Effects of modified organic material addition on soil and microbial communities in ecologically restored engineering slopes of the Qinghai-Tibetan plateau: A mesocosm study

Organic material plays an essential role in the ecological restoration of different types of surfaces with engineering damage in extremely fragile environments. An outdoor mesocosm experiment was conducted to explore the effects of modified organic material on chemical, physical properties and microbial communities of reconstructed soil in ecologically restored engineering slopes of the Qinghai-Tibetan plateau. The physical and chemical properties of the soil indicate that the addition of modified organic materials significantly improves soil nutrients. In this area, organic carbon increased by 1.87 g·kg-1 in the frame beam slopes compared with the control area, and the potassium content doubled. In addition, modified organic material effectively induced soil metabolism responses, mainly promoting the activities of soil enzymes like amylase, cellulase, urease, sucrase, and alkaline phosphatase. Moreover, addition of modified organic material noticeably changed the abundance and structure of microbial communities in soils. The enhanced concentrations of the signal molecules N-acylated-L-homoserine lactone and auto inductor peptide indicated that addition of modified organic materials significantly influenced quorum-sensing in soil microbial communities. There are differences in the soil improvement effects of different types of slopes, among which the frame grid beam has the best effect. These findings demonstrate the effect and underlying mechanisms of the addition of incorporating modified organic materials, primarily sodium carboxymethyl cellulose and anionic polyacrylamide, into the soil of engineering slopes. These results have extensive application prospects for ecological restoration in strict environments.