Water track distribution and effects on carbon dioxide flux in an eastern Siberian upland tundra landscape

Curasi, Salvatore R.; Loranty, M. M.; Natali, Susan M.

doi:10.1088/1748-9326/11/4/045002

Cited by 29 publications

(39 citation statements)

References 57 publications

(79 reference statements)

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“…, Cameron and Lantz , Curasi et al. ), but a significant effect of TWI was only observed on lichen and spruce cover in the valley. However, a weak effect of TWI does not mean that shrub growth and recruitment does not depend on moisture conditions in our study system.…”

Section: Discussionmentioning

confidence: 94%

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Spatially explicit modeling and prediction of shrub cover increase near Umiujaq, Nunavik

Lemay

Provencher‐Nolet

Bernier

et al. 2018

Ecological Monographs

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A circumpolar increase in shrub growth and cover has been underway in Arctic and subarctic ecosystems for the last few decades, but there is considerable spatial heterogeneity in this shrubification process. Although topography, hydrology, and edaphic factors are known to influence shrubification patterns, a better understanding of the landscape‐scale factors driving this phenomenon is needed to accurately predict its impacts on ecosystem function. In this study, we generated land cover change models in order to identify variables driving shrub cover increase near Umiujaq (Québec, Canada). Using land cover maps from 1990/1994 and 2010, we modeled observed changes using two contrasting conceptual approaches: binomial modeling of transitions to shrub dominance and multinomial modeling of all land cover transitions. Models were used to generate spatially explicit predictions of transition to shrub dominance in the near future as well as long‐term predictions of the abundance of different land cover types. Model predictions were validated using both field data and current Landsat‐derived trends of normalized difference vegetation index (NDVI) increase in the region in order to assess their consistency with observed patterns of change. We found that both variables related to topography and to vegetation were useful in modeling land cover changes occurring near Umiujaq. Shrubs tended to preferentially colonize low‐elevation areas and moderate slopes, while their cover was more likely to increase in the vicinity of existing shrub patches. Deterministic realizations of the spatially explicit models of land cover change had a good predictive capability, although they performed better at predicting the proportion of different cover types than at predicting the precise location of the changes. Binomial models performed as well as multinomial models, indicating that neglecting land cover changes other than shrubification does not result in decreased prediction accuracy. The predicted probabilities of shrub increase in the region were consistent with patterns of change inferred from field data, but only partly supported by recent local increases in NDVI. Our findings increase the current understanding of the factors driving shrubification, while warranting further research on its impacts on ecosystem function and on the link between land cover changes and shifts in remotely sensed vegetation indices.

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Section: Discussionmentioning

confidence: 94%

“…, Curasi et al. ) and dendrochronological data (Myers‐Smith et al. ) show that the climate sensitivity of shrub growth is higher in wetter areas.…”

Section: Discussionmentioning

confidence: 99%

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Spatially explicit modeling and prediction of shrub cover increase near Umiujaq, Nunavik

Lemay

Provencher‐Nolet

Bernier

et al. 2018

Ecological Monographs

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“…Beneath the active layer, continuous permafrost acts as a barrier that impedes deeper subsurface flow (Ge et al, 2011;Walvoord et al, 2012). Conditions in water tracks differ significantly from those in their nontrack hillslope watersheds and are characterized by a deeper active layer depth, smaller amplitude of annual soil temperature change, coarser subsurface materials (Figure 1b), thicker snowpack, and higher soil moisture and nutrient contents (Ball & Levy, 2015;Curasi et al, 2016;Harms et al, 2019;Hastings et al, 1989;McNamara et al, 1999;Paquette et al, 2018;Rushlow, 2018). Since water tracks have a higher soil moisture content and are closer to their storage capacity than are the adjacent hillslopes, it has been suggested that water tracks are one of the main source areas for runoff to downslope rivers in response to summer rainfall (McNamara et al, 1997;Rushlow & Godsey, 2017) and spring snowmelt (Paquette et al, 2018).…”

Section: Introductionmentioning

confidence: 99%

Water Tracks Enhance Water Flow Above Permafrost in Upland Arctic Alaska Hillslopes

et al. 2020

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Upland permafrost regions occupy approximately one third of the Arctic landscape. In upland regions, hydrologic fluxes are influenced by water tracks, curvilinear features on hillslopes that preferentially fill with and route water in response to snowmelt and rainfall when the soil above continuous permafrost thaws in the summer. As continued warming of the Arctic may alter hydrologic cycling leading to increased frequency of extreme hydrologic events like drought and flooding as well as modification of biogeochemical cycling, it is imperative to untangle the interplay between precipitation, runoff, and subsurface flow as water is routed from upland Arctic regions to the Arctic Ocean. This study quantifies how ground surface temperatures affect groundwater discharge from hillslopes with water tracks in the upland Arctic by employing a three‐dimensional, physically based subsurface flow model with variable saturation and freeze and thaw capabilities that is calibrated to field measurements from the Upper Kuparuk River watershed on the North Slope of Alaska, USA. Model analysis indicates that higher ground surface temperatures along water track hillslopes promote increases in groundwater discharge where water tracks act as conduits for large‐recharge events and continue to discharge groundwater into the autumn after the adjacent hillslope has frozen. Simulating the conditions that distinguish water tracks from their hillslope watersheds changes subsurface water storage and ground thermal responses but does not alter the total magnitude of groundwater discharge outside of parameter uncertainty. These findings suggest that water tracks play a complex and critical role in hydrologic cycles of the upland Arctic.

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“…In particular, our two-dimensional model does not include three-dimensional water and energy transport processes that can occur in permafrost settings such as "water tracks," which are subsurface drainage channels through which water can flow rapidly (Chapin et al, 1988;McNamara et al, 1998). Since water tracks are associated with rapid water transport, warmer soil, and deeper active layer thickness than surrounding areas (Curasi et al, 2016;Hastings et al, 1989), they would 10.1029/2018JF004611 Journal of Geophysical Research: Earth Surface likely enhance the importance of heat transport via advection which we document here. Similarly, our model is only of the subsurface, and therefore does not simulate ponding at the land surface which may occur during snowmelt or precipitation events if there is insufficient infiltration capacity; this limitation likely underestimates both the quantity and duration of groundwater recharge, particularly during spring snowmelt, and may dampen effects of changes in the water balance.…”

Section: Study Limitationsmentioning

confidence: 99%

Groundwater Controls on Postfire Permafrost Thaw: Water and Energy Balance Effects

et al. 2018

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Fire frequency and severity are increasing in high‐latitude regions, but the degree to which groundwater flow impacts the response of permafrost to fire remains poorly understood. Here we use the Anaktuvuk River Fire (Alaska, USA) as an example for simulating groundwater‐permafrost interactions following fire. We identify key thermal and hydrologic parameters controlling permafrost response to fire both with and without groundwater flow, and separate the relative influence of changes to the water and energy balances on active layer thickness. Our results show that mineral soil porosity, which influences the bulk subsurface thermal conductivity, is a key parameter controlling active layer response to fire in both the absence and presence of groundwater flow. However, including groundwater flow in models increases the perceived importance of subsurface hydrologic properties, such as the soil permeability, and decreases the perceived importance of subsurface thermal properties, such as the thermal conductivity of soil solids. Furthermore, we demonstrate that changes to the energy balance (increased soil temperature) drive increased active layer thickness following fire, while changes to the water balance (decreased groundwater recharge) lead to reduced landscape‐scale variability in active layer thickness and groundwater discharge to surface water features such as streams. These results indicate that explicit consideration of groundwater flow is critical to understanding how permafrost environments respond to fire.

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Water track distribution and effects on carbon dioxide flux in an eastern Siberian upland tundra landscape

Cited by 29 publications

References 57 publications

Spatially explicit modeling and prediction of shrub cover increase near Umiujaq, Nunavik

Spatially explicit modeling and prediction of shrub cover increase near Umiujaq, Nunavik

Water Tracks Enhance Water Flow Above Permafrost in Upland Arctic Alaska Hillslopes

Groundwater Controls on Postfire Permafrost Thaw: Water and Energy Balance Effects

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