Biological soil crusts (BSCs), composed of various combinations of cyanobacteria, bacteria, algae, fungi, lichens and bryophytes (mosses and liverworts), are widely distributed on the surface of the global arid area. BSCs play an important role in ecological functions.

BSCs are a primary source of nitrogen (N) in deserts through N-fixation. N-fixation and transformation of the BSCs are affected by the microbes within them. The microbial activities fluctuated with environmental factors like temperature and moisture, which vary seasonally.

In addition, distribution pattern of the microbial community at different spatial scales is of great significance for evaluating how the biological soil crust responds to global changes.

Researchers from the Xinjiang Institute of Ecology and Geography of the Chinese Academy of Sciences studied the N dynamics of the BSCs and the spatial distribution pattern of related bacterial diversity.

They found that with the development of BSCs, different N forms showed an increasing trend, with seasonal changes in each N form. The available N content was mainly affected by temperature and moisture in summer, and by the variation of soil temperature in winter.

The seasonal dynamics in different N forms may satisfy the diverse N uptake requirements for different plant species, which is an important nutrition mechanism for adaptation of desert plants to drought stress.

In the sanddune scale, from the top to the lowland of sanddune, BSCs changed from cyanobacterial and physical crusts to cyanobacterial-lichen crusts, with moss crusts sparsely distributed on the lowland and inter-dunes.

In the landscape scale of five major deserts in northwestern China, soil attributes and BSC developments had more profound impacts on soil bacterial communities than precipitation, and the community composition in cyanobacterial-lichen crusts differed significantly among five desert habitats.

In addition, a fast turnover rate of bacterial community communities induced by topography was observed.

The study is significant for understanding the potential responses of BSCs to climate change in desert areas. It also provides novel insights for investigating the geographical distribution and assemblage of soil bacterial communities in deserts.

Related results were published in Geoderma and Soil Biology & Biochemistry.