Tundra plant communities along the mesotopographic gradient in NE Finland

We describe plant communities along the mesotopographic gradient in the
low-elevation subcontinental mountains of NE Finland (Utsjoki region). We
sampled vascular plants, bryophytes, and lichens along 18 mesotopographic
ridge-snowbed transects comprising a total of 180 plots. We used
non-metric multidimensional scaling (NMDS) ordination with envfit to
explore the differentiation of plant communities in relation to
mesotopography, elevation, rock cover, the cover of bare ground, snow bed
size, and snowmelt time. The classification of communities was performed
using DIANA clustering. Plant communities were differentiated
along the mesotopographic gradient, snowmelt time, elevation, and rock
cover. The DIANA analysis distinguished seven clusters corresponding to
the following communities: Betula nana−Lichenes heath,
Empetrum−Myrtillus−Stereocaulon heath, Empetrum−Pleurozium−Lichenes heath,
graminoid-rich snow-protected heath, Oreojuncus trifidus–Avenella flexuosa
snow-protected heath, Polytrichastrum sexangulare–liverwort snowbed, and
Salix herbacea–Kiaeria starkei snowbed. Because of the strong impact of
snowmelt time on plant community structure and distribution of
communities, it is likely that climate change-induced changes in snow
conditions are affecting tundra vegetation, and especially snow beds are
threatened. Snowbed communities in the Utsjoki region roughly align with
previously described vegetation associations of mountain areas in NW
Europe. The assignment of the graminoid-rich snow-protected health
community remains uncertain.

我们描述了芬兰东北部Utsjoki地区低海拔次大陆山脉中沿中地形梯度分布的植物群落。我们沿18条中地形山脊-雪床样带对维管植物、苔藓植物和地衣进行采样，共包含180个样方。我们采用非度量多维尺度（NMDS）排序结合envfit方法，探索植物群落在中地形、海拔、岩石覆盖度、裸地覆盖度、雪床大小及融雪时间梯度上的分异特征。群落分类通过DIANA聚类（DIANA clustering）完成。植物群落在中地形梯度、融雪时间、海拔及岩石覆盖度上表现出显著分异。DIANA分析识别出7个集群，对应以下群落类型：Betula nana−Lichenes灌丛、Empetrum−Myrtillus−Stereocaulon灌丛、Empetrum−Pleurozium−Lichenes灌丛、富含禾草的雪保护灌丛、Oreojuncus trifidus–Avenella flexuosa雪保护灌丛、Polytrichastrum sexangulare–苔类雪床及Salix herbacea–Kiaeria starkei雪床。由于融雪时间对植物群落结构及分布具有强烈影响，气候变化引发的雪况改变可能正影响苔原植被，尤其是雪床群落面临威胁。Utsjoki地区的雪床群落大致与西北欧山区此前描述的植被群系一致，而富含禾草的雪保护灌丛群落的分类归属仍不确定。