【摘要】 由于草本植物持续上侵长白山灌木苔原,形成了强烈的灌草群落种间竞争。本研究以牛皮杜鹃-小叶章群落（Comm. Rhododendron aureum-Deyeuxia purpurea）为对象,根据小叶章的入侵程度设置4种盖度差异显著的样方（无、轻度、中度、重度入侵）,并设3个施氮水平(自然状态、添加11.8 kgN·hm^-2·a^-1及添加23.6kgN·hm^-2·a^-1),进行原位氮沉降模拟实验,监测灌木牛皮杜鹃和草本植物小叶章光合特性的差异和变化趋势,研究小叶章入侵苔原带的内在生理机制。结果显示:（1）小叶章净光合速率大于牛皮杜鹃,小叶章盖度越高、其叶绿素含量越高,而牛皮杜鹃叶绿素含量降低,随着小叶章入侵程度的增加,其净光合速率增强;（2）施氮可以提高牛皮杜鹃和小叶章的叶绿素含量和净光合速率,促进植物生长,但小叶章的增幅更大,从而增强了小叶章的竞争优势;（3）施氮和小叶章入侵具有复合作用,小叶章盖度越大,对其施氮导致小叶章净光合速率与叶绿素含量的增幅越大,而牛皮杜鹃的增幅减小。所以小叶章的成功入侵可能与其具有较高的净光合速率有关,并且施氮有利于提高小叶章的净光合速率,随着氮沉降的继续增加,更有利于小叶章的生长并提高其竞争力。更多还原

【Abstract】 As herbaceous plants continue to invade the shrub tundra of the Changbai Mountains,strong interspecific competition among mixed shrub-grass communities has formed. In this study,Comm. Rhododendron aureum-Deyeuxia purpurea was investigated to monitor the differences and changes in photosynthetic characteristics of R. aureum and D. purpurea in mixed communities. We established four different quadrats（no,mild,moderate,or severe invasion） according to differences in D. purpurea coverage degree and three nitrogen application levels(natural,11.8 kgN ·hm^-2·a^-1,23.6 kgN ·hm^-2·a^-1) under natural conditions,and determined the physiological mechanism related to D. purpurea invasion of the tundra. Results showed that:（1） The net photosynthetic rate of D. purpurea was higher than that of R. aureum. The higher the coverage of D. purpurea,the higher its chlorophyll content,whereas R. aureum showed the opposite pattern. With the increase in invasion degree,the net photosynthetic rate of D. purpurea increased.（2） Nitrogen application increased the chlorophyll content and net photosynthetic rate of R. aureum and D. purpurea and promoted plant growth. However,the growth rate of D. purpurea was larger, which enhanced its competitiveness.（3） Nitrogen application and D. purpurea invasion had a compound effect.Specifically,the greater the coverage of D. purpurea, the greater the increase in net photosynthetic rate and chlorophyll content of D. purpurea caused by nitrogen application; in contrast,the increase in R. aureum declined. Therefore,successful invasion by D. purpurea may be related to its higher net photosynthetic rate, which was enhanced by nitrogen application. Thus,an increase in nitrogen deposition would be conducive to D. purpurea growth and competitiveness.更多还原