The use of stable carbon isotope analysis in rooting studies |
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Authors: | Tony J Svejcar Thomas W Boutton |
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Institution: | (1) USDA/ARS Southwestern Livestock and Forage Research Laboratory, P.O. Box 1199, 73036 El Reno, OK, USA;(2) Stable Isotope Program, USDA/ARS Children's Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, 77030 Houston, TX, USA |
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Abstract: | Summary Stable carbon isotope analysis was evaluated as a means of predicting the relative proportions of C3 and C4 root phytomass in species mixtures. The following mixtures of C3 and C4 species were used: 1) big bluestem (Andropogon gerardii)/cheatgrass (Bromus tectorum), 2) little bluestem (Schizachyrium scoparium)/cheatgrass, and 3) sorghum (Sorghum bicolor)/sunflower (Helianthus annuus). There was a significant correlation (P<0.01) between % C4 phytomass and stable carbon isotope values for each of the three combinations (r
2>0.98). Root length per mass varied among the five species studied (10.1–94.3 m/g), which resulted in different conclusions depending on whether root values are expressed as length or mass. For example, field samples from a tallgrass prairie site were estimated to contain about 20% cheatgrass on a mass basis, whereas the figure was 68% when expressed in terms of length. The combination of stable carbon isotope analysis with length-for-mass measurements promises to be a useful means of studying root competition between C3 and C4 plants. |
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