Soil microbial community shifts explain habitat heterogeneity in two Haloxylon species from a nutrient perspective

<p><span><em>Haloxylon</em> <em>ammodendron</em> and <em>Haloxylon</em> <em>persicum</em> (as sister taxa) are dominant shrubs in the Gurbantunggut Desert. The former grows in inter-dune lowlands while the latter in sand dunes. However, little information is available regarding the possible role of soil microorganisms in their habitat heterogeneity from a nutrient perspective in deserts</span><span>. </span><span>Rhizosphere is the interface of plant-microbe-soil interactions and f</span><span>ertile islands usually occur around the roots of desert shrubs. </span><span>Given this, </span><span>we applied quantitative real-time PCR combined with MiSeq amplicon sequencing to compare their rhizosphere effects on microbial abundance and community structures at three soil depths (0–20, 20</span><span>–</span><span>40, and 40</span><span>–</span><span>60 cm). The rhizosphere effects on microbial activity (respiration) and soil properties had also been estimated. The rhizospheres of both shrubs exerted significant positive effects on microbial activity and abundance (e.g. eukarya, bacteria and </span><span>nitrogen-fixing microbes</span><span>). The rhizosphere effect of <em>H</em>. <em>ammodendron</em> on microbial activity and abundance of bacteria and </span><span>nitrogen-fixing microbes</span><span> was greater than that of <em>H</em>. <em>persicum</em>. However, </span><span>the fertile island effect of </span><span><em>H</em>. <em>ammodendron</em></span><span> was weaker than that of </span><span><em>H</em>. <em>persicum</em></span><span>.</span><span> Moreover, t</span><span>here existed distinct differences in microbial community structure between the two rhizosphere soils. </span><span>Soil-available nitrogen, especially nitrate nitrogen was shown to be a</span><span> driver</span> <span>of microbial community </span><span>differentiation </span><span>among rhizosphere and non-rhizosphere soils in the desert.</span><span> In general, the rhizosphere of <em>H</em>. <em>ammodendron</em> recruited more </span><span>copiotrophs (e.g. </span><span>Firmicutes, Bacteroidetes and Proteobacteria), </span><span>nitrogen-fixing microbes and </span><span>ammonia-oxidizing bacteria, and with stronger microbial activities. This helps it maintain a competitive advantage in relatively nutrient-rich lowlands. <em>H</em>. <em>persicum</em> relied more on </span><span>fungi, actinomycetes, archaea</span><span> (including </span><span>ammonia-oxidizing archaea</span><span>) </span><span>and</span><span> eukarya, with higher nutrient use efficiency, which help it adapt to the harsher dune crests. This study provides insights into the microbial mechanisms of habitat heterogeneity in two <em>Haloxylon</em> species in the poor desert soil. </span></p>