关键词: 高寒草甸, 根系分泌物, 有机酸, 有机碳矿化, 有机氮矿化, 土壤环境因子

Abstract:

In this study, soil degradation and nitrogen limitation in alpine meadows were addressed, and the effects of organic acids in plant root exudates on soil carbon and nitrogen mineralization were clarified. In an incubation experiment, the response of common organic acids in Kobresia myosuroides (Villars) Foiri, Gueldenstaedtia diversifolia Maxim, and Anemone rivularis Buch-Ham. were investigated for soil carbon and nitrogen mineralization in southeastern Tibet. Acetic, lactic, and fumaric acids significantly increased the content of soil available nitrogen and phosphorus but had no effect on soil total nitrogen and phosphorus. The rate of soil carbon mineralization gradually decreased with increasing cultivation time under the influence of the different organic acids. Lactic acid and 10 mg·L⁻¹ acetic acid first promoted and then inhibited the soil carbon mineralization rate over time, whereas fumaric acid generally inhibited soil carbon mineralization. In addition, except for 10 mg·L⁻¹ lactic acid, which significantly reduced cumulative soil carbon mineralization, the other concentrations of organic acids had no significant effect on cumulative soil carbon mineralization. Correlation analysis showed a significant negative correlation between acetic acid and cumulative soil carbon mineralization (r=−0.796*). The different organic acids had no significant effect on the net ammonification rate of the soil, whereas medium-to-high concentrations of acetic acid inhibited net nitrification and net nitrogen mineralization. The addition of lactic and fumaric acids had no significant effect on the net nitrification rate or the net nitrogen mineralization rate. Correlation analysis showed that acetic acid was significantly negatively correlated with the net nitrogen mineralization rate (r=−0.785*). Soil carbon mineralization was positively correlated with pH and total nitrogen, whereas the correlation between soil nitrogen mineralization and soil environmental factors differed significantly, depending on the presence of organic acids. In summary, acetic acid is the main organic acid affecting soil carbon and nitrogen mineralization, and the organic acids in root exudates, combined with soil environmental factors, regulate soil carbon and nitrogen mineralization. This study provides a scientific basis for determining carbon and nitrogen sequestration and the development of soil management strategies in ecologically fragile areas.

Key words: alpine meadow, root exudates, organic acids, organic carbon mineralization, organic nitrogen mineralization, soil environmental factors