Abstract
The partitioning among carbon (C) pools of the extra C captured under elevated atmospheric CO
2 concentration ([CO
2]) determines the enhancement in C sequestration, yet no clear partitioning rules exist. Here, we used first principles and published data from four free-air CO
2 enrichment (FACE) experiments on forest tree species to conceptualize the total allocation of to below ground (TBCA) under current [CO
2] and to predict the likely effect of elevated [CO
2]. We show that at a FACE site where leaf area index (L) of Pinus taeda L. was altered through nitrogen fertilization, ice-storm damage, and droughts, changes in L, reflecting the aboveground sink for net primary productivity, were accompanied by opposite changes in TBCA. A similar pattern emerged when data were combined from the four FACE experiments, using leaf area duration (L
D) to account for differences in growing-season length. Moreover, elevated [CO
2]-induced enhancement of TBCA in the combined data decreased from [approximately] 50% 700 g(Cm
-2y
-1) at the lowest L
D to [approximately] 30%(200 gCm
-2y
-1) at the highest L
D. The consistency of the trend in TBCA with L and its response to [CO
2] across the sites provides a norm for predictions of ecosystem C cycling, and is particularly useful for models that use L to estimate components of the terrestrial C balance.
Keywords
forests,
carbon,
CO2,
free-air CO2 enrichment (FACE),
TBCA
Citation
Palmroth, Sari; Oren, Ram; McCarthy, Heather R.; Johnsen, Kurt H.; Finzi, Adrien C.; Butnor, John R.; Ryan, Michael G.; Schlesinger, William H. 2006. Aboveground sink strength in forests controls the allocation of carbon below ground and its [CO
2]-induced enhancement. Proceedings of the National Academy of Sciences. 103(51): 19362-19367