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Contribution of new photosynthetic assimilates to respiration by perennial grasses and shrubs: Residence times and allocation patterns

  • Author(s): Carbone, MS
  • Trumbore, SE
  • et al.
Abstract

• Quantification of the fate of carbon (C) used by plant metabolism is necessary to improve predictions of terrestrial ecosystem respiration and its sources. • Here, a dual isotope (13C and 14C) pulse-label was used to determine the allocation of new C to different respiratory pathways in the early and late growing seasons for two plant functional types, perennial grasses and shrubs, in the Owens Valley, CA, USA. • Allocation differences between plant types exceeded seasonal allocation variation. Grasses respired 71 and 64% and shrubs respired 22 and 17% of the label below-ground in the early and late growing seasons, respectively. Across seasons and plant types, ∼48-61% of the label recovered was respired in 24 h, ∼68-84% in 6 d, and ∼16-33% in 6-36 d after labeling. • Three C pools were identified for plant metabolism: a fast pool with mean residence times (MRTs) of ∼0.5 and ∼1 d below- and above-ground, respectively; an intermediate pool with MRTs of 19.9 and 18.9 d; and a storage pool detected in new leaf early growing season respiration > 9 months after assimilation. Differences in allocation to fast vs intermediate C pools resulted in the mean age of C respired by shrubs being shorter (3.8-4.5 d) than that of the grasses (4.8-8.2 d).

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