兴安落叶松林细根解剖结构和化学组分对N沉降的响应

大气N沉降逐渐加强,可能会改变地下C循环和土壤C状态,促使细根结构及其化学组分发生变化。N沉降对细根动态和形态影响方面的研究较多,但对细根结构和组分的影响还没有系统的研究。于2012年5月,在大兴安岭北方森林统一立地条件下建立4个水平N肥处理,分别为对照(CK,0 g/(m· a))、低N处理(TL, 2.5 g/(m·a))、中N处理(TM, 5 g/(m·a))和高N处理(TH , 7.5 g/(m·a))。在2014年7月,植物生长季,利用挖掘法获取兴安落叶松完整根系,测定其1~5级细根在不同N沉降处理下皮层厚度、维管束直径、根系直径、维根比以及化学组分变化,旨在探讨不同水平N沉降对细根解剖结构和化学组分的影响。结果表明:落叶松细根直径、皮层厚度和维管束直径均随根序的增加而增加,而相同根序、不同水平N沉降处理之间细根直径、皮层厚度、维管束直径和维根比之间存在差异,不同直径等级根系化学组分差异显著。上述实验结果说明,N沉降可能通过影响细根直径、皮层厚度、维管束直径、维根比和化学组分来影响细根生理功能和活性,进而可能影响植物地上和地下C循环。 

Response of root anatomy and tissue chemistry to nitrogen deposition in larch forest in the Great Xing' an Mountains of northeastern China

The increase of nitrogen deposition may change the underground carbon cycle and soil carbon pool, and thus influence the structure and chemical components of fine roots. A number of researches have been done on fine root dynamics and morphological structure, but little is known of effects of nitrogen deposition on fine root structure and components. In the Great Xing' an Mountains, northeastern China, four sampling sites were set in a Larix gmelinii forest in May, 2012, i. e. , controlling site (CK,0 g/(m2· a)), low nitrogen treatment (TL, 2. 5 g/(m2·a)), medium nitrogen treatment (TM, 5. 0 g/(m2·a)) and high nitrogen treatment (TH, 7. 5·g/(m2·a)). In the growing season in July, 2014, the complete root system was dug out, and cortical thickness, stele diameter, root diameter, ratio of stele to root diameter of first five orders, and tissue chemistry ( N, C and P) under different nitrogen treatments were measured. The influence of nitrogen deposition on morphological structure and chemical component of fine roots was analyzed. It showed that, with the ascending root order, indices such asroot diameter, cortical thickness and stele diameter increased accordingly. However, there were significant differences in cortical thickness, stele diameter, root diameter and ratio of stele to root diameter in the same root order under different levels of N treatment, and root tissue chemistry also had significant difference in different diameter classes. In conclusion, nitrogen deposition may impact cortical thickness, stele diameter, root diameter, ratio of stele to root diameter of first five orders and tissue chemistry (N, C and P), thus influences the physiological functions of fine roots, and finally has impact on above﹣ and underground carbon cycle of plants.