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.

Study on Sustainable Utilization of Resources of the Damp-heat Karst Mountainous Areas in China

Damp-heat karst mountainous areas are unique areas in terms of socialeconomic development, resource endowment and eco-environment in China, where natural resources are abundant,unique and diverse. However, fragile eco-environment, undeveloped economy and culture, and conflict of human and environment should not be ignored. In the research, a framework of integration of resource-development and environment-protection in damp-heat karst was designed on basis of resource and environment integration, which was applied to Daxin County in Guangxi Province. Furthermore, some integration models were proposed, including integration of development of characteristic agricultural resources and protection of eco-environment, integration of development of manganese ore resources and protection of eco-environment, integration of development of tourism resources and protection of ecoenvironment and integration of development of clean energy and protection of eco-environment.

Rehabilitation and Sustainable Use Pattern of Rocky-desertified Land in Southwest China’s Poverty-stricken Karst Mountainous Areas——A Case Study in Benggu Township, Xichou County, Yunnan, China

The rocky desert in a karst area directly causes the lack of soil, water and forest, hence leading to the poverty there. In 1990, the villagers from the Muzhe Village in Benggu Township, Xichou County, Yunnan declared a war against rocky desert in an attempt to ask the fields for more yields. They invented a distinctive land rehabilitation and sustainable use pattern called “transforming heavenand earth” that had been practiced in Southwest China’s karst areas. The key mechanism of the pattern was to develop terraced fields with well conserved soil, water and fertility by exploding rocks in the fields, building stone walls, gathering more soil, and improving soil quality and productivity for the fields in combination with building of irrigation facilities and roads, as well as with forestation and agriculture structure adjustment. The purpose of the pattern was to alleviate poverty in the karst areas by improving soil productivity and promoting agriculturaldevelopment. A typical area was studied with the help of Participatory Rural Appraisal (PRA) and the pattern was carried out there for fifteen years, have produced excellent ecological benefits and good economic benefits. Its application in the area approved that it was a sustainable land use pattern for rocky desert areas.

Changes of hydrochemical composition and heavy metals concentration in shallow groundwater from karst hilly areas in Guiyang region,China

The quality changes of shallow groundwater from karst hilly areas in Guiyang region of China impacted by the urbanization were investigated. The results show that the major ions in shallow groundwater from the karst hilly areas are mainly composed of HCO3^-, SO4^2-, Ca^2＋ and Mg^2＋, and the concentrations scopes of NO3^-, Cl^-, K^＋ and Na^＋ of the groundwater in agricultural, residential and industrial areas are 4.5-9.6, 2.8-7.1, 3.9-6.3 and 2.5-4.9 times higher than those in the forest areas, respectively. The concentrations of As, Pb and Cd of shallow groundwater in the industrial areas are also significantly enhanced, followed by those in the residential areas and the agricultural areas. The concentrations of NO3^-, SO4^2- , As, Pb and Cd of the groundwater in the industrial areas and those of NO3^- , SO4^2-, As and Cd of shallow groundwater in the residential areas reach grade Ⅲ of the Groundwater Quality Standard of China （GB/T 14848-93）, while the concentration of NO3^- in the groundwater from the industrial areas exceeds grade V. With the process of urbanization, NO3^- is the key factor to influence the groundwater quality in karst hilly areas, followed by SO4^2-, As, Pb and Cd.

Chemical characteristics of rainwater in karst rural areas,Guizhou Province, Southwest China

The chemical composition of rainwater has been studied in a karst rural area from September 2012 to August 2013 in Guizhou Province,Southwest China.The results indicated that the VWM value of p H was 5.4,varied from 4.6 to 6.9.Ca^(2+)and NH_4^+were the major cations,and SO_4^(2-)was the dominant anion.Neutralization factors show that the acid was mainly neutralized by Ca^(2+),NH_4^+and Mg^(2+).Investigations of correlation coefficients and enrichment factors revealed that Ca^(2+)and Mg^(2+)were mainly crust origins,and NH_4^+was from agriculture and livestock manure.SO_4^(2-)and NO_3^-were mainly from anthropogenic sources.

Cultivated Land Quality Analysis of Karst Mountain Areas Based on GIS: A Case Study of Jingxi County

Agricultural land quality assessment of karst mountain areas is an impor-tant means to protect and manage cultivated land quality of karst mountain areas. With Jingxi County as a case, the data resources included achievements of cultivat-ed land grade, achievements of second land investigation, investigation of local con-ditions and the other data resources. With the overlay tool of MapGIS, attribute data of evaluation index were obtained, which can reflect agricultural land＇ characteris-tics, and agricultural land quality scores were calculated and land quality was grad-ed using the model of comprehensive evaluation of multiple factors to make further analysis on characteristics and spatial distribution. The results showed that used agricultural land is dominated by middle and high-grade lands in Jingxi County mainly, representing 68.58% of Jingxi County’s agricultural lands. On the other hand, the quality of paddy land is general y higher than that of dry land, and quality of agricultural land showed higher in middle and eastern Jingxi, and lower in north-western region, which provides references for national land management.

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.

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.

CONSULTATIVE RECOMMENDATIONS ON SUSTAINABLE DEVELOPMENT IN KARST AND ROCK-NAKED MOUNTAIN AREAS OF SOUTHWEST CHINA

The serious degradation of the ecological environment and the rapid expansion of stone desert have had a serious effect on the economic development of karst and rock-naked mountain areas in Southwest China. Moreover, these areas are still at the initial stage of industrialization, characterized by a greater significance of agriculture to the economy, face sharp contradictions among the population, the arable land and resources, and are suffering because of a shortage of investment. On the basis of this current situation, three recommendations are made in this article: "coordinating the relations among grain, ecology, population and economic development", "increasing the input of science and technology", and "adopting policies consistent with social equity in areas of poverty".

The Comparison of Contents of Malondialdehyde and Proline in the Area of Karst Area in Northweastern Guangxi Province

[Objective] To select excellent pioneer species of better ecological and economical comprehensive benefits from the common rock hill plants in Karst area in northwestern Guangxi Province.[Method] Determine the contents of malondialdehyde and proline in leaves of 65 strains of plants by thiobarbituric acid method and sultosalicylic acid method,analyze the relevance of the contents of malondialdehyde and proline by mathematics statistics and analyze the 65 kinds of rock hill plants by clustering [Result] The contents of malondialdehyde and proline are 0.005 2-0.038 1 μmol/g.There are comparably significant differences in the contents of malondialdehyde in different plants;The determination of proline contents in plant＇s leaves are 4.347-374.956 μg/ml.There are also significant differences in proline of different leaves of rock hill plants.The contents of malondialdehyde and proline can be used as a reference point in selecting pioneer plants in Karst area.But when we select the pioneer plants,not only the biological characters of the species themselves should be taken into consideration,but also the differences of Karst area environment,ecological and biological benefits and the reasonable distribution of species.[Conclusion] Pistacia chinensis,Zenia insignis,Acacia confusa,Itoa orientalis and Sophora japonica can be used as the first choices of excellent pioneer plants in Karst area in northwestern area which comparably consists with the real situation of afforestation of rock hills and recovery of plants in Guangxi.

Nestedness of bird assemblages in the karst forest fragments of southwestern Guangxi, China

The limestone region in southwestern Guangxi contains the most typical karst landforms in the world. Due to their destruction, the original forests mainly survive in nature reserves in the form of fragmented areas. From June 2009 to September 2010 we conducted an investigation of 13 relatively isolated habitats or sites, selected from each of the 13 nature reserves in southwestern Guangxi, with the least amount of anthropological activity and the largest presence of the original vegetation, in order to study the distribution of birds on forest fragments. The distribution patterns of the birds and the factors which affect them were analyzed by using the 'BINMATNEST' software and the Spearman’s rank correlation analysis, to determine: 1) whether nested patterns of birds in the karst area of southwestern Guangxi exist or not and 2) which factors are correlated with the nested patterns and the effect of these factors on forming nested patterns. The results show that the birds had statistically significant nested patterns in the karst area and the specificity of the habitat of the birds had a significant effect on the nested patterns. We suggest possible reasons for these results, based on the characteristics of the seasonal tropical rain forests in the study area and on neutral theory. We also urgently recommend that close attention be paid to the protection of the diversity of the environment for birds in all fragmented habitats.

Effects of Different Land Use Types on Soil Organic Carbon and Carbon Management Index in Karst Area

[Objective] The aim was to reveal changes of soil organic matter fraction and their corresponding carbon management indexes as affected by different land use types.[Method]Soil organic carbon,active soil organic carbon and soil carbon management index（CMI）of different land use types in Guilin Maocun karst area were studied.Sampling with field investigation and laboratory testing was carried out.Heavy potassium chromate method was adopted to determine soil organic matter.333 mmol/L KMnO4 oxidation method was used to determine active organic carbon.[Result]With active soil organic matter increasing,the differences of CMI between different land use types were bigger.The CMI value of different land uses was shrubforest paddy fielddry farmland.The statistical analysis showed that labile organic matter was related with major soil properties at a significant level.[Conclusion]Labile organic matter could be used to reveal the influence of different land use types on soil organic matter and carbon management index in karst area.

Formation process of cover collapse sinkholes related to groundwater level decline in karst areas

The decline in groundwater level is a key factor contributing to cover collapse in karst areas.In this study,the model tests and numerical simulations are conducted to reveal the breeding process and formation mechanism of cover collapse sinkholes caused by the decline of groundwater level in karst area.Firstly,the model tests confirm that the decline of groundwater level generates negative pressure at the lower edge of overlying soil.The negative pressure experiences four distinct phases during the groundwater drawdown process:rapid rise,slow decline,rapid decline,and gradual dissipation.The maximum negative pressure is influenced by the particle size distribution of the overlying soil.Then,the numerical simulations are carried out to investigate the change process of negative pressure caused by the loss of fillers in karst pipe.The simulated results indicate that the rate of groundwater decline and the thickness and initial void ratio of the overlying soil can affect the maximum negative pressure.As groundwater level drops,a negative pressure zone forms underground,causing tensile failure in the surrounding soil and creating an arched soil hole,which weakens the support for the overlying soil.This phenomenon can also lead to the collapse of the overlying soil under its self-weight.Groundwater table decline in karst areas can result in both internal and surface collapses.When the overlying soil is thin,internal and surface collapses occur simultaneously.In contrast,for thick overlying soil,internal collapse happens first,followed by a layer-by-layer collapse,ultimately forming sinkholes.Finally,the breeding process and formation mechanism of the Yujiawan Reservoir sinkholes are discussed.Geological conditions and groundwater level decline significantly affect internal collapse in karst areas,requiring careful consideration from on-site engineers.

Soil Moisture Characteristics in Karst Area with Different Land Use Types

Ecological efficiency changes of soil moisture were researched in karst areas with different land type uses, including farmland, abandoned farmland （1 y） and shrub land （1 y）, sparse wood land （15 y）, secondary forest （25 y） and the re- sults showed that physical property of soil was not a simple ＂improvement＂ process during land type evolution. Specifically, from farmland to secondary forest, the con- tent of topsoils changed from being washed away to accumulation and soil bulk density changed from increasing to decreasing. For example, soil bulk densities of abandoned farmland and shrub land increased by 6.6% and 11.57% compared with farmland, and of sparse wood land and forest land decreased by 5.0% and 10.0%. The change trend of soil bulk density was just in contrary to total porosity. Available water capacity was the lowest of shrub land, but increased in rest land types. The increase tended to be volatile in 5.1%-12.5% of different land types and water-sta- ble aggregate content （〉0.25 mm） reached the highest of sparse wood land. The destruction rate, however, was declining in the process of land type evolution and the increase was in the range of 34.0%-64.7% compared with farmland. The de- struction rate of aggregate was of negative correlation with organic matter. Water- holding capacity was the best of forest land and abandoned farmland and the poor- est of shrub land, close to sparse wood land. Water-supplying capacity from high to low was as follows： farmland〉sparse wood land〉secondary forest〉shrub land〉a- bandoned farmland. It is obvious that water-holding capacity and water-supplying capacity are not consistent, but both are closely related to the content of soil clays, porosity, and aggregate stability.

Cultivation Techniques for High-yield Corn in a Karst Area of Southwest Guizhou

The cultivation techniques for high-yield corn in a karst area of southwest Guizhou were elaborated in this research from the respects of choosing farmland, preparing farmland, picking good seeds, timely sowing, rational close planting, im-proving the quality of planting, mulching, scientific fertilization, field management, timely harvest, etc. we hoped to provide a reference for the realization of high-effi-ciency corn planting in mountain areas.

Study on Soil Erosion Model Under Different Slopes in Southwest Karst Mountain Area

The aim was to further research soil erosion characteristics and accurately predict soil erosion amount in karst areas. Based on field surveys and research achievements available, yellow soils, which are widely distributed, were chosen as test soil samples and slope, rain intensity, vegetation coverage and bare-rock ratio were taken as soil erosion factors. Artificial rain simulation instruments （needle-type） were made use of to simulate correlation of rain intensity, vegetation coverage, and bare-rock ratio with soil erosion quantity. Furthermore, multiple-factor linear regression analysis, stepwise regression analysis and multiple-factor non-linear regression analy- sis were made to establish a multiple-factor formula of soil erosion modulus with dif- ferent slopes and select regression models with high correlation coefficients. The re- sults show that a non-linear regression model reached extremely significant level or significant level （0.692〈FF〈0.988） and linear regression model achieved significant lev- el （0.523〈FF〈0.634）. The effects of erosion modulus changed from decreasing to in- creasing and the erosion factors from high to low were rain intensity, vegetation cov- erage and bare-rock ratio when slope gradient was at 6~, 16~, 26~ and 36~. The mod- el is of high accuracy for predicting gentle slope and abtupt slope, which reveals correlation of erosion modulus with erosion factors in karst areas.

Assessments on Ecological Sensitivity and Ecosystem Service Value in Karst Area Based on GIS——Taking Bijie Prefecture in Guizhou for Example

Assessments on ecological sensitivity and ecosystem service value are two important basic works in eco-functional regionalization. According to the special ecological environment in Guizhou Province,GIS technology was used in the classification evaluations of soil erosion sensitivity,acid rain sensitivity and rocky desertification sensitivity in Bijie Prefecture,and then the comprehensive evaluation on eco-environmental sensitivity was carried out. Finally,the preliminary economic estimation of ecosystem service value in Bijie Prefecture was made by means of the appraisal approach for ecosystem service proposed by Costanza.