典型草原植物叶片金属元素吸收对氮添加的响应

Leaf Metal Elements Uptake Response to Nitrogen Addition in Typical Steppe Plants

为深入探讨氮沉降影响草原植物金属养分吸收及其与土壤养分的耦合关系,以内蒙古典型草原4种主要物种为研究对象,设置0、5、10、15 g N/(m^(2)·yr)4个氮添加处理,分析不同施氮量对草原物种及群落水平植物叶片盐基、微量元素含量和储量的影响。结果表明:(1)杂类草比禾本科植物具有更高的养分浓度;(2)不同金属养分对氮沉降的响应具有高度的物种特异性;植物群落叶片盐基元素含量对氮添加无显著响应且与土壤盐基离子相关性较低;随氮添加量的增加,叶片中Mn、Cu含量增加,但Fe含量降低,草原植物微量元素失衡严重主要受土壤微量养分有效性和元素拮抗作用的影响;(3)植物金属元素地上储量的饱和阈值出现在10 g N/(m^(2)·yr);优势物种地上生物量对氮添加的非线性响应是驱动植物元素地上储量变化的主要机制。

This study aimed to investigate the impact of nitrogen(N)deposition on plant metal nutrient uptake and the coupling relationship with soil nutrients in a typical steppe of Inner Mongolia.Concentra⁃tions of base cations and trace element concentrations,as well as nutrient storage in leaves of four plant spe⁃cies and community in a typical grassland,were measured under different N addition levels,including 0,5,10,and 15 g N/(m^(2)·yr).The results showed as follows:(1)Forbs exhibited higher leaf nutrient concentrations compared to Gramineae plants.(2)The responses of leaf nutrient concentrations to N deposition showed spe⁃cies specificity.Base cations concentrations in the leaves of the community remained unchanged in response to N addition and were not correlated with soil exchangeable base cations.Mn and cuprum concentrations in the leaves of the community increased with N addition,while iron(Fe)concentration decreased,resulting in a sig⁃nificant imbalance of metal elements in grassland plants mainly by the effects of availability of soil trace ele⁃ments and antagonism.(3)The saturation threshold for aboveground storage of plant metal elements occurred at an N addition of approximately 10 g N/(m^(2)·yr).The nonlinear response of the aboveground biomass of dominant species to N addition may be the primary mechanism driving changes in aboveground metal nutrient storage.