川西亚高山针叶林主要树种对土壤中不同形态氮素的吸收差异

doi:10.17521/cjpe.2017.0165

摘要/Abstract

摘要：

在陆地生态系统中, 植物对土壤有机氮(主要指氨基酸)的获取是一个普遍的生态学现象, 然而植物对土壤有机氮的吸收速率及土壤有机氮在植物养分供应中所占比例仍不清楚。为探究土壤无机氮和有机氮对西南高寒森林植物氮源的贡献效应, 以川西亚高山针叶林两个主要树种云杉(Picea asperata)和红桦(Betula albo-sinensis)的幼苗为研究对象, 采用稳定同位素标记法对K¹⁵NO₃、¹⁵NH₄Cl和(U-¹³C₂/¹⁵N)甘氨酸3种氮素进行示踪, 分析了两个树种对无机氮(NH₄⁺-N和NO₃^–-N)和有机氮(甘氨酸)的吸收速率及其差异。结果显示: (1)云杉和红桦幼苗在施加同位素标记物2 h后, 两种幼苗细根的¹³C和¹⁵N均出现明显的富集现象, 表明两种树种幼苗均能吸收甘氨酸。(2)与甘氨酸和NH₄⁺-N相比, 云杉和红桦幼苗对NO₃^–-N有显著的偏好吸收, 其吸收速率为NH₄⁺-N和甘氨酸吸收速率的5-10倍。(3)两个树种的幼苗对甘氨酸也有较高的吸收速率, 其吸收速率高于对NH₄⁺-N的吸收速率, 表明土壤有机氮(如氨基酸)也是亚高山针叶林植物养分获取的重要氮源。

关键词: 有机氮, 无机氮, 氨基酸, 稳定同位素标记, 亚高山针叶林

Abstract:

Aims Although acquisition of soil organic nitrogen (N)(mainly amino acids) by plants is a widespread ecological phenomenon in many terrestrial ecosystems, the rate of organic N uptake and their contributions to plant nutrient supply are poorly understood. Our objective was to determine the relative contributions of inorganic N (NO₃^–-N and NH₄⁺-N) and organic N (amino acids) to plant N uptake in a high-frigid forest ecosystem.Methods The differences in the uptake rate of three different forms of N (NO₃^–-N, NH₄⁺-N and glycine) were quantified by exposing seedlings of two dominant tree species (Picea asperata and Betula albo-sinensis) in subalpine coniferous forests of western Sichuan, China, to trace quantities of K¹⁵NO₃,¹⁵NH₄Cl and (U-¹³C₂/¹⁵N) glycine.Important findings Both ¹³C and ¹⁵N were significantly enriched in fine roots 2 h after tracer application, indicating the occurrence of glycine uptake in P. asperata and B. albo-sinensis seedlings. The seedlings of two tree species had a significant preference for NO₃^–-N compared with glycine and NH₄⁺-N, and the uptake rate of NO₃^–-N was 5 to 10 times greater than that of glycine and NH₄⁺-N. The roots of seedlings in the two species took up glycine more rapidly than NH₄⁺-N, implying that soil organic N (i.e., amino acids) could be an important N source for the two species in subalpine coniferous forests. The results of this study are of great theoretical significance for understanding N utilization strategies and nutrient regulation processes in plants of the high-frigid forest ecosystems.

Key words: organic nitrogen, inorganic nitrogen, amino acid, stable isotope labeling, subalpine coniferous forest

邹婷婷, 张子良, 李娜, 袁远爽, 郑东辉, 刘庆, 尹华军. 川西亚高山针叶林主要树种对土壤中不同形态氮素的吸收差异. 植物生态学报, 2017, 41(10): 1051-1059. DOI: 10.17521/cjpe.2017.0165

Ting-Ting ZOU, Zi-Liang ZHANG, Na LI, Yuan-Shuang YUAN, Dong-Hui ZHENG, Qin LIU, Hua-Jun YIN. Differential uptakes of different forms of soil nitrogen among major tree species in subalpine coniferous forests of western Sichuan, China. Chinese Journal of Plant Ecology, 2017, 41(10): 1051-1059. DOI: 10.17521/cjpe.2017.0165

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链接本文: https://www.plant-ecology.com/CN/10.17521/cjpe.2017.0165

https://www.plant-ecology.com/CN/Y2017/V41/I10/1051

图/表 5

图1 根际土壤溶液采样器示意图。

Fig. 1 Illustration of a soil solution sampler in rhizosphere.

图2 不同采样时间云杉(A)和红桦(B)幼苗细根中13C自然丰度值(δ13C)的动态变化(平均值±标准偏差, n = 6)。柱状图中不同小写字母表示同一树种δ13C在不同取样时间差异显著(p < 0.05)。

Fig. 2 Dynamics of natural 13C abundance (δ13C) in fine roots of Picea asperata (A) and Betula albo-sinensis seedlings (B) at different sampling times (mean ± SD, n = 6). Different lowercase letters indicate significant differences in the δ13C value among sampling times within species (p < 0.05).

图3 不同采样时间云杉和红桦幼苗细根中15N自然丰度值(δ15N)动态变化(平均值±标准偏差, n = 6)。A, 15NO3–-N处理下的δ15N。B, (U-13C2/15N)甘氨酸(Glycine)处理下的δ15N。C, 15NH4+-N处理下的δ15N。柱状图中不同小写字母表示同一树种δ15N在不同取样时间差异显著(p < 0.05)。

Fig. 3 Dynamics of natural 15N abundance (δ15N) in fine roots of Picea asperata and Betula albo-sinensis seedlings at different sampling times (mean ± SD, n = 6). A, δ15N under 15NO3–-N labeling treatment. B, δ15N under glycine labeling treatment. C, δ15N for 15NH4+-N labeling treatment. Different lowercase letters indicate significant differences in the δ15N value among sampling times within species (p < 0.05).

图4 不同采样时间点云杉(A)和红桦(B)幼苗对3种不同形态N素(NO3–-N、甘氨酸和NH4+-N)的吸收速率差异(平均值±标准偏差, n = 6)。柱状图中不同小写字母表示同一时间不同形态N吸收速率差异显著(p < 0.05)。

Fig. 4 Differences in the mass-specific uptake rate for NO3–-N, glycine and NH4+-N in Picea asperata (A) and Betula albo-sinensis seedlings (B) at different sampling times (mean ± SD, n = 6). Different lowercase letters indicate significant differences in the uptake rate of different N forms at given sampling time (p < 0.05).

图5 云杉(A)和红桦(B)幼苗根系中13C和15N的单位摩尔原子百分超比值的差异(平均值±标准偏差, 6个重复)。虚线代表注射的双标记甘氨酸C:N原始值为2.0。

Fig. 5 Differences in the molar ratio of excess 13C to excess 15N derived from double-labelled (U-13C2/15N) glycine in fine roots of Picea asperata (A) and Betula albo-sinensis seedlings (B). Horizontal line represents the 2:1 injection ratio of C:N administered with the doubly labeled glycine treatment.

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