst cave size. The comprehensive influence degree of the three factors can be ranked from the strongest to the weakest as follows: the surrounding rock level, the pressure of karst cave water and karst cave size. Finally, the research results were applied to Yangzong tunnel project to verify the rationality and applicability of the prediction model of critical safety distance. The results show that the safety distance predicted based on the strength theory is relatively conservative, and the predicted results based on the numerical test are close to the reserved distance. The predicted results have a certain reference for the project of karst tunnel with water abundance. [ABSTRACT FROM AUTHOR]

Copyright of Arid Zone Research / Ganhanqu Yanjiu is the property of Arid Zone Research Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Carsologica Sinica is the property of Institute of Karst Geology, CAGS and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Carsologica Sinica is the property of Institute of Karst Geology, CAGS and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Carsologica Sinica is the property of Institute of Karst Geology, CAGS and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Arid Land Geography is the property of Chinese Academy of Sciences, Xinjiang Institute of Ecology & Geography and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In order to solve problems with conventional in-house fracturing fluid friction test device, such as small size, low pipe flow velocity, and large difference from the real flow situation on site, we use a large-scale field experimental simulation method and the fracturing pump truck as the power source to realize the friction resistance test of fracturing fluid under ultra-high-speed flow, and test a total of 16 groups of fracturing fluid samples. The results show that the friction properties of fracturing fluids prepared with different kinds of polymers are obviously different. The drag reduction rate of low-viscosity fracturing fluid and medium viscosity fracturing fluid show 4 kinds of trend with the increase of flow rate: decreasing linearly, increasing linearly, increasing first and then decreasing, and decreasing first and then increasing. The experimental device adopts a pipeline system with multiple pipe diameters and lengths, and the experimental flow rate can reach up to 100 m/s. It is currently the highest flow rate fracturing fluid flow testing experimental device known in China, which can meet the experimental requirements of future on-site large displacement construction. The experimental results have important guiding significance for the field application of fracturing fluid. [ABSTRACT FROM AUTHOR]

Copyright of Carsologica Sinica is the property of Institute of Karst Geology, CAGS and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Carsologica Sinica is the property of Institute of Karst Geology, CAGS and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Oil Drilling & Production Technology / Shiyou Zuancai Gongyi is the property of Shiyou Zuancai Gongyi Bianjibu and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Carsologica Sinica is the property of Institute of Karst Geology, CAGS and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Carsologica Sinica is the property of Institute of Karst Geology, CAGS and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Guizhou Province is located in the largest continuous karst area in the world. The karst landform accounts for 73.8% of the province's land area where 88% of its rural population live. The exposed area of carbonate rocks developed in karst reaches 130,000 km2, accounting for 73% of land area in this province. Soil erosion leads to the exposure of carbonate rocks on the surface, aggravates the process of karst rocky desertification, and causes a series of ecological and environmental problems, all of which seriously affect the development of local economy and people's life. The research on the comprehensive prevention and control of karst rocky desertification has become a scientific problem that needs to be solved urgently. In addition, bedrock and vegetation play a prominent role in soil development and formation. In different soil development stages, bedrock and vegetation types have an important impact on the soil physical and chemical properties. However, the current research on karst soils mainly focuses on the soil properties of limestone-formed soils. There is still a lack of research on the characteristics of soil developed by carbonate rock and the effects of their interactions on soil in karst areas from the perspective of vegetation-soil-bedrock system. Taking the soil developed by carbonate rock (limestone, calcareous dolomite and dolomite) as the research object, this study aims to explore the distribution characteristics and influencing factors of the soil developed by carbonate rock under different vegetation conditions in karst areas, and analyze the effects of different vegetation types, bedrock types and soil layers on soil properties. The study area is located in Huaxi district, Guiyang City, Guizhou Province. It has a subtropical monsoon climate with an average annual temperature of 14.9 °C and an average annual precipitation of 1,229 mm. Three representative plots in Huaxi district were selected, including Huaxi Reservoir, Huaxi TV Tower, and the area near the southern Guizhou University, and a total of 60 soil samples were collected from these three sample plots of different carbonate rock types. The main tree species in the study area are Cupressus funebris, Quercus, and Myrsine Africana, and grass species are Stipa bungeana and Cynodon dactylon. The soil physicochemical properties were determined by potentiometric method, Kjeldahl method, alkaline hydrolysis diffusion method, molybdenum antimony anti-colorimetric method (sodium bicarbonate extraction), and potassium dichromate oxidation with an external heating method. The particle size distribution of soil was determined by the hydrometer method. In SPSS24 software, Shapiro-Wilk test was used to test the normality of the data. Mann-Whitney U test and Kruskal-Wallis H test (multiple comparison, Bonferroni method) were used to test the difference of soil properties with different sampling depths, vegetation types and bedrock types. Scheirer-Ray-Hare test was used to determine whether vegetation type, bedrock type, soil layer, and their interactions had a significant effect on soil particles and fertility. Permutation multivariate analysis of variance (PERMANOVA) was used to analyze whether there were significant differences between two or three groups of data. Non-metric multi-dimensional (NMDS) was used to analyze the particle and fertility indexes of the soil developed by different bedrock types in the 0-20 and 20-40 cm soil layers. Redundancy analysis (RDA) was used to analyze the effects of vegetation type, bedrock type, and soil layer on changes in soil properties. These analyses were performed in the R version 4.0.3. The bedrock and vegetation types are the main factors affecting the development of carbonate rocks into soil, followed by soil layers. In 0-20 and 20-40 cm soil layers, the fertility and particles of the soil developed by limestone, limy dolomite and dolomite are significantly different. However, between the 0-20 and 20-40 cm soil layers, there is no significant difference in the nature of the soil developed from the same bedrock except the differences between gravel content (SLC) and fine particle ratio (<0.002 mm) of limestone-developed soil and the differences between available phosphorus (AP) and organic matter (SOM) content of dolomite-developed soil. In the 0-40 cm soil layer, the bedrock type significantly affects the distribution of soil pH, AP, SLC, AN, total nitrogen (TN), SOM, and 0.2-0.25 mm and 0.002-0.02 mm particles. Vegetation type significantly affects the pH value, AP, TN content of limestone-developed soil, pH, SLC, coarse particles (0.25-2 mm) and fine particles of dolomite-developed soil, and available nitrogen (AN), SOM, coarse and fine particles of soil developed by limestone dolomite. The soil layer significantly affects the distribution of SLC, coarse and fine particles in limestone-developed soil and AP in dolomite-developed soil. At present, the soil under the abandoned grassland slope and grass cover and the limestone-developed soil in the study area are likely being damaged by erosion. Therefore, according to the lithology of the parent rock, moderately changing the planting structure of vegetation on soil has a positive effect on improving soil nutrients and soil particle composition, and enhancing soil erosion resistance. Besides, the interaction of bedrock-vegetation-soil system and human activities should be comprehensively considered in the prevention and control of soil erosion in karst areas. [ABSTRACT FROM AUTHOR]

In this study, papers related to vegetation restoration and soil in rocky desertification area since 1990s have been retrieved. Based on nutrient grading standards of two national soil censuses, the soil nutrient improvement and soil stoichiometry characteristics have been explored, which can provide theoretical foundation for the ecological restoration effect and model screening of rocky desertification. Results are shown as follows, (1) The mean values of total organic carbon (TOC) and total nitrogen (TN) in the forest soil of rocky desertification areas of Southwest China are higher than those of Grade I of two national soil censuses. Total phosphorus (TP) falls into Grade II, with obvious soil nutrient improvement, while the total potassium (TK) concentration falls into the Grade V of the low potassium area. (2) According to the soil censuses, TOC and TN rank top among the five provinces/regions/cities, and TP and TK fall into Grade II and Grade IV, respectively in Guangxi Zhuang Autonomous Region, which can show the most significant increase in soil nutrient concentration. In Guizhou Province, TOC and TN are higher than those of grade I by 34% and 37%, respectively, and TP falls into Grade II and TK Grade V, reflecting obvious nutrient improvement of forest soil in rocky desertification areas of this province. In Yunnan Province, TOC and TP are higher than those of Grade I by 9% and 21% respectively. TN falls into Grade II and TK Grade V. These indexes show that soil nutrients has been improved to different degrees. TOC in Chongqing City is higher than that of Grade I by 1.75%. Both TN and TP fall into Grade II. TK, ranking top among the five provinces/regions/cities, falls into Grade IV, showing less improvement compared with that of the other three provinces. In Hunan Province, TOC, TN, TP and TK fall into Grades II, II, V, and V respectively, suggesting that Hunan Province should focus on controlling rocky desertification. (3) Indicators of TOC and TN in the soil of rocky desertification areas in Southwest China are positively correlated, and the growth of vegetation is limited by potassium. TOC, TN and TP are stored quickly in Guangxi with significant soil improvement. The soil carbon sequestration capacity of Guizhou Province is higher than that of national average. In rocky desertification areas of Yunnan Province, low TK has posed a bad effect on vegetation growth. The high concentration of TK in Chongqing is not related to TOC, TN, and TP, but nitrogen limits the growth of plants. Phosphorus and potassium elements should be supplemented in growing vegetation in Hunan Province. In conclusion, potassium should be supplemented in growing pants in rocky desertification areas of Southwest China. In addition, phosphorus and nitrogen should be supplemented in Hunan Province and Chongqing City. To strengthen the ecological management of rocky desertification and bring the management into full play, Yunnan, Hunan and Chongqing should learn the experience of ecological restoration from Guangxi. [ABSTRACT FROM AUTHOR]

Vegetation plays an important role in the flow of material energy and nutrient cycle in the ecosystem. Karst vegetation is one of the main factors to maintain the stability of karst ecosystem function. At the same time, as a medium connecting soil, atmosphere and rock, plants not only present the characteristics of water balance in hydrologic and ecological processes, but also are an important link in regional vegetation restoration which is the basis of ecological construction and rocky desertification control in karst areas. In order to comprehensively understand the research progress, development trend and hot issues of karst vegetation restoration at home and abroad, literature related to this topic from 1985 to 2021 was retrieved from the Web of Science Core Collection Database (WoS) and China National Knowledge Infrastructure (CNKI) in this study. Based on high-frequency keyword analysis, keyword co-occurrence and cluster analysis, time evolution analysis of research subject, etc., the focuses and trends of karst vegetation restoration were analyzed. The results show that 319 and 351 related articles were collected respectively in WoS and CNKI databases from 1985 to 2021, and the number of articles published in 37 years experienced an increase with fluctuation. The publishing of these articles could be divided into three stages, the first stage (before 2005), an initiation stage of the research, in which the number of articles published was small; the second stage (2005-2015), a stage with a significant increase of literature due to great attention from domestic and foreign scholars to the ecological reconstruction of karst areas; the third stage (2015-2021), a rapid development stage, in which the number of international publications saw a continuous increase, while the domestic number showed a rise with fluctuation, and the growth rate of domestic research is significantly higher than that of international research. Rocky desertification, vegetation succession, soil nutrients and species diversity are high-frequency keywords in the literature, reflecting the common concerns of domestic and foreign research. Among them, vegetation succession law, soil nutrients and species diversity are the core issues in studies on karst rocky desertification areas. International studies on karst vegetation restoration pay more attention to ecosystem services and climate change, while domestic studies mainly focus on vegetation restoration in karst rocky desertification areas in the early stage, and pay more attention to the effects of vegetation restoration on soil properties and plant community composition in the later stage. In recent years, the diverse configuration of karst vegetation restoration technology and mode, for example, Huajiang Mode, Pingshang Mode, Huanjiang Mode, Pingguo Mode, etc. put forward through test, research and development, has become one of the research focuses. In addition, environmental benefits of vegetation restoration (moisture, nutrients, soil and water loss, etc.), soil seed banks, microbe and plant functional groups, vegetation restoration and forestry industry (understory economy and ecological industry), karst plant restoration and karst carbon sink, etc. have gradually become new hot issues in the research field of karst vegetation restoration. In the research of "vegetation restoration", the issues about industrial development such as fruit forest for ecological economy, governance and management modes for ecological economy, etc. have also been taken into account. In recent years, the restoration of karst vegetation (the control of rocky desertification) in China is closely related to the projects of poverty alleviation and elimination, for example, Huajiang Mode --the establishment of comprehensive management of industry for ecological environment in medium-intensity rocky desertification areas in karst plateau canyon, Pingshang Mode--the facilitation of vegetation restoration by planting honeysuckle in the rocky desertification control of Zhenfeng county, Huanjiang Mode characterized with ecological migration, and the Pingguo Mode characterized with the dragon fruit planting in Pingguo county. Due to the slow soil formation rate, thin soil layer and easy soil erosion, the karst area falls into a typical vulnerable ecosystem in the world, and the vegetation restoration in this area is very difficult. Therefore, the vegetation restoration mode is selected for the purpose of improving soil structure and coordinating the balance among soil water, fertilizer, air and heat. In order to promote the development of karst vegetation restoration research, it is suggested to strengthen domestic and international cooperation, and to set up some observation points in the field to observe and compare the dynamics of karst vegetation restoration in different regions for a long time. By comparing the spatio-temporal changes of large scale at home and abroad, the function and significance of vegetation restoration process on ecological restoration in karst areas can be analyzed through monitoring data. Through the restoration technology, model and evaluation method of karst vegetation system, the construction of karst ecosystem and the multi-scale pattern of vegetation diversity from the perspective of life community of mountain, forest, field, lake and grass and the perspective of rural industry can be further revealed. By comparing the research at home and abroad, some new ideas will be provided for ecological restoration in karst areas. [ABSTRACT FROM AUTHOR]

Soil carbon, nitrogen and phosphorus are important factors of soil quality, which play important roles in increasing soil nutrient storage, improving soil fertility and promoting plant growth. A large number of studies have shown that returning cultivated land back to forest and grassland and converting land use patterns will lead to changes in soil nutrient status and stoichiometry. However, systematic studies on total and easy-to-use components of soil carbon, nitrogen, and phosphorus are relatively few in Pingguo karst area of Youjiang River Valley in central Guangxi. In this study, plots of three types of land use (the restored forest and grassland from cultivated land and cultivated land for sugarcane and maize) inside and near Pingguo National Field Observation and Research Station of Karst Ecosystem, Guangxi were taken as research objects, and 0-15 cm surface soil was sampled in March, 2021. The physical and chemical properties of soil, total and easy-to-use components of carbon, nitrogen and phosphorus and their relationships were analysed in order to better understand the effects of returning cultivated land back to forest and grassland and converting land utilization patterns on total and easy-to-use components of carbon, nitrogen and phosphorus of soil in karst areas. The results showed as follows: 1) Compared to cultivated land, the soil pH values of the restored forest and grassland from cultivated land increased significantly. The macro-aggregates of restored forest and grassland (42.82%, 57.11% respectively) were significantly higher than those of cultivated land for sugarcane (16.94%) and maize (5.49%), and their micro-aggregates (4.58%, 1.76% respectively) were significantly lower than those of cultivated land for sugarcane (12.42%) and maize (16.34%). Meanwhile, compared to cultivated land for sugarcane (103.39 mg⋅kg-1, 3.22 mg⋅kg-1) and that for maize (105.02 mg⋅kg-1, 3.07 mg⋅kg-1), available nitrogen of restored forest and grassland significantly increased to 156.55 and 166.49 mg⋅kg-1, respectively, while available phosphorus significantly decreased to 0.41 and 0.30 mg⋅kg-1, respectively. 2) Compared to cultivated land, the organic carbon, microbial biomass carbon and total nitrogen of soil in restored forest and grassland increased significantly. The values of soil organic carbon of restored forest and grassland (34.12 g⋅kg-1, 32.45 g⋅kg-1 respectively) were 1.98 and 1.88 times of cultivated land for sugarcane (17.26 g⋅kg-1), and 2.15 and 2.04 times of cultivated land for maize (15.89 g⋅kg-1), respectively. The values of microbial biomass carbon of soil in restored forest and grassland (985.35 mg⋅kg-1 1,110.04 mg⋅kg-1 respectively) were 2.71 and 3.05 times of cultivated land for sugarcane (364.07 mg⋅kg-1), and 3.14 and 3.54 times of cultivated land for maize (313.92 mg⋅kg-1), respectively. The values of total nitrogen of soil in restored forest and grassland (4.14 g⋅kg-1, 4.10 g⋅kg-1 Respectively) were 2.48 and 2.46 times of cultivated land for sugarcane (1.67 g⋅kg-1), and 2.19 and 2.16 times of cultivated land for maize (1.89 g⋅kg-1), respectively. The total value of phosphorus in restored grassland was the highest (1.04 g⋅kg-1), followed by that of cultivated land for maize (0.81 g⋅kg-1), and the values of dissolved phosphorus of cultivated land for sugarcane and maize were significantly higher than those of restored forest and grassland. The values of stoichiometry of carbon, nitrogen, and phosphorus, OC/TP, TN/TP of soil in restored forest were significantly higher than those of restored grassland and cultivated land, and the values of restored grassland and cultivated land did not show significant difference. 3) Soil bulk density, aggregate structure, pH value, available nitrogen and available phosphorus were significantly correlated with total and easy-to-use components of carbon, nitrogen and phosphorus of soil. Properly speaking, soil pH value, large macro-aggregates, and available nitrogen showed a significantly positive correlation with organic carbon, microbial biomass carbon, total nitrogen and microbial biomass nitrogen of soil, and a significantly negative correlation with dissolved phosphorus. Meanwhile, bulk density, micro-aggregates, and available phosphorus of soil showed a significantly negative correlation with organic carbon, microbial biomass carbon, total nitrogen and microbial biomass nitrogen of soil, and a significantly positive correlation with dissolved phosphorus. The results indicated that the measures of returning cultivated land back to forest and grassland and converting land use patterns significantly improved soil carbon, nitrogen and soil quality in karst areas. These two measures are important and effective ways to control rocky desertification and protect ecological environment in karst areas. [ABSTRACT FROM AUTHOR]

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