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

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Surface Stability in Drylands Is Influenced by Dispersal Strategy of Soil Bacteria Surface stability in drylands is influenced by dispersal strategy of soil bacteria Item Type Article Authors Elliott, David R.; Thomas, Andrew D.; Strong, Craig L.; Bullard, Joanna Citation Elliott, D.R., Thomas, A.D., Strong, C.L., Bullard, J. (2019). 'Surface stability in drylands is influenced by dispersal strategy of soil bacteria'. JGR Biogeosciences, pp, 1-23. DOI: 10.1029/2018JG004932 DOI 10.1029/2018jg004932 Publisher American Geophysical Union (AGU) Journal Journal of Geophysical Research: Biogeosciences Rights Attribution-ShareAlike 4.0 International Download date 29/09/2021 12:27:41 Item License http://creativecommons.org/licenses/by-sa/4.0/ Link to Item http://hdl.handle.net/10545/624219 Confidential manuscript submitted to JGR-Biogeosciences 1 Surface Stability in Drylands is Influenced by Dispersal 2 Strategy of Soil Bacteria 1 2 3 3 David R. Elliott , Andrew D. Thomas , Craig L. Strong , and Joanna 4 4 Bullard 1 5 Environmental Sustainability Research Centre, University of Derby, Derby, UK. 2 6 Department of Geography and Earth Sciences, Aberystwyth University, Aberystwyth, UK. 3 7 The Fenner School of Environment & Society, ANU College of Sciences, The Australian National 8 University, Canberra ACT 2601, Australia. 4 9 Department of Geography, School of Social, Political and Geographical Sciences, Loughborough 10 University, Leicestershire, UK. 11 Key Points: 12 • Microbial communities of dryland ephemeral lake bed, dunes, and river channels 13 are characterised 14 • Wind preferentially mobilises specific microbes from soil surface biocrusts 15 • Microbial dispersal adaptations may influence soil stability by promoting or in- 16 hibiting adhesion Corresponding author: D. R. Elliott, [email protected] {1{ Confidential manuscript submitted to JGR-Biogeosciences 17 Abstract 18 Microbial adaptations for survival and dispersal may directly influence landscape sta- 19 bility and potential for dust emission in drylands where biological soil crusts (biocrusts) 20 protect mineral soil surfaces from wind erosion. In the Lake Eyre basin of central Aus- 21 tralia we operated a wind tunnel on sandy soils and collected the liberated material, which 22 was subjected to DNA sequencing to identify the microbial community composition. Mi- 23 crobial composition of entrained dust was compared with that of the source sand dune 24 soil in addition to nearby claypan and nebkha soils, and water channels which together 25 form a recycling sediment transport system. Wind was found to preferentially liberate 26 359 identified taxa from sand dunes whereas 137 identified taxa were found to resist wind 27 erosion. Water channel communities included many taxa in common with the soil sam- 28 ples. We hypothesise that the ease with which soil microbes become airborne is often 29 linked to whether the organism is adapted for dispersal by wind or vegetative growth, 30 and that biocrust organisms found in water channels may sometimes use a fluvial dis- 31 persal strategy which exploits rare flooding events to rapidly colonise vast pans which 32 are common in drylands. We explain likely geomorphic implications of microbial disper- 33 sal strategies which are a consequence of organisms engineering the environment to pro- 34 vide their particular needs. By identifying microbes fitting expectations for these dis- 35 persal strategies based on differential abundance analyses, we provide a new perspective 36 for understanding the role of microbiota in landscape stability. 37 1 Introduction 38 In drylands where vegetation is sparse, soil microbes provide some ecosystem func- 39 tions that are normally delivered by plants in temperate vegetated systems [e.g. Lange 40 et al., 1992; Ferrenberg et al., 2017]. Microbes in the soil surface of drylands form bio- 41 logical soil crusts (biocrusts) which reduce erodibility by wind and water [Eldridge and 42 Leys, 2003; Liu et al., 2017], fix carbon and nitrogen [Li et al., 2012; B¨udelet al., 2018], 43 alter the surface albedo and increase water holding capacity [Singh et al., 2016; Adessi 44 et al., 2018]. Biocrusts were among the first organisms to colonise land [Beraldi-Campesi, 45 2013], therefore it is to be expected that they are well adapted to both exploit soil sur- 46 face conditions, and modify their environment for their own advantage. By identifying 47 and understanding the adaptations of biocrust organisms, we can gain insights into the 48 biotic forces that influence geomorphic processes. In this paper we investigate how in- {2{ Confidential manuscript submitted to JGR-Biogeosciences 49 dividual microbial taxa contribute to soil stability in western Queensland, Australia and 50 relate this to their hypothesised ecological strategies for survival. 51 The interactions between fluvial and aeolian processes in drylands have been demon- 52 strated as important over timescales ranging from seasons to glacial-interglacial cycles 53 [McTainsh, 1987; Langford, 1989; Bullard and McTainsh, 2003; Field et al., 2009]. Flu- 54 vial systems can deliver large quantities of sediment downstream within catchments that, 55 once deposited and desiccated, are susceptible to wind erosion. The combination of wa- 56 ter flow and wind direction can result in sediment cycling at a range of different spatial 2 57 scales from catchments exceeding 1 million km [Bullard and McTainsh, 2003] to within 58 smaller dune-pan systems [Thomas et al., 1993]. Microbiota have not generally been con- 59 sidered as a component of this fluvial - aeolian system, however it has been recognised 60 that biocrust organisms can act as ecosystem engineers [Viles, 2008]. 61 In this paper we report on the microbial ecology of a dynamic ecosystem in cen- 2 62 tral Australia comprising a 25 km claypan in the Lake Eyre basin bounded by sand dunes 63 and ephemeral river channels, where fluvial-aeolian interactions are thought to have been 64 occurring at least since the last glacial maximum about 10 ka BP [Bullard and McTainsh, 65 2003]. To provide insights into how biocrust microbial ecology affects soil stability we 66 determined the microbial composition of different dryland soils and sediments, and then 67 identified possible ecological strategies (especially dispersal mechanisms) of the microbes 68 present. As microbes were expected to be dispersed by both air and water, we also anal- 69 ysed the microbial composition of nearby river channels and airborne dust liberated by 70 in-situ wind tunnel treatment on sand dunes. By developing understanding about the 71 ecology of dryland soil microbial communities and their constituent individual taxa, it 72 should be possible to predict biological responses for various scenarios and devise inter- 73 ventions to manipulate the biotic component of geomorphic processes. This would have 74 a wide range of potential applications in land management, for example to enhance car- 75 bon storage, suppress dust emissions, and make predictions of future geomorphic activ- 76 ity under a changing climate. By comparing the microbial composition of different sys- 77 tem parts we evaluated possible dispersal strategies of individual taxa and interpreted 78 these findings in relation to soil stability and dust emissions. 86 There are a limited number of studies on the microbial content of airborne sedi- 87 ments [Acosta-Martinez et al., 2015] most of which focus on long-distance transport of {3{ Confidential manuscript submitted to JGR-Biogeosciences 79 Figure 1. Aerial view of sampling locations with identification sample types and illustrating 80 the position of transects in the landscape. Insets shows site position within Australia and the 81 general area of claypan including surrounding water channels. Main image shows a closer view 82 of dune and pan area. Lower panels show photographs of the main system compartments, with 83 markers keyed to match with aerial imagery. Arrows illustrate expected linkages between system 84 components by aeolian and hydrological transfer of sediment and inoculum. Aerial imagery from 85 Copernicus Sentinel 2 data (2015). {4{ Confidential manuscript submitted to JGR-Biogeosciences 88 pathogens relevant to human health. Studies with a more environmental focus which have 89 looked at the microbiota found naturally within major dust sources or in the air near 90 to known dust sources in Australia include De Deckker et al. [2008]; Lim et al. [2011]; 91 Abed et al. [2012]; Munday et al. [2016]. These studies have characterised microbial com- 92 munities in aerosols and dust sources, highlighting the possibility of nutrient transporta- 93 tion along with microbiota, and demonstrating potential applications of microbiome sci- 94 ence for tracing dust to its source. The authors of all of these papers pointed out that 95 due to mixing in the air, it was not possible from their data to relate the airborne mi- 96 crobiome directly to any specific source. The only previous study utilising a wind tun- 97 nel to collect airborne particles and microbes is Gardner et al. [2012], which used a py- 98 rosequencing approach to determine the association of particular microbes and diversity 99 metrics with organic matter and particle size fractions. Prior to wind-tunnel treatments 100 the soils in Gardner et al. [2012] were tilled, raked, and flattened using a lawn roller, in 101 contrast to the present study which used soils in their natural condition. Due to our method- 102 ology employing a wind tunnel we were able for the first time to unequivocally collect 103 and analyse wind eroded microbiota from a specific known natural
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