Transitory effects of elevated atmospheric CO2 on fine root dynamics in an arid ecosystem do not increase long-term soil carbon input from fine root litter

Authors


Author for correspondence:
Robert S. Nowak
Tel: +1 775 784 1656
Email: nowak@cabnr.unr.edu

Summary

  • Experimental increases in atmospheric CO2 often increase root production over time, potentially increasing soil carbon (C) sequestration.
  • Effects of elevated atmospheric CO2 on fine root dynamics in a Mojave desert ecosystem were examined for the last 4.5 yr of a long-term (10-yr) free air CO2 enrichment (FACE) study at the Nevada desert FACE facility (NDFF). Sets of minirhizotron tubes were installed at the beginning of the NDFF experiment to characterize rooting dynamics of the dominant shrub Larrea tridentata, the codominant shrub Ambrosia dumosa and the plant community as a whole.
  • Although significant treatment effects occurred sporadically for some fine root measurements, differences were transitory and often in opposite directions during other time-periods. Nonetheless, earlier root growth under elevated CO2 helped sustain increased assimilation and shoot growth.
  • Overall CO2 treatment effects on fine root standing crop, production, loss, turnover, persistence and depth distribution were not significant for all sampling locations. These results were similar to those that occurred near the beginning of the NDFF experiment but unlike those in other ecosystems. Thus, increased C input into soils is unlikely to occur from fine root litter under elevated atmospheric CO2 in this arid ecosystem.

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