1.4 ka来长白山北坡植硅体组合气候变化及林线变迁

Timberline Transition and Climatic Variation Recorded by Phytolith Assemblages from the Northern Slope of Changbai Mountains over the Last 1.4 ka

摘要: 植硅体作为一种新的环境代用指标，能很好地反映地方性植被状况，进而恢复古植被、古气候，本文把它应用于高山林线的研究中。通过研究长白山海拔最高的泥炭地赤池35 cm厚的泥炭剖面各层位的植硅体组合特征反演该地千年以来古气候特征，据此推断林线位置的变迁，研究得到以下结论：1) 赤池泥炭剖面中发现的植硅体类型多数来源于草本植物，源于木本的植硅体较少，这与泥炭地多草本植物及草本植物植硅体产量较高有关。2) 赤池泥炭植硅体组合反映出长白山暖–温–冷–凉的气候波动状况。3) 1400 a B.P.以来，长白山赤池周围的植被可能经历了明针叶林→针叶林、岳桦林过渡带→岳桦林的演替过程。4) 与长白山北坡现在林线位置相比，约1400~920 a B.P.时期林线大约上侵300 m；约920~480 a B.P.时期林线大约上侵100 m；约480 a B.P.以来周围植被为岳桦林带，林线基本不变。

Abstract: As a new substitutive index of environment, by reason that phytoliths can well reflect local vegetation condi- tion, it can be used to rebuild paleovegetation and paleoclimate. In this paper, phytoliths was used to the study of alpine timberline. Phytoliths were analyzed from the peat profile whose depth is 35 cm, located in the highest elevation, in Chichi Lake in northern slope of Changbai Mountains. Paleoenvironment was reconstructed and the change of timberline location was inferred by comparing phytolith assemblages in different layers of the peat profile. Conclusions were shown as follows: 1) there are more phytoliths produced in herbaceous plants than in woody plants, because herbs are dominant in peatland and they can produce rich phytoliths; 2) climate fluctuated from warm to mild, followed by the cold weather, after which the climate can be described as cool; 3) There were appearence of three different vegetations around Chichi Lake since 1400 a B.P.. firstly, bright coniferous forest grew in this area, followed by the transition zone of coniferous forest and erman’s birch forest, and finally replaced by the Betula ermanii forest ; 4) Comparing with present location of timberline in northern slope of Changbai Mountains, its location rose up sharply about 300 m from 1400 a B.P. to 920 a B.P., after which it dropped off about 200 m in the following 440 years, and since 480 a B.P., the location of the timberline is consistent with the present.