Abstract
Abstract The capacity of forest ecosystems to sequester C in the soil relies on the net balance between litter production above, as well as, below ground, and decomposition processes. Nitrogen mineralization and its availability for plant growth and microbial activity often control the speed of both processes. Litter production, decomposition and N mineralization are strongly interdependent. Thus, their responses to global environmental changes (i.e. elevated CO 2 , climate, N deposition, etc.) cannot be fully understood if they are studied in isolation. In the present experiment, we investigated litter fall, litter decomposition and N dynamics in decomposing litter of three Populus spp., in the second and third growing season of a short rotation coppice under FACE. Elevated CO 2 did not affect annual litter production but slightly retarded litter fall in the third growing season. In all species, elevated CO 2 lowered N concentration, resulting in a reduction of N input to the soil via litter fall, but did not affect lignin concentrations. Litter decomposition was studied in bags incubated in situ both in control and FACE plots. Litter lost between 15% and 18% of the original mass during the eight months of field incubation. On average, litter produced under elevated CO 2 attained higher residual mass than control litter. On the other end, when litter was incubated in FACE plots it exhibited higher decay rates. These responses were strongly species‐specific. All litter increased their N content during decomposition, indicating immobilization of N from external sources. Independent of the initial quality, litter incubated on FACE soils immobilized less N, possibly as a result of lower N availability in the soil. Indeed, our results refer to a short‐term decomposition experiment. However, according to a longer‐term model extrapolation of our results, we anticipate that in Mediterranean climate, under elevated atmospheric CO 2 , soil organic C pool of forest ecosystems may initially display faster turnover, but soil N availability will eventually limit the process.
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Claims 13
Claim · model-written summary
Elevated CO2 did not affect annual poplar litter production.
PopulusNot reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Elevated CO 2 did not affect annual litter production but slightly retarded litter fall in the third growing season”
t0“poplar short‐rotation coppice”
Claim · model-written summary
Elevated CO2 slightly delayed litter fall in the third season.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Elevated CO 2 did not affect annual litter production but slightly retarded litter fall in the third growing season”
t0“poplar short‐rotation coppice”
Claim · model-written summary
Elevated CO2 lowered litter nitrogen concentration in all species.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“In all species, elevated CO 2 lowered N concentration, resulting in a reduction of N input to the soil via litter fall, but did not affect lignin concentrations”
t0“poplar short‐rotation coppice”
Claim · model-written summary
Elevated CO2 reduced nitrogen input to soil through litter fall.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“In all species, elevated CO 2 lowered N concentration, resulting in a reduction of N input to the soil via litter fall, but did not affect lignin concentrations”
t0“poplar short‐rotation coppice”
Claim · model-written summary
Elevated CO2 did not affect lignin concentration.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“In all species, elevated CO 2 lowered N concentration, resulting in a reduction of N input to the soil via litter fall, but did not affect lignin concentrations”
t0“poplar short‐rotation coppice”
Claim · model-written summary
Litter lost 15% to 18% of original mass during eight months of field incubation.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Litter lost between 15% and 18% of the original mass during the eight months of field incubation”
t0“poplar short‐rotation coppice”
Claim · model-written summary
Litter produced under elevated CO2 retained more mass than control litter.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“On average, litter produced under elevated CO 2 attained higher residual mass than control litter”
t0“poplar short‐rotation coppice”
Claim · model-written summary
Litter incubated in FACE plots had higher decay rates.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“when litter was incubated in FACE plots it exhibited higher decay rates”
t0“poplar short‐rotation coppice”
Claim · model-written summary
The decomposition responses varied strongly among species.
- Outcome
- species‐specifice0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“These responses were strongly species‐specific”
t0“poplar short‐rotation coppice”
Claim · model-written summary
All litter gained nitrogen during decomposition.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“All litter increased their N content during decomposition, indicating immobilization of N from external sources”
t0“poplar short‐rotation coppice”
Claim · model-written summary
Litter incubated on FACE soils immobilized less nitrogen regardless of initial quality.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Independent of the initial quality, litter incubated on FACE soils immobilized less N”
t0“poplar short‐rotation coppice”
Claim · model-written summary
Model extrapolation anticipates faster initial turnover of forest soil organic carbon under elevated CO2 in Mediterranean climate.
- Treatment
- elevated atmospheric CO 2e0
- Outcome
- soil organic C pool of forest ecosystemse0
- Direction
- fastere0
- Setting
- Mediterranean climatee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“according to a longer‐term model extrapolation of our results, we anticipate that in Mediterranean climate, under elevated atmospheric CO 2 , soil organic C pool of forest ecosystems may initially display faster turnover”
t0“poplar short‐rotation coppice”
Claim · model-written summary
Model extrapolation anticipates that soil nitrogen availability will eventually limit turnover.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“but soil N availability will eventually limit the process”
t0“poplar short‐rotation coppice”
The same questions in other papers
co2 · molecular: metabolites · Populus (poplar)Positive and negative results
1 paper in the same direction as this paper · 1 in the opposite direction
- positive
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co2 · yield · Populus (poplar)Positive and negative results
11 in the opposite direction
- positive
- positive
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See all 12 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.