BSC: Understanding the Key Players of N2 Fixation in European Biological Soil Crusts

Biological soil crusts (BSCs) are present in habitats where the growth of vascular plants is limited and play an essential role in soil stabilization and reduction of soil erosion by wind or water. Besides their importance in CO2 fixation, it has been recently estimated that BSCs contribute greatly to the global nitrogen (N) cycle, as BSCs fix in total ~38 Tg N per year, which is ~30% of the total biological N2 fixation in terrestrial ecosystems. This input of N (and of carbon) by BSCs facilitates higher plant colonization as a long-term effect.

In many BSCs, N is considered an important factor limiting primary production, and thus N2 fixation is one of the key processes in these systems. BSCs greatly rely on the activity of N2-fixing microorganisms (diazotrophs) to provide the systems with biological available N. Most of the investigations on diazotrophs in BSCs have been focused on arid or semi-arid locations, while our knowledge on temperate BSCs is still scarce.

In this project we will investigate N2 fixation in four different European locations, with a focus on soil crusts from temperate regions. N2 fixation activity will be addressed by combining 15N2 fixation assays with sequencing of the functional marker gene for N2 fixation (the dinitrogenase reductase, nifH), as well as high-resolution Secondary Ion Mass Spectrometry (NanoSIMS). With this project we hope to shed light on the diazotrophs that drive this essential ecosystem process in temperate BSCs.

This project is funded by the Austrian Academy of Sciences.

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