Rhizosphere and non-rhizosphere soil organic carbon and its labile fractions in alpine desertified grassland affected by vegetation restoration

Abstract

Grasslands are the predominant land use type in China, which is currently encountering significant desertification issues. Consequently, restoring grassland vegetation has important implications for terrestrial carbon (C) levels and, consequently, the global C balance. This study focused on Salix cupularis, the primary plant used for desert control on the eastern edge of the Qinghai-Tibet Plateau. We analysed the rhizosphere and non-rhizosphere soil up to the depth of 60 cm after Salix cupularis growth for 0-24 years, examining soil total organic carbon (TOC) and its labile fractions. Following restoration, there was a gradual increase in TOC and its labile fractions, with the most significant changes observed in the rhizosphere soil at a depth of 0-20 cm. After 24 years of restoration, the TOC content in both rhizosphere and non-rhizosphere soil had increased by 141.74% and 39.44%, respectively. Labile organic C in the rhizosphere soil increased more rapidly and pronouncedly compared with the TOC. Specifically, dissolved organic C and easily oxidised organic C in the rhizosphere soil saw substantial increases of 211.03% and 217.65%, respectively. Meanwhile, compared with the 4 years of restoration, soil C pool management index of the 8-24 years soils increased, ranging from 15.70% to 132.21%. Therefore, long-term vegetation restoration on the eastern margin of the Qinghai-Tibet Plateau can significantly enhance TOC and its labile fractions, as well as improve soil C sink capacity and quality.

Keywords

• ecological restoration
• ecosystem
• soil labile carbon
• carbon pool management index
• soil depth