Spring coherence in dissolved organic carbon export dominates total coherence in Boreal Shield forested catchments

Abstract The wide range of forested landscapes in boreal environments store and cycle substantial amounts of carbon, although the capacity of these systems to act as either a carbon sink or source is uncertain under a changing climate. While there are clear reports of regional-scale increases in dissolved organic carbon (DOC) concentrations in streams and lakes, there remains substantial watershed-scale variability in these patterns. Coherence is a framework for examining if variables of interest within adjacent spatial units change synchronously or asynchronously through time and has been widely applied in the context of lentic hydrochemistry, and which can shed light on the relative importance of regional- vs. local-scale controls. The objective of this research was to quantify coherence in discharge, DOC concentrations, and DOC loads in forested boreal watersheds, and to what extent coherence varied by season. Coherence was assessed using data from three long-term ecological research sites spanning boreal forest environments (IISD-Experimental Lakes Area, Turkey Lakes Watershed Study, and Dorset Environmental Science Centre) that included 29,829 DOC measurements across 739 stream-years, examining correlation between stream-pairs within each site, but not between sites. Seasonal coherence in DOC export was consistent across the three sites; coherence was significantly greater in spring than all other seasons, and was strongly related to discharge coherence. Currently, the season with the greatest loads (spring) is also the most coherent season, suggesting that annual between-stream coherence may be reduced if spring becomes proportionally less important in hydrologic budgets under a changing climate. This research aids in determining which factors contribute to synchronous watershed behaviour, and which factors may contribute to the timing and extent of individual watershed-scale deviations from landscape-level patterns.

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Dissolved organic carbon mobilized from organic horizons of mature and harvested black spruce plots in a mesic boreal region

Biogeosciences ◽

10.5194/bg-17-581-2020 ◽

2020 ◽

Vol 17 (3) ◽

pp. 581-595

Author(s):

Keri L. Bowering ◽

Kate A. Edwards ◽

Karen Prestegaard ◽

Xinbiao Zhu ◽

Susan E. Ziegler

Keyword(s):

Organic Carbon ◽

Dissolved Organic Carbon ◽

Soil Temperature ◽

Soil Water ◽

Boreal Forests ◽

Temporal Variations ◽

Forest Harvesting ◽

Water Fluxes ◽

Wide Range ◽

Doc Flux

Abstract. Boreal forests are subject to a wide range of temporally and spatially variable environmental conditions driven by season, climate, and disturbances such as forest harvesting and climate change. We captured dissolved organic carbon (DOC) from surface organic (O) horizons in a boreal forest hillslope using passive pan lysimeters in order to identify controls and hot moments of DOC mobilization from this key C source. We specifically addressed (1) how DOC fluxes from O horizons vary on a weekly to seasonal basis in forest and paired harvested plots and (2) how soil temperature, soil moisture, and water input relate to DOC flux trends in these plots over time. The total annual DOC flux from O horizons contain contributions from both vertical and lateral flow and was 30 % greater in the harvested plots than in the forest plots (54 g C m−2 vs. 38 g C m−2, respectively; p=0.008). This was despite smaller aboveground C inputs and smaller soil organic carbon stocks in the harvested plots but analogous to larger annual O horizon water fluxes measured in the harvested plots. Water input, measured as rain, throughfall, and/or snowmelt depending on season and plot type, was positively correlated to variations in O horizon water fluxes and DOC fluxes within the study year. Soil temperature was positively correlated to temporal variations of DOC concentration ([DOC]) of soil water and negatively correlated with water fluxes, but no relationship existed between soil temperature and DOC fluxes at the weekly to monthly scale. The relationship between water input to soil and DOC fluxes was seasonally dependent in both plot types. In summer, a water limitation on DOC flux existed where weekly periods of no flux alternated with periods of large fluxes at high DOC concentrations. This suggests that DOC fluxes were water-limited and that increased water fluxes over this period result in proportional increases in DOC fluxes. In contrast, a flushing of DOC from O horizons (observed as decreasing DOC concentrations) occurred during increasing water input and decreasing soil temperature in autumn, prior to snowpack development. Soils of both plot types remained snow-covered all winter, which protected soils from frost and limited percolation. The largest water input and soil water fluxes occurred during spring snowmelt but did not result in the largest fluxes of DOC, suggesting a production limitation on DOC fluxes over both the wet autumn and snowmelt periods. While future increases in annual precipitation could lead to increased DOC fluxes, the magnitude of this response will be dependent on the type and intra-annual distribution of this increased precipitation.

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Predicting export of dissolved organic carbon from forested catchments in glaciated landscapes with shallow soils

Global Biogeochemical Cycles ◽

10.1029/2008gb003294 ◽

2008 ◽

Vol 22 (4) ◽

pp. n/a-n/a ◽

Cited By ~ 77

Author(s):

I. F. Creed ◽

F. D. Beall ◽

T. A. Clair ◽

P. J. Dillon ◽

R. H. Hesslein

Keyword(s):

Organic Carbon ◽

Dissolved Organic Carbon ◽

Forested Catchments ◽

Shallow Soils

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Dissolved organic carbon dynamics in two streams draining forested catchments at loch ard, Scotland

Hydrological Processes ◽

10.1002/hyp.3360080508 ◽

1994 ◽

Vol 8 (5) ◽

pp. 457-464 ◽

Cited By ~ 21

Author(s):

Ian C. Grieve

Keyword(s):

Organic Carbon ◽

Dissolved Organic Carbon ◽

Carbon Dynamics ◽

Forested Catchments

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The role of watershed characteristics, permafrost thaw, and wildfire on dissolved organic carbon biodegradability and water chemistry in Arctic headwater streams

Biogeosciences Discussions ◽

10.5194/bgd-12-4021-2015 ◽

2015 ◽

Vol 12 (5) ◽

pp. 4021-4056 ◽

Cited By ~ 5

Author(s):

J. R. Larouche ◽

B. W. Abbott ◽

W. B. Bowden ◽

J. B. Jones

Keyword(s):

Organic Carbon ◽

Dissolved Organic Carbon ◽

Aquatic Ecosystems ◽

Vegetation Type ◽

Watershed Scale ◽

Ecosystem Recovery ◽

Watershed Characteristics ◽

Stream Geomorphology ◽

Tundra Ecosystems

Abstract. In the Alaskan Arctic, rapid climate change is increasing the frequency of disturbance including wildfire and permafrost collapse. These pulse disturbances may influence the delivery of dissolved organic carbon (DOC) to aquatic ecosystems, however the magnitude of these effects compared to the natural background variability of DOC at the watershed scale is not well known. We measured DOC quantity, composition, and biodegradability from 14 river and stream reaches (watershed sizes ranging from 1.5–167 km2) some of which were impacted by permafrost collapse (thermokarst) and fire. We found that region had a significant impact on quantity and biodegradability of DOC, likely driven by landscape and watershed characteristics such as lithology, soil and vegetation type, elevation, and glacial age. However, contrary to our hypothesis, we found that streams disturbed by thermokarst and fire did not contain significantly altered labile DOC fractions compared to adjacent reference waters, potentially due to rapid ecosystem recovery after fire and thermokarst as well as the limited spatial extent of thermokarst. Overall, biodegradable DOC ranged from 4 to 46% and contrary to patterns of DOC biodegradability in large Arctic rivers, seasonal variation in DOC biodegradability showed no clear pattern between sites, potentially related to stream geomorphology and position along the river network. While thermokarst and fire can alter DOC quantity and biodegradability at the scale of the feature, we conclude that tundra ecosystems are resilient to these types of disturbance.

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Improving pH and alkalinity estimates for regional-scale acidification models: incorporation of dissolved organic carbon

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f96-081 ◽

1996 ◽

Vol 53 (7) ◽

pp. 1602-1608 ◽

Cited By ~ 6

Author(s):

D R Marmorek ◽

R M MacQueen ◽

CHR Wedeles ◽

J Korman ◽

P J Blancher ◽

...

Keyword(s):

Organic Carbon ◽

Dissolved Organic Carbon ◽

Regional Scale

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Spectral Methods to Advance Understanding of Dissolved Organic Carbon Dynamics in Forested Catchments

Forest Hydrology and Biogeochemistry - Ecological Studies ◽

10.1007/978-94-007-1363-5_6 ◽

2011 ◽

pp. 117-135 ◽

Cited By ~ 21

Author(s):

Rose M. Cory ◽

Elizabeth W. Boyer ◽

Diane M. McKnight

Keyword(s):

Organic Carbon ◽

Dissolved Organic Carbon ◽

Spectral Methods ◽

Carbon Dynamics ◽

Forested Catchments

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Influences of dissolved organic carbon on stream water chemistry in two forested catchments in central Sweden

Biogeochemistry ◽

10.1007/s10533-010-9469-7 ◽

2010 ◽

Vol 101 (1-3) ◽

pp. 229-241 ◽

Cited By ~ 7

Author(s):

Sara H. Norström ◽

Jenny L. K. Vestin ◽

Dan Bylund ◽

Ulla S. Lundström

Keyword(s):

Organic Carbon ◽

Dissolved Organic Carbon ◽

Water Chemistry ◽

Stream Water ◽

Forested Catchments ◽

Stream Water Chemistry

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Modelling the effects of climate on long-term patterns of dissolved organic carbon concentrations in the surface waters of a boreal catchment

Hydrology and Earth System Sciences ◽

10.5194/hess-12-437-2008 ◽

2008 ◽

Vol 12 (2) ◽

pp. 437-447 ◽

Cited By ~ 26

Author(s):

M. N. Futter ◽

M. Starr ◽

M. Forsius ◽

M. Holmberg

Keyword(s):

Surface Water ◽

Organic Carbon ◽

Dissolved Organic Carbon ◽

Surface Waters ◽

Organic Soils ◽

Catchment Scale ◽

Changing Climate ◽

Recovery From Acidification ◽

Carbon Concentrations ◽

Process Based Models

Abstract. Dissolved organic carbon concentrations ([DOC]) in surface waters are increasing in many regions of Europe and North America. These increases are likely driven by a combination of changing climate, recovery from acidification and change in severity of winter storms in coastal areas. INCA-C, a process-based model of climate effects on surface water [DOC], was used to explore the mechanisms by which changing climate controls seasonal to inter-annual patterns of [DOC] in the lake and outflow stream of a small Finnish catchment between 1990 and 2003. Both production in the catchment and mineralization in the lake controlled [DOC] in the lake. Concentrations in the catchment outflow were controlled by rates of DOC production in the surrounding organic soils. The INCA-C simulation results were compared to those obtained using artificial neural networks (ANN). In general, "black box" ANN models provide better fits to observed data but process-based models can identify the mechanism responsible for the observed pattern. A statistically significant increase was observed in both INCA-C modelled and measured annual average [DOC] in the lake. This suggests that some of the observed increase in surface water [DOC] is caused by climate-related processes operating in the lake and catchment. However, a full understanding of surface water [DOC] dynamics can only come from catchment-scale process-based models linking the effects of changing climate and deposition on aquatic and terrestrial environments.

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