This study assessed the trends in individual tree growth, and accompanying carbon accumulation, as trees increase in size. The authors measured 403 species all over the world, in a variety of climates, and found that individual tree growth rates continue to increase throughout trees’ lifetimes. These findings are more relevant to managers of old growth, mixed-age stands than to those of even-aged stands, but even managers of old growth forests should still consider stand-level dynamics looking to this research for management implications. While tree-level processes help us to understanding stand dynamics, management requires a more holistic view that accounts for a variety of ecological functions across the landscape.

For example, the authors note, “The rapid growth of large trees indicates that, relative to their numbers, they could play a disproportionately important role in [forest feedbacks to the global climate system] [Enquist et al., 2009]. For example, in our western USA old-growth forest plots, trees >100 cm in diameter comprised 6% of trees, yet contributed 33% of the annual forest mass growth.” However, they provide caveats, including, “ increasing individual tree growth rate does not automatically result in increasing stand productivity because tree mortality can drive orders-of-magnitude reductions in population density [Pretzsch & Biber, 2005; Kashian et al., 2005]. That is, even though the large trees in older, even-aged stands may be growing more rapidly, such stands have fewer trees. Tree population dynamics, especially mortality, can thus be a significant contributor to declining productivity at the scale of the forest stand [Coomes et al., 2012].”

Although the title of this paper generally suggests that larger trees equal more carbon sequestration, the body reveals that forest carbon dynamics are more complex. While individual trees sequester more carbon with age, other factors such as mortality and lower numbers of trees per area often result in reduced stand-level carbon accumulation, which the authors recognize. These findings of continued tree growth contradict previous belief that tree growth gradually stagnates with age, and thus can help us to better understand and model forest carbon dynamics.

See the report in TACCIMO: Stephenson, N. L., Das, A. J., Condit, R., Russo, S. E., Baker, P. J., Beckman, N. G., … & Zavala, M. A. (2014). Rate of tree carbon accumulation increases continuously with tree size. Nature.