Maintenance of C sinks sustains enhanced C assimilation during long-term exposure to elevated [CO 2] in Mojave Desert shrubs

Iker Aranjuelo, Allison L. Ebbets, R. Dave Evans, David T. Tissue, Salvador Nogués, Natasja van Gestel, Paxton Payton, Volker Ebbert, Williams W. Adams, Robert S. Nowak, Stanley D. Smith

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Abstract

During the first few years of elevated atmospheric [CO 2] treatment at the Nevada Desert FACE Facility, photosynthetic downregulation was observed in desert shrubs grown under elevated [CO 2], especially under relatively wet environmental conditions. Nonetheless, those plants maintained increased A sat (photosynthetic performance at saturating light and treatment [CO 2]) under wet conditions, but to a much lesser extent under dry conditions. To determine if plants continued to downregulate during long-term exposure to elevated [CO 2], responses of photosynthesis to elevated [CO 2] were examined in two dominant Mojave Desert shrubs, the evergreen Larreatridentata and the drought-deciduous Ambrosiadumosa, during the eighth full growing season of elevated [CO 2] treatment at the NDFF. A comprehensive suite of physiological processes were collected. Furthermore, we used C labeling of air to assess carbon allocation and partitioning as measures of C sink activity. Results show that elevated [CO 2] enhanced photosynthetic performance and plant water status in Larrea, especially during periods of environmental stress, but not in Ambrosia. δ 13C analyses indicate that Larrea under elevated [CO 2] allocated a greater proportion of newly assimilated C to C sinks than Ambrosia. Maintenance by Larrea of C sinks during the dry season partially explained the reduced [CO 2] effect on leaf carbohydrate content during summer, which in turn lessened carbohydrate build-up and feedback inhibition of photosynthesis. δ 13C results also showed that in a year when plant growth reached the highest rates in 5 years, 4% (Larrea) and 7% (Ambrosia) of C in newly emerging organs were remobilized from C that was assimilated and stored for at least 2 years prior to the current study. Thus, after 8 years of continuous exposure to elevated [CO 2], both desert perennials maintained their photosynthetic capacities under elevated [CO 2]. We conclude that C storage, remobilization, and partitioning influence the responsiveness of these desert shrubs during long-term exposure to elevated [CO 2].

Original languageEnglish
Pages (from-to)339-354
Number of pages16
JournalOecologia
Volume167
Issue number2
DOIs
StatePublished - Oct 2011

Keywords

  • Ambrosia dumosa
  • C allocation/partitioning
  • Free-air CO enrichment (FACE)
  • Larrea tridentata
  • Photosynthetic downregulation

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    Aranjuelo, I., Ebbets, A. L., Evans, R. D., Tissue, D. T., Nogués, S., van Gestel, N., Payton, P., Ebbert, V., Adams, W. W., Nowak, R. S., & Smith, S. D. (2011). Maintenance of C sinks sustains enhanced C assimilation during long-term exposure to elevated [CO 2] in Mojave Desert shrubs. Oecologia, 167(2), 339-354. https://doi.org/10.1007/s00442-011-1996-y