不同氮素添加量对大兴安岭冻土区泥炭地植物细根形态的影响模拟研究

为探讨氮素营养环境变化对冻土区泥炭地植物细根形态的影响，在大兴安岭泥炭地开展了不同浓度氮素添加模拟试验，添加量分别为0 g N m^-2 a^-1（CK）、6 g N m^-2 a^-1（N1）、12 g N m^-2 a^-1（N2）和24 g N m^-2 a^-1（N3）。在2020年8月和9月，利用微根管技术观测泥炭地不同深度（0-20 cm、20-40 cm）土壤中的植物细根形态，应用WinRHIZO图像分析软件分析根系特征。结果表明，在表层土壤（0-20 cm）中植物细根的总根长、总表面积、总体积和根长密度随施氮量增加而增加，其中8月份N3处理下细根总根长、总表面积、总体积和根长密度显著高于其他处理（P< 0.05），N2处理下细根总表面积、总体积显著高于对照组和N1处理；9月份N3处理下细根总根长和根长密度显著高于对照组，总表面积和总体积显著高于对照组和N1处理。说明高浓度氮素添加在一定程度上缓解了植物氮素限制，能够显著促进表层土壤（0-20 cm）中植物细根的生长，但对亚表层土壤（20-40 cm）中细根的影响幅度小于表层土壤。

Effects of different concentrations of nitrogen additions on fine root morphological characteristics in permafrost peatland in the Daxing'an Mountains

In order to investigate the effects of nitrogen nutrient environment changes on the morphology of fine roots in permafrost peatlands, we conducted a nitrogen additions field experiment in the Daxing''an Mountains, Northeast China. Four levels of N treatments were applied including 0 g N m^-2 a^-1 (CK), 6 g N m^-2 a^-1 (N1), 12 g N m^-2 a^-1 (N2), and 24 g N m^-2 a^-1 (N3). In August and September 2020, minirhizotron observation method was applied to monitor the morphology of fine roots in different depths (0-20 cm, 20-40 cm), and the root characteristics were analyzed by WinRHIZO software. The results showed that the total root length, total surface area, total volume and root length density of plant fine roots in the surface peat layer (0-20 cm) were increased with the increase of nitrogen application. In August, the total root length, total surface area, total volume and root length density in N3 treatment were significantly higher than those in other treatments, while in N2 treatment, total surface area and total volume of fine roots were significantly higher than those in control group and N1 treatment (P< 0.05). In September, the total root length and root length density in N3 treatment were significantly higher than those in control group, and the total surface area and total volume of fine roots in N3 treatment were significantly higher than those in control group and N1 treatment (P< 0.05). The results show that nitrogen additions can relieve the nitrogen limitation of plants and can significantly promote the growth of fine roots in the surface peat layer (0-20 cm), but the influence of fine root growth in subsurface layer (20-40 cm) is less than that in the surface peat layer.