Responses of Soil Respiration to Clipping and Grazing in a Tallgrass Prairie

Abstract

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.

Summer drought reduces total and litter-derived soil CO<sub>2</sub> effluxes in temperate grassland – clues from a <sup>13</sup>C litter addition experiment

“…In wet soils, drought has resulted in an increase of F Soil (Kim et al, 1992;Davidson et al, 2004;Sowerby et al, 2008), while for mesic and drier habitats reduced F Soil or negligible drought effects have been observed (Freeman et al, 1996;Bremer et al, 1998;Harper et al, 2005;Garten et al, 2009). Beside the short-term effects during the drought period itself, we also observed a significant reduction of cumulated F Soil over the entire 13 CO 2 measurement period by 26% from April until October (Tables 3 and 4).…”

“…Kim et al, 1992;Sowerby et al, 2008), while studies in mesic and drier habitats observed a reduction of F Soil due to increased plant and microbial stress (e.g. Bremer et al, 1998;Harper et al, 2005;Garten et al, 2009) as well as no or limited effects (Freeman et al, 1996). Furthermore, several sources (auto-and heterotrophic) contribute to F Soil with each of them probably responding differently to changes in precipitation amounts and patterns (Borken et al, 2006;Inglima et al, 2009).…”

Restoring organic matter in a cultivated, semiarid soil using crested wheatgrass

“…been shown that CO 2 flux from tallgrass prairie can be reduced by up to 49% within 2 d of clipping (Bremer et al 1998). After hay removal, C fluxes from CWG were similar to those from wheat (Fig.…”

Seasonal variation in carbon dioxide exchange over a Mediterranean annual grassland in California

“…High temperature sensitivity may include the direct physiological effect of temperature on root and microbial activities and the indirect effect related to photosynthetic assimilation and carbon allocation to roots (Davidson et al, 1998). Evidence for the indirect effect of photosynthesis on autotrophic respiration comes from a series of recent studies (Bremer et al, 1998;Högberg et al, 2001;Bowling et al, 2002). During the dry season, the main portion of ecosystem respiration comes from the more recalcitrant carbon material, which has been shown to have low temperature sensitivity (Liski et al, 1999).…”