Challenges of measuring methane over peatlands

Baldocchi, D., M. Detto, O. Sonnentag, J. Verfaillie, Y. A. Teh, W. Silver, and M. Kelly. 2012. The challenges of measuring methane fluxes and concentrations over a peatland pasture. Agricultural and Forest Meteorology 153(1): 177-187

We report on methane (CH4) concentrations and efflux densities that were measured over a drained and grazed, peatland pasture in the Sacramento-San Joaquin River Delta of California over a three year period. The site was ideal for micrometeorological flux measurements due to its very flat topography, its exposure to vigorous winds and its extended fetch along the predominant wind direction. Nevertheless, the interpretation of methane fluxes with eddy covariance proved to be extremely complicated by a number of geographical, biophysical, biogeochemical and site management factors.

Keywords: Eddy covariance . Peatland . Wetland . Cattle . Rice . Methane . Laser spectrometer . Biogeochemistry

Tracking the structural and functional development of a perennial pepperweed

Sonnentag O, Vargas R, Detto M, Runkle BRK, Kelly M, and Baldocchi DD. 2011. Tracking the structural and functional development of a perennial pepperweed (Lepidium latifolium L.) infestation using a multi-year archive of webcam imagery and eddy covariance measurements. Agricultural Forest Meteorology: 151:916-926

We explore the ability of red (R)–green (G)–blue (B) color space information to track the structural and functional development of a perennial pepperweed (Lepidium latifolium L.) infestation in California.

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Greenhouse gas emissions from a temperate peatland pasture

Teh, Y. A., W. L. Silver, O. Sonnentag, M. Detto, M. Kelly, and D. D. Baldocchi. 2011. Large Greenhouse Gas Emissions from a Temperate Peatland Pasture. Ecosystems 14: 311–325

We report greenhouse gas fluxes (CH4, CO2, N2O) from a drained peatland in the Sacramento-San Joaquin River Delta, California, USA currently managed as a rangeland.

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Carbon dioxide exchange of a pepperweed infestation

Sonnentag, O., M. Detto, B. Runkle, Y. Teh, W. Silver, M. Kelly, and D. D. Baldocchi. 2011. Carbon dioxide exchange of a pepperweed (Lepidium latifolium L.) infestation: how do flowering and mowing affect canopy photosynthesis and autotrophic respiration? J. Geophys. Res., 116, G01021, doi:10.1029/2010JG001522

We analyzed CO2 flux measurements made with eddy covariance over a pepperweed infestation in California, covering three growing seasons. We found that unmowed pepperweed caused the site to be almost CO2 neutral or a net source, and mowing during early flowering caused the site to act as a net CO2 sink.

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Isolating individual trees in a savanna woodland using lidar

Chen et al. 2006. Photogrammetric Engineering and Remote Sensing. Individual trees delineated.This study presents a new method of detecting individual treetops from lidar data and applies marker-controlled watershed segmentation into isolating individual trees in savanna woodland. The treetops were detected by searching local maxima in a canopy maxima model (CMM) with variable window sizes.

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