Characteristics of Carbon Flux in Two Biologically Crusted Soils in the Gurbantunggut Desert

Arid and semiarid areas have long been considered as carbon sources because of their low vascular plant coverage. However, some recent studies have found that carbon absorption occurs in dry areas when eddy covariance was used to examine carbon flux at the ecosystem level. The soil surface characteristic is a primary factor that determines the carbon flux. Different from other ecosystems, 40%-70% of the soil surface in arid and semiarid regions is covered by biological soil crusts.

Biological soil crusts are dormant most of the year, so examining carbon flux during these periods can enable a full understanding of this process in biologically crusted soils. However, few studies have evaluated carbon flux in biologically crusted soils. Therefore, Prof. ZHANG Yuanming and his research team chose the Gurbantunggut Desert in Northwestern China as a study site to examine carbon flux in moss- and cyanobacterial/lichen-dominated crusts, as well as bareland on clear days once a month from April to October 2010. They also investigated the carbon flux in the two biologically crusted soils after different amounts of precipitation (0, 2, 5, and 15 mm).

The results showed that carbon flux between crusted soil and bare land had no significant difference, with average values of 0.16, 0.2, and 0.12 μmol m⁻² s⁻¹ for moss-crusted soil, cyanobacterial/lichen crusted soil, and bare land, respectively. The corresponding Q₁₀ values for the three soils were 2.9, 3.5, and 1.9, respectively. Precipitation significantly elicited carbon flux, reaching a maximum value of 2.4 μmol m⁻² s⁻¹. After precipitation, the net carbon flux in light was lower than that in dark respiration. No carbon influx was observed in light condition. The average carbon flux rate and total carbon production increased exponentially with the precipitation amount. This study indicated that biological soil crusts did not increase the respiration of soil, but increased the temperature dependence of soil carbon flux because of the higher microbial biomass than bare land.

The result has been published on Catena, 2012, 96: 41-48. The paper can be downloaded from http://www.sciencedirect.com/science/article/pii/S0341816212000781.