Author
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Pritchard, Seth |
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Rogers Jr, Hugo |
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Submitted to: New Phytologist
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 7/1/2000 Publication Date: 7/1/2000 Citation: Pritchard, S.G., Rogers Jr, H.H. 2000. Spatial and temporal deployment of crop roots in co2-enriched environments. New Phytologist. 147(1):55-71. Interpretive Summary: Global atmospheric CO2 concentrations are rising and may double sometime in the next century. Since the Kyoto Protocol, there has been great scientific and public interest in the capacity of crop-lands to capture some of this extra carbon. Flow of carbon into the soil is driven mainly by growth and function of plant roots. Assessing the potential of agricultural soils to sequester carbon, therefore, depends upon an understanding of how rising atmospheric CO2 affects the birth, growth, and death of crop roots. A review of the scientific literature indicates that crops produce more roots when growing in CO2-enriched environments, but potential changes in the longevity of these roots are still unknown. Drawing from previous research, we suggest that significant changes in root longevities of crop plants are unlikely. Although crop plants growing in CO2-enriched environments typically have more, and larger roots, these changes usually occur predominantly in shallow layers of the soil. Presently, it appears that rising global atmospheric CO2 concentrations will stimulate the growth of roots and that this stimulation of root growth will increase the amount of carbon entering the soil. Research strategies that will provide further information about changes in plant rooting characteristics, and the capacity of agricultural soils to capture atmospheric CO2, have been outlined. Technical Abstract: Growth of crops in CO2-enriched atmospheres typically results in significant changes in root growth and development. The literature suggests that initiation and stimulation of lateral roots will be favored over the elongation of primary roots leading to more highly branched, shallower root systems. Such architectural shifts may render root systems less efficient, perhaps contributing to the lower specific root activities often reported. In annual crops, C allocation to belowground processes changes as vegetative growth yields to maturation and reproduction. Reductions in C allocation to roots through time may cause temporal shifts in root deployment, perhaps impacting root demography. Although there are few existing data from which to draw conclusions, especially in annual crop plants, fine root turnover will likely increase as a function of greater total fine root biomass. Significant changes in turnover as a result of decreased root longevities in crop plants are unlikely, however. Consideration of changing C allocation to roots, a more through understanding of the mechanistic controls on root longevity, and a better characterization of the rooting habits (life histories) of different crop species will further our understanding of how rising atmospheric CO2 will affect root demography. This knowledge will lead the way toward a more thorough understanding of the linkage of atmosphere with belowground plant function and also plant function with soil biology and structure. |
