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Liquid and plastic limits are important parameters of soil hydraulic properties and are important in the research of collapsing gullies. To investigate the specific ion effects on the liquid and plastic limits of collapsing gullies, soil samples from three soil layers in a soil profile（red soil layer, sandy soil layer, and detritus layer) of a stable collapsing gully located in Hetian Town of Changting County, Fujian Province, were collected and exchanged with three kinds of electrolyte solutions（Li+, Na+, and K+) to analyze the liquid and plastic limits. The main results were as follows: the red soil layer had the highest plastic limit, liquid limit, and plasticity index, followed by the sandy soil and detritus layers（P＜0.05). Correlation analysis showed that the clay content, organic matter content, cation exchange capacity, and kaolinite content were positively correlated with the plastic and liquid limits（P＜0.05). Clay and organic matter contents were significantly positively correlated with the plastic limit. The plastic limit, liquid limit, and plasticity index of the red soil layer exchanged with K+ were 5.80%, 9.53%, and 12.99% higher than those exchanged with Li+, and 3.50%, 9.77%, and 15.86% higher than those exchanged with Na+, respectively. The plastic limit, liquid limit, and plasticity index of the sandy soil layer exchanged with K+ were 7.22%, 6.69%, and 6.83% higher than those exchanged with Li+, and 4.33%, 5.27%, and 7.32% higher than those exchanged with Na+, respectively. However, the liquid and plastic limits of the detritus layers did not differ significantly. The liquid and plastic limits of the red and sandy soil layers exchanged for K+ were significantly higher than those exchanged for Li+ and Na+. Therefore, compared with Li+ and Na+, K+ could increase the liquid and plastic limits of collapsing gullies. [ABSTRACT FROM AUTHOR]

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Correlation analysis of physical and mechanical indexes of Shanghai soil was carried out. Using the support vector machine algorithm, the authors constructed a correlation analysis model of soil plasticity index, liquidity index and compressibility coefficient based on the soil indoor test data obtained from several engineering sites. Then the model parameters were optimized by combining the error indexes. Comparing the results of support vector machine model with those of traditional linear and polynomial fitting methods, it was shown that the prediction results of the model are basically consistent with the actual results, and another advantage of model is that it can carry out deeper mining from more data to improve its robustness. Considering the engineering properties of different category soils are quite different, the authors further analyzed the performance and applicability of model, and established the relationship curve between the forecast bias of each testing sample and its physical indexes. The results indicate that the error of medium compressible soil is smaller than high compressible soil, and the model is more stable and accurate, which could provide a reference for the research of soil compressibility in Shanghai.

Copyright of Chinese Journal of Applied Ecology / Yingyong Shengtai Xuebao is the property of Chinese Journal of Applied Ecology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

To understand the intra- and inter-annual population dynamics of Artemisia scoparia in the desert steppe, we set up three treatments, i.e., increasing the precipitation by 30%, reducing the precipitation by 30%, and the control (CK) in each soil habitat of aeolian sandy soil, sierozem soil, and bedrock weathered sedimentary soil. We drew up the dynamic life table to produce population survival and death curves and analyzed the population dynamics of A. scoparia in different habitats. Results showed that the survival curve of A. scoparia was approached to Deevey-1type. The survival rate was high in the early growth stage and tended to be relatively stable. The mortality rate maintained at a low level, but rose fast at the end of the growth stage. The individual survival number of A. scoparia in all habitats fluctuated at the early stage and declined at the later stage. The mortality rates of A. scoparia in habitats of both aeolian sandy soil and sierozem soil fluctuated greatly. There was no significant difference in the effects of increased and decreased precipitation treatments on the mortality rate of A. scoparia. Soil types had significant effects on all parameters, including the plant height, crown width, density, cover, and biomass of A. scoparia. Precipitation treatments had significant impacts on plant height, crown width and coverage of A. scoparia, and had no significant effect on plant density and biomass. The interactions between soil type and precipitation treatments had only a significant impact on plant height and crown width. The plasticity index of biomass in the habitat of bedrock weathered sedimentary soil was significantly higher than that in habitats of aeolian sandy soil and sierozem soil, while the plasticity index of plant coverage in the habitats of both sierozem soil and bedrock weathered sedimentary soil were significantly higher than that in the habitat of aeolian sandy soil. The density plasticity index of increased precipitation treatment was significantly higher than those of CK and the decreased precipitation treatments. The plasticity index of plant height and crown width were higher than other parameters, indicating that A. scoparia could respond to habitat changes by giving priority to these two parameters under different habitat pressures.