Microbially Mediated Soil Carbon Decomposition in High Northern Latitudes

EPA Grant Number: U916235
Title: Microbially Mediated Soil Carbon Decomposition in High Northern Latitudes
Investigators: Smith, Nicole V.
Institution: California Institute of Technology
EPA Project Officer: Lee, Sonja
Project Period: January 1, 2003 through January 1, 2006
Project Amount: $108,344
RFA: STAR Graduate Fellowships (2003) Recipients Lists
Research Category: Fellowship - Environmental Engineering , Academic Fellowships , Engineering and Environmental Chemistry


The objective of this research project is to estimate the effects of climate change on the carbon balance of northern ecosystems using a combination of passive microwave satellite data and fieldwork to constrain the heterotrophic respiration component of net ecosystem productivity (NEP).


Net ecosystem productivity is the balance between plant productivity and heterotrophic respiration, and is the net flux of carbon from an ecosystem to the atmosphere. Currently, the normalized difference vegetation index (NDVI) is used extensively to characterize changes in plant productivity over time, but there is no similar method to estimate heterotrophic respiration at a large scale. The rate of heterotrophic respiration is strongly dependent on the freeze-thaw state of an ecosystem, and I propose to construct a record of freeze-thaw cycles at latitudes above 45°N since 1978, using passive microwave satellite data. This record, validated by field data from Alaska, Canada, and Siberia, will be used to assess the impact of freeze-thaw timing changes (because of global warming) and interannual variability on northern ecosystem net ecosystem productivity and the global carbon cycle. I will develop a model of heterotrophic respiration using the freeze-thaw product as a driver of microbially mediated decomposition in soils and integrate this module into CASA, a model of net primary productivity based on NDVI. The modified version of CASA will estimate carbon fluxes to the atmosphere since 1978, and will quantify the accumulation or loss of carbon from northern ecosystems in response to recent temperature increases.

Supplemental Keywords:

fellowship, net ecosystem productivity, NEP, normalized difference vegetation index, NDVI, plant productivity, soil carbon decomposition, high northern latitudes, soils, heterotrophic respiration, net primary productivity model, CASA, carbon fluxes, carbon balance, climate change., RFA, Air, climate change, Air Pollution Effects, Atmosphere

Progress and Final Reports:

  • 2003
  • 2004
  • Final