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Sagebrush-steppe ecosystem is an important carbon sink as it encompasses 11% of North America. With a global land coverage of 47.2% or 6.15 billion hectares and an organic carbon content of 241Pg and inorganic carbon content that is as high as the organic carbon content, dryland ecosystem in general represent an important carbon pool.
My PhD research quantified the biophysical controls on spatial heterogeneity of soil respiration at the sagebrush-steppe ecosystem.
While I was based in Buffalo, NY, my summer field trip was based in Laramie and Saratoga in Wyoming
The ecological importance of sagebrush ecosystem : Plays critical role in net global carbon balance
Research Objective: Improved understanding of the dynamics of sagebrush carbon metabolism.
Theme 1: Model data fusion with Bayesian framework
Theme 1: Model data fusion with Bayesian framework
Evapotranspiration (ET or water) and Net Ecosystem Exchange (NEE or carbon) consists of superimposed sub-signals operating at different frequencies. Modelling the variation of these two processes at different time scales can lead to an improved insight of the impact of biotic and abiotic factors modulating these two fluxes as well as result in accurate estimation of Gross Primary Productivity (GPP) and Ecosystem Respiration (Re). This was achieved by simulation of carbon and water fluxes using a model-data fusion approach within a Bayesian framework by running the TREES model against eddy-flux observations at three different time steps: sub-daily (30 minutes), daily (1 day) and intermediate (7 days).
The model was tested on eddy-covariance data collected for a two-month period (June and July) on a sagebrush-steppe ecosystem in the Great Basin region of the United States of America (USA).
Mackay, D.S., D.E. Ahl, B.E. Ewers, S. Samanta*, S.T. Gower, and S.N. Burrows. 2003. Physiological tradeoffs in the parameterization of a model of canopy transpiration. Advances in Water Resources, 26(2), 179-194.
Frequentist versus Bayesian perspective on model simulation of carbon and water fluxes across sagebrush ecosystem
Theme 2: Climate Change Manipulation Experiment
Theme 2: Climate Change Manipulation Experiment
Effects of future large summer storm events due to climate change on vegetation carbon metabolism across western United States remains poorly understood. Canopy carbon metabolism of sagebrush (Artemisia tridentate) was evaluated over a period of 7 days during the two driest months (July and August) by irrigating sagebrush plots with 20 mm precipitation pulses. My study suggests ephemeral response of cold desert vegetation to future large summer storm events with important implications for the overall carbon storage capacity.
Climate Change manipulation experiment: How will sagebrush respond to large precipitation pulses?
Response of photosynthesis and respiration to large precipitation pulse. Precipitation was applied on day 0.
Activating microbes in the field: An ecologist's perspective
Collection of leaf and root samples for del13C analysis for isotope in order to determine coupling between above and below-ground plant processes.
Activating microbes in the soil: Substrate Induced Respiration
Theme 3: Spatial Analysis of Soil Respiration
Theme 3: Spatial Analysis of Soil Respiration
Patchy distribution of sagebrush (Artemisia tridentata) vegetation in the cold, semiarid sagebrush- steppe ecosystem, also known as ‘islands of fertility,’ strongly modulates the biogeochemical dynamics of the ecosystem. I tested the hypothesis that ‘islands of fertility’ influence the spatial structure of soil respiration. I employed a 3/7 cyclic sampling design, which consisted of 0.5 m diameter plots placed in a repeating pattern within a larger grid of 12 m x 12 m resulting in one hundred and forty four sample points. At each sample point, I measured soil respiration rates, aboveground vegetation cover, root biomass to 10 cm depth, and distance and dimensions of the nearest shrub at each of the four quadrants.
Scaling from point to landscape: setting up 3/7 spatial sampling grid design
Self-organizing patterns in carbon biomass. as measured by semivariogram, highlights hitherto unexplained physical mechanisms
Krig Map of aboveground biomass
Bayesian analysis of soil respiration and parameter uncertainty using WINBUGS
Bayesian analysis of soil respiration and parameter uncertainty using WINBUGS
AGU_2008.pdf
Field days at Saratoga , Wyoming.
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