ARS | Publication request: Ecosystem Warming Affects CO2 Flux in an Agricultural Soil

Submitted to: Agronomy Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: April 21, 2009
Publication Date: November 1, 2009
Citation: Wall, G.W., Garcia, R.L., Kimball, B.A., and White, J.W. (2009). Ecosystem Warming Affects CO2 Flux in an Agricultural Soil. Presented at the Annual ASA Meetings, Pittsburgh, PA, Nov. 1-5, 2009.

Technical Abstract: Global warming seems likely based on present-day climate predictions. Our objective was to characterize and quantify the interactive effects of ecosystem warming (i.e., canopy temperature, TS), soil moisture content ('S) and microbial biomass (BM: bacteria, fungi) on the intra-row soil CO2 flux (FS) of an open-field spring wheat (Triticum aestivum L. cv. Yecora Rojo) crop. A T-FACE (Temperature Free-Air Controlled Enhancement) apparatus utilizing infrared heaters was employed to elevate values of TS above the wheat crop by 1.5 and 3.0 oC during the diurnal and nocturnal periods, respectively. The experimental design was a completely Randomized Latin Square (2x3) consisting of two levels of TS (i.e., heated, reference with dummy heaters) in three replicates planted on 10 Mar. and 1 Dec. 2008. Values of intra-row FS, TS (Model LI-8100, LI-COR, Lincoln, NE) and 'S (gravimetrically) were measured from planting until canopy closure. An extraction of soil DNA enabled real-time quantitative polymerase chain reaction of bacterial and fungal markers to estimate BM. Under high 'S a 10% increase in FS was observed in the heated compared with control plots, and FS was positively correlated with an order of magnitude increase in BM. In contrast, as 'S became lower in the heated plots compared with higher 'S in the control plots, a 10% reduction in FS was observed. Characterization of the response of BM to TS under low 'S is ongoing, but preliminary results suggest that FS depends on the interactive effects of TS, 'S and BM. Consequently, a more complicated paradigm may be required to elucidate the effect of global climate change on sequestering of C in agricultural soils then previously believed. Knowledge of this interactive effect (i.e., TSx'SxBM) will enable more accurate assessments of the sustainability of cereal crop production in a future high-CO2 world.