Soil nitrogen form and plant nitrogen uptake along a boreal forest productivity gradient
Soil nitrogen form and plant nitrogen uptake along a boreal forest productivity gradient
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DOI：
10.1007/s004420100698
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发表时间：
2001-09-01
期刊：
影响因子：
2.7
通讯作者：
Näsholm, T
中科院分区：
文献类型：
--
作者：
Nordin, A;Högberg, P;Näsholm, T
我们报道了在北方森林中，沿着当地90米长的植物生产力梯度，在一个生长季节内，土壤溶液中铵(NH4+)、硝酸盐(NO3-)和氨基酸氮浓度的研究结果。沿坡度分布有3种类型：0~40m范围内的灌木灌木型、40~80m范围内的矮生草本型和90m高度上的高大草本型。此外，还研究了植物对NH_4~+、NO_3~-和甘氨酸的吸收。将三种氮素的混合物注入土壤中；一次一种氮素用N-15标记，在甘氨酸的情况下也用C-13标记。在植物生产力较低的矮灌木林中，土壤氮库以氨基酸氮为主，植物对NH4+的吸收高于对NO3-的吸收。甘氨酸的吸收与NH4+或NO3-的吸收没有显著差异。土壤NH_4~+和NO_3~-浓度随着坡度的增加而增加，植物生产力也随之增加。在低草本植物森林中，NH4+构成了土壤氮库的主要部分，植物吸收的NH4+多于NO3-或甘氨酸。在高大草本林中，NO_3~-和NH_4~+同样丰富，这两种形态共同支配着土壤的氮库。在这里，植物吸收了几乎等量的NO3-和NH4+，这种吸收是甘氨酸的几倍。除了植物在整个梯度上表现出对NH4+的总体偏好外，研究结果还表明，土壤中氨基酸和NO3-的浓度与植物对这些N形态的偏好之间存在相关性。
We present results from a study of soil solution concentrations of ammonium (NH4+), nitrate (NO3-), and amino acid N over one growing season along a local 90-m-long plant productivity gradient in a boreal forest. Three forest types are found along the gradient: an ericaceous dwarf-shrub type between 0 and 40 m, a low-herb type between 40 and 80 m, and a tall-herb type at 90 m. Soil sampling of the mor layer was performed in June, July, August and October in the three forest types. In addition, plant uptake of NH4+, NO3- and the amino acid glycine was investigated. A mixture of the three N forms was injected into the soil; one N form at a time was labeled with N-15, and in the case of glycine also with C-13. In the dwarf-shrub forest, where plant productivity was low, the soil N pool was strongly dominated by amino acid N. There, plants took up more NH4+ than NO3-. Glycine uptake did not differ significantly from either NH4+ or NO3- uptake. Along the gradient, soil concentrations of NH4+ and NO3- increased, as did plant productivity. In the low-herb forest NH4+ comprised a major portion of the soil N pool, and plants took up more NH4+ than NO3- or glycine. In the tall-herb forest, NO3- was as abundant as NH4+, and together these two N forms dominated the soil N pool. Here, plants took up nearly equal amounts of NO3- and NH4+, and this uptake exceeded that of glycine severalfold. Apart from the overall preference for NH4+ that plants exhibited throughout the gradient, the results show a correlation between soil concentrations of amino acids and NO3- and plant preferences for these N forms.