Surface Stability in Drylands Is Influenced by Dispersal Strategy of Soil Bacteria

David R Elliott,Andrew D Thomas,Craig L Strong,Joanna Bullard

doi:10.1029/2018jg004932

Abstract

AbstractMicrobial adaptations for survival and dispersal may directly influence landscape stability and potential for dust emission in drylands where biological soil crusts (biocrusts) protect mineral soil surfaces from wind erosion. In the Lake Eyre basin of central Australia we operated a wind tunnel on sandy soils and collected the liberated material, which was subjected to DNA sequencing to identify the microbial community composition. Microbial composition of entrained dust was compared with that of the source sand dune soil in addition to nearby claypan and nebkha soils and water channels that together form a recycling sediment transport system. Wind was found to preferentially liberate 359 identified taxa from sand dunes, whereas 137 identified taxa were found to resist wind erosion. Water channel communities included many taxa in common with the soil samples. We hypothesize that the ease with which soil microbes become airborne is often linked to whether the organism is adapted for dispersal by wind or vegetative growth and that biocrust organisms found in water channels may sometimes use a fluvial dispersal strategy, which exploits rare flooding events to rapidly colonize vast pans that are common in drylands. We explain likely geomorphic implications of microbial dispersal strategies which are a consequence of organisms engineering the environment to provide their particular needs. By identifying microbes fitting expectations for these dispersal strategies based on differential abundance analyses, we provide a new perspective for understanding the role of microbiota in landscape stability.

Highlights

In drylands where vegetation is sparse, soil microbes provide some ecosystem functions that are normally delivered by plants in temperate vegetated systems (e.g., Lange et al, 1992; Ferrenberg et al, 2017)
We hypothesize that the ease with which soil microbes become airborne is often linked to whether the organism is adapted for dispersal by wind or vegetative growth and that biocrust organisms found in water channels may sometimes use a fluvial dispersal strategy, which exploits rare flooding events to rapidly colonize vast pans that are common in drylands
In this paper we report on the microbial ecology of a dynamic ecosystem in central Australia comprising a 25-km2 claypan in the Lake Eyre basin bounded by sand dunes and ephemeral river channels, where Journal of Geophysical Research: Biogeosciences

Summary

Introduction

In drylands where vegetation is sparse, soil microbes provide some ecosystem functions that are normally delivered by plants in temperate vegetated systems (e.g., Lange et al, 1992; Ferrenberg et al, 2017). The interactions between fluvial and aeolian processes in drylands have been demonstrated as important over timescales ranging from seasons to glacial-interglacial cycles (McTainsh, 1987; Langford, 1989; Bullard & McTainsh, 2003; Field et al, 2009). The combination of water flow and wind direction can result in sediment cycling at a range of different spatial scales from catchments exceeding 1 × 106 km (Bullard & McTainsh, 2003) to within smaller dune-pan systems (Thomas et al, 1993). Microbiota have not generally been considered as a component of this fluvial-aeolian system; it has been recognized that biocrust organisms can act as ecosystem engineers (Viles, 2008)

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