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| Titel |
Comparison of inorganic nitrogen uptake dynamics following snowmelt and at peak biomass in subalpine grasslands |
| VerfasserIn |
N. Legay, F. Grassein, T. M. Robson, E. Personeni, M.-P. Bataillé, S. Lavorel, J.-C. Clément |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 10, no. 11 ; Nr. 10, no. 11 (2013-11-25), S.7631-7645 |
| Datensatznummer |
250085439
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| Publikation (Nr.) |
 copernicus.org/bg-10-7631-2013.pdf |
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| Zusammenfassung |
| Subalpine grasslands are highly seasonal environments and likely subject to
strong variability in nitrogen (N) dynamics. Plants and microbes typically
compete for N acquisition during the growing season and particularly at
plant peak biomass. During snowmelt, plants could potentially benefit from a
decrease in competition by microbes, leading to greater plant N uptake
associated with active growth and freeze-thaw cycles restricting microbial
growth. In managed subalpine grasslands, we expect these interactions to be
influenced by recent changes in agricultural land use, and associated
modifications in plant and microbial communities. At several subalpine
grasslands in the French Alps, we added pulses of 15N to the soil at
the end of snowmelt, allowing us to compare the dynamics of inorganic N
uptake in plants and microbes during this period with that previously
reported at the peak biomass in July. In all grasslands, while specific
shoot N translocation (per g of biomass) of dissolved inorganic nitrogen
(DIN) was two to five times greater at snowmelt than at peak biomass,
specific microbial DIN uptakes were similar between the two sampling dates.
On an area basis, plant communities took more DIN than microbial communities
at the end of snowmelt when aboveground plant biomasses were at least two
times lower than at peak biomass. Consequently, inorganic N partitioning
after snowmelt switches in favor of plant communities, allowing them to
support their growing capacities at this period of the year. Seasonal
differences in microbial and plant inorganic N-related dynamics were also
affected by past (terraced vs. unterraced) rather than current (mown vs. unmown)
land use. In terraced grasslands, microbial biomass N remained similar
across seasons, whereas in unterraced grasslands, microbial biomass N was
higher and microbial C : N lower at the end of snowmelt as compared to peak
biomass. Further investigations on microbial community composition and their
organic N uptake dynamics are required to better understand the decrease in
microbial DIN uptake. |
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