Analysis on the Characteristics and Laws of Tunnel Hydraulic Inrush in Karst Area

As highways are extended to deep mountains,high altitudes,and special geological conditions,tunnel construction becomes more and more challenging,especially the construction of tunnels in karst areas.Due to the particularity of the regional geological structure,karst is well developed in the southwest of our country,especially at areas where the problem of tunnel water inrush in karst areas is more prominent.To further ensure the safe construction and operation of tunnels,the characteristics of tunnels in karst areas is analyzed in this article.

Trade-offs and Synergies of Ecosystem Services in Karst Area of China Driven by Grain-for-Green Program

As an important means regulating the relationship between human and natural ecosystem,ecological restoration program plays a key role in restoring ecosystem functions.The Grain-for-Green Program(GFGP,One of the world’s most ambitious ecosystem conservation set-aside programs aims to transfer farmland on steep slopes to forestland or grassland to increase vegetation coverage)has been widely implemented from 1999 to 2015 and exerted significant influence on land use and ecosystem services(ESs).In this study,three ecological models(In VEST,RUSLE,and CASA)were used to accurately calculate the three key types of ESs,water yield(WY),soil conservation(SC),and net primary production(NPP)in Karst area of southwestern China from 1982 to 2015.The impact of GFGP on ESs and trade-offs was analyzed.It provides practical guidance in carrying out ecological regulation in Karst area of China under global climate change.Results showed that ESs and trade-offs had changed dramatically driven by GFGP.In detail,temporally,SC and NPP exhibited an increasing trend,while WY exhibited a decreasing trend.Spatially,SC basically decreased from west to east;NPP basically increased from north to south;WY basically increased from west to east;NPP and SC,SC and WY developed in the direction of trade-offs driven by the GFGP,while NPP and WY developed in the direction of synergy.Therefore,future ecosystem management and restoration policy-making should consider trade-offs of ESs so as to achieve sustainable provision of ESs.

Tradeoffs and synergies between ecosystem services : A comparison of the karst and non-karst area

Under the influence of various natural and human factors, the relationship between the ecosystem services provided for human beings by a karst ecosystem is becoming increasingly complex, profoundly limiting the effective and sustainable development of the social economy and ecosystem protection in karst areas. Taking Guizhou, China as an example, which includes both karst(including five different landforms) and non-karst area, the study explored and compared the tradeoff and synergy between ecosystem services in both terrain types. The results showed higher change rates of water yield and soil retention in karst areas than those in non-karst areas, with only small differences in the carbon storage and crop production change. The ecosystem service relationships in the karst area from 1995 to 2005 were consistent with the relationships in the non-karst area. However, differences were observed in most of these relationships from 2005 to 2015. The relationships between ecosystem services in different karst landforms from 1995 to 2005 remained the same, but there are differences found in the relationships of ecosystem services from 2005 to 2015. The trade-off and synergistic relationships between ecosystem services in the different landforms were closely related to the changes of climate and land use, particularly related to rainfall, rainfall erosivity, farmland, and forestland.

Groundwater resources in karst area in Southern China and sustainable utilization pattern

Occurrence conditions of groundwater in southern karst area are complicated. The water-bearing media in the karst have multiplicity, and the groundwater is hosted in holes, gaps, seams, pipes and caves. The karst water shows heterogeneity where fast and slow flow coexist, and the Darcy and non-Darcy flow coexist, and the liquid flow, the gas flow and solid flow coexist. The evaluation and investigation indicates that the mineable resource of karst groundwater is about 53.44 billion m^3/y, and the current exploitation quantity is merely 6.565 billion m^3/year. The exploitation and utilization potential is gigantic. In the region there are altogether 2 763 karst subterranean rivers with a total length of 12 687 km. The dry season runoff volume equals to 47 billion m^3/year. At present the exploitation is only 10%. Four effective utilization models of karst groundwater resources have been put forward.(1) The karst hills-depression zone formed the surface-underground united reservoir. By digging tunnels, water diversion irrigation and generating electricity, the ecological economy is developed.(2) In the deep-cut peak cluster depression area, by using the high-part Epikarst spring and constructing the regulation and storage water tank, the stereo ecological agriculture is developed.(3) In the karst peak forest plain and hilly-gully area, the pump-type underground regulating reservoir is constructed and the water-saving ecological agriculture is strengthened.(4) In the fault basin region with the surrounding groundwater runoff belting beam backwater, the water resources are jointly controlled to develop a fruit crop base within the basin.

Pool Sizes and Turnover of Soil Organic Carbon of Farmland Soil in Karst Area of Guilin

The three-pool and first-order model separates the mineralizable organic carbon into active,slow,and passive carbon pools.This paper used the model and decomposition curves of the soil organic carbon to fit the active pool and its decomposition rate,slow pool and its decomposition rate.The results showed that the size of the active pool from different profiles accounted for 2.09%-3.08% of the total soil organic carbon and the mean residue time was 3.57-17.21 days.And the size of the slow pool accounted for 3.19%-43.55% and the mean residue time was 1.12-4.94 years.Acid hydrolysis（6M HCl） was used to fractionate the passive organic carbon,which accounted for 50.83%-94.44% of the total soil organic carbon.

Study on Ecological Footprints and Sustainable Development in Karst Area——Taking Anshun as an example

[ Objective] The aim was to study the ecological footprint and sustainable development in Karst Area. [ Method] By dint of statistical da- ta of Anshun City in 2008, the ecological footprint of Anshun City was calculated. The sustainable development of ecological system in Anshun City was analyzed from the angle of balance of supply and demand. [ Result] The per capita ecological capacity was 0.447 8 hm2/cap in 2008, per capi- ta ecological footprint was 2.309 0 hm2/cap, and ecological surplus of deficit was 1.861 2 hm2/cap. It meant the EF of the present region in terms of human activities had already exceeded the benchmark of system ecological carrying capacity. The supply of natural resources can＇t fully meet people＇s needs, and land use was unsustainable. The sustainable development of Karst area can be realized through changing people＇s production and life consumption model, building resources-saving social productive consumption system, depending scientific and technological development, improving production technology, using new technology, improving resources utilization effect and developing recycle economy. [Condusion] The study provided theoretical basis for sustainable development in Karst area.

Spatio-temporal Dynamic Simulation of Urban Land Use in Karst Areas Based on CLUE-S Model——A Case Study of Dahua Yao Nationality Autonomous County in Guangxi Zhuang Autonomous Region

This article uses TM images in 1999 and 2006 in Dahua County,selects the driving factors having great impact on urban land use change,and conducts data processing using GIS software.It then uses CLUE-S model to simulate land use change pattern in 2006,and uses land use map in 2006 to test the simulation results.The results show that the simulation achieves good effect,indicating that we can use CLUE-S model to simulate the future urban land use change in karst areas,to provide scientific decision-making support for sustainable development of land use.

Temperature Changes in Typical Karst Area of Guangxi to Global Warming during 1971- 2013

The spatial and temporal variation characteristics of temperature were analyzed by using climate tendency coefficient, climatic inclination rate and Mann-Kendall catastrophe test,based on the annual and seasonal average temperatures of 28 meteorological stations in Guangxi from 1971 to 2013. Under the global warming,the annual and seasonal average temperatures in typical karst area of Guangxi had an increasing trend. The cli- mate inclination rate of annual average temperature reached a significant level, which was about 0.17 ℃/10 a, and the year of abrupt changes ap- peared in 1996. About seasonal temperature＇s trend, average temperatures of all the four seasons had an increase trend in the past 43 years, and the significant increase was happened in autumn with the temperature increase rate of 0.28 ℃/10 a, followed by increase rate of average tempera- ture in winter with 0.25 ℃/10 a. A long-term warming tendency was observed by seasonal average temperature from 1971 to 2013, especially dur- ing 2002 - 2013.

Analysis of Temporal and Spatial Changes of Cultivated Land in Karst Areas of Southwest Guangxi Based on Landscape Pattern Indices

Affected by topographical conditions,the distribution of cultivated land in karst areas is relatively fragmented.More effective cultivated land protection measures can be taken in a targeted manner by grasping the spatial and temporal distribution characteristics of regional cultivated land.In this study,with the cultivated land of four county-level administrative regions(Debao County,Jingxi City,Daxin County,and Tiancheng County)in typical karst landform areas in southwestern Guangxi as the research object,combining with the spatial analysis function of the GIS software platform,the spatial distribution characteristics and temporal and spatial changes of cultivated land in the study area were investigated from 2009 to 2020 using the quantitative analysis method of landscape pattern indices,revealing the main problems of cultivated land utilization,and the multi-dimensional management ideas of cultivated land protection in karst areas under the background of rural revitalization strategy were proposed.

Stable carbon isotopic composition of soil organic matter in the karst areas of Southwest China

This study dealt with the distribution characteristics of soil organic carbon (SOC) and the variation of stable carbon isotopic composition (δ13C values) with depth in six soil profiles, including two soil types and three vegetation forms in the karst areas of Southwest China. The δ13C values of plant-dominant species, leaf litter and soils were measured using the sealed-tube high-temperature combustion method. Soil organic carbon contents of the limestone soil profiles are all above 11.4 g/kg, with the highest value of 71.1 g/kg in the surface soil. However, the contents vary between 2.9 g/kg and 46.0 g/kg in three yellow soil profiles. The difference between the maximum and minimum δ13C values of soil organic matter (SOM) changes from 2.2‰ to 2.9‰ for the three yellow soil profiles. But it changes from 0.8‰ to 1.6‰ for the limestone soil profiles. The contrast research indicated that there existed significant difference in vertical patterns of organic carbon and δ13C values of SOM between yellow soil and limestone soil. This difference may reflect site-specific factors, such as soil type, vegetation form, soil pH value, and clay content, etc., which control the contents of different organic components comprising SOM and soil carbon turnover rates in the profiles. The vertical variation patterns of stable carbon isotope in SOM have a distinct regional character in the karst areas.

Characteristics and distributions of humic acids in two soil profiles of the southwest China Karst area

Characteristics and distributions of humic acid(HA) and soil organic matter(SOM) in a yellow soil profile and a limestone soil profile of the southwest China Karst area were systematically investigated to reveal their evolutions in different soils of the study area. The results showed that characteristics and distribution of SOM along the two soil profiles were notably different. Total organic carbon(TOC) contents of soil samples decreased just slightly along the limestone soil profile but sharply along the yellow soil profile. TOCs of the limestone soils were significantly higher than those of the corresponding yellow soils, and C/N ratios of SOMs showed a similar variation trend to that of TOCs, indicating that SOM can be better conserved in the limestone soil than in the yellow soil. The soil humic acids were exhaustively extracted and further fractionated according to their apparent molecular weights using ultrafiltration techniques to explore underlying conservation mechanisms. The result showed that C/N ratios of HAs from different limestone soil layers were relatively stable and that large molecular HA fractions predominated the bulk HA of the top soil, indicating that HA in the limestone profile was protected while bio and chemical degradations were retarded. Combined with organic elements contents and mineral contents of two soils, weconcluded that high calcium contents in limestone soils may play a key role in SOM conservation by forming complexation compounds with HAs or/and enclosing SOMs with hypergene CaCO_3 precipitation.

APPROACH OF DETERMINISTIC GEOMORPH OLOGIC INSTANTANEOUS UNIT HYDROGRAPH TO HYDROLOGICAL PROCESSES' SIMULATION IN KARST AREA

In order to analyze the condition of s pecial landform and regularity of sp ecial hydrological movement in karst area,the method of Geomorphologic Instantaneous Unit Hydrograph(GIUH)has been used to divide the river net-works into three grades in the research area and the karst hydrologic processes were simulated with Nash insta ntaneous u-nit hydrograph(NIUH).The combination of the GIUH and NIUH fully considers the moving path of wa ter particles in drainage and the regional composition of runoff at the end of the drainage,resulting in a rational combinatio n of probabili-ty of GIUH and NIUH and geomorphologic parameters which could reflect the complexity of the landform structur e of karst drainage.The results showed t hat the combined method of GIUH and NI UH has clear physical concept and acc ept-able precision,which can be widely a pplied on hydrological studies of karst area.

Application of TSD tunnel seismic prediction system in karst area

TSD is one of the classical methods of tunnel seismic prediction based on higher accuracy multi-wave multi-component seismology.The working principle of the TSD and an application example of the TSD on tunnel prediction in Chongqing are introduced in this paper.This system has two ports for speed signal and acceleration signal,and the equipment is more portable and easy to use.According to the application results we can conclude that the TSD prediction system is accurate and it has the wide application prospect in tunnel seismic detection.

Technical Specification for Application of Unmanned Aerial Vehicle( UAV) Monitoring of Rocky Desertification in Karst Area

Taking the opportunity of the third monitoring of rocky desertification in the karst area of China,Zigui County of Hubei Province applied Unmanned Aerial Vehicle( UAV) for the first time for monitoring. Through repeated trials and studies,it established technical requirements including the UAV monitoring technology for the rocky desertification,the feature point photographing,UAV video judgment of rocky desertification degree,UAV video correction misclassification subcompartment,and UAV video observation of rocky desertification control. It completed the third rocky desertification monitoring task of karst area in Zigui County.

Particle Size Characteristics of Soil in Karst Area with Different Land Use Pattern—A Case Study of Shuifang Spring,Jinfo Mt.,Chongqing

This paper tried to analyze the particle size characteristics of the soil samples in Shuifang Spring catchment area,Jinfo Mt.,Chongqing with different land use patterns that are horse race grassland, rhododendron bush,bamboos,and the grassland near the Shuifang spring.The different land usepattern in karst area is of great affection to the particle size characteristics of soil.The median diameter of the karst surface layer soil becomes gradually smaller and smaller in following sequence:horse race grassland,grassland near the Shuifang Spring,

Dry Breeding and Dry Planting Techniques for Indica Hybrid Rice in Karst Mountain Areas of Gejiu City

Based on the arable land situation in Gejiu City,upland dry planting of indica hybrid rice is being expanded in Karst mountain areas with a rainfall of over 1400 mm and an altitude of 1100-1600 m to develop grain production.This paper gives a specific description of hybrid rice upland dry seedling technology,upland transplanting technology,fertilization technology,field management,weed prevention and control technology,and disease and pest control.

Spatiotemporal Evolution of Ecological Quality in Typical Karst Ecologically Fragile Areas Based on Remote Sensing Ecological Indexes

Fast and effective remote sensing monitoring is an important means for analyzing the spatio-temporal changes in ecological quality in fragile karst regions.This study focuses on Guanling Autonomous County,a national-level demonstration county for comprehensive desertification control.Based on Landsat TM/OLI remote sensing image data from 2005,2010,2015,and 2020,remote sensing ecological indices were used to analyze the spatio-temporal changes in ecological quality in Guanling Autonomous County from 2005 to 2020.The results show that:①the variance contribution rates of the first principal component for the four periods were 66.31%,71.59%,63.18%,and 75.24%,indicating that PC1 integrated most of the characteristics of the four indices,making the RSEI suitable for evaluating ecological quality in karst mountain areas;②the remote sensing ecological index grades have been increasing year by year,with an overall trend of improving ecological quality.The area of higher-grade ecological quality has increased spatially,while fragmented patches have gradually decreased,becoming more concentrated in the low-altitude areas in the northwest and east,and there is a trend of expansion towards higher-altitude areas;③the ecological environment quality in most areas has improved,with the improvement in RSEI spatio-temporal variation becoming more noticeable with increasing slope.Areas of higher-grade quality appeared in 2010,and the range of higher-grade quality expanded with increasing slope.

Spatio-temporal Evolution and Optimization of Landscape Ecological Risk in Karst Mountainous Areas

[Objective]The ecological vulnerability and landscape ecological risk of karst mountainous areas have increased as a result of enhanced disturbance of natural resources by human activities.This paper aimed to explore the characteristics of ecological risk evolution under different landscape patterns in the region,with a view to providing reference for land classification protection,sustainable use of resources and regional ecological risk optimization in karst mountainous areas.[Method]Taking Huangping County,a typical karst mountainous area,as an example,eight evaluation factors of natural and landscape patterns were selected to construct a landscape ecological risk evaluation model,to quantitatively explore the spatio-temporal evolution of landscape ecological risk and the trend of risk level transfer in the study area from^(2)010-2018,and to reveal the complex relationship between ecological risk and topography in karst mountainous areas.[Result]①From 2010 to 2018,land use types changed to different degrees,with the most amount of woodland transferred out(1627.37 hm^(2))and the most amount of construction land transferred in(1303.93 hm^(2));a total of 3552.31 hm^(2) of land was transferred,with a change ratio of 2.13%,and there was a significant conversion between construction land,arable land,and woodland.②From 2010 to 2018,the landscape ecological risk in the study area changed significantly,and the landscape ecological risk index decreased from 0.3441 to 0.1733,showing an upward and then downward trend;the landscape ecological risk of the whole region was dominated by low-risk and lower-risk zones,and the ecological risk level generally shifted from a high level to a low level,and the ecological environment was improved.③There was a negative correlation between ecological risk and topographic position,and high-risk zones were mainly distributed among low topographic zones;with the change of time,the advantage of risk level for the selection of topography was gradually weakened,and the influence of anthropogenic factors on the ecological risk of the landscape was becoming more and more prominent.[Conclusion]This paper can provide theoretical basis for land use optimization and ecological protection in karst mountainous areas.

Spatiotemporal Interaction Between Rural Settlements and Cultivated Land in Karst Mountainous Area,China

Settlements and cultivated land are important production and living spaces in promoting rural revitalization.However,few studies have explored the relationship between rural settlements and cultivated land from spatiotemporal interaction perspective.This paper analyzed the spatiotemporal conversion and the interactive mechanism between rural settlements and cultivated land in a karst mountainous area(Qixingguan District of Guizhou Province)with fragile ecological environment in China during 2009–2018.The results showed that the expansion of rural settlements and the loss of cultivated land coexisted in Qixingguan District.Only 2.68%of the new cultivated land was reclaimed from rural settlements,whereas 85.45%of the new rural settlements occupied cultivated land.Six spatial expansion modes of rural settlements when occupying cultivated land were identified.Among these six modes,the area of the edge-expansion&along traffic roads(EA)mode accounted for 52.75%.The occupation by rural settlements made the cultivated land landscape more fragmented.The area ratio index of cultivated land to rural settlements(ARICR)of Qixingguan District averaged 18.75in 2009 and 17.21 in 2018,respectively.The ARICR reduced in all township administrative regions.Cultivated land with suitable slope condition for farming or without rocky desertification was more likely to be occupied by rural settlements.The probability of cultivated land occupied by rural settlements increased with the decrease of the distance to traffic roads,towns,and old rural settlements.The better the economic and social development of the township administrative regions,the more the ARICR decreased,while the richer the agricultural resources and the better the rural development of the township administrative regions,the less the ARICR decreased.The optimal reconstruction path of rural settlements,the comprehensive conservation path of cultivated land and the urban-rural integration development path in karst mountainous area were proposed.The findings would contribute to our understanding of the spatiotemporal interaction between rural settlements and cultivated land,and would provide a theoretical basis for promoting the coordinated development of rural man-land relationship and rural revitalization in karst areas.