[Vertical Distribution of Soil Dissolved Carbon and Its Influencing Factors in the Artificial Shelterbelt Irrigated with Saline Water in an Extreme Drought Desert].

Abstract

Dissolved carbon (DC) is the most active carbon fraction in soils. Vegetation restoration and reconstruction accelerate the carbon cycle in arid desert regions. Studying the DC distribution in soil profiles of artificial shelterbelt under saline irrigation can provide theoretical support and decision-making basis for artificial shelterbelt management, development, and utilization in arid desert areas. In this study, we took the artificial shelterbelts drip-irrigated with five different mineralization and one shifting sandy land (CK) along the Taklimakan Desert Highway as sampling plots, analyzed and discussed the vertical distribution characteristics of soil dissolved organic carbon (SDOC) and dissolved inorganic carbon (SDIC) in the 0-1 m profiles, and further analyzed their relationships among different factors. The results showed that SDOC and SDIC of CK and shelterbelts under 2.82 g·L-1 irrigation showed an "I" type distribution with a linear function relationship. The SDOC and SDIC of four other treatments showed a "Γ" type distribution with power function relationships. The fluctuation ability and contribution degree of SDOC and SDIC of different treatments in the surface layer were higher than those in the lower layers, and the fluctuation and contribution intensity of SDOC were higher than those of SDIC. Except for 2.82 g·L-1 treatment, the average SDOC contents of other treatments were 2-4 times those of SDIC. The average SDOC content of 2.82 g·L-1 treatment was lower than CK; other treatments were 3-5 times that of CK; and the average SDIC content of all treatments increased 15.0%-57.9% than CK. For the 0-5 cm layer, SDOC content increased with the irrigation water mineralization except the 2.82 g·L-1 treatment, but SDIC content firstly increased and then decreased with increasing mineralization, and that for the 4.82 g·L-1 treatment was highest. The SDOC and SDIC were positively correlated with EC, SOC, irrigation water mineralization, SIC, and soil moisture, for which they both showed a weak positive correlation with soil moisture; they were negatively correlated with soil depth. The SDOC and SDIC showed a weak negative correlation and a weak positive correlation with pH, respectively. In summary, the mineralization of irrigation water has an important impact on the vertical distribution of SDOC and SDIC, and their distribution also has close relationships with EC, SOC, SIC, soil moisture, and soil depth, which is of great significance for plantations in extremely drought deserts.