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To uncover the process of land use change and its driving mechanism of typical wetland ecosystems in the karst region, this thesis conducts a case study on Caohai National Nature Reserve (hereafter referred to as Caohai). With the support of geoinformation technology and the landscape index analysis method, it quantitatively analyzes the magnitudes, speed, and landscape patterns of land use changes over 35 years from 1985 to 2020 using continuous remote sensing images. The results show that the land use structure of Caohai has mainly undergone mutual conversion between farmland and wetland. Before 2005, 164.60 ha of farmland were converted to wetland, from 2005 to 2015, 451.79 ha of wetland were converted to farmland, and from 2015 to 2020, 979.62 ha of farmland were transformed into wetland. The trend for construction land was to decrease first and then increase, with increased construction land primarily coming from farmland and partially from shrubland and forestland. The spatial connectivity of landscape distribution showed a slow decrease to a rapid decrease, then increased and reduced again, while diversity and evenness showed the opposite trend. Rational policies and urban construction planning are essential measures for protecting wetland ecosystems in the karst region. [ABSTRACT FROM AUTHOR]

The distribution characteristics of heavy metal content in the soil of Guizhou real estate hook vine under different land use methods were explored, and the basic data for the high-quality and efficient cultivation of URM producing areas in Guizhou real estate was explored. Taking the soil of the hook vine production area as the research object, the contents of six heavy metals (Cu, As, Cd, Hg, Pb and Cr) in the root zone and non-root zone of the hook vine production area under different land use patterns were studied, and the pollution characteristics of heavy metals were evaluated by single factor and Nemerow composite index. The results showed that contents of heavy metals in URM producing areas in Guizhou are different under different forms of land use. The contents of Cu, As, Hg, Pb and Cr are invariably the highest in URM bases. It is found from the grading of soil heavy metal contents in URM producing areas, contents of all other heavy metals except Cd in forest land are compliant with standards. Under different forms of land use, only forest land is contaminated by heavy metal Cd. A certain antagonistic or synergistic action exhibits among different heavy metals. In general, soil heavy metal contents in URM producing areas in Guizhou are relatively low. Specifically, heavy metal contents in URM bases are significantly higher than those in forest land and waste land, which is mainly attributed to massive fertilization. Therefore, fertilization should be reduced in the practical production process. [ABSTRACT FROM AUTHOR]

In order to explore the physical properties of the soil in different land use patterns. In this paper, the rhizosphere and non-rhizosphere soil under different land use patterns (Uncaria rhynchophylla base, forest land and wasteland) in Uncaria rhynchophylla-producing areas of Jianhe County, Guizhou Province were studied, and the distribution characteristics of soil physical indexes under different land use patterns and their correlations were studied. The results showed that there were significant differences in soil physical properties between rhizosphere and non-rhizosphere under different land use patterns. Compared with forest land and wasteland, Uncaria rhynchophylla base can significantly increase the soil water content, soil capillary porosity, and significantly reduce the soil bulk density. The rhizosphere soil water content was as follows: Uncaria rhynchophylla base (21.09 g/cm³) < forest land (20.19 g/cm³) < wasteland (19.19 g/cm³); The variation of soil capillary porosity was as follows: Uncaria rhynchophylla base (45.04 g/cm³) > forest land (31.37 g/cm³) > wasteland (22.51 g/cm³). Most of the physical indexes of rhizosphere and non-rhizosphere soil in forest land and wasteland showed weak significant correlation. The correlation of soil physical indexes in wasteland is weak, and the correlation between soil water content in rhizosphere and soil capillary porosity is strong. Different land use patterns have a great impact on soil physical indexes, so the role of land use pattern should be considered in the process of Uncaria rhynchophylla planting. [ABSTRACT FROM AUTHOR]

Using the grid-based sampling method, 2755 soil profiles consisting of 22,057 soil samples were sampled and analyzed to study the spatial distribution and storage of soil organic carbon (SOC) in the Houzhai River Basin in Guizhou Province, a typical karst region in southwestern China. The results suggest that the total levels of SOC stored in the 0-10, 0-20, 0-30, and 0-100 cm soil layers of the Houzhai River Basin are approximately 1.48 x 108, 2.65 x 108, 3.44 x 108, and 5.39 x 108 kg C, respectively. SOC content and soil bulk density levels were found to vary depending on the land use. In the 0-50 cm soil layer, forest SOC content levels (including arbor forests, arbor--shrub mixed forests, shrubland, and shrub grassland) are generally higher than those of uncultivated land, followed by grassland and cropland (including paddy fields, arid land, sloping cropland, and abandoned cropland), gardens, and orchard. It is believed that land use is a vital factor directly affecting carbon storage patterns in the study area. Soil thickness, rock outcrop, and slope gradients are the main factors in arrangement of land use by local governments and peasants. This study has established a feasible method for assessment of SOC stock in karst mountainous areas. The findings of this study are applicable to other karst mountainous regions globally. [ABSTRACT FROM AUTHOR]

In this study, three major tea production areas (Guiding County, Duyun City, and Meitan County) in Guizhou Province were used as research objects to investigate the characteristics and influencing factors of the differences in the contents of trace elements and tea quality indexes in tea. The results showed that Meitan County had the highest content of trace elements in tea leaves of different origins, and there was no significant difference in the content of tea polyphenols, caffeine, free amino acids, and water leachate in tea leaves of different origins. The content of active ingredients (tea polyphenols, caffeine, free amino acids, and water leachate) was higher in young tea leaves. The results of random forest analysis showed that the importance of some trace elements in tea leaves on the content of tea polyphenols, caffeine, and free amino acids was significant at the levels of 0.05 and 0.01. This result suggests that the content of trace elements in tea leaves has an extremely important influence on the content of tea quality index components. [ABSTRACT FROM AUTHOR]

To study the speciation characteristics of soil Zn and its distribution in different tillage layers during paddy and drought rotation. Taking the cultivated soil under rice-rape rotation in Bozhou District, Zunyi City, Guizhou Province as the research object, the speciation characteristics and driving factors of soil Zn during rice-rape rotation were studied. In the process of rice-rape rotation, the total amount of heavy metal Zn in surface soil was greater than that in bottom soil. In the depth of 0-40 cm soil layer, the exchangeable fraction of Zn in soils was small, and residue fraction was the greatest. The exchangeable fraction of Zn in surface soils was positively correlated with carbonate bounded fraction and iron-manganese oxide bounded fraction, and negatively correlated with residue fraction. While the exchangeable fraction of Zn in bottom soil was positively correlated with iron-manganese oxide bounded fraction and organic bounded fraction, and positively correlated with residue fraction. During rice-rape rotation process, the content of Zn showed a significant surface aggregation, and was affected by different forms and contents. [ABSTRACT FROM AUTHOR]