Twitchell Island Rice

Greenhouse Gases Fluxes from a Drained and Seasonally-Flooded Peatland and a Tidal WetlandDennis Baldocchi, Matteo Detto, Joe Verfaillie, Jaclyn Hatala, Oliver Sonnentag UC Berkeley

Frank Anderson, USGS/DWR

Bay Delta Science Symposium, Sacramento, Sept 29, 2010The Big Picture Science Questions and ProblemsDrainage of Delta Peatlands has Caused over 10 m of Soil Subsidence, with Loss due to Respiration and CompactionContinued Subsidence Strains Levees, making the Water Conveyance System to 20 million people in California Vulnerable to CollapseRestoring Wetlands Can Sequester Carbon and Re-Build SoilsCarbon Farming Projects are Being Proposed and ImplementedAre 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

Wedding at Cana, Veronese, the Louvre2ObjectivesMeasure Greenhouse Gas Fluxes, Directly, Quasi-Continuously over Multiple Years with Eddy Covariance and New Generation of Laser SpectrometersConduct Greenhouse Gas Flux Measurements Over 3 Contrasting LandscapesDrained, Peatland PastureSeasonally-Flooded Rice PaddyRemnants of Natural Wetlands

Eddy Covariance TowerSonic Anemometer, CO2/H2O IRGA, inlet for CH4 Tunable diode laser spectrometer &Meteorological SensorsESPM 228 Adv Topics Micromet & Biomet

Eddy Covariance, Flux Density: mol m-2 s-1 or J m-2 s-1

5Measuring Methane with Off-Axis Infrared Laser SpectrometerLos Gatos Research

Closed pathModerate Cell Volume, 400 ccLong path length, kilometersHigh power Use:Sensor, 80 WPump, 1000 W; 30-50 lpmLow noise: 1 ppb at 1 HzStable Calibration6

Open-Path Laser Spectrometer, LI-7700, for MethaneLow Power (8 W) and no pump, Ideal for Use in Remote Locations

Site Locations

Drained Peatland Pasture: Sherman IslandSeasonally Flooded Peatland: Twitchell Island

P1. Greenhouse Gas Fluxes from Tidal WetlandsRemnants of the Delta before 1850s

Sampled from Sherman Island LeveeMethane Emission and CO2 Exchange from Tidal Wetland, Spring 2010

Sherman Island, Drained, Grazed, Peatland Pasture

April 2007-Sept, 2010

CO2 Exchange on Sherman Island:April, 2007-August, 2010

Methane Fluxes at Sherman IslandGenerally Low (~ 10 nmol m-2 s-1) except when Flooded or Cows Pass

P2. Twitchell Island, Seasonally-Flooded Peatland, Rice Paddy

Rice Paddy and USGS Tule Pilot Study, Twitchell IslandTwitchell Island Rice, 2009-2010

All Methane Flux Data

2009, The First Year of Rice Cultivation = 8.7 +/- 9.8 nmol m-2 s-1

Sherman IslandWater 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 oxidizedWhy is Methane Efflux relatively Low from the Rice?Flooding for Rice and Wildlife Mgt

Controls on Methane EffluxVariations in Oxygen in the Water ColumnWetland Vs Pasture

Flooding Inhibits Nocturnal Respiration and Daytime Photosynthesis, Compared to the Drained Peatland.

Rice Cultivation Stymies Soil C loss from DeltaRice Cultivation vs Grazed PastureRice Cultivation Evaporates 2X the Water of a Degraded Pasture

Rice Cultivation vs Grazed PastureAnnual ET = 1.37 million acre-ft = 1.69 109 m3/yAnnual Evaporation from Legal Delta at 1 km ResolutionMap and Model: Y Ryu and D. Baldocchi

SummarySeasonally Flooded Rice is a Moderate Carbon Dioxide Sink and a weak methane sourceThis was the first year rice was cultivated on this plot of land A Drained Peatland Pasture is a Strong Source of CarbonPlus grazing cows are a strong methane sourceRice Cultivation uses twice as much water as less intensive pasture. Delta Maps of ET and GPPProduct of Youngryel Ryu, D. Baldocchi, Berkeley Biometeorology LabET, Delta: 1.38 Million acre-ft per year

Preliminary data, sort by wind direction and fix bias in water tableWinter Flooding Inhibits Soil CO2 Efflux

Tide-Methane Flux CoSpectra from Levee