Abstract
BackgroundAlpine 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.ResultsAway 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.ConclusionPrompt 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.
Highlights
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
In this study we present the effect of different nitrogen availability in soil—produced by a natural gradient caused by nitrogen leaching from Alnus vegetation—on the photosynthetic performance of typical common plants in a natural alpine ecosystem
Rhododendron ferrugineum was hardly found near the Alnus bushes, while Vaccinium myrtillus or Veratrum album
Summary
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. Kaltrina et al BMC Ecol (2020) 20:23 to root symbiosis with the nitrogen-fixing Actinobacterium Frankia alni, the soil at these sites is enriched in plant-available nitrogen and a remarkable accumulation of biomass may be seen nearby. This suggests the presence of a nitrogen flow away from the alder zone into the neighboring grass and shrub zones. The effect on plant metabolism was studied by measuring the photosynthetic performance of selected dominating plant species at different sites in the N-gradient
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