Spatial and seasonal variabilities of the stable carbon isotope composition of soil CO2 concentration and flux in complex terrain. Issue 9 (14th September 2016)

• Record Type: Journal Article
• Authors: Liang, Liyin L.; Riveros‐Iregui, Diego A.; Risk, David A.
• Is Part Of: Journal of geophysical research. Volume 121:Issue 9(2016:Sep.)
• Page Start: 2328
• Page End: 2339
• Publication Date: 2016-09-14
• Subjects: stable carbon isotope -- Keeling plot -- soil respiration -- soil moisture -- carbon cycle; Geobiology -- Periodicals; Biogeochemistry -- Periodicals; Biotic communities -- Periodicals; Geophysics -- Periodicals; 577.14
• DOI: 10.1002/2015JG003193
• Languages: English
• ISSNs: 2169-8953

Abstract

Abstract: Biogeochemical processes driving the spatial variability of soil CO2 production and flux are well studied, but little is known about the variability in the spatial distribution of the stable carbon isotopes that make up soil CO2, particularly in complex terrain. Spatial differences in stable isotopes of soil CO2 could indicate fundamental differences in isotopic fractionation at the landscape level and may be useful to inform modeling of carbon cycling over large areas. We measured the spatial and seasonal variabilities of the δ 13 C of soil CO2 ( δS ) and the δ 13 C of soil CO2 flux ( δP ) in a subalpine forest ecosystem located in the Rocky Mountains of Montana. We found consistently more isotopically depleted values of δS and δP in low and wet areas of the landscape relative to steep and dry areas. Our results suggest that the spatial patterns of δS and δP are strongly mediated by soil water and soil respiration rate. More interestingly, our analysis revealed different temporal trends in δP across the landscape; in high landscape positions δP became more positive, whereas in low landscape positions δP became more negative with time. These trends might be the result of differential dynamics in the seasonality of soil moisture and its effects on soil CO2 production and flux. Our results suggest concomitant yet independent effects of water on physical (soil gas diffusivity) and biological (photosynthetic discrimination) processes that mediate δS and δP and are important when evaluating the δ 13 C of CO2 exchanged between soils and the atmosphere in complex terrain. Key Points: We show systematic spatial variability in the δ 13 C of soil CO2 and soil CO2 flux in complex terrain At the landscape level, we found different seasonal trends in the δ 13 C of soil CO2 and soil CO2 flux The spatial variability of soil moisture is a strong predictor of the δ 13 C of soil CO2 flux at the landscape scale