不同林龄杨树细根糖化学组分对氮沉降的响应

选择苏北沿海5、9和15年生杨树人工林作为实验地,采用随机区组设计,设置了N0(CK)、N1(5 g/(m²·a))、N2(10 g/(m²·a))、N3(15 g/(m²·a))、N4(30 g/(m²·a))共5个不同浓度的氮沉降处理,研究氮沉降对土壤细根糖化学组分的影响。结果表明:(1)3个林龄杨树林地下细根中可溶性糖、淀粉含量,在1 a的观测期内,最大值出现在12月份,其中可溶性糖在1 a中的变化幅度最大,最高值与最低值相差约7倍; 而作为结构性碳水化合物的纤维素和木质素在1 a的观测期内相对较为稳定。(2)随着外源氮输入增加,细根中可溶性糖、淀粉含量在N2水平最大,在N4水平则低于对照。而非结构性碳水化合物在氮增加处理的不同水平间差异不显著(p>0.05)。总之,一定浓度的氮增加,将增加细根中活性代谢物质的碳投入。(3)杨树细根生物量与非结构性碳水化合物存在显著的正相关,杨树细根糖化学组分与土壤C、N以及温湿度没有显著相关性。

The response of carbohydrates compositions in fine root of poplar at different ages to nitrogen depositions

We chose three different ages(5 years, 9 years and 15 years old)of poplar plantations in a coastal area in Dongtai city, Jiangsu province. The experiment used randomized block design with five nitrogen deposition concentration treatments, i.e. N0(CK), N1(5 g/(m²·a)), N2(10 g/(m²·a)), N3(15 g/(m²·a), N4(30 g/(m²·a))in the field. The results showed that:(1)The manimum content of soluble sugar and starch appeared in December, and soluble sugar in one year had the largest change range, the highest and the lowest differed about seven times. While the seasonal variation of structural carbohydrates(cellulose and lignin)was not obvious, and the cellulose and lignin content was relatively stable.(2)With the increase of exogenous nitrogen input, soluble sugar, starch and NSC content in the fine roots increased and then decreased, and the largest content at N2, while N4(the most nitrogen input)appeared below N0(control treatment). SC had no significant difference(p>0.05)among of levels of nitrogen increase treatments.(3)There were significantly positive correlation between fine root biomass and NSC, and no significant correlation between soil C, N and carbohydrates compositions, as well as temperature and humidity.