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Effect of Land Use on Methane Flux from Soil

^a Dep. of Microbiology, Iowa State Univ., Ames, IA 50011
^b USDA-ARS, National Soil Tilth Lab., 2150 Pammel Drive, Ames, IA 50011

View larger version (22K): [in a new window]   Fig. 1. Methane fluxes from plow-till, nonmanured agricultural sites. The small circles indicate the CH4 fluxes of eight individual chambers, and the large circles are the means at each sample date. The horizontal lines indicate the detection sensitivities for CH4 flux determinations.

View larger version (44K): [in a new window]   Fig. 2. Biweekly precipitation sums and mean daily air temperatures for 1993 and 1994. There were only minor variations between data from the four weather stations so only data from the Ames 8wsw station are presented. Annual precipitation for 1993 was 1435.6 mm (172% of 30-yr normal, 100th percentile within 105 yr, 1893–1998) and for 1994, 719 mm (86% of 30-yr normal, 37.1th percentile within 105 yr, 1893–1998). The 30-yr normal is 836 mm.

View larger version (16K): [in a new window]   Fig. 3. Methane fluxes from the No-till site. The small circles indicate the CH4 fluxes of 21 individual chambers, and the large circles are the means at each sample date. The horizontal lines indicate CH4 flux detection sensitivities.

View larger version (24K): [in a new window]   Fig. 4. Spatial distribution of CH4 flux and soil water content along the sampling transect at the Walnut Creek No-till site. Panel A shows the mean CH4 flux of each chamber for 1993 and panel B shows mean soil water content along the transect.

View larger version (28K): [in a new window]   Fig. 5. Methane fluxes from the Kluver agricultural site. Four treatments were present at this site including: a no N-fertilizer control (A), urea-ammonium-nitrate fertilizer (B), spring-broadcast swine manure (C), and spring-injected swine manure (D). The small circles indicate the CH4 fluxes of 16 individual chambers in 1993 and four individual chambers in 1994. The large circles are the means at each sample date. The horizontal lines indicate CH4 flux detection sensitivities.

View larger version (21K): [in a new window]   Fig. 6. Methane fluxes from the Nashua manure experiment site. Methane fluxes were measured the day before injected swine manure application (A) and immediately following swine manure application both between injection slots (B) and directly over injection slots (C). The small circles indicate the hourly CH4 fluxes of four individual chambers in each plot, and the large circles are chamber means in each plot. The horizontal lines indicate CH4 flux detection sensitivities.

View larger version (27K): [in a new window]   Fig. 7. Methane fluxes from the McFarland Forest site (A), the Roadside Prairie site (B), and the Doolittle Prairie site (C). At each sampling date the small circles indicate eight individual chamber fluxes and large circles are means. The horizontal lines indicate CH4 flux detection sensitivities.

View larger version (29K): [in a new window]   Fig. 8. Methane fluxes from the Landfill site. Panels A and B indicate CH4 fluxes at different sampling dates for 1993 and 1994, respectively. The small circles indicate the hourly CH4 fluxes of the eight individual chambers, and the large circles are means at each sampling date. The individual chamber fluxes plotted in Panels C and D indicate the spatial consistency of the temporal variations observed in 1993 and 1994, respectively.

View larger version (29K): [in a new window]   Fig. 9. Cumulative seasonal CH4 fluxes of each site in 1993. Boxes indicate the 25th and 75th quantiles. The heavy horizontal lines within each box indicates the mean cumulative flux, while the lighter horizontal line is the median. Error bars are the 5th and 95th quantiles.

View larger version (29K): [in a new window]   Fig. 10. Cumulative seasonal CH4 fluxes of each site in 1994. Boxes indicate the 25th and 75th quantiles. The heavy horizontal lines within each box indicates the mean cumulative flux, while the lighter horizontal line is the median. Error bars are the 5th and 95th quantiles.

View larger version (31K): [in a new window]   Fig. 11. Methane flux site ranking. Bars indicate the difference between number of positive and negative fluxes measured over the entire season expressed as a percentage of the total number of measurements performed in 1993 and 1994.