Aboveground sink strength in forests controls the allocation of carbon below ground and its [CO2] - induced enhancement

作者：Palmroth Sari^*; Oren Ram; McCarthy Heather R; Johnsen Kurt H; Finzi Adrien C; Butnor John R; Ryan Michael G; Schlesinger William H

来源：Proceedings of the National Academy of Sciences, 2006, 103(51): 19362-19367.

DOI：10.1073/pnas.0609492103

• aboveground net primary production
• free-air CO2 enrichment
• leaf area index
• nitrogen fertilization
• soil respiration

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 C 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 (L-D) to account for differences in growing-season length. Moreover, elevated [CO2]-induced enhancement of TBCA in the combined data decreased from approximate to 50% (700 gCm(-2) y(-1)) at the lowest LD to approximate to 30% (200 g C m(-2) y(-1)) at the highest L-D. The consistency of the trend in TIBCA 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.

• 出版日期2006-12-19