Soil‐surface CO 2 flux (F s ) is an important component in prairie C budgets. Although grazing is common in grasslands, its effects on F s have not been well documented. Three clipping treatments: (i) early‐season clipping (EC); (ii) full‐season clipping (FC); and (iii) no clipping (NC); which represented two grazing strategies and a control, were applied to plots in a tallgrass prairie in northeastern Kansas, USA. Measurements of F s were made with a portable gas‐exchange system at weekly to monthly intervals for 1 yr. Concurrent measurements of soil temperature and volumetric soil water content at 0.1 m were obtained with dual‐probe heat‐capacity sensors. Measurements of F s also were obtained in grazed pastures. F s ranged annually from 8.8 × 10 −3 mg m −2 S −1 during the winter to 0.51 mg m −2 s −1 during the summer, following the patterns of soil temperature and canopy growth and phenology. Clipping typically reduced F s 21 to 49% by the second day after clipping despite higher soil temperatures in clipped plots. Cumulative annual F s were 4.94, 4.04, and 4.11 kg m −2 yr −1 in NC, EC, and FC treatments, respectively; thus, dipping reduced annual F s by 17.5%. Differences in F s between EC and FC were minimal, suggesting that different grazing strategies had little additional impact on annual F s . Daily F s in grazed pastures was 20 to 37% less than F s in ungrazed pastures. Results suggest that grazing moderates F s during the growing season by reducing canopy photosynthesis and slowing translocation of carbon to the rhizosphere.
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Bremer et al. (1998) studied this question.