若干北方落叶树木叶片养分的内外迁移Ⅰ.浓度和含量的变化

研究了北方12个落叶树种单位面积叶干重、叶片灰分、有机物质和7个元素的浓度和含量在落叶前后的变化,同一元素不同树种间及同一树种不同元素间有着不同的变化模式.单位面积叶干重、叶片有机物质浓度和含量在落叶后均表现下降的趋势;所有树种叶片灰分浓度和大部分树种的灰分含量(除刺槐、胡颓子、核桃楸外)均有增加;落叶时N、P、K的单位叶面积含量均可减少约1/3～2/3;Mg含量的减少在胡颓子、核桃楸、春榆、蒙古栎、日本落叶松等5个树种中发生,其余树种表现增加;落叶中Fe含量除胡颓子下降外,其余均表现升高;落叶中Ca、Si浓度和含量在所有分析树种中均表现增加趋势.

Maximum Threshold of the Rare Earth Concentration and Crop Growth.

Soil pot experiments and hydroponic culture conducted with La, Nd, and Ce on wheat, rapeseed, soybean, and rice were carried out. The result informed the maximum threshold of optimal and poisonous application amount and medium concentration of the elements, as well as the elements contained in crop leaves, stems, and roots. The experiments also showed that the threshold was closely related with crop growth.