Patterns and determinants of plant- and microbial-derived carbon in desert riparian ecosystems: Implications for organic C accumulation

Abstract

Desert riparian ecosystems play a critical role in carbon cycling in arid regions. As a natural barrier between deserts and oases, riparian vegetation reduces the wind’s erosive effect on the soil through its leaves and branches, while its roots stabilize soil nutrients. However, the relative importance of plant- and microbial-derived carbon (C) for soil organic carbon (SOC) in desert riparian ecosystems remains an open question. Here, we investigated the variations in plant- and microbial-derived C in soil profiles (0–40 cm) across typical vegetation types (woodland, shrubland, and grassland) in desert riparian ecosystems. We observed that the SOC content, including the plant- and microbial-derived C, in desert riparian ecosystems were largely determined by vegetation types. Interestingly, the mean contribution of plant-derived C to SOC in 0–40 cm grassland vegetation was significantly higher than that in woodland and shrubland vegetation (13.74 % vs 4.95 % vs 4.35 %, respectively). Microbial-derived C contributed 5.55 %, 5.24 % and 3.25 % on the mean to SOC in 0–40 cm grassland, woodland and shrubland vegetation, respectively. Bacterial-derived C contributed more to SOC in woodland than shrubland and grassland vegetation. Soil water conditions emerged as a significant factor affecting the accumulation of plant- and microbial-derived C. Partial least squares path model (PLS-PM) showed that soil water content (SWC) can promote the accumulation of plant- and microbial-derived C by regulating soil nutrients and enzyme activities (PO and NAG). These findings provide new insights into SOC accumulation variations in desert riparian ecosystems, highlighting the distinct contributions of plant- and microbial-derived carbon under different vegetation types.