Abstract
Desert microbes are expected to be substantially sensitive to global environmental changes, such as precipitation changes and elevated nitrogen deposition. However, the effects of precipitation changes and nitrogen enrichment on their diversity and community composition remain poorly understood. We conducted a field experiment over 2 years with multi-level precipitation and nitrogen addition in a desert shrubland of northern China, to examine the responses of soil bacteria and fungi in terms of diversity and community composition and to explore the roles of plant and soil factors in structuring microbial communities. Water addition significantly increased soil bacterial diversity and altered the community composition by increasing the relative abundances of stress-tolerant (dormant) taxa (e.g., Acidobacteria and Planctomycetes); however, nitrogen addition had no substantial effects. Increased precipitation and nitrogen did not impact soil fungal diversity, but significantly shifted the fungal community composition. Specifically, water addition reduced the relative abundances of drought-tolerant taxa (e.g., the orders Pezizales, Verrucariales, and Agaricales), whereas nitrogen enrichment decreased those of oligotrophic taxa (e.g., the orders Agaricales and Sordariales). Shifts in microbial community composition under water and nitrogen addition occurred primarily through changing resource availability rather than plant community. Our results suggest that water and nitrogen addition affected desert microbes in different ways, with watering shifting stress-tolerant traits and fertilization altering copiotrophic/oligotrophic traits of the microbial communities. These findings highlight the importance of resource availability in driving the desert microbial responses to short-term environmental changes.
Highlights
Deserts occupy approximately one-third of the Earth’s land surface (Laity, 2009) and are currently experiencing widespread global environmental changes, including precipitation changes and elevated nitrogen deposition (Galloway et al, 2008; Maestre et al, 2012)
Our results showed that water addition significantly increased soil bacterial diversity, and altered the bacterial community composition, with Acidobacteria and Planctomycetes increasing but Proteobacteria and Bacteroidetes decreasing in terms of their relative abundances (Figures 1–3 and Table 1)
These results suggest that water addition tended to promote flourishing of oligotrophic taxa and depress copiotrophic taxa
Summary
Deserts occupy approximately one-third of the Earth’s land surface (Laity, 2009) and are currently experiencing widespread global environmental changes, including precipitation changes and elevated nitrogen deposition (Galloway et al, 2008; Maestre et al, 2012). Soil microbial diversity and community composition in desert biomes have been shown to differ remarkably from those in non-desert biomes (Fierer et al, 2012), suggesting that their responses to environmental changes might be distinct. It is generally hypothesized that precipitation enrichment, to nitrogen addition, could favor copiotrophic taxa over oligotrophic taxa due to water-induced increases in nitrogen availability (Li et al, 2017b); results of the impacts of precipitation changes on microbial communities are inconsistent. Water-induced indirect effects on microbial communities might be ecosystem-specific, which may contribute to previous inconsistent results among different precipitation-manipulation experiments These previous findings suggest that nitrogen addition consistently impacts microbial communities, whereas the inconsistent responses of microbes to precipitation changes may result from ecosystem-specific background/history precipitation regimes and/or water-induced indirect environmental factors
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