Changes in biomass allocation buffer low CO 2 effects on tree growth during the last glaciation

• Published in: Scientific reports Vol. 7; p. 43087
• Main Authors: Li, Guangqi, Gerhart, Laci M, Harrison, Sandy P, Ward, Joy K, Harris, John M, Prentice, I Colin
• Format: Journal Article
• Language: English
• Published: England 24.02.2017
• Subjects: Biomass; California; Carbon Dioxide - metabolism; Climate; Models, Biological; Trees - metabolism; California
• ISSN: 2045-2322
• DOI: 10.1038/srep43087

Isotopic measurements on junipers growing in southern California during the last glacial, when the ambient atmospheric [CO ] (c ) was ~180 ppm, show the leaf-internal [CO ] (c ) was approaching the modern CO compensation point for C plants. Despite this, stem growth rates were similar to today. Using a coupled light-use efficiency and tree growth model, we show that it is possible to maintain a stable c /c ratio because both vapour pressure deficit and temperature were decreased under glacial conditions at La Brea, and these have compensating effects on the c /c ratio. Reduced photorespiration at lower temperatures would partly mitigate the effect of low c on gross primary production, but maintenance of present-day radial growth also requires a ~27% reduction in the ratio of fine root mass to leaf area. Such a shift was possible due to reduced drought stress under glacial conditions at La Brea. The necessity for changes in allocation in response to changes in [CO ] is consistent with increased below-ground allocation, and the apparent homoeostasis of radial growth, as c increases today.