Integrating Biocrusts into Dust Emission Models: A Global Experimental Dataset

In global drylands, apparently bare soil between plants is frequently covered by biological soil crusts (biocrusts). Biocrusts are poikilohydric communities that play key ecosystem roles in drylands, as they regulate infiltration, evaporation and water retention, provide soil biodiversity, and control biogeochemical cycling of nutrients. Moreover, biocrusts form a rough, cohesive surface layer that prevents soil particle detachment and nutrient mobilization and lost by wind and water erosion.

Approximately 12% of the Earth surface, corresponding to 40% of the global drylands, are currently covered by biocrusts, and it has been estimated that they prevent approximately 700 Tg of dust per year from being emitted into the atmosphere. However, these estimates are based on very few available measurements and do not represent the large variability in biocrust community composition and underlying soil properties.

Within the framework of the CRUST-R forze project, we have developed a global dataset to quantify the effects of biocrusts on potential dust emission. To this end, we measured the threshold friction velocity (TFV), representing the minimum wind velocity at which the soil starts being blown away, and sediment delivery under controlled wind tunnel conditions. We investigated 177 samples representing a wide range of biocrust communities and reference soils from biocrust-dominated habitats worldwide. In addition to TFV and sediment delivery measurements, our dataset also includes functional traits related to biocrust resistance to wind erosion, such as organic matter content, aggregate stability, surface roughness, and extracellular polymeric substances (EPS) content. This database is relevant to understand the underlying mechanisms of an increase in TFV upon biocrust colonization. Our preliminary results show the high relevance of biocrusts in soil stabilization and dust prevention, supporting the explicit inclusion of biocrusts in dust emission parameterizations of Earth system models.