Controls on In-Stream and Riparian Carbon Fluxes In a Wetted Intermittent Reach
Abstract
Intermittent streams are estimated to comprise a large fraction of the global stream network and are potential dynamic hotspots of carbon fluxes. These fluxes are often higher in intermittent reaches than nearby perennial reaches. However, the key controls of these differences remain unclear, including the role of riparian soils adjacent to those streams. Therefore we sought to (1) quantify the patterns of CO2 fluxes in intermittent and perennial reaches and their adjacent riparian areas, and (2) assess the possible controls on these patterns. To do so, we measured CO2 fluxes and possible controls (including water temperature, light intensity, soil moisture, organic matter content, and soil temperature) every 10 to 20 m at coupled in-stream and riparian locations along a discontinuous stream in southeastern Idaho. The study reach spanned 250m, including (1) a downstream perennial reach located below a spring, (2) an intermittent reach above the spring, and (3) an upstream perennial reach. The segments were all wetted during the summer of 2018, but flows were significantly lower in the intermittent reach. Moisture and temperature differences between wet and dry extremes are known to affect CO2 efflux: dry stream beds have significantly higher fluxes than flowing streambeds in the same watershed. We found that in-stream CO2 fluxes in a perennial reach below the spring were significantly higher than an upstream intermittent reach. In-stream carbon fluxes increased with increasing water temperature in this same perennial reach below the spring. Adjacent riparian soil CO2 fluxes decreased with increasing light intensity in the same reach. None of the possible controls exhibited a significant relationship with CO2 flux in the intermittent reach. Soil CO2 fluxes increased with increasing organic matter in the riparian soils in the upstream perennial reach. No other relationships were significant. We conclude that deeper groundwater controls not quantified by our surface measurements may influence the balance of photosynthesis and respiration by changing flow paths that affect patterns of CO2 flux
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.H21K1812M
- Keywords:
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- 0414 Biogeochemical cycles;
- processes;
- and modeling;
- BIOGEOSCIENCESDE: 0438 Diel;
- seasonal;
- and annual cycles;
- BIOGEOSCIENCESDE: 1807 Climate impacts;
- HYDROLOGYDE: 1836 Hydrological cycles and budgets;
- HYDROLOGY