Comparisons of photosynthesis-related traits among understory lichens,mosses and vascular plant leaves in a high-elevation subalpine forest

对比高海拔亚高山森林林下地衣、藓类及维管植物叶片的光合相关性状

Many mosses and lichens thrive in high-elevation subalpine forests and even become dominant species on the forest foor.Although they play an irreplaceable ecological role in the forest,less is known about their ecophysiological status,and how their photosynthesis-related functional traits differ from those of co-occurring vascular plants.We determined the carbon,nitrogen and phosphorus concentrations and stoichiometric ratios,tissue mass per area,chlorophyll concentrations and photosynthetic light–response curves of three lichens,three mosses and four vascular plants in a subalpine forest in the eastern Tibetan Plateau of China.Trait values were compared among and within each group.The lichens possessed a higher nitrogen concentration than that of mosses.In addition,the two poikilohydric groups exhibited lower concentrations of nitrogen,phosphorus and chlorophyll,light-saturated assimilation rates and photosynthetic nutrient use effciencies,and higher light compensation points than those of vascular plant leaves.Furthermore,variations in photosynthesis-related traits for lichen species refect their different adaptation strategies to their corresponding environments.In contrast,the differences were weak among the three forest-foor mosses and the three herb species.These results demonstrate that the high abundance of understory lichens and mosses in the high-elevation subalpine forest cannot be explained by the photosynthesis-related traits.

在高海拔亚高山森林中,许多地衣和藓类植物欣欣向荣,甚至成为林地表层的优势物种。尽管它们在森林生态系统中承担着不可替代的功能,但我们对其光合作用相关的功能性状水平知之甚少,对相同生境下藓类植物和维管植物的比较研究也较为匮乏。因此,本研究选择中国青藏高原东缘亚高山林下常见的3种地衣、3种藓类和4种维管植物,测定并对比了它们的碳、氮、磷含量及化学计量比、单位面积光合组织干重、叶绿素含量及光合光响应曲线的异同。研究结果表明,林下地衣的氮含量高于藓类植物,二者的氮、磷、叶绿素、光合速率及光合氮利用效率均低于维管植物叶片。不同种类地衣的光合相关性状与其生长环境相符,而林地表层的3种藓类植物和3种草本植物的功能性状在各自功能群中的种间差异均不显著。总之,这些结果表明高海拔亚高山林下地衣和藓类植物的优势与其光合相关性状关系不大,对严酷环境较强的适应能力可能是它们得以繁荣生长的关键。