Abstract
During the first six years of atmospheric CO2 enrichment at the Duke Forest free-air CO2 enrichment (FACE) experiment, an additional sink of 52 ± 16 g C·m−2·yr−1 accumulated in the forest floor (O-horizon) of the elevated CO2 treatment relative to the ambient CO2 control in an aggrading loblolly pine (Pinus taeda L.) forest near Chapel Hill, North Carolina, USA. The experiment maintained an atmospheric CO2 concentration 200 μL/L above ambient levels in replicated (n = 3) FACE rings throughout the six-year period. This CO2-induced C sink was associated with greater inputs of organic matter in litterfall and fine-root turnover. There was no evidence that microbial decomposition was altered by the elevated CO2 treatment. Consistent with ecosystem recovery following decades of intensive agriculture, the C and N content of the mineral soil increased under both the elevated CO2 treatment and the ambient CO2 control during the six-year period. This increase is attributed to accumulation of plant residues derived from fine roots with relatively high turnover rates rather than accumulation of refractory or physically protected soil organic matter (SOM). The elevated CO2 treatment produced no detectable effect on the C and N content of the bulk mineral soils or of any particulate organic matter size fraction. Because the fumigation gas was strongly depleted in 13C, the incorporation of new C could be traced within the ecosystem. Significant decreases in δ13C of soil organic carbon (SOC) under the elevated CO2 treatment were used to estimate the mean residence times of intra-aggregate particulate organic matter and mineral-associated organic matter as well as the annual C inputs required to produce the observed changes in δ13C. Our results indicate that forest soils such as these will not significantly mitigate anthropogenic C inputs to the atmosphere. The organic matter pools receiving large annual C inputs have short mean residence times, while those with slow turnover rates receive small annual inputs.
Abstract from the paper’s OpenAlex record, shown for indexing and research. Copyright remains with the authors or the publisher. Read at the source ↗
The text the model read, with the source record’s inline markup (italics, sub- and superscripts) rendered and its character entities decoded; quote offsets refer to the raw text.
Claims 11
Claim · model-written summary
Elevated CO2 increased the forest-floor carbon sink by 52 ± 16 g C·m−2·yr−1.
- Taxon
- loblolly pine
Pinus taedae0 - Treatment
- elevated CO2 treatmente0
- Outcome
- sinke0
- Direction
- additionale0
- Value
- 52 ± 16 g C·m−2·yr−1e0
- Comparator
- ambient CO2 controle0
- Setting
- Chapel Hill, North Carolina, USAe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“an additional sink of 52 ± 16 g C·m−2·yr−1 accumulated in the forest floor (O-horizon) of the elevated CO2 treatment relative to the ambient CO2 control in an aggrading loblolly pine (Pinus taeda L.) forest near Chapel Hill, North Carolina, USA”
Claim · model-written summary
The CO2-induced carbon sink was associated with greater litterfall inputs.
PinusOrganisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“This CO2-induced C sink was associated with greater inputs of organic matter in litterfall and fine-root turnover”
t0“PINE”
Claim · model-written summary
The CO2-induced carbon sink was associated with greater fine-root turnover inputs.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“This CO2-induced C sink was associated with greater inputs of organic matter in litterfall and fine-root turnover”
t0“PINE”
Claim · model-written summary
Elevated CO2 did not measurably alter microbial decomposition.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“There was no evidence that microbial decomposition was altered by the elevated CO2 treatment”
t0“PINE”
Claim · model-written summary
Mineral-soil carbon increased under both CO2 treatments.
- Treatment
- elevated CO2 treatment and the ambient CO2 controle0
- Outcome
- C and N content of the mineral soile0
- Direction
- increasede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the C and N content of the mineral soil increased under both the elevated CO2 treatment and the ambient CO2 control during the six-year period”
t0“PINE”
Claim · model-written summary
Mineral-soil nitrogen increased under both CO2 treatments.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the C and N content of the mineral soil increased under both the elevated CO2 treatment and the ambient CO2 control during the six-year period”
t0“PINE”
Claim · model-written summary
Elevated CO2 had no detectable effect on bulk mineral-soil carbon and nitrogen.
- Treatment
- elevated CO2 treatmente0
- Outcome
- C and N content of the bulk mineral soilse0
- Direction
- no detectable effecte0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The elevated CO2 treatment produced no detectable effect on the C and N content of the bulk mineral soils or of any particulate organic matter size fraction”
t0“PINE”
Claim · model-written summary
Elevated CO2 had no detectable effect on particulate organic matter size fractions.
- Treatment
- elevated CO2 treatmente0
- Outcome
- particulate organic matter size fractione0
- Direction
- no detectable effecte0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The elevated CO2 treatment produced no detectable effect on the C and N content of the bulk mineral soils or of any particulate organic matter size fraction”
t0“PINE”
Claim · model-written summary
Elevated CO2 significantly decreased soil organic carbon δ13C.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Significant decreases in δ13C of soil organic carbon (SOC) under the elevated CO2 treatment”
t0“PINE”
Claim · model-written summary
Pools receiving large annual carbon inputs had short mean residence times.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The organic matter pools receiving large annual C inputs have short mean residence times”
t0“PINE”
Claim · model-written summary
Slow-turnover pools received small annual carbon inputs.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“those with slow turnover rates receive small annual inputs”
t0“PINE”
The same questions in other papers
co2 · nutrient: content · PinusPositive and negative results
1 in the opposite direction
- positive
co2 · growth · PinusPositive and negative results
3 papers in the same direction as this paper · 7 in the opposite direction
- positive
- positive
- positive
7 papers more in this group
See all 11 papers →Claims are grouped by organism, treatment and what was measured or targeted. A paper counts as positive when any of its claims in the group is positive.