 |
| Titel |
Environmental forcing does not induce diel or synoptic variation in the carbon isotope content of forest soil respiration |
| VerfasserIn |
D. R. Bowling, J. E. Egan, S. J. Hall, D. A. Risk |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1726-4170
|
| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 12, no. 16 ; Nr. 12, no. 16 (2015-08-31), S.5143-5160 |
| Datensatznummer |
250118081
|
| Publikation (Nr.) |
 copernicus.org/bg-12-5143-2015.pdf |
|
|
|
|
|
| Zusammenfassung |
| Recent studies have examined temporal fluctuations in the amount and carbon
isotope content (δ13C) of CO2 produced by the respiration of
roots and soil organisms. These changes have been correlated with diel cycles
of environmental forcing (e.g., sunlight and soil temperature) and with
synoptic-scale atmospheric motion (e.g., rain events and pressure-induced
ventilation). We used an extensive suite of measurements to examine soil
respiration over 2 months in a subalpine forest in Colorado, USA (the Niwot
Ridge AmeriFlux forest). Observations included automated measurements of
CO2 and δ13C of CO2 in the soil efflux, the soil gas
profile, and forest air. There was strong diel variability in soil efflux but
no diel change in the δ13C of the soil efflux (δR)
or the CO2 produced by biological activity in the soil
(δJ). Following rain, soil efflux increased significantly,
but δR and δJ did not change. Temporal
variation in the δ13C of the soil efflux was unrelated to measured
environmental variables, and we failed to find an explanation for this
unexpected result. Measurements of the δ13C of the soil efflux
with chambers agreed closely with independent observations of the isotopic
composition of soil CO2 production derived from soil gas well
measurements. Deeper in the soil profile and at the soil surface, results
confirmed established theory regarding diffusive soil gas transport and
isotopic fractionation. Deviation from best-fit diffusion model results at
the shallower depths illuminated a pump-induced ventilation artifact that
should be anticipated and avoided in future studies. There was no evidence of
natural pressure-induced ventilation of the deep soil. However, higher
variability in δ13C of the soil efflux relative to δ13C
of production derived from soil profile measurements was likely caused by
transient pressure-induced transport with small horizontal length scales. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|