用CO(NH2 )2 和Na2 SO4 模拟氮-硫沉降,采用二因素三水平法对氮-硫单一及复合沉降6 个月后尾巨桉(Eucalyptus urophylla S. T. Blake ×E. grandis Hill ex Maiden)和杉木[Cunninghamia lanceolata (Lamb.) Hook.]幼苗根、茎、叶片和全株中的全氮和全磷含量及叶片N ︰P 比的变化进行比较;在此基础上,分析了各器官间以及各器官与全株间全氮和全磷含量的相关性。对尾巨桉的研究结果表明:低和高水平(50 和100 kg·hm^-2 ·a^-1 )单一氮沉降条件下各器官和全株的全氮含量均显著高于对照、叶片N ︰P 比也高于对照,而各器官和全株的全磷含量总体上与对照无显著差异;在低和高水平(15 和30 kg·hm^-2 ·a^-1 )单一硫沉降及氮-硫复合沉降条件下,各器官和全株的全氮含量、全株的全磷含量及叶片的N ︰P 比大多显著高于对照,而各器官的全磷含量则与对照无显著差异。对杉木的研究结果表明:低和高水平单一氮沉降条件下茎、叶和全株的全氮含量均显著高于对照、根的全氮含量则低于对照,各器官和全株的全磷含量及叶片的N ︰P 比与对照无显著差异;低和高水平单一硫沉降条件下根、叶片和全株的全氮含量及叶片的N ︰P 比大多显著高于对照,而茎的全氮含量和全株的全磷含量则显著低于对照,各器官的全磷含量与对照无显著差异;氮-硫复合沉降条件下各器官和全株的全氮含量及叶片的N ︰P 比大多显著高于对照,而各器官和全株的全磷含量则与对照无显著差异。从全株的全氮和全磷含量以及叶片N ︰P 比的变幅看,2 个树种全株的全氮含量对氮-硫复合沉降的响应最强。此外,氮-硫沉降条件下2 个树种各器官间的全氮和全磷含量总体无显著相关性,仅尾巨桉根与叶片的全磷含量呈显著正相关;而尾巨桉各器官与全株的全氮和全磷含量呈显著或极显著正相关,杉木叶片与全株的全氮和全磷含量及其茎与全株的全磷含量均呈显著正相关。研究结果显示:在一定水平的短期氮-硫沉降条件下2 个树种幼苗的氮和磷含量均增加,其中氮含量对氮-硫复合沉降的响应效应最强、磷含量对单一氮沉降的响应效应最强;尾巨桉对氮-硫沉降的响应效应强于杉木,且其生长限制元素呈现由氮限制转向氮-磷共同限制的趋势。

Simulated nitrogen-sulfur depositions by CO(NH₂ )₂ and Na₂ SO₄, changes in total nitrogen and total phosphorus contents in root, stem, leaf and whole plant and N ︰P ratio in leaf of Eucalyptus urophylla S. T. Blake ×E. grandis Hill ex Maiden and Cunninghamia lanceolata (Lamb.) Hook. seedlings after nitrogen-sulfur single and complex deposited for six months were compared by two factors three levels method. On this basis, the correlations in total nitrogen and total phosphorus  contents among organs and between organs and whole plant were analyzed. The research results on E. urophylla ×E. grandis show that under single nitrogen deposition condition with low and high levels (50 and 100 kg·hm^-2 ·a^-1), total nitrogen content in organs and whole plant is significantly higher than that of the control, N ︰P ratio in leaf is also higher than that of the control, while total phosphorus content in organs and whole plant is not generally significantly different to that of the control. Under conditions of single sulfur deposition with low and high levels (15 and 30 kg·hm^-2 ·a^-1) and nitrogen-sulfur complex deposition, total nitrogen content in organs and whole plant, total phosphorus content in whole plant and N ︰P ratio in leaf are mostly significantly higher than those of the control, while total phosphorus content in organs is not significantly different to that of the control. The research results on C. lanceolata show that under single nitrogen deposition condition with low and high levels, total nitrogen content in stem, leaf and whole plant is significantly higher than that of the control, that in root is lower than that of the control, total phosphorus content in organs and whole plant and N ︰P ratio in leaf are not  significantly different to those of the control. Under single sulfur deposition  condition with low and high levels, total nitrogen content in root, leaf and whole plant and N ︰P ratio in leaf are mostly significantly higher than those of the control, while total nitrogen content in stem and total phosphorus content in whole plant are significantly lower than those of the control, and total phosphorus content in organs is not significantly different to that of the control. Under nitrogen-sulfur complex deposition conditions, total nitrogen content in organs and whole plant and N ︰P ratio in leaf are mostly significantly higher than those of the control, while total phosphorus content in organs and whole plant is not significantly different to that of the control. From the view of change ranges of total nitrogen and total phosphorus contents in whole plant and N ︰P ratio in leaf, the response of total nitrogen content in whole plant of two tree species to nitrogen- sulfur complex deposition is the strongest. In addition, under nitrogen-sulfur deposition conditions, there is generally no significant correlation in total nitrogen and total phosphorus contents among organs of two tree species, only total phosphorus content in root and leaf of E. urophylla ×E. grandis appears significantly positive correlation. While, total nitrogen and total phosphorus contents in organs and whole plant of E. urophylla ×E. grandis appear significantly or extremely significantly positive correlation, total nitrogen and total phosphorus contents in leaf and whole plant of C. lanceolata, and total phosphorus contents in its stem and whole plant all appear significantly positive correlation. It is suggested that under short-term nitrogen-sulfur deposition condition with a certain level, nitrogen and phosphorus contents in seedlings of two tree species all increase, in which, the response effect of nitrogen content to nitrogen- sulfur complex deposition is the strongest, and that of phosphorus content to single nitrogen deposition is the strongest. The response effect of E. urophylla ×E. grandis to nitrogen-sulfur deposition is stronger than that of C. lanceolata, and its growth limiting elements appear the trend of changing from nitrogen limit to nitrogen-phosphorus common limit.