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Western Geographic Science Center

 

Remote Sensing of Wetland Carbon in the Sacramento-San Joaquin River Delta


Problem:

The Sacramento-San Joaquin River Delta historically supported extensive marshes that for the last 7000 years formed an extensive temperate peatland with up to 12 meters deep peat soils, representing a substantial carbon pool. After farmland conversion in the mid nineteenth century, the Delta is now dominated by drained peat soils that through oxidation and compaction have subsided up to 10 meters, and are protected from flooding by levees. A long-term marsh restoration project conducted by USGS scientists on Twitchell Island in the Delta was designed to raise the elevation of subsided land through peat accretion, which would relieve hydrostatic pressure on Delta levees and reduce the risk of catastrophic flooding in the event of levee failure. Results from this project have shown that managed freshwater marsh restoration reverses land subsidence from farmed peat soils and also sequesters carbon at some of the highest recorded rates (Miller and Fujii 2010).

As wetland restoration expands throughout the San Francisco Bay-Delta region, there will be a need to 1) quantify large-scale belowground carbon sequestration rates in order to define eligibility for carbon offset credits in the emerging carbon trading market and 2) understand marsh resilience to sea level rise. Estimating above and belowground productivity of wetland vegetation over a large spatial extent will help to address these needs. The overall goal of this research is to develop practical and reproducible methods to quantify and map belowground net primary productivity (BNPP) of marsh vegetation from remotely sensed measurements of aboveground plant characteristics and aboveground net productivity (ANPP).

Miller, R. L., and R. Fujii. 2010. Plant community, primary productivity, and environmental conditions following wetland re-establishment in the Sacramento-San Joaquin Delta, California. Wetland Ecology and Management 18(1):1-16.



measuring spectral reflectance of vegetation see caption
An ASD, Inc. field spectrometer, measuring spectral reflectance of vegetation
Color infrared image of the Sacramento-San Joaquin River Delta

Objectives:

  1. Couple field measurements with field spectrometer readings throughout the growing season to develop new hyperspectral and multispectral indices that best model plant biophysical and biochemical parameters related to BNPP and carbon sequestration.

  2. Scale up spectral indices with hyperspectral and multispectral satellite data to produce maps of belowground biomass; determine the uncertainties, errors and accuracies in these scaled-up estimates of biomass.
Future work:

This project commences in spring 2011. We will begin field data collection at freshwater and brackish marshland sites within the Delta, and continue data collection throughout the growing season.

Methods:

The central tool of this project will be the use of a full spectrum ASD Inc. field spectrometer on loan from the Rocky Mountain Geographic Science Center to take spectral reflectance readings of emergent marsh vegetation.

Partners:

University of California, Berkeley; Randall Museum, San Francisco; NASA

Funding:

Funded by the NASA ROSES New Investigator Program in Earth Sciences.







For more information contact: Photo of Ed
Kristin Byrd

map of Puget Lowland Ecoregion<

A color infrared aerial photo of the USGS pilot wetland restoration site on Twitchell Island, in the Sacramento-San Joaquin River Delta. The west wetland maintains a 25 cm water depth and the east wetland maintains a 55 cm water depth. Click on image to open a larger version in a new window.



 

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