Pm. Wayne et Fa. Bazzaz, SEEDLING DENSITY MODIFIES THE GROWTH-RESPONSES OF YELLOW BIRCH MATERNAL FAMILIES TO ELEVATED CARBON-DIOXIDE, Global change biology, 1(5), 1995, pp. 315-324
We studied seedling growth responses to ambient and elevated CO2 (350
and 700 mu L L(-1)) of three maternal families of yellow birch (Betula
alleghaniensis), raised both individually and in high-density stands.
Seedlings in competitive, dense stands exhibited markedly lower avera
ge CO2-induced growth enhancements than individually grown plants (16%
vs. 49%). Maternal families differed in their growth responses to ele
vated CO2. However, differences among families were contingent upon de
nsity; families which exhibited the greatest CO2-induced growth at low
density exhibited the least CO2-responsiveness at high density. These
data are discussed in two separate contexts; the reliability of estim
ates of the CO2 fertilization potential of forest species based solely
on individually grown plants, and the potential evolutionary conseque
nces of rising CO2 on regenerating forest tree populations.