Changes of treelines and alpine vegetation in relation to post‐glacial climate dynamics in northern Fennoscandia based on pollen and chironomid records
Changes of treelines and alpine vegetation in relation to post‐glacial climate dynamics in northern Fennoscandia based on pollen and chironomid records
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DOI：
10.1002/jqs.678
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发表时间：
2002-05
影响因子：
2.3
通讯作者：
H. Seppä;M. Nyman;A. Korhola;J. Weckström
中科院分区：
文献类型：
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作者：
H. Seppä;M. Nyman;A. Korhola;J. Weckström
来自各种独立指标的古气候记录提供了北芬诺斯坎迪亚冰期后温度和土壤水分变化的证据。我们使用芬兰北部高海拔湖泊Toskaljavri的花粉百分比、花粉流入、气孔和摇蚊记录，来评估那里的树线和高山植被对这些气候变化的反应。证据表明，全新世早期凉爽潮湿的气候支持了9600卡地区的白桦林。年BP之后，气温上升引发了松树在8300卡路里的迁移。YR BP。在6100-4000卡。该地区的YR BP海拔树线是由松树形成的，与现代山桦达到更高海拔的情况形成了鲜明对比。高山植被也表现出明显的变化。在7000-4000卡路里的干燥气候期间，北部羊茅典型的干旱、少营养的植物群落扩大。Yr BP，并在4000卡后因凉爽和潮湿条件而下降。YR BP。高山植物群落倾向于湿润的地方，表现出相反的格局，在4000卡后向湿润的气候变化后扩大。YR BP。在冗余分析(RDA)中，反映潮湿地点典型高山植被的花粉类型的变化在总摇蚊组合中的变异性中占统计上的显著比例。虽然摇蚊群落的变化似乎遵循高山植被演替的主要模式，但本研究并不支持树线位置的变化与摇蚊地层学之间的直接联系。相反，这些数据表明，陆地和水生环境都直接对同一个终极原因做出了反应，即全新世气候变化。版权所有©2002 John Wiley&Sons，Ltd.
Palaeoclimatic records derived from a variety of independent proxies provide evidence of post‐glacial changes of temperature and soil moisture in northern Fennoscandia. We use pollen percentage, pollen influx, stomatal and chironomid records from Toskaljavri, a high‐altitude lake in northern Finland, to assess how treelines and alpine vegetation there have responded to these climate changes. The evidence suggests that the cool, moist climate of the early Holocene supported birch forest in the area 9600 cal. yr BP onwards and that a rise of temperature triggered the immigration of pine at 8300 cal. yr BP. At 6100–4000 cal. yr BP altitudinal treeline in the area was formed by pine, in contrast to the modern situation where mountain birch reaches a higher elevation. Alpine vegetation also demonstrates clear changes. Plant communities typical of dry, oligotrophic heaths of northern Fennoscandia expanded during the dry climatic period at 7000–4000 cal. yr BP and decreased in response to cooler and moister conditions after 4000 cal. yr BP. Alpine plant communities favouring moist sites show an inverse pattern, expanding after a change towards moister climate after 4000 cal. yr BP. In a redundancy analysis (RDA), a statistically significant proportion of the variability in the total chironomid assemblages was captured by changes in the pollen types reflecting alpine vegetation typical of moist sites. Although chironomid community changes appeared to follow the major patterns in the alpine vegetation succession, the present study does not support a direct link between the changing treeline position and chironomid stratigraphy. Rather, the data indicate that the terrestrial and aquatic environments have each responded directly to the same ultimate cause, namely changing Holocene climate. Copyright © 2002 John Wiley & Sons, Ltd.