NREL Seminar: Elise Pendall, Univ. of Wyoming
Friday, November 6, 2009, 11:00 AM
Natural and Environmental Sciences Building, B215, Francis Clark Conference Room

NREL Fall 2009 Seminar Series: 'Using Stable Isotopes to Understand Ecological Processes and Global Change'

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This Friday's seminar will be presented by Elise Pendall, University of Wyoming.

Title: "Partitioning of soil respiration at the PHACE experiment: A two-method comparison"

When: Friday, Nov. 2, 11 a.m. to noon

Where: B215, Francis Clark Conference Room, Natural and Environmental Sciences Building

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Abstract

Elevated CO2 and warming are both known to stimulate soil respiration rates, leading to concerns regarding soil-related feedback effects on climate change. We investigated soil C cycling at the Prairie Heating and CO2 Enrichment (PHACE) experiment that combines Free-Air CO2 Enrichment (ambient and elevated [600 ppm] CO2 concentration), experimental warming (1.5¢ªC daytime, 3¢ªC nighttime) and irrigation in native grassland near Cheyenne, WY.

We measured soil respiration rates and applied two methods (root exclusion and stable isotopes) to partition the total flux into root respiration and decomposition components, during the growing season of 2008. We hypothesized that soil respiration and decomposition would be stimulated by elevated CO2 and experimental warming, and that root exclusion would provide more comprehensive results in comparison with stable isotope partitioning.

Elevated CO2 stimulated decomposition on root exclusion plots by ~40% at ambient temperature and 60% at elevated temperature; decomposition was 35% of total soil respiration on ambient CO2 plots, and 52% of soil respiration on elevated CO2 plots. Stable isotope partitioning suggested that warming in combination with elevated CO2 enhanced decomposition of older soil organic matter, in comparison to unwarmed, elevated CO2 plots.

The 13C value of soil respiration in non-vegetated plots demonstrated the time that labile substrates remained available for decomposition. Uncertainties in stable isotope partitioning can be propagated using a hierarchical Bayesian approach. This research suggests that although root exclusion causes disturbance, it can be applied in situations that do not allow stable isotope partitioning, and is reasonably straightforward to interpret.

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Event Contact: Laurie Richards can be reached at (970) 491-1991

Sponsored by the Natural Resource and Ecology Laboratory.