Methane Emissions of Rice Increased by Elevated Carbon Dioxide and Temperature
- Leon H. Allen *a,
- Stephan L. Albrechtb,
- Wilfredo Colón-Guaspc,
- Stephen A. Covelld,
- Jeffrey T. Bakere,
- Deyun Panf and
- Kenneth J. Bootef
- a USDA Agricultural Research Service and Agronomy Department, University of Florida, P.O. Box 110965, Gainesville, FL 32611-0965
b USDA Agricultural Research Service, Columbia Plateau Conservation Research Center, P.O. Box 370, Pendleton, OR 97801
c School of Science and Technology, Universidad del Este, P.O. Box 2010, Carolina, Puerto Rico 00984-2010
d Environmental Planning Branch, Air National Guard Readiness Center, 3500 Fetchet Ave., Andrews Air Force Base, MD 20762
e USDA Agricultural Research Service, Cropping Systems Research Laboratory, Big Spring, TX 79720
f Agronomy Department, University of Florida, P.O. Box 110500, Gainesville, FL 32611-0500
Methane (CH4) effluxes by paddy-culture rice (Oryza sativa L.) contribute about 16% of the total anthropogenic emissions. Since radiative forcing of CH4 at current atmospheric concentrations is 21 times greater on a per mole basis than that of carbon dioxide (CO2), it is imperative that the impact of global change on rice CH4 emissions be evaluated. Rice (cv. IR72) was planted in sunlit, closed-circulation, controlled-environment chambers in which CH4 efflux densities were measured daily. The CO2 concentration was maintained at either 330 or 660 μmol mol−1 Air temperatures were controlled to daily maxima and minima of 32/23, 35/26, and 38/29°C at each CO2 treatment. Emissions of CH4 each day were determined during a 4-h period after venting and resealing the chambers at 0800 h. Diurnal CH4 effluxes on 77, 98, and 119 d after planting (DAP) were obtained similarly at 4-h intervals. Emissions over four-plant hills and over flooded bare soil were measured at 53, 63, and 100 DAP. Emissions were negligible before 40 DAP. Thereafter, emissions were observed first in high-CO2, high-temperature treatments and reached a sustained maximum efflux density of about 7 mg m−2 h−1 (0.17 g m−2 d−1) near the end of the growing season. Total seasonal CH4 emission was fourfold greater for high-CO2, high-temperature treatments than for the low-CO2, low-temperature treatment, probably due to more root sloughing or exudates, since about sixfold more acetate was found in the soil at 71 DAP. Both rising CO2 and increasing temperatures could lead to a positive feedback on global warming by increasing the emissions of CH4 from rice.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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