【摘要】 <正> 森林生态系统中,氮累积的速度及数量对各生物组分的发生、繁育、演替以及生物生产量都起着重要作用。生物固氮是大气中氮素向森林生态系统输入的一个重要途径,包括土壤中自生固氮菌的固氮以及某些森林植物与特定的根瘤菌、放线菌等微生物的共生固氮作用。据统计,生物固氮的数量占整个生态系统输入量的6/7。长白山的森林是北温带地域内植被较为复杂,垂直分布带非常明显的针、阔叶天然林。从海拔500米的针阔混交林带到2,000米的亚高山岳桦带,经初步调查,高等植物中就有12个种具有结瘤固氮能力。其中分布较广、结瘤较多的是东北赤杨[Alnus mandshurica(Call.)更多还原

【Abstract】 Alnus mandshurica （Call.） Hand.-Mazz. and A. sibirica var. hisruta （Turez.） Koidz. are widely distributed in forest regions of northeastern China as major non-leguminous nodulated tree species with N₂-fixation. This paper summarizes the results of the research on effects of ecological factors on N₂-fixation of alder nodules. The results show that sufficient light condition is essential in raising N₂-fixing capability of the two species. The level of acetylene reduction of nodules partly depends on photosynthesis of the plant. The peak of diurnal course in acetylene reduction appears at 13: 00 hr. after the appearance of higher photosynthetic rate in early morning. The lower capability in N₂-fixation by A. mandshurica growing at high altitude is due to the lower temperature besides genetic factors.更多还原