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Long-Term Studies (Woody Plants -- Pine Trees: Miscellaneous) -- Summary
Clues as to how earth's trees will respond to future increases in atmospheric CO2 concentration may be obtained from studies of how they have responded to historical increases in the air's CO2 content; and we here review what has been learned in this regard -- via studies of this type -- for two less-analyzed species of pine tree: Aleppo pine (Pinus halepensis Mill.) and Shortleaf pine (Pinus echinata Mill.).

In the case of the first species, Rathgeber et al. (2003) used tree-ring width and density chronologies (in both earlywood and latewood) from 21 stands of Aleppo pines in the Provence region of southeast France, in order to calibrate the BIOME3 biogeochemistry model of forest productivity in terms of growth responses to known historical changes in atmospheric temperature, precipitation and CO2 concentration, after which they used the calibrated model to calculate changes in the mean productivity of the same forest stands that could be expected to result from changes in these parameters driven by a doubling of the air's CO2 content, as calculated by Meteo-France's ARPEGE atmospheric general circulation model when downscaled to that specific part of the country.

In response to the predicted changes in climate, this work revealed that forest productivity increased moderately for all stands (17% to 24%); while in response to the aerial fertilization effect of the doubling of the air's CO2 content, it rose considerably more (72% to 86%). Even more impressively, when the climatic changes and atmospheric CO2 increase were considered together, forest productivity increased still more (107% to 141%).

This latter response range is even greater than what is implied by the sum of the individual responses, due to the amplifying synergy that exists among the atmospheric compositional and climatic factors with respect to their combined impact on basic plant physiological processes. Therefore, the researchers concluded that "although the detected effects of global change during the 20th century were slight, acceleration of these changes is likely to lead to great changes in the future productivity of P. halepensis forests." Indeed, their study suggests -- based on real-world-derived relationships -- that a doubling of the air's CO2 content could well more than double the growth of Aleppo pine forests in southeast France.

Working with Shortleaf pine in the Ozark Mountains of Missouri, USA, Voelker et al. (2006) cross-dated a large number of increment cores and aligned the ring-width data by pith date for accurate age-constant assessments of growth over the past 150 years, thereby circumventing "changes in growth trend associated with differences in physiological functioning during development, as well as the need for statistical detrending that removes an unknown degree of long-term environmental signal, the so-called segment length curse that applies to standard dendrochronological investigations." In addition, they similarly analyzed previously acquired data for Shortleaf pine stretching back in time to nearly AD 1600. This work revealed that since 1850 the stem growth of the trees had risen "coincidently with increases in atmospheric CO2," such that the overall trend in ring-width in recent years was "nearly two times that" experienced prior to 1850. In addition, they found that "long-term increases in radial growth appear unrelated to historical disturbance levels for the region, to long-term changes in relevant climatic variables, or to productivity of sites sampled." Consequently, the four Department of Forestry researchers from the University of Missouri (USA) concluded that as the atmosphere's CO2 concentration continues to rise, aided by continued nitrogen deposition, it will likely "stimulate further increases in the rates of stand development and carbon storage."

In conclusion, therefore, if the past is prologue to the future, we can expect great things (like greatly enhanced growth and development) from earth's Aleppo and Shortleaf pines, as the air's CO2 content continues its upward trajectory.

Rathgeber, C., Nicault, A., Kaplan, J.O. and Guiot, J. 2003. Using a biogeochemistry model in simulating forests productivity responses to climatic change and [CO2] increase: example of Pinus halepensis in Provence (south-east France). Ecological Modelling 166: 239-255.

Voelker, S.L., Muzika, R.-M., Guyette, R.P. and Stambaugh, M.C. 2006. Historical CO2 growth enhancement declines with age in Quercus and Pinus. Ecological Monographs 76: 549-564.

Last updated 17 March 2010