Characteristics of Soil Aggregates and Organic Carbon Content for Ecological Restoration Slopes at Xiangjiaba Hydropower Station

Abstract

[Objective] The effects of ecological engineering restoration technology on soil aggregate stability and organic carbon distribution were analyzed in order to provide a scientific basis for improving soil structure stability and carbon sink function of different ecological restoration slopes at Xiangjiaba Hydropower Station. [Methods] Four different ecological restoration slopes at Xiangjiaba Hydropower Station were studied: vegetation concrete (CBS), thick base material spraying (TB), frame beam covering soil (FB), and external soil spraying (SS). The distribution and stability of soil aggregates and the characteristics of organic carbon content were determined by the wet sieve method for two natural restoration slopes: natural forest (NF) and abandoned land (AS, used as the control). [Results] ① The soil for each slope was dominated by large aggregates >0.25 mm. The macroaggregate content in natural forest was the highest (81.83%). The vegetation concrete and thick base material slope had the second highest macroaggregate contents, and the macroaggregate content of waste residue land was the lowest (55.19%). The MWD and GMD values of the four artificial ecological restoration slopes were lower than the values of the natural forest, and higher than the values of the waste residue land. The values of the thick substrate slope were the highest (2.96 mm and 1.47 mm), respectively. The fractal dimension (D) of the soil spray seeding and slag field was significantly higher (p0.25 mm were the highest in all ecological restoration slope measures. In addition to soil spray seeding and waste residue land, other restoration measures and natural forests had the largest contribution rate of >2 mm soil aggregates. ③ Correlation analysis showed that SOC was significantly positively correlated with MWD, GMD, and R0.25 (p5 mm and 5—2 mm were significantly positively correlated with soil MWD, GMD, R0.25, and SOC (p<0.01), and significantly negatively correlated with D (p<0.01). [Conclusion] In the study area of Xiangjiaba Hydropower Station, thick substrate spraying technology and vegetation concrete ecological restoration technology improved soil structure and organic carbon pool similarly to natural forest. The improvement effect of external soil spraying technology was poor.

Keywords

• ecological restoration slope
• aggregate stability
• soil organic carbon
• xiangjiaba hydropower station