Chen Yueqin, Ruan Honghua
Co-Innovation Center for Sustainable Forestry in Southern China, Nanjing Forestry University, Nanjing, China.
PLoS One. 2025 Jun 25;20(6):e0324615. doi: 10.1371/journal.pone.0324615. eCollection 2025.
With the continuous development of urbanization, nitrogen deposition has affected the regeneration capacity of urban forest soil. This study focused on Quercus acutissima Carruth forest in a southern city Hefei in China. The effects of different nitrogen addition rates on both the soil respiration rate and the soil properties of urban forests were studied. In addition, the effects of seasonal changes on soil respiration were also analyzed. The experimental results showed that low nitrogen addition rate (5 g·m-2·yr-1) increased soil respiration rate by about 11% in summer, but decreased it by about 6% in winter, with a range of 5% to 20%. High nitrogen addition (15 g·m-2·yr-1) significantly increased soil temperature by about 12% in summer (p < 0.05), and significantly decreased soil temperature by about 13% in winter (p < 0.05), indicating the seasonal regulation effect of nitrogen addition on soil temperature. As a result, the soil respiration rate was 3.26 ± 0.45 μmol m-2·s-1 in summer and 0.51 ± 0.07 μmol m-2·s-1 in winter. The results indicated that the high nitrogen addition had a significant effect on soil respiration rate, which increased in summer and decreased in winter. Soil moisture content and temperature had significant effects on soil respiration rate, especially in the suburban test site. Nitrogen addition significantly increased soil total nitrogen and nitrate nitrogen contents (p < 0.05), but had no significant effect on soil pH value. Structural equation modeling analysis showed that nitrogen addition promoted soil microbial activity, releases heat, and thus increases soil temperature. Meanwhile, this method affected soil respiration rate, soil moisture, soil total nitrogen, and nitrate nitrogen content, directly or indirectly regulating soil heterotrophic respiration and autotrophic respiration. In conclusion, this study revealed the significant effects of nitrogen addition on urban forest soil respiration and its components, which provided data support and theoretical reference for understanding the dynamic changes of urban ecosystem carbon cycle, and was of great significance for guiding future urban greening and ecological protection work.
随着城市化的不断发展，氮沉降已影响到城市森林土壤的再生能力。本研究聚焦于中国南方城市合肥的麻栎林。研究了不同氮添加速率对城市森林土壤呼吸速率和土壤性质的影响。此外，还分析了季节变化对土壤呼吸的影响。实验结果表明，低氮添加速率（5克·平方米·年−1）使夏季土壤呼吸速率提高了约11%，但冬季降低了约6%，变化范围为5%至20%。高氮添加量（15克·平方米·年−1）使夏季土壤温度显著升高约12%（p < 0.05），冬季显著降低约13%（p < 0.05），表明氮添加对土壤温度具有季节调节作用。结果显示，夏季土壤呼吸速率为3.26±0.45微摩尔·平方米·秒−1，冬季为0.51±0.07微摩尔·平方米·秒−1。结果表明，高氮添加对土壤呼吸速率有显著影响，夏季升高而冬季降低。土壤含水量和温度对土壤呼吸速率有显著影响，尤其是在郊区试验点。氮添加显著提高了土壤全氮和硝态氮含量（p < 0.05），但对土壤pH值无显著影响。结构方程模型分析表明，氮添加促进了土壤微生物活动，释放热量，从而提高了土壤温度。同时，该方法直接或间接影响土壤呼吸速率、土壤水分、土壤全氮和硝态氮含量，调节土壤异养呼吸和自养呼吸。总之，本研究揭示了氮添加对城市森林土壤呼吸及其组分的显著影响，为理解城市生态系统碳循环的动态变化提供了数据支持和理论参考，对指导未来城市绿化和生态保护工作具有重要意义。
