Slide 1

Greenhouse Gases Fluxes from a Drained and Seasonally-Flooded Peatland and a Tidal Wetland Dennis Baldocchi, Matteo Detto, Joe Verfaillie, Jaclyn Hatala, Oliver Sonnentag UC Berkeley Frank Anderson, USGS/DWR Bay Delta Science Symposium, Sacramento, Sept 29, 2010 Slide 2 The Big Picture Science Questions and Problems Drainage of Delta Peatlands has Caused over 10 m of Soil Subsidence, with Loss due to Respiration and Compaction Continued Subsidence Strains Levees, making the Water Conveyance System to 20 million people in California Vulnerable to Collapse Restoring Wetlands Can Sequester Carbon and Re-Build Soils Carbon Farming Projects are Being Proposed and Implemented Are there Un-Intended Consequences to Ecological Restoration for Carbon Sequestration? Flooding can lead to Methane Production and Huge Evaporation in a Region where Water is Scarce and Precious Slide 3 Objectives Measure Greenhouse Gas Fluxes, Directly, Quasi- Continuously over Multiple Years with Eddy Covariance and New Generation of Laser Spectrometers Conduct Greenhouse Gas Flux Measurements Over 3 Contrasting Landscapes Drained, Peatland Pasture Seasonally-Flooded Rice Paddy Remnants of Natural Wetlands Slide 4 Eddy Covariance Tower Sonic Anemometer, CO2/H2O IRGA, inlet for CH4 Tunable diode laser spectrometer & Meteorological Sensors Slide 5 ESPM 228 Adv Topics Micromet & Biomet Eddy Covariance, Flux Density: mol m -2 s -1 or J m -2 s -1 Slide 6 Measuring Methane with Off-Axis Infrared Laser Spectrometer Los Gatos Research Closed path Moderate Cell Volume, 400 cc Long path length, kilometers High power Use: Sensor, 80 W Pump, 1000 W; 30-50 lpm Low noise: 1 ppb at 1 Hz Stable Calibration Slide 7 Open-Path Laser Spectrometer, LI-7700, for Methane Low Power (8 W) and no pump, Ideal for Use in Remote Locations Slide 8 Site Locations Drained Peatland Pasture: Sherman Island Seasonally Flooded Peatland: Twitchell Island Slide 9 P1. Greenhouse Gas Fluxes from Tidal Wetlands Remnants of the Delta before 1850s Sampled from Sherman Island Levee Slide 10 Methane Emission and CO 2 Exchange from Tidal Wetland, Spring 2010 Slide 11 Sherman Island, Drained, Grazed, Peatland Pasture April 2007-Sept, 2010 Slide 12 CO 2 Exchange on Sherman Island: April, 2007-August, 2010 Slide 13 Methane Fluxes at Sherman Island Generally Low (~ 10 nmol m -2 s -1 ) except when Flooded or Cows Pass Slide 14 P2. Twitchell Island, Seasonally-Flooded Peatland, Rice Paddy Slide 15 Rice Paddy and USGS Tule Pilot Study, Twitchell Island Slide 16 Twitchell Island Rice, 2009-2010 Slide 17 All Methane Flux Data Slide 18 2009, The First Year of Rice Cultivation = 8.7 +/- 9.8 nmol m -2 s -1 Sherman Island Slide 19 Water table Depth? shallower will be more mixed and more aerated? Ample Oxygen (~40% of saturation)? Strong Delta winds mix and Circular Pumping aerate water Virgin Land for Rice, relatively depleted surface C pools? Expected peat to be a larger source of C substrate than heavy Clay soils in the Sac Valley Methane Efflux will increase with subsequent cultivation?? Upper layers of soils have been heavily oxidized Why is Methane Efflux relatively Low from the Rice? Slide 20 Flooding for Rice and Wildlife Mgt Controls on Methane Efflux Variations in Oxygen in the Water Column Slide 21 Wetland Vs Pasture Flooding Inhibits Nocturnal Respiration and Daytime Photosynthesis, Compared to the Drained Peatland. Slide 22 Rice Cultivation Stymies Soil C loss from Delta Rice Cultivation vs Grazed Pasture Slide 23 Rice Cultivation Evaporates 2X the Water of a Degraded Pasture Rice Cultivation vs Grazed Pasture Slide 24 Annual ET = 1.37 million acre-ft = 1.69 10 9 m 3 /y Annual Evaporation from Legal Delta at 1 km Resolution Map and Model: Y Ryu and D. Baldocchi Slide 25 Summary Seasonally Flooded Rice is a Moderate Carbon Dioxide Sink and a weak methane source This was the first year rice was cultivated on this plot of land A Drained Peatland Pasture is a Strong Source of Carbon Plus grazing cows are a strong methane source Rice Cultivation uses twice as much water as less intensive pasture. Slide 26 Delta Maps of ET and GPP Product of Youngryel Ryu, D. Baldocchi, Berkeley Biometeorology Lab ET, Delta: 1.38 Million acre-ft per year Slide 27 Preliminary data, sort by wind direction and fix bias in water table Winter Flooding Inhibits Soil CO2 Efflux Slide 28 Tide-Methane Flux CoSpectra from Levee