中文摘要：

设计5个氮肥（NH4NO3）添加水平（g·m^-2）：0（CK）、10．0（N1）、20．0（N2）、40．0（N3）和50．0（N4），研究了沙地樟子松幼苗生长与生理学指标的季节变化。结果表明，添加氮肥促进了幼苗的高生长、相对生长速率、单株总生物量的增加，对叶片相对含水量没有影响；N4水平促进了叶片脯氨酸含量的积累。单叶重、株高、地径、叶重比、叶绿素（a＋b）、叶绿素a以及叶绿索b含量等均在N3水平下达到最大值。在1个生长季的观测中，添加氮肥主要促进了樟子松幼苗在5～7月份的生长，其中N3水平对樟子松幼苗生长发育的促进作用最大。

英文摘要：

Five nitrogen （NH4NO3） fertilization levels （g·m^-2）, i.e., 0 （CK）, 10.0 （N1）, 20.0 （N2）, 40.0 （N3） and 50.0 （N4）, were employed to evaluate the effects of nitrogen fertilization on the growth and leaf physiological characteristics of Pinus sylvestris vat. mongolica seedlings on sandy soil. Indexes of growth and foliar physiology were measured in May, July, and September, respectively. Nitrogen addition significantly increased plant height, relative growth rate, and biomass per plant, but not for relative water content in leaves. Obvious proline accumulation was found for N4 level. The highest values of biomass per leaf, plant height, basal diameter, leaf mass ratio, contents of chlorophyll （a ＋ b ）, chlorophyll a and chlorophyll b were found for N3 treatment. Nitrogen addition mainly promoted the growth of P. sylvestris var. mongolica seedlings during May to July, and the N3 level was optimum among the five levels.