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由于土壤氮同位素组成被认为是气候环境变化和自然生态系统氮循环过程的可能指示,开展全球不同区域、不同生态系统氮同位素组成的研究将有助于对这个可能性的认识.对中国黄土高原中西部不同环境条件下的现代植物和相应的土壤氮同位素进行了调查,氮同位素组成变化范围分别为:植物根:-5.1‰～1.9‰;植物残体:-6.6‰～2.9‰;土壤:-1.2‰～5.8‰.结果表明:(1)土壤与植物有相近的变化趋势,但土壤的氮同位素组成较植物根的氮同位素要偏正,其Δδ15N值变化范围为:0.3‰～7.2‰,平均值为:4.1‰,表明植物分解过程氮同位素存在分馏;(2)该地区现代生态系统的氮同位素对降水和温度变化有明显的响应,沿西北到东南方向,年平均降水每增加100mm可能导致土壤氮同位素组成偏负约1.31‰,随温度的增加,土壤氮同位素也趋向偏负;(3)在降水和温度共同增加的影响下,植物根系、植物残体和土壤的氮同位素偏负,这个现象可能归因于降水是该地区植物-土壤氮同位素变化的主要控制因素.尽管目前对植物-土壤氮同位素组成变化与降水和温度关系的机制尚不清楚,但初步的研究结果表明土壤的氮同位素组成可能为黄土高原环境变化示踪提供指示.
Since soil nitrogen isotope composition is considered as a possible indicator of climatic and environmental changes and the nitrogen cycle of natural ecosystems, carrying out studies on the nitrogen isotope composition of different ecosystems in different regions of the world will help to understand this possibility.For the Loess Plateau The modern plant and corresponding soil nitrogen isotope under different environmental conditions in central and western China were investigated. The ranges of nitrogen isotope composition were as follows: plant root: -5.1 ‰ ~ 1.9 ‰; plant residue: -6.6 ‰ -2.9 ‰; soil: -1.2 ‰ ~5.8 ‰ .The results showed that: (1) There was a similar trend between soil and plant, but the nitrogen isotope composition of soil was more positive than that of plant root, and the range of Δδ15N was 0.3 ‰ ~ 7.2 ‰ , With an average of 4.1 ‰, indicating the existence of fractionation of nitrogen isotopes during plant decomposition. (2) The nitrogen isotopes of modern ecosystems in the area respond obviously to precipitation and temperature changes. For every 100 mm increase in annual average precipitation along the northwest to southeast, The soil nitrogen isotope composition may be negatively correlated with about 1.31 ‰. With the increase of temperature, the soil nitrogen isotope tends to be negative. (3) Under the influence of the increase of precipitation and temperature, , Plant residues and soil nitrogen isotopes are negative, this phenomenon may be attributed to precipitation as the main controlling factor of plant-soil nitrogen isotope variation.Although the current mechanism of the relationship between plant-soil nitrogen isotope composition and precipitation and temperature It is unclear, but preliminary results suggest that the nitrogen isotope composition of soils may provide an indication of environmental changes in the Loess Plateau.