模拟氮沉降和接种外生菌根真菌对马尾松(Pinus massoniana)幼苗营养元素的影响

量化植物地上部和地下部元素含量对于理解和预测植物养分平衡如何响应大气氮沉降的变化至关重要。通过盆栽试验研究了氮沉降增加背景下外生菌根真菌对马尾松幼苗营养元素的影响。对马尾松幼苗进行了接种两种外生菌根真菌：（彩色豆马勃（Pisolithus tinctorius，Pt）与厚环乳牛肝菌（Suillus grevillei，Sg））以及4种氮素浓度添加：0 kg N hm^-2a^-1（N0）、正常氮沉降30 kg N hm^-2a^-1（N30）、中度氮沉降60 kg N hm^-2a^-1（N60）、重度氮沉降90 kg N hm^-2a^-1（N90），共12个处理，测定了马尾松地上部和地下部大量元素和微量元素的含量。结果表明：施氮改变了营养元素在马尾松幼苗地上部和地下部的含量，马尾松幼苗磷（P）、钙（Ca）、铁（Fe）、锰（Mn）等元素均在N60时达到临界值，而当输入的量超过了马尾松对氮的需求时，氮沉降会使马尾松营养元素含量较最适浓度时降低，地上部碳（C）随施氮浓度的升高先升高后降低，N随施氮浓度的升高而升高，根系和叶片钾（K）、Ca、镁（Mg）均随施氮浓度的升高而降低，施氮也降低了根系C及微量元素的含量。但在同一施氮浓度下，接种外生菌根真菌（EMF）后能够提高大多数元素的含量，N90时接种厚环乳牛肝菌（Sg）和彩色豆马勃（Pt）的叶片N含量与对照相比分别提高112.6%和138.6%，根系N含量分别提高73.1%、71.6%；N60时接种Sg和Pt的植株叶片P含量比不施氮未接种对照分别提高了166.3%、132.9%，根系P含量分别提高了40.8%、38.5%。EMF能够维持植物养分平衡，从而降低高施氮量对植物的影响效果。这为未来气候变化情景中氮沉降增加下接种EMF可以调节植物元素含量，从而达到更适应环境的元素平衡来促进生长提供理论依据。

Effects of nitrogen addition and ectomycorrhizal fungi on nutrient elements of Pinus massoniana seedlings

Quantifying the content of elements in the aboveground and underground parts of plants is significant to understand and predict how plant nutrient balance responds to changes in atmosphere nitrogen deposition. A field experiment with ectomycorrhizal fungi and nitrogen was established to investigate effects on nutrient elements in Pinus massoniana seedlings under the background of increased nitrogen deposition. Seedlings were subject to nitrogen additions, which were 0 kg N hm^-2a^-1 (N0), normal nitrogen deposition 30 kg N hm^-2a^-1 (N30), moderate nitrogen deposition 60 kg N hm^-2a^-1 (N60), severe nitrogen deposition 90 kg N hm^-2a^-1 (N90), and symbiosis with ectomycorrhizal fungi (EMF), which was Pisolithus tinctorius and Suillus grevillei, a total of 12 treatments. The contents of macronutrients and micronutrients in the leaves and roots of plants were determined. It was found that nitrogen addition changed the content of nutrient elements in the aboveground and underground parts of Pinus.massoniana, and P, Ca, Fe and Mn of seedlings reached the critical value at N60. When the input amount exceeded the nitrogen requirement of seedlings, nitrogen deposition would reduce the content of nutrient elements in Pinus massoniana compared with the optimum concentration. With the increase of nitrogen application concentration, the C content in leaves of Pinus massoniana seedlings increased at first and then decreased, and reached the maximum at N60, while the nitrogen content in aboveground and underground parts increased with the increase of nitrogen application concentration. The contents of K, Ca and Mg in roots and leaves decreased with the increase of nitrogen application concentration, and nitrogen application also decreased the contents of C and micronutrients in roots. Nitrogen application also decreased the content of root C and micronutrients. However, under the same nitrogen addition, EMF could increase the content of most elements. Compared with the control, the leaf N content of N90 inoculated with Sg and Pt increased by 112.6% and 138.6%, respectively, and the root N content increased by 73.1% and 71.6%, respectively. Compared with the control without nitrogen application, the leaf P content of the plants inoculated with Sg and Pt increased by 166.3% and 132.9%, respectively, and the root P content increased by 40.8% and 38.5%, respectively. EMF can maintain the balance of plant nutrients, thus reducing the effect of high nitrogen application on plants. It provides a theoretical basis for inoculating EMF under the increase of nitrogen deposition in the future climate change scenarios to regulate the element content of plants, so as to achieve more environmental element balance to promote growth.