Journal Article

Stream water carbon controls in seasonally snow-covered mountain catchments: impact of inter-annual variability of water fluxes, catchment aspect and seasonal processes

McIntosh, Jennifer, Brooks, Paul D., Harpold, Adrian, Ray, James, Meixner, Thomas, Litvak, Marcy, Kanduc, Tjasa, Perdrial, Julia N., Chorover, Jon, Zapata-Rios, Xavier, Troch, Peter A.

2014

Overview

Stream water carbon (C) export is one important pathway for C loss from seasonally snow-covered mountain ecosystems and an assessment of overarching controls is necessary. However, such assessment is challenging because changes in water fluxes or flow paths, seasonal processes, as well as catchment specific characteristics play a role. For this study we elucidate the impact of: (i) changes in water flux (by comparing years of variable wetness), (ii) catchment aspect [north-facing (NF) vs. south-facing (SF)] and (iii) season (snowmelt vs. summer) on all forms of dissolved stream water C [dissolved organic C (DOC), chromophoric dissolved organic matter (CDOM) and dissolved inorganic C (DIC)] in forested catchments within the Valles Caldera National Preserve, New Mexico. The significant correlation between annual water and C fluxes (e.g. DOC r² = 0.83, p < 0.02) confirms annual stream water discharge as the overarching control on C efflux, likely from a well-mixed ground water reservoir as indicated by previous research. However, CDOM exhibited a dominantly terrestrial fluorescence signature (59–71 %) year round, signaling a strong riparian and near stream soil control on CDOM composition. During snowmelt, the role of water as C transporter was superimposed on its control as C reservoir, when the NF stream transported significantly more soil C (40 % DOC, 56 % DIC) than the SF stream as a result of hillslope flushing. Inter-annual variations in winter precipitation were paramount in regulating annual stream C effluxes, e.g., reducing C effluxes three-fold after a dry (relative to wet) winter season. During the warmer summer months % dissolved oxygen saturation decreased, δ¹³CDIC increased and CDOM assumed a more microbial signature, consistent with heterotrophic respiration in the stream and riparian soils. As a result of stream C incubation and soil respiration, [Formula: see text] increased up to 12 times atmospheric values leading to substantial degassing.

• Publisher: Springer-Verlag,Springer,Springer International Publishing,Springer Nature B.V
• Subject: Animal and plant ecology / Animal, plant and microbial ecology / Annual precipitation / Annual variations / Biogeochemistry / Biogeosciences / Biological and medical sciences / Calderas / Carbon / Catchments / conservation areas / Creeks / Creeks & streams / Degassing / Dissolved organic carbon / Dissolved organic matter / Dissolved oxygen / Earth and Environmental Science / Earth Sciences / Earth, ocean, space / Ecosystems / Efflux / Environmental Chemistry / Environmental impact / Exact sciences and technology / Flow paths / Fluorescence / Fluxes / forested watersheds / Fundamental and applied biological sciences. Psychology / Geographic information systems / Groundwater / Groundwater reservoirs / Hydrology / Hydrology. Hydrogeology / Isotope geochemistry / Isotope geochemistry. Geochronology / Life Sciences / Microorganisms / Mountain ecosystems / Mountains / New Mexico / Organic soils / Oxygen content / Precipitation / Reservoirs / Respiration / Riparian soils / Rivers / Seasons / Snow / Snow cover / Snowmelt / Soil / soil respiration / Soil water / Stream flow / Stream water / Streams / Summer / Synecology / Terrestrial ecosystems / topographic slope / Vegetation / Water discharge / Water reservoirs / Watersheds / Winter