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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.)

In order to find out the spatial variation characteristics and sampling spacing of soil bulk density, 100 m×100 m area was selected for the mature forest of Cunninghamia lanceolata, and a total of 100 plots were set up by grid method (10 m×10 m). The spatial heterogeneity of soil bulk density in different soil depths (0-20, 20-40 cm) was analyzed by classical statistics and geostatistics, and the optimal sampling spacing and sampling number were explored by "resampling". The purpose of this paper is to reduce the consumption of manpower and material resources for soil bulk density sampling. In this study:the soil bulk density and the coefficient of variation of soil increase with the increase of the soil layer, the coefficient of variation is middle variation, 0-20 cm, and the optimal model of 20-40 cm is the exponential model and the spherical model, and the spatial distribution is plaque-like, and belongs to the medium-space self-correlation. The increase of sampling spacing will lead to the pattern of "decrease-stability-limit" of sampling number. Although the coefficient of variation does not change much, it can obtain a more real coefficient of variation of soil bulk density. The variation degree of spatial autocorrelation, fitting effect and nugget below 20 m×20 m sampling spacing are better. In the analysis of spatial variation in small scale (100 m×100 m), the sampling spacing is 20 m×20 m and the sampling number is arranged 25, which can not only meet the accuracy of Kriging interpolation, but also save manpower and material resources. [ABSTRACT FROM AUTHOR]

In order to study how the response of soil DOC leaching to nitrogen deposition under different soil thickness in karst system, using karst lime soil as the test sample, three different soil thickness( 10 cm,25 cm,50 cm) leaching tubes were designed by soil column leaching method. The leaching tube was made of PVC material with a diameter of 20 cm. Three different nitrogen depositions,LN( 191. 08 g/m2),MN( 254. 78 g/m2), and HN( 318. 47 g/m2) were selected, and perennial ryegrass was applied to the soil surface. The results showed that nitrogen deposition had a certain effect on soil DOC leaching. Soil thickness had a significant effect on soil DOC leaching. The shallower the soil thickness, the larger the nitrogen deposition, the larger the DOC leaching loss, and vice versa. This study can provide some reference and basis for solving the soil carbon cycle problem and soil quality evaluation of karst system. [ABSTRACT FROM AUTHOR]

To study the relationship between the spatial distribution characteristics of soil organic carbon (SOC) and land use in karst river basins, 22 057 soil samples from 2 755 soil profiles were collected with a grid- sampling method at a 150 m scale in the Houzhai River Basin. The SOC density characteristics under different land uses were analyzed. The results indicate that human disturbance, soil thickness and rock outcrop are critical factors to SOC density in the Houzhai River Basin. The land uses in the Houzhai River Basin with SOC density (0-100 cm) in descended order are paddy lands, arid lands, artificial fruit forestlands, garden lands, grasslands, abandoned lands, sloping croplands, arbor- shrub mixed forestlands, arbor forestlands, uncultivated lands, shrub lands and shrub- grass lands. The average SOC density in the top 1 m soil of Houzhai River Basin is 8.70 kg/m2 which is a little lower than the average SOC density in China (10.83 kg/m2), and the SOC storage in the Houzhai River Basin is 5.39×108 kg. In conclusion, scientific and reasonable rearrangement and management of land uses could enlarge the SOC storage capacity in a karst river basin. [ABSTRACT FROM AUTHOR]

In order to illustrate the distribution pattern of soil organic carbon density (SOCD) and its main influencing factors in small karst watershed, this paper quantitatively analyzed the spatial heterogeneity and distribution characteristics of SOCD using 2 755 thoroughly investigated soil profiles consisting of 23 536 soil samples with geo- statistical analysis, and analyzed the major influencing factors of SOCD with canonical analysis. The result showed that the SOCD decreases gradually with soil depth's increasing in the Houzhai Basin; in particular, the maximum value is 12.47 kg/m2 and the minimum value is 0.11 kg/m2. The average SOCD at 100 cm depth is 12.11 kg/m2, which is higher than the value at national level. An optimal fitting model for the SOCD in this basin is Gaussian model, showing a moderate spatial correlation. The Kriging interpolation suggested that the soil carbon density is higher in the east region, while lower in the south region, showing an ascending trend from the middle to the surrounding area. In the Houzhai Basin, the SOCD at the depth of 100 cm differs in soil with different vegetation types, different soil utilization types and different soil types. The soil thickness is positively correlated with organic carbon content, and gravel content, slope direction, slope, soil bulk density and the rock exposed rate are negatively correlated with organic carbon density. Soil thickness, rock coverage and gravel content are the principal influencing factors of SOCD in the Houzhai Basin, among which soil thickness has the greatest impact. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Agro-Environment Science is the property of Journal of Agro-Environment Science Editorial Board 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.)