Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, SE-901 83 Umeå, Sweden.
Department of Forest Genetics and Plant Physiology, Umeå Plant Science Center, Swedish University of Agricultural Sciences, SE-901 83 Umeå, Sweden.
New Phytol. 2012 Jul;195(2):329-334. doi: 10.1111/j.1469-8137.2012.04169.x. Epub 2012 May 4.
• Nitrogen (N) availability has a major impact on a wide range of biogeochemical processes in terrestrial ecosystems. Changes in N availability modify the capacity of plants to sequester carbon (C), but despite the crucial importance for our understanding of terrestrial ecosystems, the relative contribution of different N forms to plant N nutrition in the field is not known. Until now, reliably assessing the highly dynamic pool of plant-available N in soil microsites was virtually impossible, because of the lack of adequate sampling techniques. • For the first time we have applied a novel microdialysis technique for disturbance-free monitoring of diffusive fluxes of inorganic and organic N in 15 contrasting boreal forest soils in situ. • We found that amino acids accounted for 80% of the soil N supply, while ammonium and nitrate contributed only 10% each. In contrast to common soil extractions, microdialysis revealed that the majority of amino acids are available for plant and mycorrhizal uptake. • Our results suggest that the N supply of boreal forest soils is dominated by organic N as a major component of plant-available N and thus as a regulator of growth and C sequestration.
• 氮（N）的有效性对陆地生态系统中广泛的生物地球化学过程有重大影响。N 有效性的变化改变了植物固定碳（C）的能力，但尽管其对陆地生态系统的理解至关重要，但在野外，不同 N 形态对植物 N 营养的相对贡献仍不清楚。直到现在，由于缺乏足够的采样技术，实际上仍无法可靠地评估土壤微生境中高度动态的植物可利用 N 库。 • 我们首次应用一种新的微透析技术，对 15 种不同的北方森林土壤中无机和有机 N 的扩散通量进行无干扰原位监测。 • 我们发现，氨基酸占土壤 N 供应的 80%，而铵和硝酸盐各仅占 10%。与常见的土壤提取方法不同，微透析显示大多数氨基酸可被植物和菌根吸收。 • 我们的研究结果表明，北方森林土壤的 N 供应主要由有机 N 组成，有机 N 是植物可利用 N 的主要成分，也是生长和 C 固定的调节剂。
