Distinct abundance patterns of nitrogen functional microbes in desert soil profiles regulate soil nitrogen storage potential along a desertification development gradient

With ongoing global climate change and human activities, increasing desertification plays a predominant role in increasing soil nutrient losses. Soil nitrogen (N) is the essential limiting nutrient supporting plant growth and evaluating soil nutrient content, especially in desert ecosystems. N microbial processes will ultimately restore and maintain the balance in the soil N cycle, but the damage caused by desertification to soil N functional microorganisms associated with N supply, transformation, and loss is poorly understood. We examined changes in soil N and N functional gene (NFG) abundances within vertical profiles (i.e., soil depths of 0–100 cm) throughout the desertification process. We found that the abundance of N functional genes (NFGs) (except the N-fixation gene) decreased during the desertification process, almost all NFGs were attenuated along the vertical profiles, and available phosphorus (AP), soil water content (SWC) and pH were the best explanatory variables. The sums of (AOA + AOB) (associated with available N transformation) and (nirK + nirS + qnorB + nosZ) (associated with N loss) significantly decreased as desertification progressed, leading to decreased N transformation and loss potential. The (nifH + chiA) associated with available N supply increased along the desertification process gradient, suggesting enhanced potential for the acquisition available N. The increased ratio of (nifH + chiA + AOA + AOB)/(nirK + nirS + qnorB + nosZ) (associated with available N storage) collaboratively contributed to enhanced available N storage potential throughout the desertification process. Our results lay the foundation for better understanding the distinct responses of NFGs to desertification and the process through which they ultimately regulate available N storage in the degraded soils of desert ecosystems.