Beech (Fagus sylvatica) and silver fir (Abies alba) are often cultivated in mixed stands and, hence, compete for water and nutrients. Besides nitrogen (N), also phosphorus (P) is an important nutrient for growth and development. Beech trees in Central Europe grow on both P-poor and P-rich soils, thereby showing similar growth and low variation in foliar P. The central aim of the present study was to test the hypothesis that variations in foliar P contents of beech are driven by seasonal changes rather than by the competition with silver fir. It was further hypothesized that P contents in silver fir needles depend on needle age and forest site. To test these hypotheses, P contents and P fractions, i.e. organic-bound P (Porg) and inorganic phosphate P (Pi), were measured in the foliage of beech trees from pure beech and mixed beech/silver fir plots as well as in needles of silver fir of the mixed plots. The forest sites investigated are located in Central Europe in the Black Forest, Germany, and in Croatia near the south-eastern distribution limit of beech and are all poor in plant-available soil P. The analyses showed that the main driver of P contents and P fractions in beech leaves at all forest sites is the season and that competition with silver fir had no effect. Hence, the present results demonstrate the high plasticity of beech trees to adapt to both poor plant-available soil P and competition with silver fir. Total P contents of silver fir needles were higher at the Croatian site compared to the Black Forest sites and originated from higher foliar Pi contents. One third of the P present in current-year needles in late summer was remobilized and exported until the needles reached the age of 1 year. The difference in P contents between current-year and 1-year-old needles can be seen as the amount of P resorbed from 1-year-old needles in summer during the generation of new needles to support the P demand of current-year needles for growth and development.

中文翻译：

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欧洲山毛榉 (Fagus sylvatica L.) 的叶面磷营养取决于季节，但不受与银杉 (Abies alba Mill) 共同栽培的影响。

山毛榉 (Fagus sylvatica) 和银杉 (Abies alba) 经常混合种植，因此会争夺水分和养分。除氮 (N) 外，磷 (P) 也是生长发育的重要营养素。中欧的山毛榉树生长在贫磷和富磷土壤上，因此显示出相似的生长和叶面磷的低变化。本研究的中心目的是检验山毛榉​​叶面磷含量变化是驱动的假设通过季节性变化而不是通过与银杉的竞争。进一步假设银杉针叶中的 P 含量取决于针叶年龄和林地。为了检验这些假设、P 含量和 P 分数，即有机结合的 P (Porg) 和无机磷酸盐 P (Pi)，在纯山毛榉和混合山毛榉/银冷杉地块的山毛榉树叶以及混合地块的银冷杉针叶中测量。调查的林地位于中欧的德国黑森林和克罗地亚靠近山毛榉分布东南部的地区，植物可利用土壤磷含量均较差。 分析表明，磷含量和磷含量的主要驱动因素所有林地的山毛榉叶子中的 P 分数是季节性的，与银杉的竞争没有影响。因此，目前的结果表明，山毛榉树的高可塑性能够适应贫瘠的植物可利用土壤磷和与银杉的竞争。与黑森林站点相比，克罗地亚站点的银杉针叶的总磷含量更高，并且源于较高的叶面磷含量。夏末当年针中存在的磷的三分之一被重新动员并出口，直到针达到 1 岁。当年针和1年针P含量的差异可以看成是夏季新针产生过程中从1年针吸收的P量，以支持当年针的P需求为成长和发展。