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The abiotic contribution to total CO2 flux for soils in arid zone.
- Source :
- Biogeosciences Discussions; 2015, Vol. 12 Issue 14, p11217-11244, 28p, 3 Charts, 5 Graphs
- Publication Year :
- 2015
-
Abstract
- As an important component of ecosystem carbon budgets, soil carbon dioxide (CO<subscript>2</subscript>) flux is determined by a combination of a series of biotic and abiotic processes. Although there is evidence that the abiotic component can be important in total soil CO<subscript>2</subscript> flux, its relative importance has never been systematically assessed. In this study, the total soil CO<subscript>2</subscript> flux (R<subscript>total</subscript>) was partitioned into biotic (R<subscript>biotic</subscript>) and abiotic (R<subscript>abiotic</subscript>) components over eight typical landscapes in a desert-oasis ecotone, including cotton field, hops field, halophyte garden, reservoir edge, native saline desert, alkaline soil, dune crest and interdune lowland in the Gurbantunggut Desert, and the relative importance of these two components was analyzed. Results showed that R<subscript>abiotic</subscript> always contributed to R<subscript>total</subscript> for the eight landscapes, but the degree of contribution varied greatly. In the cotton and hops fields, the ratio of R<subscript>abiotic</subscript> to R<subscript>total</subscript> was extremely low (< 10%); whereas R<subscript>abiotic</subscript> was dominant in the alkaline soil and dune crest. Statistically, R<subscript>abiotic</subscript>=R<subscript>total</subscript> decreased logarithmically with rising R<subscript>biotic</subscript>, suggesting that R<subscript>abiotic</subscript> strongly affected R<subscript>total</subscript> when R<subscript>biotic</subscript> was low. This pattern confirms that soil CO<subscript>2</subscript> flux is predominantly biological in most ecosystems, but R<subscript>abiotic</subscript> can dominate when biological processes are weak. On a diurnal basis, R<subscript>abiotic</subscript> resulted in no net gain or loss of carbon but its effect on instantaneous CO<subscript>2</subscript> flux was significant. Temperature dependence of R<subscript>total</subscript> varied among the eight landscapes, determined by the predominant components of CO<subscript>2</subscript> flux: with R<subscript>biotic</subscript> driven by soil temperature and R<subscript>abiotic</subscript> regulated by the rate of change in temperature. Namely, declining temperature resulted in negative R<subscript>abiotic</subscript> (CO<subscript>2</subscript> went into soil), while rising temperature resulted in a positive R<subscript>abiotic</subscript> (CO<subscript>2</subscript> released from soil). Furthermore, without recognition of R<subscript>abiotic</subscript>, R<subscript>biotic</subscript> would have been either overestimated (for daytime) or underestimated (for nighttime). Thus, recognition that abiotic component in total soil CO<subscript>2</subscript> flux is ubiquitous in soils has widespread consequences for the understanding of carbon cycling. While the abiotic flux will not change net daily soil CO<subscript>2</subscript> exchange and not likely directly constitute a carbon sink, it can alter transient soil CO<subscript>2</subscript> flux significantly, either in magnitude or in its temperature dependency. [ABSTRACT FROM AUTHOR]
Details
- Language :
- English
- ISSN :
- 18106277
- Volume :
- 12
- Issue :
- 14
- Database :
- Complementary Index
- Journal :
- Biogeosciences Discussions
- Publication Type :
- Academic Journal
- Accession number :
- 108758533
- Full Text :
- https://doi.org/10.5194/bgd-12-11217-2015