Effects of Burning on Soil CO2 Efflux and Microbial Biomass

Changes in soil CO2 efflux before and after burning at the SA02 site are shown in Fig. 7a, with values from the CF site shown for comparison. Before the burning on August 9 and 10, values of soil CO2 efflux were slightly higher at the CF site (641.7-744.2mg CO2m—2h—1) than at the SA02 site (484.4-543.3 mg CO2m—2h—1). There was no significant change in soil CO2

y = 195.38e0-0681x R2 = 0.9825

0 5 10 15 20 25 30 35 Soil temperature at -5 cm (°C)

Figure 6: Relationship between soil CO2 efflux and soil temperature at the SA01 site (a) and the CP site (b) in 2001. Soil temperatures (—5 cm) were measured inside of the chamber just after each efflux measurement. Vertical bars represent 7 one SE of the mean (n — 25). The SA01 site was burned on 16 August 2001. The regression lines are significant (n — 9, p< 0.001 for the SA01 site and n — 10, p< 0.001 for the CP site).

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Days after burning

Days after burning

Figure 7: Soil CO2 efflux (a), soil temperature (b), and SWC (c) at the SA02 and CF sites before and after burning in 2002. Soil temperature at -5 cm was obtained from data recorded continuously every 30 min outside of the CO2 efflux chambers. SWC over a depth of 0-12 cm was measured inside of the chamber for each efflux measurement. Vertical bars represent 7 one SE of the mean (n — 25 for the SA02 site and n — 5 for the CF site). The SA02 site was burned on 10 August 2002. Superscript letters indicate the results of one-way ANOVA; means with the same letters are not significantly different by Scheffe's test at each site (p — 0.05).

efflux at the CF site during August 9-20, and values ranged between 540.5-822.2 mg CO2m~2h~1. Significant increases in soil CO2 efflux were detected on August 14 and 16 (four and six days after the burning) at the SA02 site, and CO2 efflux values were 58 and 28% higher than those at the CF site on August 14 and 16, respectively. However, soil CO2 effluxes on August 18 and 20 (8 and 10 days after the burning) at the SA02 site decreased to similar levels as those of the CF site (581.27201.8,

686.4 7 344.3 mg CO2m_2h_1 at the SA02 site and 693.37222.5,

540.5 7156.3 mg CO2m~2h_1 at the CF site). Soil temperature at -5 cm and SWC showed no significant differences (t-test, p<0.05) between the SA02 and CF sites, indicating that the burning may have enhanced soil CO2 efflux, at least for several days after the burning.

Soil ATP concentrations in the 0-5 cm layer were slightly higher at the CF site than at the SA02 site (Fig. 8). Soil ATP concentration slightly declined in the 2 days after burning at the SA02 site, but had significantly increased by 6 days after burning. On the contrary, there were no significant differences in soil ATP concentrations between 2 and 8 days after burning at the control unburned CF site.

Days after burning

Figure 8: Soil ATP concentration (nmol g_1 soil) as a measure of microbial biomass in the surface soil (0-5 cm) at the CF site (o) and at the SA02 site (•). Vertical bars represent 7 one SE of the mean (n — 5). The SA02 site was burned on 10 August 2002. Superscript letters indicate the results of oneway ANOVA; means with the same letters are not significantly different by Scheffe's test at each site (p — 0.05).

Days after burning

Figure 8: Soil ATP concentration (nmol g_1 soil) as a measure of microbial biomass in the surface soil (0-5 cm) at the CF site (o) and at the SA02 site (•). Vertical bars represent 7 one SE of the mean (n — 5). The SA02 site was burned on 10 August 2002. Superscript letters indicate the results of oneway ANOVA; means with the same letters are not significantly different by Scheffe's test at each site (p — 0.05).

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