Seasonal and inter-annual variability in 13C composition of ecosystem carbon fluxes in the U.S. Southern Great Plains

Journal Article · Wed Sep 22 04:00:00 EDT 2010 · Tellus B

OSTI ID:1009515

Torn, M S; Biraud, S; Still, C J; Riley, W J; Berry, J A

The {delta}{sup 13}C signature of terrestrial carbon fluxes ({delta}{sub bio}) provides an important constraint for inverse models of CO{sub 2} sources and sinks, insight into vegetation physiology, C{sub 3} and C{sub 4} vegetation productivity, and ecosystem carbon residence times. From 2002-2009, we measured atmospheric CO{sub 2} concentration and {delta}{sup 13}C-CO{sub 2} at four heights (2 to 60 m) in the U.S. Southern Great Plains (SGP) and computed {delta}{sub bio} weekly. This region has a fine-scale mix of crops (primarily C{sub 3} winter wheat) and C{sub 4} pasture grasses. {delta}{sub bio} had a large and consistent seasonal cycle of 6-8{per_thousand}. Ensemble monthly mean {delta}{sub bio} ranged from -25.8 {+-} 0.4{per_thousand} ({+-}SE) in March to -20.1 {+-} 0.4{per_thousand} in July. Thus, C{sub 3} vegetation contributed about 80% of ecosystem fluxes in winter-spring and 50% in summer-fall. In contrast, prairie-soil {delta}{sub 13}C values were about -15{per_thousand}, indicating that historically the region was dominated by C{sub 4} vegetation and had more positive {delta}{sub bio} values. Based on a land-surface model, isofluxes ({delta}{sub bio} x NEE) in this region have large seasonal amplitude because {delta}{sub bio} and net ecosystem exchange (NEE) covary. Interannual variability in isoflux was driven by variability in NEE. The large seasonal amplitude in {delta}{sub bio} and isoflux imply that carbon inverse analyses require accurate estimates of land cover and temporally resolved {sup 13}CO{sub 2} and CO{sub 2} fluxes.

• Research Organization: Ernest Orlando Lawrence Berkeley National Laboratory, Berkeley, CA (US)
• Sponsoring Organization: Earth Sciences Division
• DOE Contract Number: AC02-05CH11231
• OSTI ID: 1009515
• Report Number(s): LBNL-4004E
• Journal Information: Tellus B, Journal Name: Tellus B
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
58 GEOSCIENCES
AMPLITUDES
CARBON
CARBON SINKS
CROPS
ECOSYSTEMS
PASTURES
PHYSIOLOGY
PLANTS
PRODUCTIVITY
WHEAT