Climatic Influence on Wetland Biogeochemistry and Function Using an Elevational Sequence in the Rocky Mountains, WYAnna Schwyter, Karen VaughanEcosystem Science and Management Department, University of Wyoming*Contact Anna Schwyter, aschwyte@uwyo.edu

BA C K G R O U N D

• Alpine and sub-alpine wet meadows in the Rocky Mountains are highelevation wetlands with vital ecological significance.

• This research seeks to examine climate as a driver of redoximorphic featuredevelopment and wetland functional processes by using an elevationalgradient of three montane wetland meadows in the Snowy RangeMountains of Wyoming.

o The elevation gradient serves as a proxy for climate with the MAT rangingfrom 6 to 1 ̊C and MAP from 50 to 120 cm as elevation increases.

o This gradient allows for the analysis of how decreasing temperatures andincreasing precipitation influence soil properties, processes, and function.

• At three wetland study sites (~9,000, 10,000 and 11,000 ft elevation),monitoring locations were established in wetland, transition and uplandzones.

STUDY DESIGN

Depth toWater table

Automated recording well at

each of the 3wetness zones

Soiltemperature

Automated recording sensors at 10 and 30 cm depth within each of the 3

wetness zones

Soilmorphology

Full morphological characterization at

each of the 3 wetness zones

IRISfilms

Films installed at prescribed growing degree days at each

of the 3 wetness zones

C:NDynamics

Soil organic C, nitrate and

ammonium analyzed at each of the 3wetness zones

SITE DESCRIPTIONS

Left: illustration of elevation and zone gradients for wetlands included in study, as elevation increases, mean annual temperature decreases and mean annual precipitation increases; top right: general location of the Snowy Range Mountains in Wyoming; Bottom right: Transition zone of 11,000 ft elevation wetland.

Above: IRIS films deployed in August 2019 at the 11,000 ft wetland.

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Wet Transition Upland

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Wet Dry Upland

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Soil Profiles

Right to left: 10,000 ft elevation site wet, transition and upland zones.

Upland

Transition

Wet

REDUCTION IN SOILS

• IRIS films (constructed of 10 mil PVC sheets) were painted with ironoxide paint (combination of ferrihydrite and goethite).

• Under anaerobic conditions microorganisms use Fe3+ in the paint asterminal electron acceptor. For example:

Fe(OH)3 + 3H+ → Fe2+ + 3H2O

Orange Fe3+ is reduced to colorless Fe2+

• Soluble ferrous iron (Fe2+) is removed from IRIS film as evidenced bypigment removal from IRIS films.

Above: painting PVC with iron oxide paint that were later cut into IRIS films.

KE Y PO IN T S

• Increase in elevation leads to decrease in temperature, and we see less evidence of reduction on IRISfilms as elevation increases.

• Increased wetness (discerned by visual evidence of water table) shows increased reduction on IRIS films.

o Soil conditions could be too cold for IRIS to show evidence of reduction, while wetland hydrology isin fact present.

FUTURE/PLANNED WORK

• Water table depth and duration will be analyzed to determine if wetland hydrology is met across thewetland gradients at each elevation.

• Analysis of soil physical and chemical characteristics will be performed to examine linkages between soilmorphology and redox status.

• Soil temperature data will be explored to explore the impacts on reduction of Fe, SOC content, andredoximorphic feature expression.

• Soil carbon and nitrogen content will be used to examine SOC storage dynamic across the gradient.

• Soil morphological features will be described along additional transects to investigate heterogeneity ofsoil at the study sites.

REFERENCES

Rabenhorst, M. C., and K. L. Castenson. 2005. Temperature Effects on Iron Reduction in a Hydric Soils. Soil Science, New Brunswick, NJ.

Rabenhorst, M. C., and S. N. Burch. 2006. Synthetic Iron Oxides as an Indicator of Reduction in Soils (IRIS). Soil Sci. Soc. Am. J. 70:1227-1236.

USDA NRCS Snow Telemetry (SNOTEL) Network.

Soil

dep

th

Above: As elevation increases from 9,000 ft to 11,000 ft, evidence of reduction on IRIS films decreases. Temporal variation between sites may be due to temperature and hydrology. Variation between zones is evidence of the wetness gradient, each each upland site showing less <10% reduction in the upper 25 cm due to dry soil conditions.*Mean monthly temperatures are from SNOTEL sites at 8,440, 10,240 and 10,500 ft elevation, respectively.

White area=Fe3+ has been reduced

Orange area=Fe3+ remains, no reduction

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10,000 ftSite

11,000 ftSite

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July

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IRIS film reduction from upper 25 cm

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September

IRIS films installed in July 2019

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Mean Monthly

Temp (⁰C)

16.5 14.0 12.7 15.2 13.5 12.3 11.9 10.0 8.4