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氮(N)沉降正在对全球森林生态系统产生显著影响。目前关于氮沉降如何通过影响树木不同径级细根碳水化合物含量,进而影响树木生理特征及生长的机制尚不清楚。本文以2年生油松(Pinus tabuliformis)幼苗细根为对象,研究了短期(2年)氮添加(0、3、6、9g N·m~(-2)·a~(-1),分别记为N0、N3、N6、N9)对不同径级(0~0.5、0.5~1和1~2 mm)细根中非结构性碳水化合物(NSC)和结构性碳水化合物(SC)含量的影响。结果表明:(1)0~0.5 mm细根中碳水化合物含量(512.97 mg·g~(-1))显著低于1~2 mm细根中碳水化合物含量(638.83 mg·g-1)。0~0.5 mm细根中NSC、可溶性糖和淀粉含量显著低于0.5~1及1~2mm;(2)随着细根径级的增加,SC含量和纤维素含量呈增加趋势,而木质素含量呈降低趋势。N添加对3个径级细根中不同碳水化合物组分的影响不同。N添加对0~0.5和0.5~1mm细根中NSC、可溶性糖和淀粉含量均无显著影响,但N9处理显著降低了1~2 mm细根中NSC和可溶性糖含量(16.20%和29.90%),对淀粉含量无显著影响。此外,N3处理显著增加了0~0.5 mm细根中可溶性糖含量(69.65%);(3)N添加对细根中SC、木质素含量没有显著影响,但N3处理显著增加了最细两级根(0~0.5和0.5~1 mm)纤维素含量(35.3%和57.0%),N9处理显著降低了1~2 mm细根中纤维素含量(30.39%);(4)N3处理显著增加了0~0.5 mm细根中NSC/SC,而对另两级根系中该比率无显著影响。结果表明,N添加可能通过影响最细两级根(0~0.5和0.5~1 mm)中NSC、可溶性糖含量及NSC/SC影响植物细根的生理功能和生长。
Nitrogen (N) deposition is having a significant impact on global forest ecosystems. At present, it is unclear how nitrogen deposition affects the physiological characteristics and growth of trees by affecting the content of carbohydrate in fine roots of different diameter classes. In this paper, the short-term (2 years) nitrogen addition (0, 3, 6, 9 g N · m -2 · a -1) was studied in the roots of 2-year Pinus tabuliformis seedlings (N0, N3, N6, N9) on the contents of non-structural carbohydrates (NSC) and structural carbohydrates (SC) in fine roots with different diameters (0 ~ 0.5, 0.5 ~ 1 and 1 ~ 2 mm) . The results showed that: (1) The content of carbohydrate (512.97 mg · g ~ (-1)) in 0 ~ 0.5 mm fine roots was significantly lower than that in 1 ~ 2 mm fine roots (638.83 mg · g-1). The content of NSC, soluble sugar and starch in 0-0.5 mm fine roots were significantly lower than 0.5-1 and 1-2 mm. (2) With the increase of fine root diameter, SC content and cellulose content increased, while lignin Content decreased. The effect of N addition on different carbohydrate components in the three diameter fine roots is different. N addition had no significant effect on the content of NSC, soluble sugar and starch in fine roots of 0 ~ 0.5 and 0.5 ~ 1 mm, but N9 treatment significantly reduced the content of NSC and soluble sugar in fine roots of 1 ~ 2 mm (16.20% and 29.90%) , No significant effect on starch content. In addition, N3 treatment significantly increased soluble sugar content (69.65%) in fine roots of 0-0.5 mm; (3) N addition had no significant effect on SC and lignin content in fine roots, but N3 treatment significantly increased the finest two levels Cellulose content of roots (0 ~ 0.5 and 0.5 ~ 1 mm) (35.3% and 57.0%), N9 treatment significantly reduced the cellulose content of fine roots of 1 ~ 2 mm (30.39%); (4) N3 treatment significantly increased 0 ~ 0.5 mm fine roots in NSC / SC, while no significant effect on the ratio of the other two root system. The results showed that the addition of N could affect the physiological function and growth of plant fine roots by affecting the NSC, soluble sugar content and NSC / SC in the finest roots (0 ~ 0.5 and 0.5 ~ 1 mm).