Palmitic acid triggers rhizosphere acidification to facilitate microbial nitrogen fixation: A perspective for phytoremediation of desertification alpine grassland via artificial root exudation mimicking

Fei Yan; Qian Huang; Dongming Chen; Xin Zheng; Rui Yin; Kangqi Zhang; Yan Lu; Yanfu Bai; Feida Sun; Jiqiong Zhou; Zhouwen Ma; Geng Sun; Christopher W N Anderson; Ran Xue; Lin Liu

doi:10.1016/j.jenvman.2025.126349

Palmitic acid triggers rhizosphere acidification to facilitate microbial nitrogen fixation: A perspective for phytoremediation of desertification alpine grassland via artificial root exudation mimicking

J Environ Manage. 2025 Jun 26:390:126349. doi: 10.1016/j.jenvman.2025.126349. Online ahead of print.

Authors

Fei Yan¹, Qian Huang¹, Dongming Chen², Xin Zheng¹, Rui Yin¹, Kangqi Zhang¹, Yan Lu³, Yanfu Bai¹, Feida Sun¹, Jiqiong Zhou¹, Zhouwen Ma¹, Geng Sun⁴, Christopher W N Anderson⁵, Ran Xue⁶, Lin Liu⁷

Affiliations

¹ College of Grassland Science and Technology, Sichuan Agricultural University, Chengdu, 611130, Sichuan, China.
² College of Grassland Science and Technology, Sichuan Agricultural University, Chengdu, 611130, Sichuan, China; Sichuan Ganzi Tibetan Autonomous Prefecture, Grassland Technology Research and Extension Center, Kangding, 626000, Sichuan, China.
³ Sichuan Grassland General Works Station, Chengdu, 610081, Sichuan, China.
⁴ China-Croatia "Belt and Road" Joint Laboratory on Biodiversity and Ecosystem Services, CAS Key Laboratory of Mountain Ecological Restoration and Bioresource Utilization & Ecological Restoration and Biodiversity Conservation Key Laboratory of Sichuan Province, Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu, 610041, China.
⁵ School of Agriculture and Environment, Massey University, Manawatu Campus, Private Bag 11222, Palmerston North, New Zealand.
⁶ College of Grassland Science and Technology, Sichuan Agricultural University, Chengdu, 611130, Sichuan, China. Electronic address: rxue@sicau.edu.cn.
⁷ College of Grassland Science and Technology, Sichuan Agricultural University, Chengdu, 611130, Sichuan, China. Electronic address: liulinsky@126.com.

PMID: 40577867
DOI: 10.1016/j.jenvman.2025.126349

Abstract

Organic acids can enhance inorganic nitrogen transformation in rhizosphere soil, however the specific influence of long-chain organic acids on the community and functional structure of soil microorganisms that control nitrogen cycling is poorly understood. Organic acids have shown potential to increase the resilience of alpine ecosystems against desertification. To address this knowledge gap, we conducted a controlled experiment in a microcosm rhizosphere system. Using artificial roots (7.85 cm² surface area), we amended Qinghai-Tibet Plateau soil with palmitic acid for 45 days at three secretion rates (½ × , 1 × , and 2 × the in situ rate of 3.20 μg C d^-1 cm^-2), corresponding to 12.56, 25.12, and 50.24 μg C d^-1 root^-1 respectively, with a control group receiving only osmoregulation solution. The results revealed a remarkable 81 % increase in soil NH₄⁺-N concentration at the highest addition rate of palmitic acid. Moreover, both microbial biomass and the abundance of nitrogen-fixing genes nifK (12.25 times), nifH (7.63 times), and nifD (27.33 times) increased significantly, alongside a substantial rise in the relative abundance of Azospirillum (12.9-fold). Notably, 82 % of biomarkers in the high-rate palmitic acid treatment were linked to nitrogen fixation. The structural equation model indicated a direct impact of nitrogen fixation on NH₄⁺-N concentration. Our findings suggest that palmitic acid primarily enhances microbial biomass and drives nitrogen fixation processes through its decline to pH, rather than serving as a direct carbon source. Consequently, within the range of our experimental setup, the preferential selection of plant species with a high root exudation rate of palmitic acid can optimize NH₄⁺-N retention in rhizosphere soil, thereby promoting plant growth and facilitating vegetation restoration across the desertification alpine grasslands in the Qinghai-Tibet Plateau.

Keywords: Alpine grassland; Desertification restoration; Microbial functional taxa; Nitrogen cycle; Root exudate.