Abstract
Abstract. Ecosystem engineers (EEs) are present in every environment and are known to strongly influence ecological processes and thus shape the distribution of species and resources. In this study, we assessed the direct and indirect effect of two EEs (perennial shrubs and ant nests), individually and combined, on the composition and function of arid soil bacterial communities. To that end, topsoil samples were collected in the Negev desert highlands during the dry season from four patch types: (1) barren soil; (2) under shrubs; (3) near ant nests; or (4) near ant nests situated under shrubs. The bacterial community composition and potential functionality were evaluated in the soil samples (14 replicates per patch type) using 16S rRNA gene amplicon sequencing together with physico-chemical measures of the soil. We have found that the EEs affected the community composition differently. Barren patches supported a soil microbiome, dominated by Rubrobacter and Proteobacteria, while in EE patches Deinococcus-Thermus dominated. The presence of the EEs similarly enhanced the abundance of phototrophic, nitrogen cycle, and stress-related genes. In addition, the soil characteristics were altered only when both EEs were combined. Our results suggest that arid landscapes foster unique communities selected by patches created by each EE(s), solo or in combination. Although the communities' composition differs, they support similar potential functions that may have a role in surviving the harsh arid conditions. The combined effect of the EEs on soil microbial communities is a good example of the hard-to-predict non-additive features of arid ecosystems that merit further research.
Highlights
Hot desert environments are characterized by long droughts interspersed by intermittent and unpredictable rain events
It is characterized by 90 mm annual rainfall and average monthly temperatures fluctuating from 13 ◦C (January) to 35 ◦C (August)
When verifying with a Kruskal–Wallis test and a Dunn test on the values of these soil variables (Table A2), we see that the differences between patch types are significant (Shrub & nest of M. ebeninus (Nest) vs. all other patches, p < 0.05)
Summary
Hot desert environments are characterized by long droughts interspersed by intermittent and unpredictable rain events. Water and nutrients in hot desert environments are scarce and unevenly distributed across the land, resulting in patches of contrasting productivities. High-productivity patches, called resource islands, are defined by large concentrations of organic matter and nutrients (Bachar et al, 2012; Ben-David et al, 2011; Schlesinger et al, 1996; West, 1981). These resource islands can be formed through the redistribution of nutrients and water by ecosystem engineers (EEs), such as perennial plants or invertebrates (Wilby et al, 2001; Wright et al, 2006).
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