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Article ; Online: Advanced monitoring of soil-vegetation co-dynamics reveals the successive controls of snowmelt on soil moisture and on plant seasonal dynamics in a mountainous watershed

Baptiste Dafflon / Emmanuel Léger / Nicola Falco / Haruko M. Wainwright / John Peterson / Jiancong Chen / Kenneth H. Williams / Susan S. Hubbard

Frontiers in Earth Science, Vol

2023 Volume 11

Abstract: Evaluating the interactions between above- and below-ground processes is important to understand and quantify how ecosystems respond differently to atmospheric forcings and/or perturbations and how this depends on their intrinsic characteristics and ... ...

Abstract	Evaluating the interactions between above- and below-ground processes is important to understand and quantify how ecosystems respond differently to atmospheric forcings and/or perturbations and how this depends on their intrinsic characteristics and heterogeneity. Improving such understanding is particularly needed in snow-impacted mountainous systems where the complexity in water and carbon storage and release arises from strong heterogeneity in meteorological forcing and terrain, vegetation and soil characteristics. This study investigates spatial and temporal interactions between terrain, soil moisture, and plant seasonal dynamics at the intra- and inter-annual scale along a 160 m long mountainous, non-forested hillslope-to-floodplain system in the upper East River Watershed in the upper Colorado River Basin. To this end, repeated UAV-based multi-spectral aerial imaging, ground-based soil electrical resistivity imaging, and soil moisture sensors were used to quantify the interactions between above and below-ground compartments. Results reveal significant soil-plant co-dynamics. The spatial variation and dynamics of soil water content and electrical conductivity, driven by topographic and soil intrinsic characteristics, correspond to distinct plant types, with highest plant productivity in convergent areas. Plant productivity in heavy snow years benefited from more water infiltration as well as a shallow groundwater table depth. In comparison, low snowpack years with an early first bare-ground date, which are linked to an early increase in plant greenness, imply a short period of saturated conditions that leads to lower average and maximum greenness values during the growing season. Overall, these results emphasize the strong impact of snowpack dynamics, and terrain and subsurface characteristics on the heterogeneity in plant type and seasonal dynamics.
Keywords	hillslope ; snow impact ; soil moisture ; vegetation growth ; seasonal dynamic ; Science ; Q
Subject code	550
Language	English
Publishing date	2023-05-01T00:00:00Z
Publisher	Frontiers Media S.A.
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article ; Online: Resolution matters when modeling climate change in headwaters of the Colorado River

Lauren M Foster / Kenneth H Williams / Reed M Maxwell

Environmental Research Letters, Vol 15, Iss 10, p

2020 Volume 104031

Abstract: The continued growth of Southwestern cities depends on reliable water export from Rocky Mountain headwaters, which provide ∼85% of Colorado River Basin (CRB) streamflow. Despite being more sensitive to warming temperatures, alpine systems are simplified ... ...

Abstract	The continued growth of Southwestern cities depends on reliable water export from Rocky Mountain headwaters, which provide ∼85% of Colorado River Basin (CRB) streamflow. Despite being more sensitive to warming temperatures, alpine systems are simplified in the regional-scale models currently in use to plan for future water supply. We used an integrated hydrologic model that couples groundwater and surface water with snow and vegetation processes to examine the effect of topographic simplifications as a result of grid coarsening in a representative CRB headwater basin. High-resolution (100 m) simulations predicted headwater streamflow losses of 16% by 2050 while coarse-resolution (1 km) simulations predict only 12%, suggesting that regional-scale models (coarser than 1 km) likely overestimate future Colorado River Basin water supplies.
Keywords	integrated modeling ; resolution ; climate change ; headwater hydrology ; Colorado river ; Environmental technology. Sanitary engineering ; TD1-1066 ; Environmental sciences ; GE1-350 ; Science ; Q ; Physics ; QC1-999
Language	English
Publishing date	2020-01-01T00:00:00Z
Publisher	IOP Publishing
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article ; Online: Effect of elevation, season and accelerated snowmelt on biogeochemical processes during isolated conifer needle litter decomposition

Laura T. Leonard / Eoin L. Brodie / Kenneth H. Williams / Jonathan O. Sharp

PeerJ, Vol 9, p e

2021 Volume 11926

Abstract: Increased drought and temperatures associated with climate change have implications for ecosystem stress with risk for enhanced carbon release in sensitive biomes. Litter decomposition is a key component of biogeochemical cycling in terrestrial ... ...

Abstract	Increased drought and temperatures associated with climate change have implications for ecosystem stress with risk for enhanced carbon release in sensitive biomes. Litter decomposition is a key component of biogeochemical cycling in terrestrial ecosystems, but questions remain regarding the local response of decomposition processes to climate change. This is particularly complex in mountain ecosystems where the variable nature of the slope, aspect, soil type, and snowmelt dynamics play a role. Hence, the goal of this study was to determine the role of elevation, soil type, seasonal shifts in soil moisture, and snowmelt timing on litter decomposition processes. Experimental plots containing replicate deployments of harvested lodgepole and spruce needle litter alongside needle-free controls were established in open meadows at three elevations ranging from 2,800–3,500 m in Crested Butte, Colorado. Soil biogeochemistry variables including gas flux, porewater chemistry, and microbial ecology were monitored over three climatically variable years that shifted from high monsoon rains to drought. Results indicated that elevation and soil type influenced baseline soil biogeochemical indicators; however, needle mass loss and chemical composition were consistent across the 700 m elevation gradient. Rates of gas flux were analogously consistent across a 300 m elevation gradient. The additional variable of early snowmelt by 2–3 weeks had little impact on needle chemistry, microbial composition and gas flux; however, it did result in increased dissolved organic carbon in lodgepole porewater collections suggesting a potential for aqueous export. In contrast to elevation, needle presence and seasonal variability of soil moisture and temperature both played significant roles in soil carbon fluxes. During a pronounced period of lower moisture and higher temperatures, bacterial community diversity increased across elevation with new members supplanting more dominant taxa. Microbial ecological resilience was demonstrated with a ...
Keywords	Climate change ; Earth systems science ; Biogeochemistry ; Decomposition ; Early snowmelt ; Soil respiration ; Medicine ; R ; Biology (General) ; QH301-705.5
Subject code	550
Language	English
Publishing date	2021-08-01T00:00:00Z
Publisher	PeerJ Inc.
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article ; Online: Hidden Processes During Seasonal Isolation of a High-Altitude Watershed

Jessica Z. Buser-Young / Laura L. Lapham / Andrew R. Thurber / Kenneth H. Williams / Frederick S. Colwell

Frontiers in Earth Science, Vol

2021 Volume 9

Abstract: Biogeochemical processes capable of altering global carbon systems occur frequently in Earth’s Critical Zone–the area spanning from vegetation canopy to saturated bedrock–yet many of these phenomena are difficult to detect. Observation of these processes ...

Abstract	Biogeochemical processes capable of altering global carbon systems occur frequently in Earth’s Critical Zone–the area spanning from vegetation canopy to saturated bedrock–yet many of these phenomena are difficult to detect. Observation of these processes is limited by the seasonal inaccessibility of remote ecosystems, such as those in mountainous, snow- and ice-dominated areas. This isolation leads to a distinct gap in biogeochemical knowledge that ultimately affects the accuracy and confidence with which these ecosystems can be computationally modeled for the purpose of projecting change under different climate scenarios. To examine a high-altitude, headwater ecosystem’s role in methanogenesis, sulfate reduction, and groundwater-surface water exchange, water samples were continuously collected from the river and hyporheic zones (HZ) during winter isolation in the East River (ER), CO watershed. Measurements of continuously collected ER surface water revealed up to 50 μM levels of dissolved methane in July through September, while samples from 12 cm deep in the hyporheic zone at the same location showed a spring to early summer peak in methane with a strong biogenic signature (<65 μM, δ13C-CH4, −60.76‰) before declining. Continuously collected δ18O-H2O and δ2H-H2O isotopes from the water column exhibited similar patterns to discrete measurements, while samples 12 cm deep in the hyporheic zone experienced distinct fluctuations in δ18O-H2O, alluding to significant groundwater interactions. Continuously collected microbial communities in the river in the late fall and early winter revealed diverse populations that reflect the taxonomic composition of ecologically similar river systems, including taxa indicative of methane cycling in this system. These measurements captured several biogeochemical components of the high-altitude watershed in response to seasonality, strengthening our understanding of these systems during the winter months.
Keywords	biogeochemistry ; autonomous sampler ; microbiome ; methane ; spring-melt ; high-altitude watershed ; Science ; Q
Subject code	550
Language	English
Publishing date	2021-05-01T00:00:00Z
Publisher	Frontiers Media S.A.
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article ; Online: Production of hydrogen peroxide in an intra-meander hyporheic zone at East River, Colorado

Xiu Yuan / Tongxu Liu / Patricia Fox / Amrita Bhattacharyya / Dipankar Dwivedi / Kenneth H. Williams / James A. Davis / T. David Waite / Peter S. Nico

Scientific Reports, Vol 12, Iss 1, Pp 1-

2022 Volume 10

Abstract: Abstract The traditionally held assumption that photo-dependent processes are the predominant source of H2O2 in natural waters has been recently questioned by an increrasing body of evidence showing the ubiquitiousness of H2O2 in dark water bodies and in ...

Abstract	Abstract The traditionally held assumption that photo-dependent processes are the predominant source of H2O2 in natural waters has been recently questioned by an increrasing body of evidence showing the ubiquitiousness of H2O2 in dark water bodies and in groundwater. In this study, we conducted field measurement of H2O2 in an intra-meander hyporheic zone and in surface water at East River, CO. On-site detection using a sensitive chemiluminescence method suggests H2O2 concentrations in groundwater ranging from 6 nM (at the most reduced region) to ~ 80 nM (in a locally oxygen-rich area) along the intra-meander transect with a maxima of 186 nM detected in the surface water in an early afternoon, lagging the maximum solar irradiance by ∼ 1.5 h. Our results suggest that the dark profile of H2O2 in the hyporheic zone is closely correlated to local redox gradients, indicating that interactions between various redox sensitive elements could play an essential role. Due to its transient nature, the widespread presence of H2O2 in the hyporheic zone indicates the existence of a sustained balance between H2O2 production and consumption, which potentially involves a relatively rapid succession of various biogeochemically important processes (such as organic matter turnover, metal cycling and contaminant mobilization). More importantly, this study confirmed the occurrence of reactive oxygen species at a subsurface redox transition zone and further support our understanding of redox boundaries on reactive oxygen species generation and as key locations of biogeochemical activity.
Keywords	Medicine ; R ; Science ; Q
Subject code	550
Language	English
Publishing date	2022-01-01T00:00:00Z
Publisher	Nature Portfolio
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article ; Online: A comparison of lodgepole and spruce needle chemistry impacts on terrestrial biogeochemical processes during isolated decomposition

Laura T. Leonard / Kristin Mikkelson / Zhao Hao / Eoin L. Brodie / Kenneth H. Williams / Jonathan O. Sharp

PeerJ, Vol 8, p e

2020 Volume 9538

Abstract: This study investigates the isolated decomposition of spruce and lodgepole conifer needles to enhance our understanding of how needle litter impacts near-surface terrestrial biogeochemical processes. Harvested needles were exported to a subalpine meadow ... ...

Abstract	This study investigates the isolated decomposition of spruce and lodgepole conifer needles to enhance our understanding of how needle litter impacts near-surface terrestrial biogeochemical processes. Harvested needles were exported to a subalpine meadow to enable a discrete analysis of the decomposition processes over 2 years. Initial chemistry revealed the lodgepole needles to be less recalcitrant with a lower carbon to nitrogen (C:N) ratio. Total C and N fundamentally shifted within needle species over time with decreased C:N ratios for spruce and increased ratios for lodgepole. Differences in chemistry correlated with CO2 production and soil microbial communities. The most pronounced trends were associated with lodgepole needles in comparison to the spruce and needle-free controls. Increased organic carbon and nitrogen concentrations associated with needle presence in soil extractions further corroborate the results with clear biogeochemical signatures in association with needle chemistry. Interestingly, no clear differentiation was observed as a function of bark beetle impacted spruce needles vs those derived from healthy spruce trees despite initial differences in needle chemistry. These results reveal that the inherent chemistry associated with tree species has a greater impact on soil biogeochemical signatures during isolated needle decomposition. By extension, biogeochemical shifts associated with bark beetle infestation are likely driven more by changes such as the cessation of rhizospheric processes than by needle litter decomposition.
Keywords	Soil biogeochemistry ; Needle Decomposition ; Nutrient Cycling ; Soil Respiration ; Bark Beetle Disturbance ; Lodgepole ; Medicine ; R ; Biology (General) ; QH301-705.5
Subject code	550
Language	English
Publishing date	2020-07-01T00:00:00Z
Publisher	PeerJ Inc.
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article: Uranium Retention in a Bioreduced Region of an Alluvial Aquifer Induced by the Influx of Dissolved Oxygen

Pan, Donald / Karrie A. Weber / Kenneth H. Williams / Mark J. Robbins

Environmental science & technology. 2018 July 11, v. 52, no. 15

2018

Abstract: Reduced zones in the subsurface represent biogeochemically active hotspots enriched in buried organic matter and reduced metals. Within a shallow alluvial aquifer located near Rifle, CO, reduced zones control the fate and transport of uranium (U). Though ...

Abstract	Reduced zones in the subsurface represent biogeochemically active hotspots enriched in buried organic matter and reduced metals. Within a shallow alluvial aquifer located near Rifle, CO, reduced zones control the fate and transport of uranium (U). Though an influx of dissolved oxygen (DO) would be expected to mobilize U, we report U immobilization. Groundwater U concentrations decreased following delivery of DO (21.6 mg O2/well/h). After 23 days of DO delivery, injection of oxygenated groundwater was paused and resulted in the rebound of groundwater U concentrations to preinjection levels. When DO delivery resumed (day 51), groundwater U concentrations again decreased. The injection was halted on day 82 again and resulted in a rebound of groundwater U concentrations. DO delivery rate was increased to 54 mg O2/well/h (day 95) whereby groundwater U concentrations increased. Planktonic cell abundance remained stable throughout the experiment, but virus-to-microbial cell ratio increased 1.8–3.4-fold with initial DO delivery, indicative of microbial activity in response to DO injection. Together, these results indicate that the redox-buffering capacity of reduced sediments can prevent U mobilization, but could be overcome as delivery rate or oxidant concentration increases, mobilizing U.
Keywords	aquifers ; dissolved oxygen ; groundwater ; microbial activity ; organic matter ; oxidants ; plankton ; sediments ; uranium ; Colorado
Language	English
Dates of publication	2018-0711
Size	p. 8133-8145.
Publishing place	American Chemical Society
Document type	Article
ISSN	1520-5851
DOI	10.1021/acs.est.8b00903
Database	NAL-Catalogue (AGRICOLA)

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Article: Predicting the impact of land management decisions on overland flow generation: Implications for cesium migration in forested Fukushima watersheds

Siirila-Woodburn, Erica R / Carl I. Steefel / Jens T. Birkholzer / Kenneth H. Williams

Advances in water resources. 2018 Mar., v. 113

2018

Abstract: The effects of land use and land cover (LULC) change on environmental systems across the land surface's “critical zone” are highly uncertain, often making prediction and risk management decision difficult. In a series of numerical experiments with an ... ...

Abstract	The effects of land use and land cover (LULC) change on environmental systems across the land surface's “critical zone” are highly uncertain, often making prediction and risk management decision difficult. In a series of numerical experiments with an integrated hydrologic model, overland flow generation is quantified for both present day and forest thinning scenarios. A typhoon storm event in a watershed near the Fukushima Dai-ichi Nuclear Power Plant is used as an example application in which the interplay between LULC change and overland flow generation is important given that sediment-bound radionuclides may cause secondary contamination via surface water transport. Results illustrate the nonlinearity of the integrated system spanning from the deep groundwater to the atmosphere, and provide quantitative tools when determining the tradeoffs of different risk-mitigation strategies.
Keywords	cesium ; decision making ; forest thinning ; forested watersheds ; groundwater ; hydrologic models ; land use and land cover maps ; nuclear power ; overland flow ; power plants ; prediction ; radionuclides ; risk management ; surface water ; typhoons ; water resources
Language	English
Dates of publication	2018-03
Size	p. 42-54.
Publishing place	Elsevier Ltd
Document type	Article
ZDB-ID	2023320-6
ISSN	1872-9657 ; 0309-1708
ISSN (online)	1872-9657
ISSN	0309-1708
DOI	10.1016/j.advwatres.2018.01.008
Database	NAL-Catalogue (AGRICOLA)

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Article: Streamflow partitioning and transit time distribution in snow-dominated basins as a function of climate

Fang, Zhufeng / Rosemary W.H. Carroll / Rina Schumer / Ciaran Harman / Daniel Wilusz / Kenneth H. Williams

Elsevier B.V. Journal of hydrology. 2019 Mar., v. 570

2019

Abstract: Snowmelt is the principal control on the timing and magnitude of water flow through mountainous watersheds. The effects of precipitation type and quantity on storage and hydrologic connectivity in mountainous systems were explored by combining the ... ...

Abstract	Snowmelt is the principal control on the timing and magnitude of water flow through mountainous watersheds. The effects of precipitation type and quantity on storage and hydrologic connectivity in mountainous systems were explored by combining the observed stable isotope δ18O in rain, snow, snowmelt, and streamflow with numerically simulated hydrologic boundary fluxes and inverse techniques applied to transient travel time distributions (TTD) using StorAge Selection (SAS) functions. Hydrologic simulations of the East River (ER, 85 km2), a snow-dominated Colorado River headwater basin, for water years 2006–2017 were used to test a diverse set of snow accumulation scenarios. During the snowmelt period, the ER released younger water during high storage periods across seasonal and annual timescales (an “inverse storage effect”). Additionally, more young water was released from storage during wet years than during dry years. However, wet years also appeared to increase hydrologic connectivity, which simultaneously flushed older water from the basin. During years with reduced snowpack, flow paths were inactivated and snowmelt remained in the subsurface to become older water that was potentially reactivated in subsequent wet years. Incremental warming in hydrologic model simulations was used to evaluate TTD sensitivity to precipitation changing from snow to rain. Despite the altered timing of boundary fluxes because of warming, years with basin average precipitation above 3.25 mm d−1 (1200 mm y−1) were resilient to temperature increases up to 10 °C with respect to annual water balance partitioning and streamflow TTD. In contrast, years with less precipitation were sensitive to increased temperatures, showing marked increases in the fraction of inflow lost to evapotranspiration. Younger water was preferentially lost to evapotranspiration, which led to an increase in the mean age of streamflow in drier years.
Keywords	basins ; climate ; evapotranspiration ; hydrologic models ; mountains ; oxygen ; rain ; rivers ; simulation models ; snow ; snowmelt ; snowpack ; stable isotopes ; storage time ; stream flow ; temperature ; watersheds ; Colorado River
Language	English
Dates of publication	2019-03
Size	p. 726-738.
Publishing place	Elsevier B.V.
Document type	Article
ZDB-ID	1473173-3
ISSN	0022-1694
ISSN	0022-1694
DOI	10.1016/j.jhydrol.2019.01.029
Database	NAL-Catalogue (AGRICOLA)

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Article: Transport and humification of dissolved organic matter within a semi-arid floodplain

Dong, Wenming / Benjamin Gilbert / Jiamin Wan / Kenneth H. Williams / Tetsu K. Tokunaga

Journal of environmental sciences (China). 2017 July, v. 57

2017

Abstract: In order to understand the transport and humification processes of dissolved organic matter (DOM) within sediments of a semi-arid floodplain at Rifle, Colorado, fluorescence excitation–emission matrix (EEM) spectroscopy, humification index (HIX) and ... ...

Abstract	In order to understand the transport and humification processes of dissolved organic matter (DOM) within sediments of a semi-arid floodplain at Rifle, Colorado, fluorescence excitation–emission matrix (EEM) spectroscopy, humification index (HIX) and specific UV absorbance (SUVA) at 254nm were applied for characterizing depth and seasonal variations of DOM composition. Results revealed that late spring snowmelt leached relatively fresh DOM from plant residue and soil organic matter down into the deeper vadose zone (VZ). More humified DOM is preferentially adsorbed by upper VZ sediments, while non- or less-humified DOM was transported into the deeper VZ. Interestingly, DOM at all depths undergoes rapid biological humification process evidenced by the products of microbial by-product-like (i.e., tyrosine-like and tryptophan-like) matter in late spring and early summer, particularly in the deeper VZ, resulting in more humified DOM (e.g., fulvic-acid-like and humic-acid-like substances) at the end of year. This indicates that DOM transport is dominated by spring snowmelt, and DOM humification is controlled by microbial degradation, with seasonal variations. It is expected that these relatively simple spectroscopic measurements (e.g., EEM spectroscopy, HIX and SUVA) applied to depth- and temporally-distributed pore-water samples can provide useful insights into transport and humification of DOM in other subsurface environments as well.
Keywords	absorbance ; dissolved organic matter ; floodplains ; fluorescence ; humification ; plant residues ; seasonal variation ; sediments ; snowmelt ; soil organic matter ; spectral analysis ; spectroscopy ; spring ; summer ; vadose zone ; Colorado
Language	English
Dates of publication	2017-07
Size	p. 24-32.
Publishing place	Elsevier B.V.
Document type	Article
ZDB-ID	1092300-7
ISSN	1878-7320 ; 1001-0742
ISSN (online)	1878-7320
ISSN	1001-0742
DOI	10.1016/j.jes.2016.12.011
Database	NAL-Catalogue (AGRICOLA)

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