Record Details
Biological and physical influences on soil ¹⁴CO₂ seasonal dynamics in a temperate hardwood forest
ScholarsArchive at Oregon State University
| Field | Value |
|---|---|
| Title | Biological and physical influences on soil ¹⁴CO₂ seasonal dynamics in a temperate hardwood forest |
| Names |
Phillips, C. L.
(creator) McFarlane, K. J. (creator) Risk, D. (creator) Desai, A. R. (creator) |
| Date Issued | 2013-12-09 (iso8601) |
| Note | This is the publisher’s final pdf. The published article is copyrighted by the author(s) and published by Copernicus Publications on behalf of the European Geosciences Union. The published article can be found at: http://www.biogeosciences.net/. |
| Abstract | While radiocarbon (¹⁴C) abundances in standing stocks of soil carbon have been used to evaluate rates of soil carbon turnover on timescales of several years to centuries, soil-respired ¹⁴CO₂ measurements are an important tool for identifying more immediate responses to disturbance and climate change. Soil Δ¹⁴CO₂ data, however, are often temporally sparse and could be interpreted better with more context for typical seasonal ranges and trends. We report on a semi-high-frequency sampling campaign to distinguish physical and biological drivers of soil Δ¹⁴CO₂ at a temperate forest site in northern Wisconsin, USA. We sampled ¹⁴CO₂ profiles every three weeks during snow-free months through 2012 in three intact plots and one trenched plot that excluded roots. Respired Δ¹⁴CO₂ declined through the summer in intact plots, shifting from an older C composition that contained more bomb ¹⁴C to a younger composition more closely resembling present ¹⁴C levels in the atmosphere. In the trenched plot, respired Δ¹⁴CO₂ was variable but remained comparatively higher than in intact plots, reflecting older bomb-enriched ¹⁴C sources. Although respired Δ¹⁴CO₂ from intact plots correlated with soil moisture, related analyses did not support a clear cause-and-effect relationship with moisture. The initial decrease in Δ¹⁴CO₂ from spring to midsummer could be explained by increases in ¹⁴C-deplete root respiration; however, Δ¹⁴CO₂ continued to decline in late summer after root activity decreased. We also investigated whether soil moisture impacted vertical partitioning of CO₂ production, but found this had little effect on respired Δ¹⁴CO₂ because CO₂ contained modern bomb C at depth, even in the trenched plot. This surprising result contrasted with decades to centuries-old pre-bomb CO₂ produced in lab incubations of the same soils. Our results suggest that root-derived C and other recent C sources had dominant impacts on respired Δ¹⁴CO₂ in situ, even at depth. We propose that Δ¹⁴CO₂ may have declined through late summer in intact plots because of continued microbial turnover of root-derived C, following declines in root respiration. Our results agree with other studies showing declines in the ¹⁴C content of soil respiration over the growing season, and suggest inputs of new photosynthates through roots are an important driver. |
| Genre | Article |
| Access Condition | http://creativecommons.org/licenses/by/3.0/us/ |
| Identifier | Phillips, C. L., McFarlane, K. J., Risk, D., and Desai, A. R.: Biological and physical influences on soil ¹⁴CO₂ seasonal dynamics in a temperate hardwood forest, Biogeosciences, 10, 7999-8012. doi:10.5194/bg-10-7999-2013, 2013. |
