Yan Fei, Huang Qian, Chen Dongming, Zheng Xin, Yin Rui, Zhang Kangqi, Lu Yan, Bai Yanfu, Sun Feida, Zhou Jiqiong, Ma Zhouwen, Sun Geng, Anderson Christopher W N, Xue Ran, Liu Lin
College of Grassland Science and Technology, Sichuan Agricultural University, Chengdu, 611130, Sichuan, China.
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.
J Environ Manage. 2025 Aug;390:126349. doi: 10.1016/j.jenvman.2025.126349. Epub 2025 Jun 26.
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 cm 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 cm), corresponding to 12.56, 25.12, and 50.24 μg C d root respectively, with a control group receiving only osmoregulation solution. The results revealed a remarkable 81 % increase in soil NH-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 NH-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 NH-N retention in rhizosphere soil, thereby promoting plant growth and facilitating vegetation restoration across the desertification alpine grasslands in the Qinghai-Tibet Plateau.
有机酸可以促进根际土壤中无机氮的转化，然而，长链有机酸对控制氮循环的土壤微生物群落和功能结构的具体影响尚不清楚。有机酸已显示出提高高山生态系统抗荒漠化能力的潜力。为了填补这一知识空白，我们在一个微观根际系统中进行了一项对照实验。我们使用人工根（表面积7.85平方厘米），以三种分泌速率（原位速率3.20μg C d cm的1/2、1倍和2倍），即分别对应于每根12.56、25.12和50.24μg C d，用棕榈酸改良青藏高原土壤45天，对照组仅接受渗透调节溶液。结果显示，在棕榈酸添加量最高时，土壤铵态氮浓度显著增加了81%。此外，微生物生物量以及固氮基因nifK（12.25倍）、nifH（7.63倍）和nifD（27.33倍）的丰度均显著增加，同时固氮螺菌的相对丰度大幅上升（12.9倍）。值得注意的是，高剂量棕榈酸处理中82%的生物标志物与固氮有关。结构方程模型表明固氮对铵态氮浓度有直接影响。我们的研究结果表明，棕榈酸主要通过降低pH值来提高微生物生物量并驱动固氮过程，而不是作为直接的碳源。因此，在我们的实验设置范围内，优先选择棕榈酸根系分泌率高的植物物种可以优化根际土壤中铵态氮的保留，从而促进植物生长并推动青藏高原荒漠化高山草原的植被恢复。
