Changing Source‐Transport Dynamics Drive Differential Browning Trends in a Boreal Stream Network

Fork, Megan L.; Sponseller, Ryan A.; Laudon, Hjalmar

doi:10.1029/2019wr026336

Cited by 35 publications

(34 citation statements)

References 51 publications

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“…These shifts are consistent with carbon production and accumulation in seasonally disconnected surface soils during summer (e.g., Winterdahl et al., 2011) but also highlight the biogeochemical distinctiveness of rain‐driven episodes, which have garnered less attention than snowmelt in high latitude landscapes. More broadly, a recent assessment at the same forested stream monitoring site shows that long‐term changes in the concentration and vertical distribution of DOC in riparian soil solution has reduced the occurrence of transport limitation in favor of chemostasis over the last 20 years (Fork et al., 2020). Finally, a major consequence of distinct C‐Q relationships among carbon forms is an emergent pattern in the overall composition of supply with changing discharge (Figure 4a).…”

Section: Discussionmentioning

confidence: 99%

Integrating Discharge‐Concentration Dynamics Across Carbon Forms in a Boreal Landscape

Gómez‐Gener

Hotchkiss

Laudon

et al. 2021

Water Resources Research

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The flux of terrestrial carbon across land‐water boundaries influences the overall carbon balance of landscapes and the ecology and biogeochemistry of aquatic ecosystems. The local consequences and broader fate of carbon delivered to streams is determined by the overall composition of carbon inputs, including the balance of organic and inorganic forms. Yet, our understanding of how hydrologic fluxes across different land‐water interfaces regulate carbon supply remains poor. We used 7 years of data from three boreal catchments to test how different land‐water interfaces (i.e., forest, wetland, and lake) modulate concentration‐discharge (C‐Q) relationships for dissolved organic carbon (DOC), carbon dioxide (CO2), and methane, as well as the balance among forms (e.g., DOC:CO2). Seasonal patterns in concentrations and C‐Q relationships for individual carbon forms differed across catchments. DOC varied between chemostasis and transport limitation in the forest catchment, between supply limitation and chemostasis in the wetland catchment, and was persistently chemostatic in the lake outlet stream. Carbon gases were supply limited overall, but exhibited chemostasis or transport limitation in the forest and wetland catchments linked to elevated flow in summer and autumn. Unique C‐Q relationships for individual forms reflected the properties of different interfaces and underpinned changes in the composition of lateral carbon supply. Accordingly, DOC dominated the carbon flux during snowmelt, whereas gas evasion increased in relative importance during other times of the year. Integrating the C‐Q dynamics of individual carbon forms provides insight into the shifting composition of lateral export, and thus helps to predict how hydrologic changes may alter the fate of carbon supplied to streams.

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Section: Discussionmentioning

confidence: 99%

Integrating Discharge‐Concentration Dynamics Across Carbon Forms in a Boreal Landscape

Gómez‐Gener

Hotchkiss

Laudon

et al. 2021

Water Resources Research

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“…To overcome the constraints of both approaches, one way forward is to combine the strengths of these two approaches into a framework that promotes basic research in long‐term monitored catchments (Tetzlaff et al, 2017), especially when they include several catchments of different scales and land‐use (Laudon & Sponseller, 2018). The heterogeneity inherent to boreal landscapes provides a unique template in this context because of the large spatial variability in the coverage of forests and peatlands that regulates much of the spatial and temporal complexity of soils, hydrology, and biogeochemistry (Fork et al, 2020; Laudon et al, 2011). The study of stream networks also makes it possible to assess the influence of more seldomly studied headwaters to downstream ecosystems (Bishop et al, 2008).…”

Section: Introductionmentioning

confidence: 99%

Northern landscapes in transition: Evidence, approach and ways forward using the Krycklan Catchment Study

Laudon

Hasselquist

Peichl

et al. 2021

Hydrological Processes

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Improving our ability to detect changes in terrestrial and aquatic systems is a grand challenge in the environmental sciences. In a world experiencing increasingly rapid rates of climate change and ecosystem transformation, our ability to understand and predict how, when, where, and why changes occur is essential for adapting and mitigating human behaviours. In this context, long-term field research infrastructures have a fundamentally important role to play. For northern boreal landscapes, the Krycklan Catchment Study (KCS) has supported monitoring and research aimed at revealing these changes since it was initiated in 1980. Early studies focused on forest regeneration and microclimatic conditions, nutrient balances and forest hydrology, which included monitoring climate variables, water balance components, and stream water chemistry. The research infrastructure has expanded over the years to encompass a 6790 ha catchment, which currently includes 11 gauged streams, ca. 1000 soil lysimeters, 150 groundwater wells, >500 permanent forest inventory plots, and a 150 m tall tower (a combined ecosystem-atmosphere station of the ICOS, Integrated Carbon Observation System) for measurements of atmospheric gas concentrations and biosphere-atmosphere exchanges of carbon, water, and energy. In addition, the KCS has also been the focus of numerous high resolution multi-spectral LiDAR measurements and large scale experiments. This large collection of equipment and data generation supports a range of disciplinary studies, but more importantly fosters multi-, trans-, and interdisciplinary research opportunities. The KCS attracts a broad collection of scientists, including biogeochemists, ecologists, foresters, geologists, hydrologists, limnologists, soil scientists, and social scientists, all of whom bring their knowledge and experience to the site. The combination of long-term monitoring, shorter-term research projects, and large-scale experiments, including manipulations

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“…The role of t‐DOC has been extensively studied in lake ecosystems while its importance to primary production and food webs in streams has received less attention (but see Burrows et al, 2021; Kuglerová et al, 2021), despite a recent study showing that browning may be particularly strong in forested headwater streams (Fork, Sponseller, & Laudon, 2020). Especially peatland drainage, practiced to enhance forest growth on moist soils, has been detected to be a major factor causing browning of boreal streams (Asmala et al, 2019; Nieminen et al, 2021).…”

Section: Introductionmentioning

confidence: 99%

Dark matters: Contrasting responses of stream biofilm to browning and loss of riparian shading

Jyväsjärvi

Rajakallio

Brüsecke

et al. 2022

Global Change Biology

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Concentrations of terrestrial‐derived dissolved organic carbon (DOC) in freshwater ecosystems have increased consistently, causing freshwater browning. The mechanisms behind browning are complex, but in forestry‐intensive regions browning is accelerated by land drainage. Forestry actions in streamside riparian forests alter canopy shading, which together with browning is expected to exert a complex and largely unpredictable control over key ecosystem functions. We conducted a stream mesocosm experiment with three levels of browning (ambient vs. moderate vs. high, with 2.7 and 5.5‐fold increase, respectively, in absorbance) crossed with two levels of riparian shading (70% light reduction vs. open canopy) to explore the individual and combined effects of browning and loss of shading on the quantity (algal biomass) and nutritional quality (polyunsaturated fatty acid and sterol content) of the periphytic biofilm. We also conducted a field survey of differently colored (4.7 to 26.2 mg DOC L−1) streams to provide a ‘reality check’ for our experimental findings. Browning reduced greatly the algal biomass, suppressed the availability of essential polyunsaturated fatty acids, especially eicosapentaenoic acid (EPA), and sterols, but increased the availability of terrestrial‐derived long‐chain saturated fatty acids (LSAFA). In contrast, loss of shading increased primary productivity, which resulted in elevated sterol and EPA contents of the biofilm. The field survey largely repeated the same pattern: biofilm nutritional quality decreased significantly with increasing DOC, as indicated particularly by a decrease of the ω‐3:ω‐6 ratio and increase in LSAFA content. Algal biomass, in contrast, was mainly controlled by dissolved inorganic nitrogen (DIN) concentration, while DOC concentration was of minor importance. The ongoing browning process is inducing a dramatic reduction in the nutritional quality of the stream biofilm. Such degradation of the major high‐quality food source available for stream consumers may reduce the trophic transfer efficiency in stream ecosystems, potentially extending across the stream‐forest ecotone.

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Changing Source‐Transport Dynamics Drive Differential Browning Trends in a Boreal Stream Network

Cited by 35 publications

References 51 publications

Integrating Discharge‐Concentration Dynamics Across Carbon Forms in a Boreal Landscape

Integrating Discharge‐Concentration Dynamics Across Carbon Forms in a Boreal Landscape

Northern landscapes in transition: Evidence, approach and ways forward using the Krycklan Catchment Study

Dark matters: Contrasting responses of stream biofilm to browning and loss of riparian shading

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