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29 results on '"Sponseller, R. A."'

1. Topography and Time Shape Mire Morphometry and Large-Scale Mire Distribution Patterns in the Northern Boreal Landscape

Author

Ehnvall, B., Ratcliffe, J. L., Nilsson, M. B., Oquist, M. G., Sponseller, R. A., Grabs, Thomas, Ehnvall, B., Ratcliffe, J. L., Nilsson, M. B., Oquist, M. G., Sponseller, R. A., and Grabs, Thomas

Abstract

Peatlands are major terrestrial soil carbon stores, and open mires in boreal landscapes hold a considerable fraction of the global peat carbon. Despite decades of study, large-scale spatiotemporal analyses of mire arrangement have been scarce, which has limited our ability to scale-up mire properties, such as carbon accumulation to the landscape level. Here, we use a land-uplift mire chronosequence in northern Sweden spanning 9,000 years to quantify controls on mire distribution patterns. Our objectives include assessing changes in the spatial arrangement of mires with land surface age, and understanding modifications by upland hydrotopography. Characterizing over 3,000 mires along a 30 km transect, we found that the time since land emergence from the sea was the dominant control over mire coverage, especially for the establishment of large mire complexes. Mires at the youngest end of the chronosequence were small with heterogenous morphometry (shape, slope, and catchment-to-mire areal ratios), while mires on the oldest surfaces were variable in size, but included larger mires with more complex shapes and smaller catchment-to-mire ratios. In general, complex topography fragmented mires by constraining the lateral expansion, resulting in a greater number of mires, but reduced total mire area regardless of landscape age. Mires in this study area occurred on slopes up to 4%, indicating a hydrological boundary to peatland expansion under local climatic conditions. The consistency in mire responses to spatiotemporal controls illustrates how temporal limitation in peat initiation and accumulation, and topographic constraints to mire expansion together have shaped present day mire distribution patterns. Peatlands store nearly one third of the global soil carbon, despite covering only around three percent of the land surface. Open mires, which are characteristic peatland types at high latitudes, represent an important peat carbon store. Few studies have explored how mire pa

Published
2024
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5. Global patterns and controls of nutrient immobilization on decomposing cellulose in riverine ecosystems

Author

Costello, D. M. (David M.), Tiegs, S. D. (Scott D.), Boyero, L. (Luz), Canhoto, C. (Cristina), Capps, K. A. (Krista A.), Danger, M. (Michael), Frost, P. C. (Paul C.), Gessner, M. O. (Mark O.), Griffiths, N. A. (Natalie A.), Halvorson, H. M. (Halvor M.), Kuehn, K. A. (Kevin A.), Marcarelli, A. M. (Amy M.), Royer, T. V. (Todd, V), Mathie, D. M. (Devan M.), Albarino, R. J. (Ricardo J.), Arango, C. P. (Clay P.), Aroviita, J. (Jukka), Baxter, C. V. (Colden, V), Bellinger, B. J. (Brent J.), Bruder, A. (Andreas), Burdon, F. J. (Francis J.), Callisto, M. (Marcos), Camacho, A. (Antonio), Colas, F. (Fanny), Cornut, J. (Julien), Crespo-Perez, V. (Veronica), Cross, W. F. (Wyatt F.), Derry, A. M. (Alison M.), Douglas, M. M. (Michael M.), Elosegi, A. (Arturo), Eyto, E. (Elvira), Ferreira, V. (Veronica), Ferriol, C. (Carmen), Fleituch, T. (Tadeusz), Shah, J. J. (Jennifer J. Follstad), Frainer, A. (Andre), Garcia, E. A. (Erica A.), Garcia, L. (Liliana), Garcia, P. E. (Pavel E.), Giling, D. P. (Darren P.), Gonzales-Pomar, R. K. (R. Karina), Graca, M. A. (Manuel A. S.), Grossart, H.-P. (Hans-Peter), Guerold, F. (Francois), Hepp, L. U. (Luiz U.), Higgins, S. N. (Scott N.), Hishi, T. (Takuo), Iniguez-Armijos, C. (Carlos), Iwata, T. (Tomoya), Kirkwood, A. E. (Andrea E.), Koning, A. A. (Aaron A.), Kosten, S. (Sarian), Laudon, H. (Hjalmar), Leavitt, P. R. (Peter R.), Lemes da Silva, A. L. (Aurea L.), Leroux, S. J. (Shawn J.), LeRoy, C. J. (Carri J.), Lisi, P. J. (Peter J.), Masese, F. O. (Frank O.), McIntyre, P. B. (Peter B.), McKie, B. G. (Brendan G.), Medeiros, A. O. (Adriana O.), Milisa, M. (Marko), Miyake, Y. (Yo), Mooney, R. J. (Robert J.), Muotka, T. (Timo), Nimptsch, J. (Jorge), Paavola, R. (Riku), Pardo, I. (Isabel), Parnikoza, I. Y. (Ivan Y.), Patrick, C. J. (Christopher J.), Peeters, E. T. (Edwin T. H. M.), Pozo, J. (Jesus), Reid, B. (Brian), Richardson, J. S. (John S.), Rincon, J. (Jose), Risnoveanu, G. (Geta), Robinson, C. T. (Christopher T.), Santamans, A. C. (Anna C.), Simiyu, G. M. (Gelas M.), Skuja, A. (Agnija), Smykla, J. (Jerzy), Sponseller, R. A. (Ryan A.), Teixeira-de Mello, F. (Franco), Vilbaste, S. (Sirje), Villanueva, V. D. (Veronica D.), Webster, J. R. (Jackson R.), Woelfl, S. (Stefan), Xenopoulos, M. A. (Marguerite A.), Yates, A. G. (Adam G.), Yule, C. M. (Catherine M.), Zhang, Y. (Yixin), Zwart, J. A. (Jacob A.), Costello, D. M. (David M.), Tiegs, S. D. (Scott D.), Boyero, L. (Luz), Canhoto, C. (Cristina), Capps, K. A. (Krista A.), Danger, M. (Michael), Frost, P. C. (Paul C.), Gessner, M. O. (Mark O.), Griffiths, N. A. (Natalie A.), Halvorson, H. M. (Halvor M.), Kuehn, K. A. (Kevin A.), Marcarelli, A. M. (Amy M.), Royer, T. V. (Todd, V), Mathie, D. M. (Devan M.), Albarino, R. J. (Ricardo J.), Arango, C. P. (Clay P.), Aroviita, J. (Jukka), Baxter, C. V. (Colden, V), Bellinger, B. J. (Brent J.), Bruder, A. (Andreas), Burdon, F. J. (Francis J.), Callisto, M. (Marcos), Camacho, A. (Antonio), Colas, F. (Fanny), Cornut, J. (Julien), Crespo-Perez, V. (Veronica), Cross, W. F. (Wyatt F.), Derry, A. M. (Alison M.), Douglas, M. M. (Michael M.), Elosegi, A. (Arturo), Eyto, E. (Elvira), Ferreira, V. (Veronica), Ferriol, C. (Carmen), Fleituch, T. (Tadeusz), Shah, J. J. (Jennifer J. Follstad), Frainer, A. (Andre), Garcia, E. A. (Erica A.), Garcia, L. (Liliana), Garcia, P. E. (Pavel E.), Giling, D. P. (Darren P.), Gonzales-Pomar, R. K. (R. Karina), Graca, M. A. (Manuel A. S.), Grossart, H.-P. (Hans-Peter), Guerold, F. (Francois), Hepp, L. U. (Luiz U.), Higgins, S. N. (Scott N.), Hishi, T. (Takuo), Iniguez-Armijos, C. (Carlos), Iwata, T. (Tomoya), Kirkwood, A. E. (Andrea E.), Koning, A. A. (Aaron A.), Kosten, S. (Sarian), Laudon, H. (Hjalmar), Leavitt, P. R. (Peter R.), Lemes da Silva, A. L. (Aurea L.), Leroux, S. J. (Shawn J.), LeRoy, C. J. (Carri J.), Lisi, P. J. (Peter J.), Masese, F. O. (Frank O.), McIntyre, P. B. (Peter B.), McKie, B. G. (Brendan G.), Medeiros, A. O. (Adriana O.), Milisa, M. (Marko), Miyake, Y. (Yo), Mooney, R. J. (Robert J.), Muotka, T. (Timo), Nimptsch, J. (Jorge), Paavola, R. (Riku), Pardo, I. (Isabel), Parnikoza, I. Y. (Ivan Y.), Patrick, C. J. (Christopher J.), Peeters, E. T. (Edwin T. H. M.), Pozo, J. (Jesus), Reid, B. (Brian), Richardson, J. S. (John S.), Rincon, J. (Jose), Risnoveanu, G. (Geta), Robinson, C. T. (Christopher T.), Santamans, A. C. (Anna C.), Simiyu, G. M. (Gelas M.), Skuja, A. (Agnija), Smykla, J. (Jerzy), Sponseller, R. A. (Ryan A.), Teixeira-de Mello, F. (Franco), Vilbaste, S. (Sirje), Villanueva, V. D. (Veronica D.), Webster, J. R. (Jackson R.), Woelfl, S. (Stefan), Xenopoulos, M. A. (Marguerite A.), Yates, A. G. (Adam G.), Yule, C. M. (Catherine M.), Zhang, Y. (Yixin), and Zwart, J. A. (Jacob A.)

Abstract

Microbes play a critical role in plant litter decomposition and influence the fate of carbon in rivers and riparian zones. When decomposing low-nutrient plant litter, microbes acquire nitrogen (N) and phosphorus (P) from the environment (i.e., nutrient immobilization), and this process is potentially sensitive to nutrient loading and changing climate. Nonetheless, environmental controls on immobilization are poorly understood because rates are also influenced by plant litter chemistry, which is coupled to the same environmental factors. Here we used a standardized, low-nutrient organic matter substrate (cotton strips) to quantify nutrient immobilization at 100 paired stream and riparian sites representing 11 biomes worldwide. Immobilization rates varied by three orders of magnitude, were greater in rivers than riparian zones, and were strongly correlated to decomposition rates. In rivers, P immobilization rates were controlled by surface water phosphate concentrations, but N immobilization rates were not related to inorganic N. The N:P of immobilized nutrients was tightly constrained to a molar ratio of 10:1 despite wide variation in surface water N:P. Immobilization rates were temperature-dependent in riparian zones but not related to temperature in rivers. However, in rivers nutrient supply ultimately controlled whether microbes could achieve the maximum expected decomposition rate at a given temperature. Collectively, we demonstrated that exogenous nutrient supply and immobilization are critical control points for decomposition of organic matter.

Published
2022

8. Metabolism overrides photo‐oxidation in CO₂ dynamics of Arctic permafrost streams

Author

Rocher‐Ros, G. (Gerard), Harms, T. K. (Tamara K.), Sponseller, R. A. (Ryan A.), Väisänen, M. (Maria), Mörth, C. (Carl‐Magnus), and Giesler, R. (Reiner)

Abstract

Global warming is enhancing the mobilization of organic carbon (C) from Arctic soils into streams, where it can be mineralized to CO₂ and released to the atmosphere. Abiotic photo‐oxidation might drive C mineralization, but this process has not been quantitatively integrated with biological processes that also influence CO₂ dynamics in aquatic ecosystems. We measured CO₂ concentrations and the isotopic composition of dissolved inorganic C (δ¹³CDIC) at diel resolution in two Arctic streams, and coupled this with whole‐system metabolism estimates to assess the effect of biotic and abiotic processes on stream C dynamics. CO₂ concentrations consistently decreased from night to day, a pattern counter to the hypothesis that photo‐oxidation is the dominant source of CO₂. Instead, the observed decrease in CO₂ during daytime was explained by photosynthetic rates, which were strongly correlated with diurnal changes in δ¹³CDIC values. However, on days when modeled photosynthetic rates were near zero, there was still a significant diel change in δ¹³CDIC values, suggesting that metabolic estimates are partly masked by O₂ consumption from photo‐oxidation. Our results suggest that 6–12 mmol CO₂‐C m⁻² d⁻¹ may be generated from photo‐oxidation, a range that corresponds well to previous laboratory measurements. Moreover, ecosystem respiration rates were 10 times greater than published photo‐oxidation rates for these Arctic streams, and accounted for 33–80% of total CO₂ evasion. Our results suggest that metabolic activity is the dominant process for CO₂ production in Arctic streams. Thus, future aquatic CO₂ emissions may depend on how biotic processes respond to the ongoing environmental change.

Published
2021

9. Multiple stressors in small streams in the forestry context of Fennoscandia:the effects in time and space

Author

Kuglerová, L. (Lenka), Hasselquist, E. M. (Eliza Maher), Sponseller, R. A. (Ryan Allen), Muotka, T. (Timo), Hallsby, G. (Göran), Laudon, H. (Hjalmar), Kuglerová, L. (Lenka), Hasselquist, E. M. (Eliza Maher), Sponseller, R. A. (Ryan Allen), Muotka, T. (Timo), Hallsby, G. (Göran), and Laudon, H. (Hjalmar)

Abstract

In this paper we describe how forest management practices in Fennoscandian countries, namely Sweden and Finland, expose streams to multiple stressors over space and time. In this region, forestry includes several different management actions and we explore how these may successively disturb the same location over 60–100 year long rotation periods. Of these actions, final harvest and associated road construction, soil scarification, and/or ditch network maintenance are the most obvious sources of stressors to aquatic ecosystems. Yet, more subtle actions such as planting, thinning of competing saplings and trees, and removing logging residues also represent disturbances around waterways in these landscapes. We review literature about how these different forestry practices may introduce a combination of physicochemical stressors, including hydrological change, increased sediment transport, altered thermal and light regimes, and water quality deterioration. We further elaborate on how the single stressors may combine and interact and we consequently hypothesise how these interactions may affect aquatic communities and processes. Because production forestry is practiced on a large area in both countries, the various stressors appear multiple times during the rotation cycles and potentially affect the majority of the stream network length within most catchments. We concluded that forestry practices have traditionally not been the focus of multiple stressor studies and should be investigated further in both observational and experimental fashion. Stressors accumulate across time and space in forestry dominated landscapes, and may interact in unpredictable ways, limiting our current understanding of what forested stream networks are exposed to and how we can design and apply best management practices.

Published
2021

10. Habitat patchiness, ecological connectivity and the uneven recovery of boreal stream ecosystems from an experimental drought

Author

Truchy, A. (Amélie), Sarremejane, R. (Romain), Muotka, T. (Timo), Mykrä, H. (Heikki), Angeler, D. G. (David G.), Lehosmaa, K. (Kaisa), Huusko, A. (Ari), Johnson, R. K. (Richard K.), Sponseller, R. A. (Ryan A.), McKie, B. G. (Brendan G.), Truchy, A. (Amélie), Sarremejane, R. (Romain), Muotka, T. (Timo), Mykrä, H. (Heikki), Angeler, D. G. (David G.), Lehosmaa, K. (Kaisa), Huusko, A. (Ari), Johnson, R. K. (Richard K.), Sponseller, R. A. (Ryan A.), and McKie, B. G. (Brendan G.)

Abstract

Ongoing climate change is increasing the occurrence and intensity of drought episodes worldwide, including in boreal regions not previously regarded as drought prone, and where the impacts of drought remain poorly understood. Ecological connectivity is one factor that might influence community structure and ecosystem functioning post‐drought, by facilitating the recovery of sensitive species via dispersal at both local (e.g. a nearby habitat patch) and regional (from other systems within the same region) scales. In an outdoor mesocosm experiment, we investigated how impacts of drought on boreal stream ecosystems are altered by the spatial arrangement of local habitat patches within stream channels, and variation in ecological connectivity with a regional species pool. We measured basal ecosystem processes underlying carbon and nutrient cycling: (a) algal biomass accrual; (b) microbial respiration; and (c) decomposition of organic matter, and sampled communities of aquatic fungi and benthic invertebrates. An 8‐day drought event had strong impacts on both community structure and ecosystem functioning, including algal accrual, leaf decomposition and microbial respiration, with many of these impacts persisting even after water levels had been restored for 3.5 weeks. Enhanced connectivity with the regional species pool and increased aggregation of habitat patches also affected multiple response variables, especially those associated with microbes, and in some cases reduced the effects of drought to a small extent. This indicates that spatial processes might play a role in the resilience of communities and ecosystem functioning, given enough time. These effects were however insufficient to facilitate significant recovery in algal growth before seasonal dieback began in autumn. The limited resilience of ecosystem functioning in our experiment suggests that even short‐term droughts can have extended consequences for stream ecosystems in the world‘s vast boreal regi

Published
2020

11. Global patterns and drivers of ecosystem functioning in rivers and riparian zones

Author

Tiegs, SD, Costello, DM, Isken, MW, Woodward, G, McIntyre, PB, Gessner, MO, Chauvet, E, Griffiths, NA, Flecker, AS, Acuna, V, Albarino, R, Allen, DC, Alonso, C, Andino, P, Arango, C, Aroviita, J, Barbosa, MVM, Barmuta, LA, Baxter, CV, Bell, TDC, Bellinger, B, Boyero, L, Brown, LE, Bruder, A, Bruesewitz, DA, Burdon, FJ, Callisto, M, Canhoto, C, Capps, KA, Castillo, MM, Clapcott, J, Colas, F, Colon-Gaud, C, Cornut, J, Crespo-Perez, V, Cross, WF, Culp, JM, Danger, M, Dangles, O, de Eyto, E, Derry, AM, Diaz Villanueva, V, Douglas, MM, Elosegi, A, Encalada, AC, Entrekin, S, Espinosa, R, Ethaiya, D, Ferreira, V, Ferriol, C, Flanagan, KM, Fleituch, T, Shah, JJF, Frainer, A, Friberg, N, Frost, PC, Garcia, EA, Lago, LG, Garcia Soto, PE, Ghate, S, Giling, DP, Gilmer, A, Goncalves, JF, Gonzales, RK, Graca, MAS, Grace, M, Grossart, H-P, Guerold, F, Gulis, V, Hepp, LU, Higgins, S, Hishi, T, Huddart, J, Hudson, J, Imberger, S, Iniguez-Armijos, C, Iwata, T, Janetski, DJ, Jennings, E, Kirkwood, AE, Koning, AA, Kosten, S, Kuehn, KA, Laudon, H, Leavitt, PR, Lemes da Silva, AL, Leroux, SJ, Leroy, CJ, Lisi, PJ, MacKenzie, R, Marcarelli, AM, Masese, FO, Mckie, BG, Oliveira Medeiros, A, Meissner, K, Milisa, M, Mishra, S, Miyake, Y, Moerke, A, Mombrikotb, S, Mooney, R, Moulton, T, Muotka, T, Negishi, JN, Neres-Lima, V, Nieminen, ML, Nimptsch, J, Ondruch, J, Paavola, R, Pardo, I, Patrick, CJ, Peeters, ETHM, Pozo, J, Pringle, C, Prussian, A, Quenta, E, Quesada, A, Reid, B, Richardson, JS, Rigosi, A, Rincon, J, Risnoveanu, G, Robinson, CT, Rodriguez-Gallego, L, Royer, TV, Rusak, JA, Santamans, AC, Selmeczy, GB, Simiyu, G, Skuja, A, Smykla, J, Sridhar, KR, Sponseller, R, Stoler, A, Swan, CM, Szlag, D, Teixeira-de Mello, F, Tonkin, JD, Uusheimo, S, Veach, AM, Vilbaste, S, Vought, LBM, Wang, C-P, Webster, JR, Wilson, PB, Woelfl, S, Xenopoulos, MA, Yates, AG, Yoshimura, C, Yule, CM, Zhang, YX, Zwart, JA, Tiegs, SD, Costello, DM, Isken, MW, Woodward, G, McIntyre, PB, Gessner, MO, Chauvet, E, Griffiths, NA, Flecker, AS, Acuna, V, Albarino, R, Allen, DC, Alonso, C, Andino, P, Arango, C, Aroviita, J, Barbosa, MVM, Barmuta, LA, Baxter, CV, Bell, TDC, Bellinger, B, Boyero, L, Brown, LE, Bruder, A, Bruesewitz, DA, Burdon, FJ, Callisto, M, Canhoto, C, Capps, KA, Castillo, MM, Clapcott, J, Colas, F, Colon-Gaud, C, Cornut, J, Crespo-Perez, V, Cross, WF, Culp, JM, Danger, M, Dangles, O, de Eyto, E, Derry, AM, Diaz Villanueva, V, Douglas, MM, Elosegi, A, Encalada, AC, Entrekin, S, Espinosa, R, Ethaiya, D, Ferreira, V, Ferriol, C, Flanagan, KM, Fleituch, T, Shah, JJF, Frainer, A, Friberg, N, Frost, PC, Garcia, EA, Lago, LG, Garcia Soto, PE, Ghate, S, Giling, DP, Gilmer, A, Goncalves, JF, Gonzales, RK, Graca, MAS, Grace, M, Grossart, H-P, Guerold, F, Gulis, V, Hepp, LU, Higgins, S, Hishi, T, Huddart, J, Hudson, J, Imberger, S, Iniguez-Armijos, C, Iwata, T, Janetski, DJ, Jennings, E, Kirkwood, AE, Koning, AA, Kosten, S, Kuehn, KA, Laudon, H, Leavitt, PR, Lemes da Silva, AL, Leroux, SJ, Leroy, CJ, Lisi, PJ, MacKenzie, R, Marcarelli, AM, Masese, FO, Mckie, BG, Oliveira Medeiros, A, Meissner, K, Milisa, M, Mishra, S, Miyake, Y, Moerke, A, Mombrikotb, S, Mooney, R, Moulton, T, Muotka, T, Negishi, JN, Neres-Lima, V, Nieminen, ML, Nimptsch, J, Ondruch, J, Paavola, R, Pardo, I, Patrick, CJ, Peeters, ETHM, Pozo, J, Pringle, C, Prussian, A, Quenta, E, Quesada, A, Reid, B, Richardson, JS, Rigosi, A, Rincon, J, Risnoveanu, G, Robinson, CT, Rodriguez-Gallego, L, Royer, TV, Rusak, JA, Santamans, AC, Selmeczy, GB, Simiyu, G, Skuja, A, Smykla, J, Sridhar, KR, Sponseller, R, Stoler, A, Swan, CM, Szlag, D, Teixeira-de Mello, F, Tonkin, JD, Uusheimo, S, Veach, AM, Vilbaste, S, Vought, LBM, Wang, C-P, Webster, JR, Wilson, PB, Woelfl, S, Xenopoulos, MA, Yates, AG, Yoshimura, C, Yule, CM, Zhang, YX, and Zwart, JA

Abstract

River ecosystems receive and process vast quantities of terrestrial organic carbon, the fate of which depends strongly on microbial activity. Variation in and controls of processing rates, however, are poorly characterized at the global scale. In response, we used a peer-sourced research network and a highly standardized carbon processing assay to conduct a global-scale field experiment in greater than 1000 river and riparian sites. We found that Earth’s biomes have distinct carbon processing signatures. Slow processing is evident across latitudes, whereas rapid rates are restricted to lower latitudes. Both the mean rate and variability decline with latitude, suggesting temperature constraints toward the poles and greater roles for other environmental drivers (e.g., nutrient loading) toward the equator. These results and data set the stage for unprecedented “next-generation biomonitoring” by establishing baselines to help quantify environmental impacts to the functioning of ecosystems at a global scale.

Published
2019

12. Global patterns and drivers of ecosystem functioning in rivers and riparian zones

Author

Tiegs, S. D. (Scott D.), Costello, D. M. (David M.), Isken, M. W. (Mark W.), Woodward, G. (Guy), McIntyre, P. B. (Peter B.), Gessner, M. O. (Mark O.), Chauvet, E. (Eric), Griffiths, N. A. (Natalie A.), Flecker, A. S. (Alex S.), Acuna, V. (Vicenc), Albarino, R. (Ricardo), Allen, D. C. (Daniel C.), Alonso, C. (Cecilia), Andino, P. (Patricio), Arango, C. (Clay), Aroviita, J. (Jukka), Barbosa, M. V. (Marcus V. M.), Barmuta, L. A. (Leon A.), Baxter, C. V. (Colden V.), Bell, T. D. (Thomas D. C.), Bellinger, B. (Brent), Boyero, L. (Luz), Brown, L. E. (Lee E.), Bruder, A. (Andreas), Bruesewitz, D. A. (Denise A.), Burdon, F. J. (Francis J.), Callisto, M. (Marcos), Canhoto, C. (Cristina), Capps, K. A. (Krista A.), Castillo, M. M. (Maria M.), Clapcott, J. (Joanne), Colas, F. (Fanny), Colon-Gaud, C. (Checo), Cornut, J. (Julien), Crespo-Perez, V. (Veronica), Cross, W. F. (Wyatt F.), Culp, J. M. (Joseph M.), Danger, M. (Michael), Dangles, O. (Olivier), de Eyto, E. (Elvira), Derry, A. M. (Alison M.), Diaz Villanueva, V. (Veronica), Douglas, M. M. (Michael M.), Elosegi, A. (Arturo), Encalada, A. C. (Andrea C.), Entrekin, S. (Sally), Espinosa, R. (Rodrigo), Ethaiya, D. (Diana), Ferreira, V. (Veronica), Ferriol, C. (Carmen), Flanagan, K. M. (Kyla M.), Fleituch, T. (Tadeusz), Shah, J. J. (Jennifer J. Follstad), Frainer, A. (Andre), Friberg, N. (Nikolai), Frost, P. C. (Paul C.), Garcia, E. A. (Erica A.), Lago, L. G. (Liliana Garcia), Garcia Soto, P. E. (Pavel Ernesto), Ghate, S. (Sudeep), Giling, D. P. (Darren P.), Gilmer, A. (Alan), Goncalves, J. F. (Jose Francisco, Jr.), Gonzales, R. K. (Rosario Karina), Graca, M. A. (Manuel A. S.), Grace, M. (Mike), Grossart, H.-P. (Hans-Peter), Guerold, F. (Francois), Gulis, V. (Vlad), Hepp, L. U. (Luiz U.), Higgins, S. (Scott), Hishi, T. (Takuo), Huddart, J. (Joseph), Hudson, J. (John), Imberger, S. (Samantha), Iniguez-Armijos, C. (Carlos), Iwata, T. (Tomoya), Janetski, D. J. (David J.), Jennings, E. (Eleanor), Kirkwood, A. E. (Andrea E.), Koning, A. A. (Aaron A.), Kosten, S. (Sarian), Kuehn, K. A. (Kevin A.), Laudon, H. (Hjalmar), Leavitt, P. R. (Peter R.), Lemes da Silva, A. L. (Aurea L.), Leroux, S. J. (Shawn J.), Leroy, C. J. (Carri J.), Lisi, P. J. (Peter J.), MacKenzie, R. (Richard), Marcarelli, A. M. (Amy M.), Masese, F. O. (Frank O.), Mckie, B. G. (Brendan G.), Oliveira Medeiros, A. (Adriana), Meissner, K. (Kristian), Milisa, M. (Marko), Mishra, S. (Shailendra), Miyake, Y. (Yo), Moerke, A. (Ashley), Mombrikotb, S. (Shorok), Mooney, R. (Rob), Moulton, T. (Tim), Muotka, T. (Timo), Negishi, J. N. (Junjiro N.), Neres-Lima, V. (Vinicius), Nieminen, M. L. (Mika L.), Nimptsch, J. (Jorge), Ondruch, J. (Jakub), Paavola, R. (Riku), Pardo, I. (Isabel), Patrick, C. J. (Christopher J.), Peeters, E. T. (Edwin T. H. M.), Pozo, J. (Jesus), Pringle, C. (Catherine), Prussian, A. (Aaron), Quenta, E. (Estefania), Quesada, A. (Antonio), Reid, B. (Brian), Richardson, J. S. (John S.), Rigosi, A. (Anna), Rincon, J. (Jose), Risnoveanu, G. (Geta), Robinson, C. T. (Christopher T.), Rodriguez-Gallego, L. (Lorena), Royer, T. V. (Todd V.), Rusak, J. A. (James A.), Santamans, A. C. (Anna C.), Selmeczy, G. B. (Geza B.), Simiyu, G. (Gelas), Skuja, A. (Agnija), Smykla, J. (Jerzy), Sridhar, K. R. (Kandikere R.), Sponseller, R. (Ryan), Stoler, A. (Aaron), Swan, C. M. (Christopher M.), Szlag, D. (David), Teixeira-de Mello, F. (Franco), Tonkin, J. D. (Jonathan D.), Uusheimo, S. (Sari), Veach, A. M. (Allison M.), Vilbaste, S. (Sirje), Vought, L. B. (Lena B. M.), Wang, C.-P. (Chiao-Ping), Webster, J. R. (Jackson R.), Wilson, P. B. (Paul B.), Woelfl, S. (Stefan), Xenopoulos, M. A. (Marguerite A.), Yates, A. G. (Adam G.), Yoshimura, C. (Chihiro), Yule, C. M. (Catherine M.), Zhang, Y. X. (Yixin X.), Zwart, J. A. (Jacob A.), Tiegs, S. D. (Scott D.), Costello, D. M. (David M.), Isken, M. W. (Mark W.), Woodward, G. (Guy), McIntyre, P. B. (Peter B.), Gessner, M. O. (Mark O.), Chauvet, E. (Eric), Griffiths, N. A. (Natalie A.), Flecker, A. S. (Alex S.), Acuna, V. (Vicenc), Albarino, R. (Ricardo), Allen, D. C. (Daniel C.), Alonso, C. (Cecilia), Andino, P. (Patricio), Arango, C. (Clay), Aroviita, J. (Jukka), Barbosa, M. V. (Marcus V. M.), Barmuta, L. A. (Leon A.), Baxter, C. V. (Colden V.), Bell, T. D. (Thomas D. C.), Bellinger, B. (Brent), Boyero, L. (Luz), Brown, L. E. (Lee E.), Bruder, A. (Andreas), Bruesewitz, D. A. (Denise A.), Burdon, F. J. (Francis J.), Callisto, M. (Marcos), Canhoto, C. (Cristina), Capps, K. A. (Krista A.), Castillo, M. M. (Maria M.), Clapcott, J. (Joanne), Colas, F. (Fanny), Colon-Gaud, C. (Checo), Cornut, J. (Julien), Crespo-Perez, V. (Veronica), Cross, W. F. (Wyatt F.), Culp, J. M. (Joseph M.), Danger, M. (Michael), Dangles, O. (Olivier), de Eyto, E. (Elvira), Derry, A. M. (Alison M.), Diaz Villanueva, V. (Veronica), Douglas, M. M. (Michael M.), Elosegi, A. (Arturo), Encalada, A. C. (Andrea C.), Entrekin, S. (Sally), Espinosa, R. (Rodrigo), Ethaiya, D. (Diana), Ferreira, V. (Veronica), Ferriol, C. (Carmen), Flanagan, K. M. (Kyla M.), Fleituch, T. (Tadeusz), Shah, J. J. (Jennifer J. Follstad), Frainer, A. (Andre), Friberg, N. (Nikolai), Frost, P. C. (Paul C.), Garcia, E. A. (Erica A.), Lago, L. G. (Liliana Garcia), Garcia Soto, P. E. (Pavel Ernesto), Ghate, S. (Sudeep), Giling, D. P. (Darren P.), Gilmer, A. (Alan), Goncalves, J. F. (Jose Francisco, Jr.), Gonzales, R. K. (Rosario Karina), Graca, M. A. (Manuel A. S.), Grace, M. (Mike), Grossart, H.-P. (Hans-Peter), Guerold, F. (Francois), Gulis, V. (Vlad), Hepp, L. U. (Luiz U.), Higgins, S. (Scott), Hishi, T. (Takuo), Huddart, J. (Joseph), Hudson, J. (John), Imberger, S. (Samantha), Iniguez-Armijos, C. (Carlos), Iwata, T. (Tomoya), Janetski, D. J. (David J.), Jennings, E. (Eleanor), Kirkwood, A. E. (Andrea E.), Koning, A. A. (Aaron A.), Kosten, S. (Sarian), Kuehn, K. A. (Kevin A.), Laudon, H. (Hjalmar), Leavitt, P. R. (Peter R.), Lemes da Silva, A. L. (Aurea L.), Leroux, S. J. (Shawn J.), Leroy, C. J. (Carri J.), Lisi, P. J. (Peter J.), MacKenzie, R. (Richard), Marcarelli, A. M. (Amy M.), Masese, F. O. (Frank O.), Mckie, B. G. (Brendan G.), Oliveira Medeiros, A. (Adriana), Meissner, K. (Kristian), Milisa, M. (Marko), Mishra, S. (Shailendra), Miyake, Y. (Yo), Moerke, A. (Ashley), Mombrikotb, S. (Shorok), Mooney, R. (Rob), Moulton, T. (Tim), Muotka, T. (Timo), Negishi, J. N. (Junjiro N.), Neres-Lima, V. (Vinicius), Nieminen, M. L. (Mika L.), Nimptsch, J. (Jorge), Ondruch, J. (Jakub), Paavola, R. (Riku), Pardo, I. (Isabel), Patrick, C. J. (Christopher J.), Peeters, E. T. (Edwin T. H. M.), Pozo, J. (Jesus), Pringle, C. (Catherine), Prussian, A. (Aaron), Quenta, E. (Estefania), Quesada, A. (Antonio), Reid, B. (Brian), Richardson, J. S. (John S.), Rigosi, A. (Anna), Rincon, J. (Jose), Risnoveanu, G. (Geta), Robinson, C. T. (Christopher T.), Rodriguez-Gallego, L. (Lorena), Royer, T. V. (Todd V.), Rusak, J. A. (James A.), Santamans, A. C. (Anna C.), Selmeczy, G. B. (Geza B.), Simiyu, G. (Gelas), Skuja, A. (Agnija), Smykla, J. (Jerzy), Sridhar, K. R. (Kandikere R.), Sponseller, R. (Ryan), Stoler, A. (Aaron), Swan, C. M. (Christopher M.), Szlag, D. (David), Teixeira-de Mello, F. (Franco), Tonkin, J. D. (Jonathan D.), Uusheimo, S. (Sari), Veach, A. M. (Allison M.), Vilbaste, S. (Sirje), Vought, L. B. (Lena B. M.), Wang, C.-P. (Chiao-Ping), Webster, J. R. (Jackson R.), Wilson, P. B. (Paul B.), Woelfl, S. (Stefan), Xenopoulos, M. A. (Marguerite A.), Yates, A. G. (Adam G.), Yoshimura, C. (Chihiro), Yule, C. M. (Catherine M.), Zhang, Y. X. (Yixin X.), and Zwart, J. A. (Jacob A.)

Abstract

River ecosystems receive and process vast quantities of terrestrial organic carbon, the fate of which depends strongly on microbial activity. Variation in and controls of processing rates, however, are poorly characterized at the global scale. In response, we used a peer-sourced research network and a highly standardized carbon processing assay to conduct a global-scale field experiment in greater than 1000 river and riparian sites. We found that Earth’s biomes have distinct carbon processing signatures. Slow processing is evident across latitudes, whereas rapid rates are restricted to lower latitudes. Both the mean rate and variability decline with latitude, suggesting temperature constraints toward the poles and greater roles for other environmental drivers (e.g., nutrient loading) toward the equator. These results and data set the stage for unprecedented “next-generation biomonitoring” by establishing baselines to help quantify environmental impacts to the functioning of ecosystems at a global scale.

Published
2019

14. Seasonal variability of the OMZ off Peru in a high-resolution regional coupled model

Author

Dewitte, Boris, Montes, Ivonne, Garcon, Veronique, Ramos, Marcel, Paulmier, Aurélien, Pizarro, Oscar, Vergara, Oscar, Schelker, J., Sponseller, R., Ring, E., Högbom, L., Löfgren, S., Laudon, H., Laboratoire d'Etudes en Géophysique et Océanographie Spatiales (LEGOS NOUMEA), Institut national des sciences de l'Univers (INSU - CNRS)-Institut de recherche pour le développement [IRD] : UR065-Centre National de la Recherche Scientifique (CNRS), Helmholtz Centre for Ocean Research [Kiel] (GEOMAR), Laboratoire d'études en Géophysique et océanographie spatiales (LEGOS), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Université Fédérale Toulouse Midi-Pyrénées-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Inria Chile, Universidad Diego Portales [Santiago] (UDP)-Universidad de la frontera [Chile]-Universidad de Concepción [Chile]-Pontificia Universidad Católica de Chile (UC)-Institut National de Recherche en Informatique et en Automatique (Inria)-Pontificia Universidad Católica de Valparaíso (PUCV)-Universidad Adolfo Ibáñez [Santiago]-Universidad de Valparaiso [Chile]-Universidad Tecnica Federico Santa Maria [Valparaiso] (UTFSM), Departamento de Geofísica,Centro de Investigación Oceanográfica en el Pacífico Sur-Oriental/Programa Regional de Oceanografía Física y Clima (DGEO), Universidad de Concepción [Chile], Insitute for Environmental Assessment, Swedish University of Agricultural Sciences (SLU), Department of Ecology and Environmental Science [Umeå], Umeå University, Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut de recherche pour le développement [IRD] : UR065, Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), Universidad de Valparaiso [Chile]-Universidad Tecnica Federico Santa Maria [Valparaiso] (UTFSM)-Universidad Adolfo Ibáñez [Santiago]-Pontificia Universidad Católica de Valparaíso (PUCV)-Institut National de Recherche en Informatique et en Automatique (Inria)-Pontificia Universidad Católica de Chile (UC)-Universidad de Concepción [Chile]-Universidad de la frontera [Chile]-Universidad Diego Portales [Santiago] (UDP), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Universidad Diego Portales [Santiago] (UDP)-Universidad de la frontera [Chile]-Pontificia Universidad Católica de Chile (UC)-Institut National de Recherche en Informatique et en Automatique (Inria)-Pontificia Universidad Católica de Valparaíso (PUCV)-Universidad Adolfo Ibáñez [Santiago]-Universidad de Valparaiso [Chile]-Universidad Tecnica Federico Santa Maria [Valparaiso] (UTFSM)-Universidad de Concepción - University of Concepcion [Chile], and Universidad de Concepción - University of Concepcion [Chile]

Subjects
[SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere
Abstract

International audience; TS2 In addition to being one of the most productive upwelling systems, the oceanic region off Peru is embedded in one of the most extensive oxygen minimum zones (OMZs) of the world ocean. The dynamics of the OMZ off Peru remain uncertain, partly due to the scarcity of data and 5 to the ubiquitous role of mesoscale activity on the circulation and biogeochemistry. Here we use a high-resolution coupled physical/biogeochemical model simulation to investigate the seasonal variability of the OMZ off Peru. The focus is on characterizing the seasonal cycle in dissolved O 2 (DO) eddy 10 flux at the OMZ boundaries, including the coastal domain, viewed here as the eastern boundary of the OMZ, considering that the mean DO eddy flux in these zones has a significant contribution to the total DO flux. The results indicate that the seasonal variations of the OMZ can be interpreted 15 as resulting from the seasonal modulation of the mesoscale activity. Along the coast, despite the increased seasonal low DO water upwelling, the DO peaks homogeneously over the water column and within the Peru Undercurrent (PUC) in austral winter, which results from mixing associated with the 20 increase in both the intraseasonal wind variability and baro-clinic instability of the PUC. The coastal ocean acts therefore as a source of DO in austral winter for the OMZ core, through eddy-induced offshore transport that is also shown to peak in austral winter. In the open ocean, the OMZ can be di-25 vided vertically into two zones: an upper zone above 400 m, where the mean DO eddy flux is larger on average than the mean seasonal DO flux and varies seasonally, and a lower part, where the mean seasonal DO flux exhibits vertical-zonal propagating features that share similar characteristics 30 than those of the energy flux associated with the annual ex-tratropical Rossby waves. At the OMZ meridional boundaries where the mean DO eddy flux is large, the DO eddy flux has also a marked seasonal cycle that peaks in austral winter (spring) at the northern (southern) boundary. In the 35 model, the amplitude of the seasonal cycle is 70 % larger at the southern boundary than at the northern boundary. Our results suggest the existence of distinct seasonal regimes for the ventilation of the OMZ by eddies at its boundaries. Implications for understanding the OMZ variability at longer 40 timescales are discussed.

Published
2016
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17. Sources of and processes controlling CO2 emissions change with the size of streams and rivers

Author

Hotchkiss, E. R., Hall, R. O., Jr., Sponseller, R. A., Butman, D., Klaminder, J., Laudon, H., Rosvall, Martin, Karlsson, J., Hotchkiss, E. R., Hall, R. O., Jr., Sponseller, R. A., Butman, D., Klaminder, J., Laudon, H., Rosvall, Martin, and Karlsson, J.

Abstract

Carbon dioxide (CO2) evasion from streams and rivers to the atmosphere represents a substantial flux in the global carbon cycle(1-3). The proportions of CO2 emitted from streams and rivers that come from terrestrially derived CO2 or from CO2 produced within freshwater ecosystems through aquatic metabolism are not well quantified. Here we estimated CO2 emissions from running waters in the contiguous United States, based on freshwater chemical and physical characteristics and modelled gas transfer velocities at 1463 United States Geological Survey monitoring sites. We then assessed CO2 production from aquatic metabolism, compiled from previously published measurements of net ecosystem production from 187 streams and rivers across the contiguous United States. We find that CO2 produced by aquatic metabolism contributes about 28% of CO2 evasion from streams and rivers with flows between 0.0001 and 19,000 m(3) s(-1). We mathematically modelled CO2 flux from groundwater into running waters along a stream-river continuum to evaluate the relationship between stream size and CO2 source. Terrestrially derived CO2 dominates emissions from small streams, and the percentage of CO2 emissions from aquatic metabolism increases with stream size. We suggest that the relative role of rivers as conduits for terrestrial CO2 efflux and as reactors mineralizing terrestrial organic carbon is a function of their size and connectivity with landscapes.

Published
2015
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21. Applying resilience thinking to production ecosystems

Author

Rist, L., Felton, A., Nyström, M., Troell, M., Sponseller, R. A., Bengtsson, J., Österblom, H., Lindborg, R., Tidåker, P., Angeler, D. G., Milestad, Rebecka, Moen, J., Rist, L., Felton, A., Nyström, M., Troell, M., Sponseller, R. A., Bengtsson, J., Österblom, H., Lindborg, R., Tidåker, P., Angeler, D. G., Milestad, Rebecka, and Moen, J.

Abstract

Production ecosystems typically have a high dependence on supporting and regulating ecosystem services and while they have thus far managed to sustain production, this has often been at the cost of externalities imposed on other systems and locations. One of the largest challenges facing humanity is to secure the production of food and fiber while avoiding long-term negative impacts on ecosystems and the range of services that they provide. Resilience has been used as a framework for understanding sustainability challenges in a range of ecosystem types, but has not been systematically applied across the range of systems specifically used for the production of food and fiber in terrestrial, freshwater, and marine environments. This paper applied a resilience lens to production ecosystems in which anthropogenic inputs play varying roles in determining system dynamics and outputs. We argue that the traditional resilience framework requires important additions when applied to production systems. We show how sustained anthropogenic inputs of external resources can lead to a "coercion'' of resilience and describe how the global interconnectedness of many production systems can camouflage signals indicating resilience loss., QC 20140818

Published
2014
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23. Applying resilience thinking to production ecosystems

Author

Rist, L., primary, Felton, A., additional, Nyström, M., additional, Troell, M., additional, Sponseller, R. A., additional, Bengtsson, J., additional, Österblom, H., additional, Lindborg, R., additional, Tidåker, P., additional, Angeler, D. G., additional, Milestad, R., additional, and Moen, J., additional

Published
2014
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24. Sources of and processes controlling CO2 emissions change with the size of streams and rivers.

Author

Hotchkiss, E. R., Hall Jr, R. O., Sponseller, R. A., Butman, D., Klaminder, J., Laudon, H., Rosvall, M., and Karlsson, J.

Subjects
RIVERS, CRESTS (Hydrology), CARBON cycle, ECOLOGICAL succession, CARBON dioxide
Abstract

Carbon dioxide (CO2) evasion from streams and rivers to the atmosphere represents a substantial flux in the global carbon cycle. The proportions of CO2 emitted from streams and rivers that come from terrestrially derived CO2 or from CO2 produced within freshwater ecosystems through aquatic metabolism are not well quantified. Here we estimated CO2 emissions from running waters in the contiguous United States, based on freshwater chemical and physical characteristics and modelled gas transfer velocities at 1463 United States Geological Survey monitoring sites. We then assessed CO2 production from aquatic metabolism, compiled from previously published measurements of net ecosystem production from 187 streams and rivers across the contiguous United States. We find that CO2 produced by aquatic metabolism contributes about 28% of CO2 evasion from streams and rivers with flows between 0.0001 and 19,000 m3 s−1. We mathematically modelled CO2 flux from groundwater into running waters along a stream-river continuum to evaluate the relationship between stream size and CO2 source. Terrestrially derived CO2 dominates emissions from small streams, and the percentage of CO2 emissions from aquatic metabolism increases with stream size. We suggest that the relative role of rivers as conduits for terrestrial CO2 efflux and as reactors mineralizing terrestrial organic carbon is a function of their size and connectivity with landscapes. [ABSTRACT FROM AUTHOR]

Published
2015
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25. Nitrogen export from a boreal stream network following forest harvesting: seasonal nitrate removal and conservative export of organic forms.

Author

Schelker, J., Sponseller, R., Ring, E., Högbom, L., Löfgren, S., and Laudon, H.

Subjects
NITROGEN, NONMETALS, LOGGING, WATERSHEDS
Abstract

Boreal streams are under pressure from large scale disturbance by forestry. Recent scenarios predict an increase in forest production in Scandinavia to meet market demands and to mitigate higher anthropogenic CO2 emissions. Increased fertilization and shorter forest rotations are anticipated which will likely enhance the pressure on boreal streams in the near future. Among the major environmental impacts of forest harvesting is the increased mobilization of inorganic nitrogen (N), primarily as nitrate (NO3-) into surface waters. But whereas NO3- inputs to first-order streams have been previously described, their downstream fate and impact is not well understood. We evaluated the downstream fate of N inputs in a boreal landscape that has been altered by forest harvests over a 10 year period to estimate the effects of multiple clear-cuts on aquatic N export in a boreal stream network. Small streams showed substantial leaching of NO3- in response to harvests with concentrations increasing by ~ 15 fold. NO3- concentrations at two sampling stations further downstream in the network were strongly seasonal and increased significantly in response to harvesting at the medium size, but not at the larger stream. Nitrate removal efficiency, Er, calculated as the percentage of "forestry derived" NO3- that was retained within the landscape using a mass balance model was highest during the snow melt season followed by the growing season, but declined continuously throughout the dormant season. In contrast, export of organic N from the landscape indicated little removal and was essentially conservative. Overall, net removal of NO3- between 2008 and 2011 accounted for ~ 70% of the total NO3- mass exported from harvested patches distributed across the landscape. These results highlight the capacity and limitation of N-limited terrestrial and aquatic ecosystems to buffer inorganic N mobilization that arises from multiple clear-cuts within meso-scale boreal watersheds. [ABSTRACT FROM AUTHOR]

Published
2015
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26. Connecting precipitation inputs and soil flow pathways to stream water in contrasting boreal catchments.

Author

Peralta‐Tapia, A., Sponseller, R. A., Tetzlaff, D., Soulsby, C., and Laudon, H.

Subjects
STABLE isotopes, GROUNDWATER flow, WATERSHEDS, SOLIFLUCTION, TAIGAS, HYDROLOGIC cycle
Abstract

Stable isotopes of water are one of the most widely used tools to track the pathways of precipitation inputs to streams. In the past, soils have often been treated as black-boxes through which precipitation is routed to streams without much consideration of how, when, and where water is transported along soil and groundwater flow paths. Here, we use time series of stable isotopes (18O) in precipitation, soil/groundwater, and stream water to evaluate how landscape structure and heterogeneity influence seasonal hydrological patterns characteristic of boreal headwater catchments. To do this, we collected water throughout a full year at three adjacent catchments draining forest, mire, and mire/lake ecosystems within the Krycklan Experimental Catchment of northern Sweden. Isotope time series from forest and mire groundwater piezometers showed spatial and temporal heterogeneity in the dominant hydrologic flow pathways connecting precipitation to stream flow at different sites. The isotopic signature of stream water suggested strong connections to the dominant landscape elements within each catchment. These connections translated into greater temporal variability in the isotopic response of streams draining lake and wetland patches, and a much more attenuated pattern in the forest-dominated catchment. Overall, seasonal changes in the isotopic composition of streams and groundwater illustrate how differences in landscape structure result in variable hydrological patterns in the boreal landscape. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Published
2015
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28. Sources of and processes controlling CO2emissions change with the size of streams and rivers

Author

Hotchkiss, E. R., Hall Jr, R. O., Sponseller, R. A., Butman, D., Klaminder, J., Laudon, H., Rosvall, M., and Karlsson, J.

Abstract

Carbon dioxide (CO2) evasion from streams and rivers to the atmosphere represents a substantial flux in the global carbon cycle. The proportions of CO2emitted from streams and rivers that come from terrestrially derived CO2or from CO2produced within freshwater ecosystems through aquatic metabolism are not well quantified. Here we estimated CO2emissions from running waters in the contiguous United States, based on freshwater chemical and physical characteristics and modelled gas transfer velocities at 1463 United States Geological Survey monitoring sites. We then assessed CO2production from aquatic metabolism, compiled from previously published measurements of net ecosystem production from 187 streams and rivers across the contiguous United States. We find that CO2produced by aquatic metabolism contributes about 28% of CO2evasion from streams and rivers with flows between 0.0001 and 19,000 m3s−1. We mathematically modelled CO2flux from groundwater into running waters along a stream–river continuum to evaluate the relationship between stream size and CO2source. Terrestrially derived CO2dominates emissions from small streams, and the percentage of CO2emissions from aquatic metabolism increases with stream size. We suggest that the relative role of rivers as conduits for terrestrial CO2efflux and as reactors mineralizing terrestrial organic carbon is a function of their size and connectivity with landscapes.

Published
2015
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