植物体内特别是叶片的P含量特征及其与环境的关系一直是植物生理生态学研究的一个热点。已有研究发现, 与全球植物数据相比, 中国植物叶片的P含量相对较低, 导致N/P高于全球平均水平, 并推测这是由于中国土壤全P含量较低引起的。该研究选取内蒙古草地来验证这一假设, 分析了36个样地57种优势植物叶片的P含量与土壤全P和有效P含量的关系。主要结果如下: 内蒙古草地叶片P含量较低而N/P较高, 与之前的研究结论一致; 在种群、样地和物种3个水平上, 叶片P含量、N/P与土壤P含量都没有显著的相关关系, 尽管土壤有效P含量的解释力高于土壤全P; 另一方面, 内蒙古草地土壤的有效P含量与全国土壤普查的结果接近, 高于美国及澳大利亚的平均值, 但低于世界土壤信息库里报道的全球土壤有效P平均值。鉴于内蒙古草地土壤的全P和有效P含量都不能准确反映叶片P含量, 且土壤的有效P含量也并不明显低于世界其他地区, 因此植物叶片P含量低、N/P高是由于土壤P含量低引起的这一假设在内蒙古草地不成立, 而且叶片P含量也与土壤P的可利用性无关。
Aims Phosphorus status and N/P stoichiometry in plant leaves have been studied intensively with recent focus on large-scale patterns and driving factors. Studies of Chinese terrestrial plants found that leaf P was considerably lower than the global average, resulting in a higher N/P, probably due to the low soil total P content at the national scale. Inner Mongolia grassland offers a diverse array of taxa and soil conditions to examine the correlation between leaf and soil P concentrations. Our objective was to determine how and to what extent soil total and available P modify leaf P across the study region. Methods Leaf samples of 57 species were collected at 36 sites across Inner Mongolia grassland during July and August 2007. We determined leaf P concentration, N/P, soil total and available P concentrations and tested pairwise relationships between leaf and soil variables at species-by-site, inter-specific and inter-site levels. Important findings Findings of relatively low leaf P and high N/P across Inner Mongolia grassland were consistent with previous findings. Neither soil total nor available P appeared to be related with leaf P concentration, although soil available P had a stronger explanatory power than soil total P content. Moreover, Inner Mongolian grassland did not show a great shortage of soil available P compared with USA, Australia and the global average. The hypothesis that low leaf P and high N/P of plants are caused by low soil P content do not hold in Inner Mongolian grassland. Instead, neither soil total nor available P shapes the pattern of leaf P and N/P across this grassland.