CO emissions from degrading plant matter (I). Measurements

CO emissions from degrading deciduous leaf and grass matter have been inves tigated in laboratory and field measurements. CO emissions are induced both photochemically and thermally. Photochemical CO production can be describe d by a 2nd-order polynomial in light intensity and exhibits a hysteresis ef fect, not previously reported. Humid material showed higher CO emissions th an dry material. A preliminary, relative action spectrum for the photochemi cally induced CO emissions is presented. Although UV irradiation caused mos t of the CO production, visible light also caused up to 40% of the emission s. We propose a cleavage of the cellulose chain as the important step prior to CO production. Thermal CO emissions from degrading plant material obey an Arrhenius type equation (presented for several species in this paper), b ur emissions are lower than those induced photochemically. During our field measurements on dry grasses in a South African savanna we found a strong i nfluence of incident radiation intensity and temperature on measured CO flu xes. Solely photochemical CO production from the grasses is calculated by s ubtraction of soil fluxes and thermally induced grass CO emissions from the total CO emissions. CO emissions and hysteresis differ between the grasses investigated and may be interpreted by the grass' colour and their archite cture. Deposition of CO on the soils was much lower than CO emission from t he dry grasses during daytime. Nighttime data show that possible thermal CO production from the grasses may partially compensate for CO deposition on the soils for several hours after sunset depending on temperature.