A comparison of14C,86Rb, and total excavation for determination of root distributions of individual plants

✍ Scribed by D. G. Milchunas; C. A. Lee; W. K. Lauenroth; D. P. Coffin

• Publisher: Springer
• Year: 1992
• Tongue: English
• Weight: 609 KB
• Volume: 144
• Category: Article
• ISSN: 0032-079X
• DOI: 10.1007/bf00018853

✦ Synopsis

Individual grass (Bouteloua gracilis) and shrub (Gutierrezia sarothrae) plants were either excavated as monoliths on nail boards, exposed to ~4CO2, or stem-injected with ~6Rb to compare the ability of the techniques to determine horizontal and vertical distribution of roots. The vertical distribution or roots directly under plant centers obtained by coring most closely correlated with monolith root length. ~4C activity greatly overestimated near-surface roots and underestimated deep roots. 86Rb activity did not follow the pattern of geometric decrease in root biomass with depth. Comparisons of both isotopes with monolith root length, over both horizontal and vertical axes, indicated that ~4C activity was consistently concentrated near the soil surface, and S6Rb activity was highly variable and randomly distributed. 14C may better represent root activity than root mass, and stem-injection methods can result in nonuniform labeling of roots. Caution should be exercised when using tracers to infer root biomass distributions. Resource partitioning between shrubs and grasses is discussed in relation to soil water dynamics in this semiarid grassland.