Soil carbon and nitrogen cycling and storage throughout the soil profile in a sweetgum plantation after 11 years of CO2-enrichment
- ORNL
- Chapman University
Increased partitioning of carbon (C) to fine roots under elevated [CO2], especially deep in the soil profile, could alter soil C and nitrogen (N) cycling in forests. After more than 11 years of free-Air CO2 enrichment in a Liquidambar styraciflua L. (sweetgum) plantation in Oak Ridge, TN, USA, greater inputs of fine roots resulted in the incorporation of new C (i.e., C with a depleted 13C) into root-derived particulate organic matter (POM) pools to 90-cm depth. Even though production in the sweetgum stand was limited by soil N availability, soil C and N content increased over time, and were greater throughout the soil profile under elevated [CO2] at the conclusion of the experiment. However, greater C inputs under elevated [CO2] did not result in increased net N immobilization or C mineralization rates in long-term laboratory incubations, and did not appear to prime the decomposition of older SOM. The 13CO2 of the C mineralized from the incubated soil closely tracked the 13C of the labile POM pool in the elevated [CO2] treatment, especially in shallower soil, and did not indicate the decomposition of older (i.e., pre-experiment) SOM. While potential C mineralization rates were positively and linearly related to total soil organic matter (SOM) C content in the top 30 cm of soil, this relationship did not hold in deeper soil. Taken together with an increased mean residence time of C in deeper soil pools, these findings indicate that C inputs from relatively deep roots under elevated [CO2] may have increased potential for long-term storage. Expanded representation of biogeochemical cycling throughout the soil profile may improve model projections of future forest responses to rising atmospheric [CO2].
- Research Organization:
- Oak Ridge National Laboratory (ORNL); Oak Ridge National Environmental Research Park
- Sponsoring Organization:
- SC USDOE - Office of Science (SC)
- DOE Contract Number:
- AC05-00OR22725
- OSTI ID:
- 1042824
- Journal Information:
- Global Change Biology, Journal Name: Global Change Biology Journal Issue: 5 Vol. 18; ISSN GCBIFE; ISSN 1354-1013
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
54 ENVIRONMENTAL SCIENCES
AVAILABILITY
CARBON
FACE
FORESTS
Liquidambar styraciflua
MINERALIZATION
NITROGEN
ORGANIC MATTER
PARTICULATES
PRODUCTION
SOILS
STORAGE
carbon mineralization
elevated [CO2]
fine roots
mineral-associated organic matter
nitrogen mineralization
particulate organic matter
soil depth