Ellsworth et al. (2012), as they describe it, “compiled a comprehensive dataset measured over ten years for a temperate pine forest of Pinus taeda, but also including deciduous species, primarily Liquidambar styraciflua,” which they derived from “over one thousand controlled-response curves of photosynthesis as a function of environmental drivers (light, atmospheric CO2 concentration [Ca] and temperature) measured at canopy heights up to 20 meters over eleven years (1996-2006),” from which they generated “parameterizations for leaf-scale models for the Duke free-air CO2 enrichment (FACE) experiment.”
The eight researchers report that the enhancement of light-saturated leaf net photosynthesis (Anet) in P. taeda trees by elevated Ca of +200 ppm was 67% for current-year needles in the upper crown of the trees in summer conditions over the ten-year period, while previous-year foliage Anet was enhanced by 30%, with the result that “the mean stimulation in light-saturated Anet averaged over the growing season of all years and across canopy positions and needle age classes was 53 ± 7%.” And they add that “the photosynthetic enhancement responses to elevated Ca are mirrored in part by the pine biomass accumulation responses to elevated Ca across different years.”
