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| Titel |
Carbon dioxide and energy exchanges in two intensively managed grasslands in the maritime climate region |
| VerfasserIn |
Matthias Peichl, Paul Leahy, Gerard Kiely |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250056619
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| Zusammenfassung |
| Compared to global grasslands, grasslands in the maritime climate region may exhibit a
distinct net ecosystem exchange (NEE) of carbon dioxide (CO2) due to the absence of severe
winter snow cover, summer soil water deficits or heat stress. In addition, intensive
grassland management is common in this region, thus providing another important
control on NEE. Here, we investigate the CO2 and energy exchanges in two maritime
grasslands (Dripsey and Wexford) located in southern Ireland, using eddy-covariance
data collected since 2003. Both sites generally showed consistent and large annual
uptake of CO2 within the range of about 250 to 450 g C m-2 y-1. Reduced CO2
uptake or small net CO2 loss however was observed at the Wexford grassland during
years in which periodic planting of winter kale and grass reseeding occurred during
spring/early summer. Following grass harvesting events, CO2 uptake (i.e. NEE),
ecosystem photosynthesis (GEP) and respiration (RE) were reduced during 3-4
weeks. In contrast, grazing events primarily resulted in a decrease of GEP and
consequently CO2 uptake, without apparent effect on RE. Both grazing and harvesting
events led to a temporary increase in the Bowen ratio, primarily through enhanced
sensible heat flux. Effects from the first harvest cut on CO2 and energy exchange were
more pronounced compared to a second cut within a year. Similarly, early grazing
events altered CO2 exchange more than late summer grazing events. Latter ones
however resulted in a greater and longer lasting change (i.e. increase) of the Bowen
ratio compared to early grazing events. On an annual scale, silage management
resulted in lower annual CO2uptake and Bowen ratio compared to years in which the
grassland was predominantly used for grazing. Our study suggests that i) a prolonged
growing season and the lack of climatic constraints may allow enhanced annual CO2
uptake in maritime grasslands compared to global grasslands, and ii) that the choice
of management regime (i.e. grazing versus silage, forage crop planting and grass
re-seeding) may considerably alter the annual CO2 exchange and energy partitioning.
Furthermore, additional C fluxes that determine the net biome production have a
large potential for modifying the net grassland C balance of these grasslands. The
consideration of contrasting effects from grassland management practices on carbon
and energy exchange processes is essential to evaluate implications from current
and future management regimes on regional carbon, water and energy budgets. |
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