Karst Rocky Desertification Research Articles

Response of Anatomical Features of Broadlesf Tree Root in Karst Area to Soil Erosion

Karst rocky desertification occurred in the southwest part of China was a seriously environmental problem, it is very important that expressing, dating, and reconstructing karst soil erosion process and history for understanding geomorphology of karst rocky desertification. Whereas accurately understanding karst soil erosion met a great obstacle of measuring problem for karst soil erosion from underground due to the dualistic systems of overground and underground. This was first time using exposed root anatomical features to imply karst soil erosion in China. Exposed and unexposed root samples in Puding, Guizhou, China were collected, and anatomical features were compared, parameters were measured, so as to obtain indicated information of soil erosion. Annual ring width could be appropriately applied to study the relationship of tree growth with environmental factors for the average sensitivity was larger than 0.2 for annual ring responding to soil layer. Tree root anatomical features were compared between exposed and unexposed root. The annual ring of unexposed root was smoothly increased from pith and decreased slowly when closed to bark, vessel size was the same and evenly distributed in each ring. Annual ring, pattern of vessel, and vessel size of exposed root was the same as unexposed root in prophase but an obviously mutation followed, annual ring narrowed, vessel lumen area reduced, vessel number decreased. After this mutation, a regular trend was shown but annual ring was narrower than unexposed root. From the anatomical changes of exposed root, the exact time of root exposure can be identified and the beginning of soil erosion happening. The response of anatomical features of tree root to soil erosion can offered a new method for the study of karst soil erosion and soil erosion historical record.

Characteristic of Rocky Desertification and Comprehensive Improving Model in Karst Peak-Cluster Depression in Guohua,Guangxi,China

Karst rocky desertification is a geo-ecological problem in Southwest China. Preventing and controlling rocky desertification has become critical. So,the Longhe,Pingguo,Guangxi Province in southwestern china, a typical serious rocky desertification area, were selected as the study area. After investigation and researches to the environments and regional economics in detail, the stereo eco-agriculture in different geomorphologic position of the peak -cluster depression has been built and was considered as an available model for the comprehensive improvement to rocky desertification. For about four years, the comprehensive improvement of rocky desertification in the experimental area has achieved good results. The vegetation is gradually restored, the annual mean income of the local people has increased by about 20%, and the new local ecological industry is formed.

Dynamic Analyzing in Karst Rocky Desertification Based on the Landscape Model Spatial Pattern

Small watershed is the basic element of rocky desertification management in karst area. For strengthening the comprehensive management plan, it is necessary to extend the management in a larger scale as the basis of the ecological management in small watershed. It is to make the quantitative analysis of the rock desertification landscape pattern dynamic changes based on the landscape types model in the study area of Tongjin vallage of Dafang county. The study basis is the geographic information system. The key technology is the landscape spatial pattern analyzing methods. By the quantitative model statistically analyzed the related indices of two periods rocky desertification landscape.It is indicated that the whole landscape pattern becomes more complex.But different degrees of rocky desertification landscape pattern have improvements.Higher rocky desertification imporved to the low one. Among them,the most obvious change is moderate and intensive rocky desertification. The comparasion analysis among the rock desertification spatial pattern in the typical karst area will reveal the ecological management meaning and provide the reference for the coming-up planning.

Remote sensing of indicators for evaluating karst rocky desertification

Remote sensing of indicators for evaluating karst rocky desertification

Spatio-temporal evolution of rocky desertification and its driving forces in karst areas of Northwestern Guangxi, China

Rocky desertification (RD) is a process of land degradation that often results in extensive soil erosion, bedrock exposure and considerable decrease of land productivity. The spatio-temporal evolution of RD not only reflects regional ecological environmental changes but also directly impacts regional economic and social development. The study area, Hechi, is a typical karst peak cluster depression area in southwest China. Remote sensing, geographic information systems (GIS) and statistical techniques were employed to examine the evolution, including the identification of driving forces, of karst RD in the Northwestern Guangxi. The results indicate that RD became most apparent between 1990 and 2005 when areas of various types of RD increased. Within the karst RD landscape, slight RD was identified as the matrix of the landscape while potential RD had the largest patch sizes. Extremely strong RD, with the simplest shape, was the most influenced by human activities. Overall the landscape evolved from fragmented to agglomerate within the 15-year timeframe. Land condition changes were categorized as five types; desertified, recovered, unchanged, worsened, and alleviated land. The largest turnover within the RD landscape was between slight and moderate RD. With regards to the driving forces all RD had been increasingly influenced by human activities (i.e., the stronger the RD, the stronger the intensity of human disturbances). Dominant impact factors of the RD landscape had shifted from town influence and bare rock land in 1990 to bare rock and grassland in 2005. Moreover, the impacts of stony soil, mountainous proportion and river density on RD increased over time, while that of others decreased. The significant factors included human activities, land use, soil types, environmental geology, and topography. However, only anthropogenic factors (human activities and land use) were reported as leading factors whereas the others acted simply as constraining factors.

Mechanism of cultivation soil degradation in rocky desertification areas under dry/wet cycles

Karst rocky desertification is a process of land degradation involving serious soil erosion, extensive exposure of basement rocks. It leads to drastic decrease in soil productivity and formation of a desert-like landscape. In this regard, changes in climatic conditions are the main origin of the soils degradation. Indeed, soils subjected to successive dry/wet cycling processes caused by climate change develop swelling and shrinkage deformations which can modify their water retention properties, thus inducing the degradation of soil–water capacity. The ecological characteristics of cultivation soils in karst areas, Southwest of China, are extremely easy to be affected by external environmental factors due to its shallow bedding and low vegetation coverage. Based on the analysis of the climate (precipitation) of this region during the past decades, an experimental study has been conducted on a cultivated soil obtained from the typical karst area in southwestern China. Firstly, the soil–water properties have been investigated. The measured soil–water retention curve shows that the air-entry value of the soil is between 50 and 60 kPa, while the residual saturation is about 12%. Based on the experimental results, three identifiable stages of de-saturation have been defined. Secondly, a special apparatus was developed to investigate the volume change behavior of the soil with controlled suction cycles. The vapor equilibrium technique was used for the suction control. The obtained results show that under the effect of dry/wet cycles, (1) the void ratio of the cultivated soil is continuously decreasing, leading to a gradual soil compaction. (2) The permeability decreases, giving rise to a deterioration of water transfer ability as well as a deterioration of soil–water retention capacity. It is then obvious that the long-term dry/wet cycling process caused by the climate change induce a continuously compaction and degradation of the cultivated soil in karst rocky desertification areas.

Characteristics of red clay creep in karst caves and loss leakage of soil in the karst rocky desertification area of Puding County, Guizhou, China

The loss of surface soil and water in the karst rocky desertification area of carbonate rock in Chenqi village, Puding County, Guizhou Province was monitored in this study. The results show that the major form of surface soil loss in the area is the loss of soil through underground channels. A creep test of red clay formed by loss through underground channels was conducted. The results of the test show that the creep curve of the red clay samples includes two stages: attenuation creep stage and stable creep stage. The creep law for the red clay samples in the karst cave can be described by Buger’s model. The parameters of Buger’s equation were deduced by fitting the creep curve, which provides the reference for analyzing the surface soil loss leaking through the underground channels.

Design and Application of Regional Kar st Rocky Deser tification Information System

Using ArcGIS software as a basic platform,taking Du'an County as a case,and by the aid of spatial superimposing analysis and geographical statistical analysis methods among them,Regional Karst Rocky Desertification Information System,or RKRDIS,a specialty GIS based on Arc Objects,is designed out.In this system,specialty analytic model of Karst rocky desertification is taken as the nucleus,with spatial data as information materials,with the computer network as transport vehicle,in order to realize abstracting "information" from "data".The information processing technology supports data analysis,query,display and management for Karst Rocky Desertification research,and provides spatial data analysis of Karst rocky desertification for dynamic monitoring,driving diagnosis,early-warming analysis,calamity assessment,and policy making. Development of this system involves a variety of knowledge and professional skills like GIS,software engineering,natural geography,remote sensing,database design,computer technology and,etc.,and is indeed a comprehensive integration of multidisciplinary knowledge.In particular,space analysis on Karst desertification disaster data,such as temporal-spatial monitoring,drive diagnosis,etc.,is a full incarnation of features unique to GIS technology,since assembly system development method and method of management of space data by using relationship database,system structure based on C/S model,customized user interface and complete user functions,can better satisfy the requirements for application by users.So this is definitely a beneficial attempt that GIS technological application has ever been made in Karst desertification disaster field. The system can provide new study methods and means for integrated assessment and analysis of Karst desertification by using geographical information system in combination with mathematical models,and for prevention and treatment of disasters in Karst desertification areas.Moreover,it is of particular importance for providing guidance to the scientific treatment and construction in Karst desertification areas.

Spectral indices for estimating ecological indicators of karst rocky desertification

Karst rocky desertification is a process of land desertification associated with human disturbance of the fragile eco-geological setting of karst ecosystems. The fractional cover of photosynthetic vegetation (PV), non-photosynthetic vegetation (NPV), bare soil and exposed bedrock are key ecological indicators of the extent and degree of land degradation in karst regions. In this study, field spectral-reflectance measurements were used to develop a karst rocky desertification synthesis index (KRDSI) based on unique spectral features observed in non-vegetation land-cover types (NPV, bare soil and exposed bedrock) and were used to estimate the fractional cover of NPV, bare soil and exposed bedrock. Compared with linear spectral unmixing (LSU) using a tied-spectrum transform, the KRDSI is more consistent with the field measurement of non-vegetation land-cover fractions. This study indicates that ecological indicators of karst rocky desertification can be extracted relatively simply with the combination of vegetation indices and KRDSI values.

Using the radial basis function network model to assess rocky desertification in northwest Guangxi, China

Karst rocky desertification is a progressive process of land degradation in karst regions in which soil is severely, or completely, eroded. This process may be caused by natural factors, such as geological structure, and population pressure leading to poor ecosystem health and lagging economic development. Karst rocky desertification is therefore a significant obstacle to sustainable development in southwest China. We applied a radial basis function network model to assess the risk of karst rocky desertification in northwest Guangxi, a typical karst region located in southwest China. Factors known to influence karst rocky desertification were evaluated using remote sensing and geographic information systems techniques to classify the 23 counties in the study area from low to extreme risk of karst rocky desertification. Counties with extreme or strong karst rocky desertification risk (43.48%, nearly half of the study area) were clustered in the north, central and southeast portions of the study area. Counties with low karst rocky desertification (30.43%) were located in the west, northeast and southwest of the study area. The spatial distribution of karst rocky desertification was moderately correlated to population density.

Rocky desertification risk zone delineation in karst plateau area: A case study in Puding County, Guizhou Province

Karst rocky desertification is a geo-ecological problem in Southwest China. The rocky desertification risk zone delineation could be used as a guide for the regional and hierarchical rocky desertification management and prevention. We chose the middle and lower reaches of the Houzhai underground basin on the karst plateau in Puding County, Guizhou Province, China as the study area and selected land use type, elevation, slope, aspect, lithology and settlement buffer as the main driving factors of the rocky desertification. The potential risk of rocky desertification was quantified with the factor-weights union method and statistical analysis method. Five grades of rocky desertification risk were delineated based on Geographic Information System. The extremely low, low, moderate, high and extremely high rocky desertification risk zones accounted for 5.01%, 44.17%, 33.92%, 15.59% and 1.30%, respectively. As a whole, the rocky desertification risk level was moderate because the area of low and moderate rocky desertification risk zones occupied 78.09% of the study area. However, more than half of the area (about 50.81%) was predicted to have moderate rocky desertification risk and above, indicating that the study area was subject to rocky desertification. Rocky desertification risk was higher in the southeast and lower in the northwest of the study area. Distinct differences in the distribution of rocky desertification risk zones corresponding to different factors have been found.

Relationships between rocky desertification and spatial pattern of land use in typical karst area, Southwest China

Karst rocky desertification is a typical type of land degradation in the Southwest China. An attempt was made to study quantitatively the relationships between rocky desertification and spatial pattern of land use through applying spatial analysis of Geographical Information System in Nandong underground river system, a typical karst area, Southwest China. The spatial distribution of rocky desertification and spatial pattern of land use were obtained from interpreting Landsat Images in Nandong area in 2007 by supervised classifications, and verified and rectified through field survey. The results indicate that: (1) the total land deserted area covers 378.3 km2, or 23.4% of the total area, of which intense, moderate and slight rocky desertification covers 269.46, 54.2, and 54.63 km2, respectively, in Nandong area. (2) There is an obvious effect of spatial pattern of land use on rocky desertification. With the increase of elevation and slope, there is a higher occurrence ratio of rocky desertification in the cultivated land and grass land. Also, more than half of total rocky desertification was dominated within the areas of 4 km from the construction land, and 97% of total rocky desertification was dominated within the areas of 10 km from the construction land in Nandong area. And what can be known from the data is that the primary effect distance of human on rocky desertification from the construction land is 4 km, and the farthest effect distance of human on rocky desertification from the construction land is 10 km in Nandong area.

The Rise of Agrarian Capitalism with Chinese Characteristics: Agricultural Modernization, Agribusiness and Collective Land Rights

In what forms are agribusinesses entering agriculture and interacting with farmers? How are land, labor and capital now controlled by corporate and individual actors, and then organized into agricultural production? How does such control and organization shape the relationships between the actors? In this article we argue that agrarian capitalism is expanding in China. The means of production, such as capital and land, are increasingly controlled by agribusiness, while direct producers increasingly sell their labor for a living. We document various forms in which agribusiness companies are conducting transactions with individual agricultural producers. We also argue that China's unique system of land rights featuring collective ownership but individualized usage rights has acted as a powerful force in shaping interactions between agribusiness and direct producers. It provides farmers with a source of economic income and political bargaining power, and restricts corporate actors from dispossessing farmers of their land. We find strong norms protecting farmers' collective land rights in the agricultural sector, contrary to the received wisdom about weak protection of land rights in China. In the rest of the paper, we first review the policy context in which this transformation has taken place. Next we introduce our method of data collection, summarize the five forms of agribusiness-farmer interaction found in our study, and analyze each of the five forms in depth. We conclude with a discussion of the causes and characteristics of the rise of agrarian capitalism, with a focus on the role of the land rights system.

The relations between land use and karst rocky desertification in a typical karst area, China

Karst rocky desertification (KRD) is one major type of desertification which is under irrational human impact on the vulnerable eco-geo-environment. In this study, Zhudong fengcong rocky desertification landscape was selected to investigate the land use types distribution law in different rock types and the KRD land in different land use types. KRD data was determined by user–computer interactive interpreting method from Aster images in 2004, according to the exposed ratio of rock, the coverage of vegetation and soil in 0.2 km2 unit, integrating with land utilizing present situation map, hydrogeology map, relief map, vegetation map, soil distribution map, as well as the practical investigation and the population census datum in 2002. Results showed that the occurrence ratio of KRD land is different in land use types and rocky assemblages obviously; land cover has a strong impact upon KRD. The sloping cropland distributed in homogenous limestone has a higher occurrence ratio of light KRD, secondly, is in the limestone interbedded with clastic rock. Light KRD land was dominated by shrubland, and sloping cropland accounts for 11.67% of it, moderate KRD land was dominated by moderate coverage grass slopes, strong and extremely strong KRD was dominated by rocky dry land which is difficult to use.

Spatial pattern of Karst rock desertification in the Middle of Guizhou Province, Southwestern China

Karst rocky desertification is a typical type of land degradation in the Southwestern China. It has great ecological and economical implications for the local people. Landsat images from the middle of Guizhou Province collected in 1974, 1993 and 2001 were used for change detection of the pattern of Karst rocky desertification. The results show the following findings: (1) Desertification area expanded drastically in 27 years, at an increasing rate about 116.2 km2/year. (2) High areas (900–1,500 m) are the most affected. (3) Areas with the slope 25° are also easily tend to be Karst rocky deserted. (4) The process of Karst rocky desertification is nearly irreversible. Few areas of Karst rocky desertification could be meliorated to non-desertification land. (5) Most of the degraded lands are located in the south and the central of the study region, and the meliorated land areas are sparsely located in the east and the west part of the region. All these findings would provide bases for the decision-making of the local government to improve the Karst rocky desertification

Biogeochemical cycling of nutrients in karstic catchments, southwestern China: Linkages to changes of eco-environments

In southwestern China, karst rocky desertification, a process of land degradation, takes place widely due to human impacts on the fragile karstic ecological systems, which includes soil erosion, extensive exposure of basement rocks, and drastic decrease in soil productivity. A study on biogeochemical cycling of nutrients in the karstic catchments has been carried out to understand the relationships between degradation of ecological system and nutrient cycling. Our studies on chemical and isotopic compositions ( 6 13C, 6 34S, 5 15N, 87Sr/S6Sr) of river, lake, rain, and ground water in the karstic catchments of southwestern China provided important information on the sources of major ions to them, chemical weathering rates of river basins, fluxes of dissolved materials from the drainage basins, and on their linkages to changes of ecological systems and environments. The weathering rates of carbonate rocks and the fluxes of nutrients from the river basins are high as compared with karstic terrains in the world. Comparative studies on the carbon isotopic composition of dissolved inorganic carbon in surface water of karstic and none-karstic catchments indicate that more dissolved inorganic carbon in the karstic rivers originated from respiration of soil organic carbon. The interrelationships between isotopic composition and chemical composition of the surface water suggest that the high weathering rates of carbonate rocks and large fluxes of carbon, sulfur, and nitrogen from the karstic river basins may be ascribed to the roles of sulfur and nitrogen cycling in the catchments. Weathering of carbonate rocks by sulfuric and nitric acids can give rise to a net source of CO2 to atmosphere through precipitation of carbonate minerals, which will change our view that weathering of carbonate rocks can neither subtract nor produce greenhouse gas in atmosphere from a long-term point of view. The sulfur and nitrogen isotopic compositions respectively of sulfate and nitrate ions in rain and ground and surface waters indicate important anthropogenic sources of these ions, in addition to natural origin. It is concluded that human activities can disturb the natural cycling of nutrients, and result in changes in ecological environments.

Variations of nutrient element contents of plants and soils in the process of karst rocky desertification

Variations of nutrient element contents of plants and soils in the process of karst rocky desertification

Analysis of soil biogeochemical characteristics in the process of karst rocky desertification

Analysis of soil biogeochemical characteristics in the process of karst rocky desertification

Assessment of karst rocky desertification using the radial basis function network model and GIS technique: a case study of Guizhou Province, China

Karst rocky desertification in karst areas of Southwest China is an obstacle for the sustainable development of the locality. While many researchers have studied this issue, this study quantified the various indicators affecting desertification, using GIS technology to extract spatial data and to construct a RBFN (radial basis function network) model for Guizhou province. By calibrating sample data of the different levels of karst rocky desertification, the model parameters were established, and then the assessment of karst rocky desertification. Results show that in counties of Southwestern Guizhou Province karst rocky desertification is severe, counties in northern Guizhou have moderate desertification, and southeastern counties are affected lightly. Comparison of the results with other research shows conformity with actual conditions, proving the reasonability and applicability of the RBFN model.

Design and application of dynamic monitoring and visualization management information system of karst land rocky desertification

In order to study the spatial-temporal change and environmental management of regional karst LUCC (land use and land cover change) and its causative environmental effect—rocky desertification by integrating qualitative analysis and quantitative analysis, and relying on RS, GIS and GPS (3S) techniques, karst land rocky derification dynamic monitoring and visualization management information system (KLRD.DMVM.IS) is framed, which includes design aim and structure model, function design, database design and model system design. The model system design gives priority to dynamic monitoring, drive force diagnosis, comprehensive evaluation and decision support of karst rocky desertification. From the viewpoint of model type, mathematic expression and its meaning, the dynamic monitoring models are concretely devised to reflect the spatial and temporal changing features and the trend of karst LUCC and rocky desertification. Taking Du’an Yao Autonomic County of Guangxi as an example, the KLRD. DMVM.IS is systematically analyzed in the application of the process and trend of karst LUCC and rocky desertification in Du’an County, and it provides the technical support for the study on karst land rocky desertification.