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Aims

Biological soil crusts (BSCs) can affect soil properties including water dynamics and cycling of soil carbon and nitrogen in dryland ecosystems. Previous research has mostly focused on effects of BSCs on soil water distribution or carbon and nitrogen fixation in the surface soil layer. Thus, little is known about effects of BSCs on properties throughout the soil profile. In the current study, we assessed the effects of BSCs on the distribution of soil water content (SW), soil organic carbon content (SOC) and soil total nitrogen content (STN) throughout the soil profile as well as the influence of water conditions on the effects of BSCs.

Methods

In a field investigation in Mu Us Sand land, North China, soil samples were taken from plots with and without BSCs on 13 and 28 September 2006, respectively. On the two sampling dates, average soil gravimetric water content was 3.83% (+/- 1.29%) and 5.08% (+/- 0.89%), respectively, which were regarded as low and high water conditions. Soil samples were collected every 5 cm to a depth of 60 cm, and SW, SOC and STN were measured in the laboratory.

Important Findings

(i) BSCs affected profile distribution of SW, SOC and STN. In addition, water conditions within the plots significantly modified BSCs’ effects on the profile distribution of SW, but marginally affected the effects on SOC and STN. (ii) Under high water conditions, SW in the surface soil layer (0-10 cm) was higher in soils with BSCs compared to those without BSCs, while the opposite was true in the deep soil layer (30-55 cm). (iii) Under low water conditions, SW was lower with BSCs compared with no BSCs in near-surface (5-20 cm) and deep (25-40 cm) soil layers. (iv) BSCs affected SOC and STN only in the surface soil layer (0-5 cm) and were modified by plot water conditions.