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| Titel |
Evergreen shrub traits and peatland carbon cycling under high nutrient load |
| VerfasserIn |
Tuula Larmola, Vi Bui, Jill L. Bubier, Meng Wang, Meaghan Murphy, Tim R. Moore |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250123532
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| Publikation (Nr.) |
 EGU/EGU2016-2807.pdf |
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| Zusammenfassung |
| The reactive nitrogen (N) assimilated by plants is usually invested in chlorophyll to improve
light harvesting capacity and in soluble proteins such as Rubisco to enhance carbon (C)
assimilation. We studied the effects of simulated atmospheric N deposition on different traits
of two evergreen shrubs Chamaedaphne calyculata and Rhododendron groenlandicum in a
nutrient-poor Mer Bleue Bog, Canada that has been fertilized with N as NO3 and NH4 (2-8
times ambient annual wet deposition) with or without phosphorus (P) and potassium (K) for
7-12 years. We examined how nutrient addition influences the plant performance at leaf and
canopy level and linked the trait responses with ecosystem C cycling. At the leaf level, we
measured physiological and biochemical traits: CO2 exchange and chlorophyll
fluorescence, an indicator of plant stress in terms of light harvesting capacity; and to study
changes in photosynthetic nutrient use efficiency, we also determined the foliar
chlorophyll, N, and P contents. At the canopy level, we examined morphological
and phenological traits: growth responses and leaf longevity during two growing
seasons. Regardless of treatment, the majority of leaves showed no signs of stress in
terms of light harvesting capacity. The plants were N saturated: with increasing
foliar N content, the higher proportion of N was not used in photosynthesis. Foliar
net CO2 assimilation rates did not differ significantly among treatments, but the
additions of N, P, and K together resulted in higher respiration rates. The analysis of
the leaf and canopy traits showed that the two shrubs had different strategies: C.
calyculata was more responsive to nutrient additions, more deciduous-like, whereas R.
groenlandicum maintained evergreen features under nutrient load, shedding its leaves
even later in the season. In all, simulated atmospheric N deposition did not benefit
the photosynthetic apparatus of the dominant shrubs, but resulted in higher foliar
respiration, contributing to stress and a weaker ecosystem C sink. Thus, elevated
atmospheric deposition of nutrients to these systems may endanger C storage in peatlands. |
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