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| Titel |
Responses of desert, semi-arid grassland and scrub-oak ecosystems to elevated CO2 |
| VerfasserIn |
Kristina Luus, Anthony Walker, Martin De Kauwe, Bruce Hungate, J. Patrick Megonigal, Meng Lu, Lynn Fenstermaker, Robert Nowak, Jack Morgan, Belinda Medlyn, Richard Norby, Sönke Zaehle |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250094587
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| Publikation (Nr.) |
 EGU/EGU2014-10008.pdf |
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| Zusammenfassung |
| We compared observations from free air CO2 enrichment (FACE) experiments at dry (desert,
semi-arid grassland and scrub-oak) sites, to predictions from a suite of ecosystem models
with differing complexity, ranging from a parsimonious forest growth model (GDAY) to a
comprehensive land surface model (OCN). Dry ecosystems have often been predicted to
increase in net primary productivity (NPP) and net C uptake over time in response to
elevated CO2 (eCO2) because of increased N fixation, and alleviation of drought-stress
due to reduced stomatal conductance. However, experiments at the Nevada Desert
FACE (NDFF), the semi-arid prairie grassland FACE (PHACE), and the scrub-oak
Kennedy Space Center open-top chamber experiment (KSCO), have revealed that dry
ecosystems display a more complex biogeochemical response to eCO2. Insights into the
processes determining the responses of dry ecosystems to eCO2 were gained by
evaluating model estimates against site data, and by dissecting model responses to eCO2.
Site level findings at PHACE indicated that eCO2 enabled more rapid C turnover,
resulting in a net ecosystem C loss. Conversely, at PHACE, models such as OCN
simulated a decrease in N leaching and an increase in NPP because of eCO2, leading to
increased C storage. Leaf cover and NPP at KSCO initially increased with eCO2 before
declining due to reduced N fixation and increased N leaching. At NDFF, eCO2 only
increased plant growth during one abnormally wet year; in subsequent years, soil crust
cyanobacteria decreased in abundance, and gains in biomass were not sustained. In OCN
simulations at NDFF, eCO2 increased water-use efficiency and NPP in years with
average to above-average precipitation. Through examination of the reasons for
discrepancies between observed and modeled ecosystem responses to eCO2, processes
determining the biogeochemical responses of dry ecosystems to eCO2 were elucidated. |
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