Preliminary Investigation of Climate Change Impacts on Soil Water and Carbon Dynamics
2004 Research Initiation Award Report
Investigators
Helga Van Miegroet—Associate Professor, Dept. Watershed Sciences and Dept
Forest, Range and Wildlife Sciences, College of Natural Resources, Utah State
University
David Chandler—Assistant Professor, Dept. of Plants, Soils and Climate,
College of Agriculture, Utah State University
Michelle Baker—Assistant Professor, Dept. Biology, College of Science,
Utah State University
Janis Boettinger—Associate Professor, Dept. of Plants, Soils and
Climate, College of Agriculture, Utah State University
Summary
A pilot study was initiated at USU’s T.W. Daniel Experimental Forest in the Bear
River Range to investigate the effects of climate change on soil microclimate
(temperature and moisture regime) and soil organic carbon dynamics (SOC
distribution, quality, decomposition, leaching) in four vegetation types
(conifer forest, aspen, sagebrush, and grass-forb communities) that are
representative for the Intermountain West. A total of 36-5 by 5 m plots were
laid out in Sunset Ridge to the West of Doc’s Meadow in the T.W. Daniel
Experimental Forest in a randomized block design with three blocks and three
treatments (control, additional summer precipitation, accelerated winter
snowmelt [not yet implemented]) in four vegetation types. The forest types are
aspen [Populus tremuloides] and conifer (mixture of fir [Abies lasiocarpa] and
spruce [Picea engelmannii]); the rangeland types are sagebrush steppe
[Artemisia tridentata] and grass-forb meadow. In the summer of 2004, logistics
for field irrigation were developed and starting in July 2005, two summer
irrigation applications of 25 mm each were applied to mimic the predicted
increase in monsoonal rainfall. Summer rainfall additions are slated to
continue provided adequate support is available. Snow manipulation treatment
will be postponed until sufficient funds have been obtained.
Progress to date:
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Plot installation and fencing of the experimental units.
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Improvement of the access road to Doc’s Meadow and installation of locked gate
to allow traffic of research vehicles, but exclude other motorized vehicles.
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Development and construction of portable irrigation system; installation of the
temporary water storage tanks; implementation of water delivery to the site.
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Full pedon description in each block of three plots (12 pedons total) with bulk
density measurements and subsampling of each horizon in 2004 for carbon
analysis and further fractionation.
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Additional soil sampling in September 2005 for further characterization of C
quality.
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Installation of instruments in all control and irrigation plots (24 plots
total) including:
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TDR’s measuring soil moisture at 0-25cm and 25-50 cm soil depth.
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Tensiometers at 10 and 50 cm soil depth (soil water tension).
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Tension lysimeters at 10 and 50 cm (soil solution chemistry).
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Mini temperature data loggers (Onset Tidbits) installed at 15 cm soil depth in
all plots.
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ECH2O soil moisture probes between 0-20 cm in depth. Readings have been taken
in 2005 before and after irrigation, and with every field respiration
measurement.
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Dataloggers, climate station and solar panels (in progress).
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Attempted to sample soil solutions during snowmelt period in June 2005. Only 28
samples could be extracted from a total of 48 lysimeters due to dry soil
conditions. So far we have been unable to extract any soil solutions in Fall.
All samples were analyzed for DOC.
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Two irrigations of 25 mm each were implemented in July 2005.
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Field measurements of soil respiration were taken in control and irrigated
plots in summer-fall 2004 (4 measurements), and summer 2005 (7 measurements).
Ongoing activities:
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Characterization of soil organic quality using a combination of biological,
chemical and physical fractionation techniques.
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Lab Calibration of the ECH2O probes.
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Exploring alternative process to characterize water-soluble organic carbon
phase given the difficulty in extracting soil water samples with lysimeters
(even during snowmelt).
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Compilation and analysis of soil moisture, soil temperature, SOC dynamics data.
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Snow depth measurements.
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Further instrumentation of the field sites.
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Re-fencing of the entire field site to protect various instruments outside the
plots (solar panel, climate station, data logger, relay station) from animal
damage.
Contact Information
Helga Van Miegroet
helgavm‹at›cc.usu.edu