Biological soil crust development affects physicochemical characteristics of soil surface in semiarid ecosystems

Water and nutrients are scarce resources in arid and semiarid ecosystems. In these regions, biological soil crusts (BSCs) occupy a large part of the soil surface in the open spaces surrounding patches of vegetation. BSCs affect physicochemical soil properties, such as aggregate stability, water retention, organic carbon (OC) and nitrogen (N) content, associated with primary ecosystem processes like water availability and soil fertility. However, the way BSCs modify soil surface and subsurface properties greatly depends on the type of BSC. We hypothesised that physicochemical properties of soil crusts and of their underlying soils would improve with crust development stage. Physicochemical properties of various types of soil crusts (physical crusts and several BSC development stages) and of the underlying soil (soil layers 0–1 cm and 1–5 cm underneath the crusts) in two semiarid areas in SE Spain were analysed. The properties that differed significantly depending on crust development stage were aggregate stability, water content (WC) (at −33 kPa and −1500 kPa), OC and N content. Aggregate stability was higher under well-developed BSCs (cyanobacterial, lichen and moss crusts) than under physical crusts or incipient BSCs. WC, OC and N content significantly increased in the crust and its underlying soil with crust development, especially in the first centimetre of soil underneath the crust. Our results highlight the significant role of BSCs in water availability, soil stability and soil fertility in semiarid areas.

This work was funded by the Spanish Ministry of Science and Technology and the European Union ERDF under the PROBASE (CGL2006–11619/HID), CARBORAD (CGL2011-27493) and BACARCOS (CGL2011-29429) research projects, and by the Junta de Andalucía (Andalusian Regional Govt.) Ministry of Innovation, Science and Business under the GEOCARBO (RNM-3721), GLOCHARID and COSTRAS (RNM–3614) projects, which also received ERDF funds. The first author received an FPI fellowship from the Spanish Government (BES–2007–15218). We are grateful to Cecilio Oyonarte for his guidance in laboratory methods, Montserrat Guerrero and Manuel Salvador for their help in the lab work, and Adrián Escudero and Jordi Moya for their assistance with statistical analysis. Deborah Fuldauer revised the English language usage in the manuscript. The authors are grateful to anonymous referees for valuable comments and suggestions that helped to improve the quality of the paper.

Peer reviewed