Re-assessment of plant carbon dynamics at the Duke free-air CO₂ enrichment site

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McCarthy HR, R Oren, KH Johnsen, A Gallet-Budynek, SG Pritchard, CW Cook, SL LaDeau, RB Jackson, AC Finzi. 2010.
Re-assessment of plant carbon dynamics at the Duke free-air CO₂ enrichment site: interactions of atmospheric [CO₂] with nitrogen and water availability over stand development.
New Phytologist 185: 514-528, dx.doi.org/10.1111/j.1469-8137.2009.03078.x.

Summary

• The potential for elevated [CO₂]-induced changes to plant carbon (C) storage, through modifications in plant production and allocation of C among plant pools, is an important source of uncertainty when predicting future forest function. Utilizing 10 yr of data from the Duke free-air CO₂ enrichment site, we evaluated the dynamics and distribution of plant C.
• Discrepancy between heights measured for this study and previously calculated heights required revision of earlier allometrically based biomass determinations, resulting in higher (up to 50%) estimates of standing biomass and net primary productivity than previous assessments.
• Generally, elevated [CO₂] caused sustained increases in plant biomass production and in standing C, but did not affect the partitioning of C among plant biomass pools. Spatial variation in net primary productivity and its [CO₂]-induced enhancement was controlled primarily by N availability, with the difference between precipitation and potential evapotranspiration explaining most interannual variability. Consequently, [CO₂]-induced net primary productivity enhancement ranged from 22 to 30% in different plots and years.
• Through quantifying the effects of nutrient and water availability on the forest productivity response to elevated [CO₂], we show that net primary productivity enhancement by elevated [CO₂] is not uniform, but rather highly dependent on the availability of other growth resources.

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