Form and function relationships revealed by long‐term research in a semiarid mountain catchment

McNamara, J. P.; Benner, S. G.; Poulos, Michael J.; Pierce, J. L.; Chandler, D. G.; Kormos, Patrick R.; Marshall, Hans‐Peter; Flores, Alejandro N.; Seyfried, M. S.; Glenn, Nancy F.; Aishlin, P. S.

doi:10.1002/wat2.1267

Cited by 13 publications

(26 citation statements)

References 55 publications

(99 reference statements)

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“…However, the approach taken by Petersky and Harpold (2018) Our approach demonstrates the utility of remote sensing and object-based processing in the temporal domain for detecting ephemeral snow and estimating snow ephemerality based on climate and topography. New tools and techniques are needed because current understanding of ephemeral snow is based upon few field observations, oversimplifications of shallow snowpack energetics, and remote sensing products that consistently underestimate snow ephemerality (Kelleners, Chandler, McNamara, Gribb, & Seyfried, 2010;McNamara et al, 2018;Kormos et al, 2014;Petersky & Harpold, 2018). Our RF approach, combined with an object-based method that accounts for missing data, was able to capture the <60-day threshold with high fidelity at all elevations (RMSE <16 days over study domain), despite larger error at higher elevations.…”

Section: Discussionmentioning

confidence: 99%

The sensitivity of snow ephemerality to warming climate across an arid to montane vegetation gradient

2018

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Shifts from longer seasonal snowpacks to shorter, ephemeral snowpacks (snowpacks that persist for <60 days) due to climate change will alter the timing and rates of water availability. Ephemeral snowmelt has less predictable timing and lowers soil water availability during the growing season. The Great Basin, United States is an ideal system to study snow ephemerality across a broad climate gradient. To identify the climatic controls on snow ephemerality, we analysed moderate resolution imaging spectroradiometer (MODIS) snow‐covered products from water years 2001–2015 using an object‐based mapping approach and a random forest model. Winter temperature and precipitation were the most influential variables on the maximum snow duration. We predict that warming the average winter air temperature by 2 and 4°C would reduce the areal extent of seasonal snow by 14.7 and 47.8%, respectively (8.8% of the Great Basin's areal extent is seasonal in the historical record), with shifts to ephemeral snowpack concentrated in lower elevations and warmer regions. The combination of warming and interannual precipitation variability (i.e., reductions of 25%) had different effects on vegetation types. Vegetation types that have had consistent seasonal snow cover in their historical record are likely to have lower resilience to a new hydrologic regime, with earlier and more intermittent snowmelt causing a longer but drier growing season. Implications of increased snow ephemerality on vegetation productivity and susceptibility to disturbance will depend on local topography, subsurface water storage, and physiological adaptations. Nevertheless, patterns found in this study can help target management intervention to species that are most at risk.

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Section: Discussionmentioning

confidence: 99%

The sensitivity of snow ephemerality to warming climate across an arid to montane vegetation gradient

2018

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“…The geology of DCEW is predominantly biotite granodiorite of the Atlanta Lobe of the Idaho Batholith which is Cretaceous in age (Johnson et al, 1988). Soils tend to be relatively thin (max depth of 1.2 m) (Williams et al, 2009) and coarse‐grained and are classified as loamy sands and sandy loams (Gribb et al, 2009); a thin veneer of wind‐blown loess covers portions of the basin (McNamara et al, 2018). Soil characteristics also vary with aspect, with steeper north‐facing slopes having thicker soil depths, more organic matter and silt, higher porosity, and greater water storage than gentler south‐facing slopes (Geroy et al, 2011).…”

Section: Site Description and Datamentioning

confidence: 99%

The Utility of Information Flow in Formulating Discharge Forecast Models: A Case Study From an Arid Snow‐Dominated Catchment

Tennant

Larsen

Bellugi

et al. 2020

Water Resources Research

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Streamflow forecasts often perform poorly because of improper representation of hydrologic response timescales in underlying models. Here, we use transfer entropy (TE), which measures information flow between variables, to identify dominant drivers of discharge and their timescales using sensor data from the Dry Creek Experimental Watershed, ID, USA. Consistent with previous mechanistic studies, TE revealed that snowpack accumulation and partitioning into melt, recharge, and evaporative loss dominated discharge patterns and that snow‐sourced baseflow reduced the greatest amount of uncertainty in discharge. We hypothesized that machine learning models (MLMs) specified in accordance with the dominant lag timescales, identified via TE, would outperform timescale‐agnostic models. However, while lagged‐variable random forest regressions captured the dominant process—seasonal snowmelt—they ultimately did not perform as well as the unlagged models, provided those models were specified with input data aggregated over a range of timescales. Unlagged models, not constrained by timescales of the dominant processes, more effectively represented variable interactions (e.g., rain‐on‐snow events) playing a critical role in translating precipitation into streamflow over long, intermediate, and short timescales. Meanwhile, long short‐term memory (LSTM) models were effective in internally identifying the key lag and aggregation scales for predicting discharge. Parsimonious specification of LSTM models, using only daily unlagged precipitation and temperature data, produced the highest performing predictions. Our findings suggest that TE can identify dominant streamflow controls and the relative importance of different mechanisms of streamflow generation, useful for establishing process baselines and fingerprinting watersheds. However, restricting MLMs based on dominant timescales undercuts their skill at learning these timescales internally.

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“…Runoff from snowdominated sagebrush uplands occurs primarily during the spring snowmelt season as streamflow, but hillslope runoff does occur during winter rainfall events on frozen soil or snow (Blackburn et al, 1990;Pierson and Wight, 1991;Seyfried and Wilcox, 1995;Pierson et al, 2001a;Godsey et al, 2018). The quantity and timing of runoff from these systems are strongly regulated by the amount and distribution of accumulated snow, the onset and duration of the snowmelt period, soil water conditions, and above-and below-ground hillslope hydrologic connectivity (McNamara et al, 2005;Seyfried et al, 2009;Williams et al, 2009;Nayak et al, 2010;Chauvin et al, 2011;McNamara et al, 2018). Snowfall in sloping sagebrush uplands is commonly redistributed into extensive drifts that dictate the water available for runoff and that regulate the length of the runoff period (Flerchinger and Cooley, 2000;Winstral et al, 2013;Kormos et al, 2017).…”

Section: Introductionmentioning

confidence: 99%

Interaction of wind and cold‐season hydrologic processes on erosion from complex topography following wildfire in sagebrush steppe

Vega

Williams

Brooks

et al. 2020

Earth Surf Processes Landf

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Wildfire is a natural component of sagebrush (Artemisia spp.) steppe rangelands that induces temporal shifts in plant community physiognomy, ground surface conditions, and erosion rates. Fire alteration of the vegetation structure and ground cover in these ecosystems commonly amplifies soil losses by wind‐ and water‐driven erosion. Much of the fire‐related erosion research for sagebrush steppe has focused on either erosion by wind over gentle terrain or water‐driven erosion under high‐intensity rainfall on complex topography. However, many sagebrush rangelands are geographically positioned in snow‐dominated uplands with complex terrain in which runoff and sediment delivery occur primarily in winter months associated with cold‐season hydrology. Current understanding is limited regarding fire effects on the interaction of wind‐ and cold‐season hydrologic‐driven erosion processes for these ecosystems. In this study, we evaluated fire impacts on vegetation, ground cover, soils, and erosion across spatial scales at a snow‐dominated mountainous sagebrush site over a 2‐year period post‐fire. Vegetation, ground cover, and soil conditions were assessed at various plot scales (8 m2 to 3.42 ha) through standard field measures. Erosion was quantified through a network of silt fences (n = 24) spanning hillslope and side channel or swale areas, ranging from 0.003 to 3.42 ha in size. Sediment delivery at the watershed scale (129 ha) was assessed by suspended sediment samples of streamflow through a drop‐box v‐notch weir. Wildfire consumed nearly all above‐ground live vegetation at the site and resulted in more than 60% bare ground (bare soil, ash, and rock) in the immediate post‐fire period. Widespread wind‐driven sediment loading of swales was observed over the first month post‐fire and extensive snow drifts were formed in these swales each winter season during the study. In the first year, sediment yields from north‐ and south‐facing aspects averaged 0.99–8.62 t ha−1 at the short‐hillslope scale (~0.004 ha), 0.02–1.65 t ha−1 at the long‐hillslope scale (0.02–0.46 ha), and 0.24–0.71 t ha−1 at the swale scale (0.65–3.42 ha), and watershed scale sediment yield was 2.47 t ha−1. By the second year post fire, foliar cover exceeded 120% across the site, but bare ground remained more than 60%. Sediment yield in the second year was greatly reduced across short‐ to long‐hillslope scales (0.02–0.04 t ha−1), but was similar to first‐year measures for swale plots (0.24–0.61 t ha−1) and at the watershed scale (3.05 t ha−1). Nearly all the sediment collected across all spatial scales was delivered during runoff events associated with cold‐season hydrologic processes, including rain‐on‐snow, rain‐on‐frozen soils, and snowmelt runoff. Approximately 85–99% of annual sediment collected across all silt fence plots each year was from swales. The high levels of sediment delivered across hillslope to watershed scales in this study are attributed to observed preferential loading of fine sediments into swale channels by aeolian processes in ...

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Form and function relationships revealed by long‐term research in a semiarid mountain catchment

Cited by 13 publications

References 55 publications

The sensitivity of snow ephemerality to warming climate across an arid to montane vegetation gradient

The sensitivity of snow ephemerality to warming climate across an arid to montane vegetation gradient

The Utility of Information Flow in Formulating Discharge Forecast Models: A Case Study From an Arid Snow‐Dominated Catchment

Interaction of wind and cold‐season hydrologic processes on erosion from complex topography following wildfire in sagebrush steppe

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