Karst Areas Of China Research Articles

Characteristics of woody plant regeneration in karren-habitats successional plant communities in Yunnan Shilin karst area of China

Aims Degraded karst ecosystems appear around the world and include the European Dinaric Karst and the South China Karst. The relationship between karst habitats and biodiversity and response to disturbance are essential for karst vegetation succession. Our objective was to study woody plant regeneration in different successional stages in karren-habitats of Yunnan Shilin (Stone forest) Geopark,China. Methods Based on relationships among karrens,soils and plants,we divided karren-habitats into five types:solution corridors; solution wells or shafts; kluft karren; deep solution pits; and solution rock debris. We sampled seedlings and sprouts of woody species in zonal forest,secondary forest,shrubland,shrub tussock and rocky-desertified grassland that encompass succession in karst plant communities. The Shannon-Wiener,Pielou,Simpson and Margalef diversity indices were calculated. Important findings The length and width of each karren-habitat was different and the percentage of karren-habitat changed within the five communities and with disturbance intensity. The fruiting species and number of seedlings decreased with karst vegetation degradation,and the number of sprouts reached a maximum in shrubland and decreased respectively toward the zonal vegetation and rocky-desertified grassland. The Shannon-Wiener and Pielou indices for sprouts in the karren-habitat background communities decreased with plant community degradation,and the Simpson index increased. The Shannon-Wiener and Pielou indices for seedlings were highest in shrubland. The seedlings and sprouts in the five kinds of karren-habitats had different values of biodiversity depending on the succession stage. It is inferred that plants of different successional stages have different regeneration strategies. Sprouting plays an important role in the early stages,and seeding is more important toward the zonal plant community. This is partly because some karren-habitats have remains such as stumps and roots of some species that can repeatedly sprout with continuous disturbance. After the disturbance stops,these sprouts can mature and set seed and seedling regeneration can play a major role towards the middle and late stages of succession. The different karren-habitats play different roles in biodiversity conservation and natural restoration of karst plant communities during succession.

Variation in solvent-extractable lipids and n-alkane compound-specific carbon isotopic compositions with depth in a southern China karst area soil

Because literatures about the lipid compositions of modern soils in karst areas are scarce, we have studied the soil horizons overlying the Heshang (和尚) Cave that has provided paleoclimate records from speleothem lipid contents. Our analysis reveals a series of n-alkanes, free fatty acids, n-alkanols and n-alkan-2-ones distribution and relative abundance changing with the depth, and in which the ratios of the lower molecular weight to higher molecular weight n-alkanes, free fatty acids, n-alkanols and n-alkan-2-ones have a peak at a subsurface depth of 5 to 10 cm. An accompanying peak in 17β(H), 21β(H)-hop-22(29)-ene (diploptene) and a shift to less negative n-alkane carbon isotopic values also identify this layer in the karst soil. This pattern indicates the existence of a subsurface soil layer in which the microorganisms that produce these compounds are especially abundant. The carbon isotopic values of individual plant wax n-alkanes are about 3‰ greater at the base of the 30- to 40-cm soil profile than in the surface layer, probably as a result of selective microbial degradation of n-alkanes from different primary sources. The lipids and carbon isotopic values of individual plant wax n-alkanes study of the overlying soil show a strong microbial activity in this karst soil and help in interpreting the lipid compositions and specific carbon isotopic value of n-alkanes of the stalagmites of the Heshang Cave for paleoenvironmental reconstructions.

Hydrogeochemical effects of secondary forest in Guangxi Nongla karst areas in China

Rainfall, throughfall, stemflow and spring were studied in a secondary forest during a wet season from April to August in 2006. Some of the chemicals in throughfall, stemflow and spring were increased in contrast with incident rainfall. Specifically, Cl−, HCO3−, Na+ and Ca2+ were leached negatively in throughfall, but K+ and Mg2+ were leached positively. In stemflow, Cl− and Na+ were leached negatively, the others were leached positively and their concentrations were higher than those in throughfall. Total carbon, organic carbon and inorganic carbon in throughfall and stemflow were increased as rainfall went through the secondary forest. The concentration of free CO2 in rainfall was lower than both, throughfall and stemflow; the relationship between total acidity and free CO2 was linear. pH of throughfall and stemflow , such as maximum, minimum and mean, were lower than that of rainfall and the extent of pH in spring was changed minimally. We came to a conclusion that rainfall via the secondary forest can lead to further erosion, accelerate the biogeochemical cycle in epikarst zone, enhance the effective state of alkali elements in the soil, supply vegetation with more nutrients and advance vegetation’s growth and succession, which are reasonably sufficient to form a stable karst ecosystem.

The impact of land use and land cover changes on land surface temperature in a karst area of China

Satellite images have been used extensively to study temporal changes in land use and land cover (LULC) in China. However, few studies have been conducted in the karst areas despite the large area and population involved and the fragile ecosystem. In this study, LULC changes were examined in part of Guizhou Province of southern China from 1991 to 2001 based on Landsat Thematic Mapper (TM) images of November 7, 1991, December 5, 1994, and December 19, 2001. Land surface temperature (LST) and normalized difference vegetation index (NDVI) were computed based on LULC types. The results show that agricultural land decreased, while urban areas expanded dramatically, and forest land increased slightly. Barren land increased from 1991 to 1994, and then decreased from 1994 to 2001. These changes in LULC widened the temperature difference between the urban and the rural areas. The change in LST was mainly associated with changes in construction materials in the urban area and in vegetation abundance both in the urban and rural areas. Vegetation had a dual function in the temperatures of different LULC types. While it could ease the warming trend in the urban or built-up areas, it helped to keep other lands warmer in the cold weather. The study also reveals that due to the government's efforts on reforestation, rural ecosystems in some of the study area were being restored. The time required for the karst ecosystem to recover was shorter than previously thought.

EVIDENCE FROM SATELLITE IMAGES OF HUMAN-RELATED ENVIRONMENTAL CHANGE IN GUIZHOU PROVINCE, CHINA 1991–1998

Karst area accounts for about 15% of the total land area in the world, where over I billion people live. There are many environmental problems caused by human's activities in the karst area. These environmental problems are serious, unique, and need to be dealt with urgently. Although much research has been done on land use (LU) and land cover (LC) change detection using satellite images and GIS, little has focused on the karst area. This paper takes Guizhou Province, a typical karst area in China, as an example and studies the impact of land use and land cover on the environment for the period of 1991 to 1998. Three Landsat TM scenes, acquired in November 1991, December 1994 and December 1998 respectively, were used in the study. Land use/cover is classified into five categories: water, natural vegetation, agricultural, urban or built-up, and barren land. A hybrid unsupervised/supervised method is used in the classification. To achieve a higher accuracy, 120 classes are assigned in the original unsupervised classification, and then they are combined into 5 classes. Based on the information obtained from unsupervised classification, 400 sites, or about 3 from each of the 120 unsupervised classes, were carefully chosen as training sites in the supervised classification. The study suggests that Guizhou had experienced significant changes in land use and land cover due to human's activities. Agricultural land continued to decrease from 1991 to 1998; urban area expanded dramatically in that period; the area of forest increased slightly; the area of barren land increased from 1991 to 1994, but it decreased again from 1994 to 1998. The study indicates that the driving forces for the changes were the result of strong economy, governmental policies, poor planning, low educational level, and the nature of the fragile ecosystem in the karst area. Some recommendations are proposed for better land use planning and ecosystem protection there.

CO2 source-sink in karst processes in karst areas of China

CO₂ source-sink in karst processes in karst areas of China

Stable Carbon Isotope Geochemical and Hydrochemical Features in the System of Carbonate–H2O–CO2 and Their Implications—Evidence from Several Typical Karst Areas of China

AbstractOn the basis of hydrochemical observation and experimental calculation, the features of stable carbon isotope geochemistry in the karst dynamic systems of the Guilin Karst Experimental Site, Huanglong Ravine and Wujiangdu Dam Site are summarized in this study. Furthermore, an attempt has been made to solve several geochemical problems, such as the origin of CO2 in the system, kinetic fractionation of carbon isotopes during calcite deposition, hydrochemistry and formation of tufa, and carbon—14 dating of tufa of hydrothermal origin. The results show that three kinds of karst dynamic system can be distinguished: (1) the shallow system, such as the Guilin Karst Experimental Site, in which soil CO2 provides the an active agent for karst processes; (2) the geothermal system, such as the Huanglong Ravine, in which metamorphic or/and juvenile CO2 is the source of activity for karst; (3) the anthropogenic system, such as the Wujiangdu Dam Site, in which the stable carbon isotope geochemical and hydrochemical features have been greatly affected by human activity.

Two Mechanisms of Tufa Formation in the Cement Grouting Tunnels at Wujiangdu Hydropower Station of Guizhou

Wujiangdu Hydropower Station of Guizhou is one of the biggest hydroelectric projects built in karst areas of China. It has a dam 165 m high, with a capacity of 630,000 kW. Its electric energy production is 3.34 billion kW-·h/a. Since its launching in 1979, the station has contributed a lot to the economy in Southwest China.