Responses of Soil Respiration to Clipping and Grazing in a Tallgrass Prairie
1998
Bremer, Dale J. | Ham, Jay M. | Owensby, Clenton E. | Knapp, Alan K.
Soil-surface CO₂ flux (Fₛ) is an important component in prairie C budgets. Although grazing is common in grasslands, its effects on Fₛ 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 Fₛ 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 Fₛ also were obtained in grazed pastures. Fₛ 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 Fₛ 21 to 49% by the second day after clipping despite higher soil temperatures in clipped plots. Cumulative annual Fₛ were 4.94, 4.04, and 4.11 kg m⁻² yr⁻¹ in NC, EC, and FC treatments, respectively; thus, dipping reduced annual Fₛ by 17.5%. Differences in Fₛ between EC and FC were minimal, suggesting that different grazing strategies had little additional impact on annual Fₛ. Daily Fₛ in grazed pastures was 20 to 37% less than Fₛ in ungrazed pastures. Results suggest that grazing moderates Fₛ during the growing season by reducing canopy photosynthesis and slowing translocation of carbon to the rhizosphere. Contribution no. 98-234-J from the Kansas Agric. Exp. Station.
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