BACKGROUND Alpine alder vegetation acts upon the nearby grass and dwarf shrub vegetation by the nitrogen supply from the symbiotic bacteria Frankia alni of Alnus viridis. This has been studied in two transects concerning plant distribution, plant diversity, nitrate concentration in soil and photosynthetic performance of specific marker plants. RESULTS Away from the alder stand, a band of some meters was dominated by Calamagrostis varia which then was followed by alpine dwarf shrub vegetation. Nitrate in the soil showed a concentration decrease away from the alder stand leading to values near the detection limit in the dwarf shrub zone. Within these three zones, plant species were distributed according to their N-index, given in the ecological literature. Three dominant species, Calamagrostis varia, Rhododendron ferrugineum and Vaccinium myrtillus were examined at sites of different N-availability in the horizontal transect for their photosynthetic performance, by measuring the prompt fluorescence, the OJIP named polyphasic rise of chlorophyll-a fluorescence. All three plant species showed signs of stress in the fluorescence rise kinetics at decreased nitrate availability. These are similar to other known stress effects such as faster reduction of the primary acceptor or an electron supply limitation on the donor site of photosystem II. CONCLUSION Prompt chlorophyll-a fluorescence data of the examined leaves in a natural vegetation system showed the effects of a decrease in the essential nutrient nitrogen and in a manner parallel to changes in plant diversity. The selected marker plants behaved differently towards decreasing nitrogen concentrations in soil.

中文翻译：

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高山生态、植物多样性和标记植物在赤杨灌木诱导的氮梯度下的光合性能。

背景技术高山桤木植被通过来自桤木(Alnus viridis)的共生细菌Frankia alni的氮供应作用于附近的草和矮灌木植被。这已经在两个样带中进行了研究，涉及植物分布、植物多样性、土壤中的硝酸盐浓度和特定标记植物的光合作用性能。结果远离桤木林，几米长的地带以Calamagrostis varia为主，其次是高山矮灌木植被。远离桤木林地，土壤中的硝酸盐浓度降低，导致矮灌木区的值接近检测限。在这三个区域内，植物物种根据生态文献中给出的氮指数进行分布。通过测量瞬时荧光，OJIP 将其命名为叶绿素-a 荧光的多相上升，在水平样带的不同氮有效性位点检查了三种优势物种：Calamagrostis varia、Rhododendron ferrugineum 和 Vaccinium myrtillus 的光合性能。当硝酸盐可用性降低时，所有三种植物物种的荧光上升动力学均表现出应激迹象。这些与其他已知的应力效应类似，例如主要受体的更快还原或光系统 II 供体位点上的电子供应限制。结论 自然植被系统中受检叶子的即时叶绿素-a 荧光数据显示了必需营养氮减少的影响，并且其影响方式与植物多样性的变化平行。所选标记植物在降低土壤中氮浓度方面表现不同。