Paw U, K.T. (Atmospheric Science, University of California, Atmospheric Science, Univ. of California, One Shields Ave., Davis, CA, 95616; Phone: 530-752-1510; Fax: 530-752-1793; Email: ktpawu@ucdavis.edu)

Eddy-covariance Measurements of Carbon Exchange from Fields with Different Tillage Treatments in the Central Valley of California

Kyaw Tha Paw U *, A.J. Ideris, A. P. King, Liyi Xu, John Kochendorfer, A.A. Matista, T.C. Hsiao, D.E. Rolston.

Eddy-covariance data analyzed were collected between the Fall of 2003 and the late summer of 2004, for fields with two different tillage treatments. Initially, both fields were bare (approximately from September to January), and then soil with weeds (approximately January to April), recently prepared soil (April), and finally a maize agroecosystem (April/May onwards). Our results show a clear pattern as a function of season, weed growth, and cultural timing. Diurnal patterns were evident in all months, first related to a temperature dependence of soil respiration, and then later related to the light dependence of photosynthesis. Differences were found between the two treatments, and methods were conducted to examine if the differences were real or artifacts of the two-biomicrometeorological eddy-covariance systems.