The seasonal and successional variations of carbon release from biological soil crust-covered soil

Biological soil crusts play key roles in global carbon cycles in terms of carbon exchange between pedosphere and the atmosphere, yet few explorations have been conducted regarding how seasonal variations and successional patterns of the crusts influence C release in temperate desert ecosystems. The carbon release of four soil cover types (mobile dune sand, algae-, mixed- and moss-crusted) was measured in PVC mesocosms both before, in relatively dry conditions, and immediately after natural rainfall events. Intact crusts at a 10 cm level were removed from the southeast edges of Tengger Desert, China. Amounts of released C from the four soil cover types accounted for 18.4%-23.1%, 46.9%-52.3%, and 27.7%-31.1% of total C released in the spring, summer, and fall seasons, respectively. The annual C release amounts were 56.6 gCm−2 yr−1 for the mobile dune sand, 67.9 gCm−2 yr−1 for the algae-crusted soil, 90.3 and 128.8 gCm−2 yr−1 for the mixed-crusted soil and moss-crusted soil. Linear regression analyses suggest a significant positive relationship between seasonal accumulative rainfall and carbon release amounts. These findings indicate that variations in the amount of seasonal rainfall and the succession of the crusts significantly change the carbon output patterns in the sandy desert ecosystem.