Effects of land-use type on soil organic carbon and carbon pool management index through arbuscular mycorrhizal fungi pathways

Carbon pool management index (CPMI) can be used to indicate the stability of soil carbon and assess the effect of anthropogenic activities on soil carbon dynamics of different land-use types. The impacts of land-use types on CPMI are usually evaluated through soil organic carbon (SOC) fractions and contents, which are closely related to arbuscular mycorrhizal fungi (AMF) and its secretory product (Glomalin-related soil protein, GRSP). However, most previous studies focused on the effects of GRSP on SOC fractions, and few studies paid attention to the influence of AMF to SOC fractions and CPMI. This study was to investigate the interrelationship between SOC fractions and contents, AMF growth and colonization status, GRSP contents and CPMI at the soil depths from 0 to100 cm among four land-use types (woodland, grassland, farmland, abandoned land) in Songnen Grassland, Northeast China. The results showed that the content of SOC in woodland was 2.35 times higher than that of abandoned land, with an order as follow: woodland > grassland > farmland > abandoned land. The readily oxidizable organic carbon content in soil ranged from 1.12 to 1.31 g kg-1, with a sequence of from high to low: woodland > farmland > grassland > abandoned land. Carbon in GRSP accounted for 4.57-14.91% of SOC in the 0-100 cm soil depths. The structural equation modeling revealed that land-use types had two pathways to affect CPMI through GRSP: (i) directly via total GRSP content; (ii) or indirectly via hyphal length density of AMF. This study demonstrates the effects of land-use on soil organic carbon and carbon pool management index through glomalin related soil protein and other colonization traits of arbuscular mycorrhizal fungi, and suggests the suitable management methods of land use for future carbon-neutral policy in farming-pastoral ecotone area of Northeastern China.