Rising Carbon Dioxide Concentrations and "Woody Thickening"
Bragg, F.J., Prentice, I.C., Harrison, S.P., Eglinton, G., Foster, P.N., Rommerskirchen, F. and Rullkotter, J. 2013. Stable isotope and modeling evidence for CO2 as a driver of glacial-interglacial vegetation shifts in southern Africa. Biogeosciences 10: 2001-2010.
The seven scientists report that their data suggested "a large increase in C3 relative to C4 plant dominance after the Last Glacial Maximum." And "using a process-based biogeography model that explicitly simulates 13C discrimination," they showed that "precipitation and temperature changes cannot explain the observed shift in δ13C values," which led them to conclude that "the physiological effect of increasing CO2 concentration is decisive, altering the C3/C4 balance and bringing the simulated and observed δ13C values into line."
In further discussing their findings, Bragg et al. say their results "have implications for the interpretation of the trend towards increased tree density in savannas, known as 'woody thickening'," noting that "an increase of CO2 concentration from 280 to 380 ppm should have increased the potential growth rates of C3 plants during the industrial era by ~ 15 to 20%." And they add that "a continued increase from 380 ppm to 550 ppm should cause a further increase of similar magnitude in the potential growth rates of C3 plants," which increase "would be expected to increase the competitive ability of C3 plants" and "further increase woody plant cover today, just as it did during the worldwide reforestation after the Last Glacial Maximum."
Archer, S., Boutton, T.W. and Hibbard, K.A. 2001. Trees in grasslands: biogeochemical consequences of woody plant expansion. In: Schulze, E.-D., Heimann, M., Harrison, S.P., Holland, E.A., Lloyd, J., Prentice, I.C. and Schimel, D.S. (Eds.). Global Biogeochemical Cycles in the Climate System. Academic Press, San Diego, California, USA, pp. 115-137.
Archer, S., Schimel, D.S. and Holland, E.A. 1995. Mechanisms of shrubland expansion: land use, climate or CO2? Climatic Change 29: 91-99.
Bond, W.J. and Midgley, G.F. 2000. A proposed CO2-controlled mechanism of woody plant invasion in grasslands and savannas. Global Change Biology 6: 865-869.
Bond, W.J., Midgley, G.F. and Woodward, F.I. 2003. The importance of low atmospheric CO2 and fire in promoting the spread of grasslands and savannas. Global Change Biology 9: 973-982.
Ehleringer, J.R., Cerling, T.E. and Helliker, B.R. C4 photosynthesis, atmospheric CO2 and climate. Oecologia 112: 285-299.
Kgope, B.S., Bond, W.J. and Midgley, G.F. 2010. Growth responses of African savanna trees implicate atmospheric [CO2] as a driver of past and current changes in savanna tree cover. Austral Ecology 35: 451-463.
Macinnis-Ng, C., Zeppel, M., Williams, M. and Eamus, D. 2011. Applying a SPA model to examine the impact of climate change on GPP of open woodlands and the potential for woody thickening. Ecohydrology 4: 379-393.
Street-Perrott, F.A., Huang, Y., Perrott, R.A., Eglinton, G., Barker, P., Khelifa, L.B., Harkness, D.D. and Olago, D.O. 1997. Impact of lower atmospheric carbon dioxide on tropical mountain ecosystems. Science 278: 1422-1426.