氮沉降对长白山苔原植被影响的试验研究

Experimental Study on the Effects of Nitrogen Deposition on the Tundra Vegetation of the Changbai Mountains

为了探讨氮沉降增加对苔原植被的影响,特别是对草本植物侵入苔原的作用,在长白山高山苔原带进行了连续4 a的人工氮沉降模拟实验,测定3种设定的氮沉降水平下牛皮杜鹃(Rhododendron chrysanthum)、笃斯越橘(Vaccinium uliginosum)和小叶章(Deyeuxia angustifolia)的生长状况和群落结构变化。研究结果表明:1与牛皮杜鹃、笃斯越橘等苔原本地种相比,氮沉降量增加更有利于侵入的小叶章生长;牛皮杜鹃生长对氮沉降量变化响应微弱,氮沉降量增加能明显抑制笃斯越橘的生长。2无小叶章侵入的牛皮杜鹃和笃斯越橘斑块在不同氮沉降量条件下,群落结构变化不明显,氮沉降增加不是小叶章侵入苔原带的直接原因。3在小叶章侵入牛皮杜鹃和笃斯越橘斑块后,氮沉降量增加强化了小叶章的竞争能力,逐渐取代牛皮杜鹃或笃斯越橘,成为优势种,推动高山苔原向高山草甸转化。因此,随着氮沉降量的不断增加,长白山苔原带将面临退化与草甸化。

In order to explore the effects of increased nitrogen deposition on alpine tundra vegetation change, especially the herb invasion, in Changbai Mountains, the experiments of simulated increased nitrogen deposition were conducted over four years in the alpine tundra zone of the Changbai Mountains. The experiment included three nitrogen deposition treatments. The changes of growth and community structure were measured for Rhododendron chrysanthum, Vaccinium uliginosum and Deyeuxia angustifolia. The main results were as follows: 1)Compared to the Rhododendron chrysanthum, Vaccinium uliginosum and other tundra native species, the increase of nitrogen deposition is more conducive to the growth of Deyeuxia angustifolia, it was no significant response to increase of nitrogen deposition for growth of Rhododendron chrysanthum, it was significantly suppressed by increase of nitrogen deposition for growth of Vaccinium uliginosum. 2) The structure of Rhododendron chrysanthum and Vaccinium uliginosum community with no Deyeuxia angustifolia invasion did not change obviously. That shows that the increase of nitrogen deposition is not the direct reason of invasion of Deyeuxia angustifolia to tundra communities. 3) When Deyeuxia angustifolia invades the Rhododendron chrysanthum and Vaccinium uliginosum community, the increased nitrogen deposition contributes to the competitive ability of Deyeuxia angustifolia. And it promotes the transformation of alpine tundra to alpine meadow. With the increasing amount of nitrogen deposition, the tundra zone of the Changbai Mountains may face degradation and transform into tundra meadow.