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Carbon Sequestration and Storage Capacity of Older Trees and Forests


View over the Telephone Gap area slated to be logged in Vermont. Photo Credit: Standing Trees

Mature and old-growth trees and stands are powerhouses of carbon absorption and carbon storage throughout their lives and well after they die. Older and larger trees store significant amounts of carbon, sequestered over decades to centuries of growth. Importantly, they maintain their carbon sequestration abilities as they age, continuing to pull carbon dioxide from the atmosphere and storing the carbon in the trunk, branches, leaves, roots, and soil while returning the oxygen to the atmosphere. Upon death, this carbon transfers from live to dead carbon accounting pools, where it slowly decomposes as new vegetation maintains and increases the carbon balance.


On the scale of an individual tree, research increasingly indicates that the rate of carbon accumulation continuously increases as the tree grows older and larger. The mechanisms behind this phenomenon are the tree’s leaves (or needles) providing greater leaf area. More leaf area means more light can be intercepted via photosynthesis, which means more atmospheric carbon is absorbed. Moreover, the increase in the rate of carbon accumulation occurs even as a tree’s overall growth becomes less efficient. As a recent study concluded: “[L]arge, old trees do not act simply as senescent carbon reservoirs but actively fix large amounts of carbon compared to smaller trees; at the extreme, a single big tree can add the same amount of carbon to the forest within a year as is contained in an entire mid-sized tree.”


Although carbon dynamics operate differently at the stand-level, the rate of carbon accumulation in a stand of trees does not suddenly collapse as forests mature, absent major disturbance (e.g., by insect infestation). As a stand of trees ages, that rate will peak around the time the canopy closes. The timing of the peak varies based on species and growing conditions (e.g., climate, competition). This peak in carbon sequestration has been linked to the age of maturity by different studies, with one of these studies providing a correlation between stand age and diameter at breast height, making these measures of maturity operational in the field. Following the sequestration peak, the rate of accumulation in some conditions will decelerate toward equilibrium (carbon in equaling carbon out); in others, it will remain relatively constant, decelerating gradually, if at all. But, as a general matter, the rate of carbon accumulation remains robust well into a stand’s lifespan, and this rate is often still higher for older stands than much younger stands. Studies at the Forest Service’s Wind River research facility in southwester Washington documented that old-growth forests continue to perform net carbon sequestration even after 500 years. Additionally, a recent study shows that in eastern forests, unmanaged stands are equally if not more effective at storing carbon than managed (logged) stands.


Older trees and forests can store their accumulated carbon for centuries. As a healthy tree ages and continues to absorb carbon, the total amount of its stored carbon increases. Older, larger trees can hold a substantial portion of a forest’s total above-ground carbon even though they account for a relatively small percent of the trees. Further, research indicates that, once dead, such trees often decay more slowly than smaller, younger trees, holding onto their stored carbon for decades to centuries as they decay in the forest. Even then not all carbon is lost to the atmosphere—much is absorbed into the forest soil. Logging removes trees that would otherwise become snags and dead wood, therefore virtually all managed forests have less dead wood and less carbon storage per capita than unmanaged mature and old-growth forests.


Moreover, the relationship between stand or tree age and susceptibility to natural disturbances is not simple. Some species of trees become more vulnerable to certain disturbances as they age—mature lodgepole pine, for instance, tends to be susceptible to mountain pine beetle. But older trees often possess features that make them more resistant to fire than younger trees, such as the thicker bark that comes with increasing age and size, and lower branch self-pruning in some species that limits fire crown spread. Further, relatively little of the carbon held by older trees is combusted. Fires—including severe ones—consume mostly the duff, understory vegetation, and live foliage, but not the tree stem where most of the carbon is stored. And, as noted, even if disturbance kills them, the carbon of dead older and larger trees can persist in the forest for extremely long periods.


It is when such trees are removed from the forest that they start to rapidly lose carbon. The logging, manufacture, use, and decay of wood products emits stored carbon over a relatively short time. But carbon accounting—including by the Forest Service—often neglects logging-related emissions, overstates substitution benefits, and ignores the lost sequestration potential of letting trees grow.


  1. Krankina, O. N. et al. “High-Biomass Forests of the Pacific Northwest: Who Manages Them and How Much is Protected?” Environmental Management (2014) 54:112-121. https://doi.org/10.1007/s00267-014-0283-1; https://www.oregon.gov/ODF/ForestBenefits/Documents/Forest%20Carbon%20Study/High-Biomass-Forestry-of-the-PNW-Who-manages-them-and-how-much-is-protected-Krankina.pdf.

  2. Stephenson, N. L. et al. “Rate of tree carbon accumulation increases continuously with tree size.” Nature (2014) 507: 90-93. https://doi.org/10.1038/nature12914; Köhl, M. et al. “The impact of tree age on biomass growth and carbon accumulation capacity: A retrospective analysis using tree ring data of three tropical tree species grown in natural forests of Suriname.” PLoS ONE (2017) 12(8): e0181187. https://doi.org/10.1371/journal.pone.0181187; Sillett, S.C. et al. “Increasing wood production through old age in tall trees.” Forest Ecology and Management (2010) 259(5): 976-994. https://doi.org/10.1016/j.foreco.2009.12.003; Xu, C-Y. et al. “Age-related decline of stand biomass accumulation is primarily due to mortality and not to reduction in NPP associated with individual tree physiology, tree growth or stand structure in a Quercus-dominated forest.” Journal of Ecology (2012) 100(2): 428-440. https://doi.org/10.1111/j.1365-2745.2011.01933.x.

  3. Stephenson, N. L. et al. “Rate of tree carbon accumulation increases continuously with tree size.” Nature (2014) 507: 90-93. https://doi.org/10.1038/nature12914.

  4. Ibid.

  5. Ibid.

  6. Xu, C-Y. et al. “Age-related decline of stand biomass accumulation is primarily due to mortality and not to reduction in NPP associated with individual tree physiology, tree growth or stand structure in a Quercus-dominated forest.” Journal of Ecology (2012) 100(2): 428-440. https://doi.org/10.1111/j.1365-2745.2011.01933.x; Acker, S. A. et al. “Trends in bole biomass accumulation, net primary production and tree mortality in Pseudotsuga menziesii forests of contrasting age.” Tree physiology (2002) 22(2-3): 213-7. https://doi.org/10.1093/treephys/22.2-3.213; Lorenz K. and R. Lal. “Effects of disturbance, succession and management on carbon sequestration” In: “Carbon sequestration in forest ecosystems.” Dordrecht: Springer (2010) 103-157. https://doi.org/10.1007/978-90-481-3266-9_3.

  7. He, L. et al. “Relationships between net primary productivity and forest stand age in U.S. forests.” Global Biogeochemical Cycles (2012) 26(3): 1-16. https://doi.org/10.1029/2010GB003942; Birdsey R.A. et al. “Assessing carbon stocks and accumulation potential of mature forests and larger trees in U.S. federal lands.” Frontiers in Forests and Global Change (2023) 5: 1074508. https://doi.org/10.1890/07-2006.1.

  8. Birdsey R.A. et al. “Assessing carbon stocks and accumulation potential of mature forests and larger trees in U.S. federal lands.” Frontiers in Forests and Global Change (2023) 5: 1074508. https://doi.org/10.1890/07-2006.1; Barnett K. et al. “Classifying, inventorying, and mapping mature and old-growth forests in the United States.” Frontiers in Forests and Global Change (2023) 5: 1070372. https://doi.org/10.3389/ffgc.2022.1070372.

  9. Birdsey R.A. et al. “Assessing carbon stocks and accumulation potential of mature forests and larger trees in U.S. federal lands.” Frontiers in Forests and Global Change (2023) 5: 1074508. https://doi.org/10.1890/07-2006.1.

  10. Hudiburg, T.W. et al. “Carbon dynamics of Oregon and Northern California forests and potential land-based carbon storage.” Ecological applications: a publication of the Ecological Society of America (2009) 19(1): 163-180. https://doi.org/10.1890/07-2006.1; Pregitzer, K.S. and E.S. Euskirchen. “Carbon cycling and storage in world forests: biome patterns related to forest age.” Global Change Biology (2004) 10(12): 2052-2077. https://doi.org/10.1111/j.1365-2486.2004.00866.x.

  11. Gough, C.M. et al. “Disturbance, complexity, and succession of net ecosystem production in North America's temperate deciduous forests.” Ecosphere (2016) 7(6): e01375. https://doi.org/10.1002/ecs2.1375.

  12. He, L. et al. “Relationships between net primary productivity and forest stand age in U.S. forests.” Global Biogeochemical Cycles (2012) 26(3): 1-16. https://doi.org/10.1029/2010GB003942; Birdsey R.A. et al. “Assessing carbon stocks and accumulation potential of mature forests and larger trees in U.S. federal lands.” Frontiers in Forests and Global Change (2023) 5: 1074508. https://doi.org/10.1890/07-2006.1; Law, B.E. et al. “Changes in carbon storage and fluxes in a chronosequence of ponderosa pine.” Global Change Biology (2003) 9(4): 510-524. https://doi.org/10.1046/j.1365-2486.2003.00624.x; Keeton, W.S. et al. “Late-successional biomass development in northern hardwood-conifer forests of the Northeastern United States.” Forest Science (2011) 57(6): 489-505. https://doi.org/10.1093/forestscience/57.6.489.

  13. Jarvis, B. “Why Old-Growth Trees Are Crucial to Fighting Climate Change - Nature is already socking away a lot of carbon for us. It could soak up a lot more—if we help.” Wired (2020) https://www.wired.com/story/trees-plants-nature-best-carbon-capture-technology-ever/.

  14. Faison, E.K. et al. “Adaptation and mitigation capacity of wildland forests in the northeastern United States.” Forest Ecology and Management (2023) 544, 121145. https://doi.org/10.1016/j.foreco.2023.121145.

  15. Xu, C-Y. et al. “Age-related decline of stand biomass accumulation is primarily due to mortality and not to reduction in NPP associated with individual tree physiology, tree growth or stand structure in a Quercus-dominated forest.” Journal of Ecology (2012) 100(2): 428-440. https://doi.org/10.1111/j.1365-2745.2011.01933.x; Pregitzer, K.S. and E.S. Euskirchen. “Carbon cycling and storage in world forests: biome patterns related to forest age.” Global Change Biology (2004) 10(12): 2052-2077. https://doi.org/10.1111/j.1365-2486.2004.00866.x; Mildrexler, D.J. et al. “Large trees dominate carbon storage in forests east of the Cascade Crest in the United States Pacific Northwest.” Frontiers in Forests and Global Change (2020) 3. https://doi.org/10.3389/ffgc.2020.594274

  16. Mildrexler, D.J. et al. “Large trees dominate carbon storage in forests east of the Cascade Crest in the United States Pacific Northwest.” Frontiers in Forests and Global Change (2020) 3. https://doi.org/10.3389/ffgc.2020.594274; Lutz, J.A. et al. “Global importance of large‐diameter trees.” Global Ecology and Biogeography (2018) 27(7): 849-864. https://doi.org/10.1111/geb.12747; Brown, S.L. et al. “Spatial distribution of biomass in forests of the eastern USA.” Forest Ecology and Management (1999) 123(1): 81-90. https://doi.org/10.1016/S0378-1127(99)00017-1.

  17. Harmon, M.E. et al. “Ecology of coarse woody debris in temperate ecosystems.” Advances in Ecological Research (2004) 34: 59-234. https://doi.org/10.1016/S0065-2504(03)34002-4; Herrmann, S. et al. “Decomposition dynamics of coarse woody debris of three important central European tree species.” Forest Ecosystems (2015) 2: 27. https://doi.org/10.1186/s40663-015-0052-5; Lutz, J.A., et al. “The importance of large-diameter trees to the creation of snag and deadwood biomass.” Ecological Processes (2021) 10: 28. https://doi.org/10.1186/s13717-021-00299-0; Stenzel, J.E. et al. “Fixing a snag in carbon emissions estimates from wildfires.” Global change biology (2019) 25(11): 3985-3994. https://doi.org/10.1111/gcb.14716.

  18. Magnússon, R.Í. et al. “Tamm Review: Sequestration of carbon from coarse woody debris in forest soils.” Forest Ecology and Management (2016) 377: 1-15. https://doi.org/10.1016/j.foreco.2016.06.033.

  19. Lutz, J.A. et al. “The importance of large-diameter trees to the creation of snag and deadwood biomass.” Ecological Processes (2021) 10, 28. https://doi.org/10.1186/s13717-021-00299-0; https://ecologicalprocesses.springeropen.com/counter/pdf/10.1186/s13717-021-00299-0.pdf.

  20. Carroll, A.L. et al. “Effect of climate change on range expansion by the mountain pine beetle in British Columbia.” The Bark Beetles, Fuels, and Fire Bibliography (2003) 195. https://digitalcommons.usu.edu/barkbeetles/195.

  21. Agee, James. “Fire Ecology of Pacific Northwest Forests.” Island Press (1993) 121-24.

  22. Schwilk, D.W. and D.D. Ackerly. “Flammability and serotiny as strategies: correlated evolution in pines.” Oikos (2003) 94(2): 326-336. https://doi.org/10.1034/j.1600-0706.2001.940213.x.

  23. Stenzel, J.E. et al. “Fixing a snag in carbon emissions estimates from wildfires.” Global change biology (2019) 25(11): 3985-3994. https://doi.org/10.1111/gcb.14716; Law, B.E. and R.H. Waring. “Carbon implications of current and future effects of drought, fire and management on Pacific Northwest forests.” Forest Ecology and Management (2015) 355: 4-14. https://doi.org/10.1016/j.foreco.2014.11.023; Campbell, J.L. et al. “Pyrogenic carbon emission from a large wildfire in Oregon, United States.” Journal of Geophysical Research (2007) 112(G4). https://doi.org/10.1029/2007JG000451.

  24. Campbell, J.L. et al. “Carbon emissions from decomposition of fire-killed trees following a large wildfire in Oregon, United States.” Journal of Geophysical Research (2016) 121(3): 718-730. https://doi.org/10.1002/2015JG003165; Sparks, A.M. et al. “Impacts of fire radiative flux on mature Pinus ponderosa growth and vulnerability to secondary mortality agents.” International Journal of Wildland Fire (2017) 26(1): 95-106. https://doi.org/10.1071/WF16139.

  25. Law, B.E. et al. “Land use strategies to mitigate climate change in carbon dense temperate forests.” Proceedings of the National Academy of Sciences (2018) 115(14): 3663-3668. https://doi.org/10.1073/pnas.1720064115; Hudiburg, T.W. et al. “Meeting GHG reduction targets requires accounting for all forest sector emissions.” Environmental Research Letters (2019) 14: 095005. https://doi.org/10.1088/1748-9326/ab28bb.

  26. “Office of Sustainability & Climate: Timber Harvest & Carbon.” United States Department of Agriculture (2020). https://www.fs.usda.gov/sites/default/files/TimberHarvest-Carbon-3pg-v3.pdf (last accessed August 25, 2023).

  27. Hudiburg, T.W. et al. “Meeting GHG reduction targets requires accounting for all forest sector emissions.” Environmental Research Letters (2019) 14: 095005. https://doi.org/10.1088/1748-9326/ab28bb; Harmon, M.E. “Have product substitution carbon benefits been overestimated? A sensitivity analysis of key assumptions.” Environmental Research Letters (2019) 14: 065008. https://doi.org/10.1088/1748-9326/ab1e95.


















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The Worth More Standing report spotlights federal forest-management practices that are liquidating mature and old-growth forests and trees every day. It includes 10 examples that are part of a pervasive pattern of federal forest mismanagement that routinely sidesteps science to turn carbon-storing giants into lumber. Learn what actions you can take to protect Climate Forests across the country.

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