Submitted to: USDA Symposium on Natural Resource Management to Offset Greenhouse Gas Emissions
Publication Type: Abstract Only
Publication Acceptance Date: October 20, 2002
Publication Date: November 19, 2002
Citation: Skinner, R.H., Sanderson, M.A., Dell, C.J. 2002. Photosynthetic carbon uptake and below ground partitioning in temperate pastures [abstract]. USDA Symposium on Natural Resource Management to Offset Greenhouse Gas Emissions. p. 195. Technical Abstract: Long-term carbon sequestration is influenced by the ability of the plant community to fix carbon dioxide, and by the amount and distribution of carbon that is partitioned to roots where it becomes less susceptible to re-release into the atmosphere. We examined the effects of harvest strategy (grazed vs. cut) and level of plant species diversity (2, 3 or 11 planted species per pasture) on mid-day canopy photosynthesis and on the amount and distribution of root biomass in cool-season, temperate pastures during two growing seasons. Cut plots tended to have greater standing aboveground biomass when photosynthetic measurements were taken than grazed plots. Grazing increased photosynthesis in a relatively wet year but not when water was limiting. When canopy cover was equal, however, grazed plots had 13% higher photosynthetic rates than cut plots. There was also greater root biomass in the grazed compared with the cut pastures with no year by harvest strategy interaction. Diverse species mixtures (three and eleven species) had greater photosynthetic rates than the two-species mixture, especially during a dry year. Diverse mixtures had increased root biomass in a dry year and concentrated a greater proportion of their root biomass in the lower soil profile in both years, due primarily to the inclusion of more deep-rooted species in the diverse mixtures. Increasing species diversity, and grazing rather than clipping not only increased photosynthetic rates but also increased the potential for carbon sequestration by partitioning more carbon to roots.