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| Titel |
The impacts of drainage, nutrient status and management practice on the full carbon balance of grasslands on organic soils in a maritime temperate zone |
| VerfasserIn |
F. Renou-Wilson, C. Barry, C. Müller, D. Wilson |
| 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 ; 11, no. 16 ; Nr. 11, no. 16 (2014-08-19), S.4361-4379 |
| Datensatznummer |
250117553
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| Publikation (Nr.) |
 copernicus.org/bg-11-4361-2014.pdf |
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| Zusammenfassung |
Temperate grasslands on organic soils are diverse due to edaphic properties
but also to regional management practices and this heterogeneity is
reflected in the wide range of greenhouse gas (GHG) flux values reported in
the literature. In Ireland, most grasslands on organic soils were drained
several decades ago and are managed as extensive pastures with little or no
fertilisation. This study describes a 2-year study of the net ecosystem
carbon balance (NECB) of two such sites. We determined GHG fluxes and
waterborne carbon (C) emissions in a nutrient-rich grassland and compared it
with values measured from two nutrient-poor organic soils: a deep-drained
and a shallow-drained site. Carbon dioxide (CO2), methane (CH4)
and nitrous oxide (N2O) fluxes were determined using the chamber
technique, and fluvial C fluxes were estimated by combining drainage water
concentrations and flows.
The nutrient-rich site was an annual source of CO2 (233 g C m−2 yr−1),
CH4 neutral, and a small source of N2O (0.16 g N2O-N m−2 yr−1).
Net ecosystem exchange (NEE) at the shallow-drained nutrient-poor site was −89 and −99 g C m−2 yr−1 in Years
1 and 2 respectively, and NEE at the deep-drained nutrient-poor site
was 85 and −26 g C m−2 yr−1 respectively. Low CH4 emissions
(1.3 g C m−2 yr−1) were recorded at the shallow-drained nutrient-poor site. Fluvial exports from the nutrient-rich site totalled 69.8 g C m−2 yr−1 with 54% as dissolved organic C. Waterborne C
losses from the nutrient-poor site reflected differences in annual runoff
totalling 44 g C m−2 yr−1 in Year 1 and 30.8 g C m−2 yr−1 in Year 2.
The NECB of the nutrient-rich grassland was 663 g C m−2 yr−1 with
biomass exports being the major component accounting for 53%. The NECB of
the nutrient-poor deep-drained site was less than half of the nutrient-rich
site (2-year mean 267 g C m−2 yr−1). Although NEE at the nutrient-poor shallow-drained site was negative in both years, high biomass export
meant it was a net C source (2-year mean NECB 103 g C m−2 yr−1).
While the impacts of the nutrient and drainage status on NEE, biomass
exports and fluvial C losses were confirmed, inter-regional differences in
management practice and climate were also significant factors which impacted
on the overall NECB of these ecosystems. Contrary to expectation, the NECB
of nutrient-poor drained organic soils under grasslands is not necessarily a
large C source and this has implications for Ireland's choice of national
GHG inventory reporting methodologies. This study can also aid the
development of strategies to deliver reduced emissions tailored to local
grassland types. |
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