Variable flushing mechanisms and landscape structure control stream DOC export during snowmelt in a set of nested catchments
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Stream DOC dynamics during snowmelt have been the focus of much research, and numerous DOC mobilization and delivery mechanisms from riparian and upland areas have been proposed. However, landscape structure controls on DOC export from riparian and upland landscape elements remains poorly understood. We investigated stream and groundwater DOC dynamics across three transects and seven adjacent but diverse catchments with a range of landscape characteristics during snowmelt (April 15–July 15) in the northern Rocky Mountains, Montana. We observed a range of DOC export dynamics across riparian and upland landscape settings and varying degrees of hydrologic connectivity between the stream, riparian, and upland zones. DOC export from riparian zones required a hydrologic connection across the riparian–stream interface, and occurred at landscape positions with a wide range of upslope accumulated area (UAA) and wetness status. In contrast, mobilization of DOC from the uplands appeared restricted to areas with a hydrologic connection across the entire upland–riparian–stream continuum, which generally occurred only at areas with high UAA, and/or at times of high wetness. Further, the relative extent of DOC-rich riparian and wetland zones strongly influenced catchment DOC export. Cumulative stream DOC export was highest from catchments with a large proportion of riparian to upland area, and ranged from 6.3 to 12.4 kg ha−1 across the study period. This research suggests that the spatial/temporal intersection of hydrologic connectivity and DOC source areas drives stream DOC export.
KeywordsCatchment DOC Flushing Landscape structure Snowmelt Stream
This work was funded by National Science Foundation (NSF) grant EAR-0337650 to B.L. McGlynn, and fellowships awarded to V.J. Pacific (from the Inland Northwest Research Alliance—INRA, and the Big Sky Institute NSF GK-12 Program) and K.G. Jencso (INRA). Extensive logistic collaboration was provided by the Tenderfoot Creek Experimental Forest and the USDA, Forest Service, Rocky Mountain Research Station, especially Ward McCaughey. Airborne Laser Mapping was provided by the NSF-supported Center for Airborne Laser Mapping (NCALM). We are grateful to Diego Riveros-Iregui and Austin Allen for field assistance, and Galena Ackerman and John Mallard for performing laboratory analyses.
- Farnes PE, Shearer RC, McCaughey WW, Hanson KJ (1995) Comparisons of hydrology, geology and physical characteristics between Tenderfoot Creek Experimental Forest (East Side) Montana, and Coram Experimental Forest (West Side) Montana. Final Report RJVA-INT-92734. USDA Forest Service. Intermountain Research Station, Forestry Sciences Laboratory, Bozeman, Montana, 19 pGoogle Scholar
- Freer J, McDonnell JJ, Beven KJ, Peters NE, Burns DA, Hooper RP, Aulenbach B, Kendall C (2002) The role of bedrock topography on subsurface stormflow. Water Resour Res 38. doi: 10.1029/2001WR000872
- Holdorf HD (1981) Soil resource inventory, Lewis and Clark National Forest, interim in-service report. On file with the Lewis and Clark National Forest. Forest Supervisor’s Office, Great FallsGoogle Scholar
- Jencso KJ, McGlynn BL, Gooseff KE, Bencala KE, Wondzell SM (in review) Hillslope hydrologic connectivity controls riparian groundwater turnover: implications of catchment structure for riparian buffering and stream water sources. Water Resour ResGoogle Scholar
- McGlynn BL, McDonnell JJ (2003) Role of discrete landscape units in controlling catchment dissolved organic carbon dynamics. Water Resour Res 39. doi: 10.1029/2002WR001525
- McGlynn BL, Seibert J (2003) Distributed assessment of contributing area and riparian buffering along stream networks. Water Resour Res 39. doi: 10.1029/2002WR001521
- Pacific VJ, McGlynn BL, Riveros-Iregui DA, Welsch D, Epstein H (2008) Variability in soil CO2 production and surface CO2 efflux across riparian-hillslope transitions. Biogeochemistry. doi: 10.1007/s10533-008-9258-8
- Pacific VJ, McGlynn BL, Riveros-Iregui DA, Epstein HE, Welsch DL (2009) Differential soil respiration responses to changing hydrologic regimes. Water Resour Res. doi: 10.1029/2009WR007721
- Riveros-Iregui DA, McGlynn BL (2009) Landscape structure controls soil CO2 efflux variability in complex terrain: scaling from point observations to catchment scale fluxes. J Geophys Res Biogeosci. doi: 10.1029/2008JG000885
- Riveros-Iregui DA, McGlynn BL, Epstein HE, Welsch DL (2008) Interpretation and evaluation of combined measurement techniques for soil CO2 efflux: surface chambers and soil CO2 concentration probes. J Geophys Res Biogeosci. doi: 10.1029/2008JG000811
- Riveros-Iregui DA, McGlynn BL, Epstein HE, Welsch D, Marshall L (in review) A landscape-scale assessment of a process soil CO2 production and transport model. J Geophys Res BiogeosciGoogle Scholar