Title: Aboveground sink strength in forests controls the allocation of carbon below ground and its [CO2]-induced enhancement
Author: Palmroth, Sari; Oren, Ram; McCarthy, Heather R.; Johnsen, Kurt H.; Finzi, Adrien C.; Butnor, John R.; Ryan, Michael G.; Schlesinger, William H.
Source: Proceedings of the National Academy of Sciences. 103(51): 19362-19367
Description: The partitioning among carbon (C) pools of the extra C captured under elevated atmospheric CO2 concentration ([CO2]) determines the enhancement in C sequestration, yet no clear partitioning rules exist. Here, we used first principles and published data from four free-air CO2 enrichment (FACE) experiments on forest tree species to conceptualize the total allocation of to below ground (TBCA) under current [CO2] and to predict the likely effect of elevated [CO2]. 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 (LD) to account for differences in growing-season length. Moreover, elevated [CO2]-induced enhancement of TBCA in the combined data decreased from [approximately] 50% 700 g(Cm-2y-1) at the lowest LD to [approximately] 30%(200 gCm-2y-1) at the highest LD. The consistency of the trend in TBCA with L and its response to [CO2] 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
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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 [CO2]-induced enhancement. Proceedings of the National Academy of Sciences. 103(51): 19362-19367.