Synthesis of four long-term, DOE supported, CO2 enrichment experiments show that young temperate forests increase carbon uptake at climate-change relevant timescales.
A synthesis of long-term, DOE-supported experiments shows that in young temperate forests, tree biomass growth increased by 30 % in response to a decade of CO2-enrichment. This response was predictable with knowledge of the plant production response to CO2, and the relationship of wood production to whole plant production under ambient CO2 conditions.
CO2-fertilization is the stimulation of gains in plant biomass by increased atmospheric CO2, which creates a feedback on the rate of increase in atmospheric CO2. The complexity combined with the global and decadal scales of this process means that estimates of the size of the feedback remain uncertain. By synthesizing the longest running experiments in forest or woody ecosystems this study develops understanding of the processes that determine CO2-fertilisation at longer timescales and ecosystem spatial scales.
Stimulation of photosynthesis by increasing atmospheric CO2 can increase plant production, but at longer timescales, may not necessarily increase plant biomass because all the additional production could be in short-lived tissues such as leaves and fine-roots. An international team of scientists, led by Oak Ridge National Laboratory, analyzed the four decade-long CO2 enrichment experiments in forests that measured total plant production and biomass (including below-ground). Using statistical mixed-models they showed that CO2 enrichment increased biomass increment by 1.05 ± 0.26 kg C m-2 over a full decade. This response was predictable with knowledge of the production response to CO2 (0.16 ± 0.03 kg C m-2 y-1) and the biomass retention rate (slope of the relationship between biomass increment and cumulative production; 0.55 ± 0.17) which was independent of CO2. An ensemble of terrestrial ecosystem models failed to predict both terms correctly, but with different reasons among sites. These results demonstrate that a decade of CO2 enrichment stimulates live-biomass increment in temperate, early-succession, forest ecosystems. CO2-independence of the biomass retention rate highlights the value of understanding ambient conditions for interpreting CO2 responses.
Contacts (BER PM)
Terrestrial Ecosystem Science
Anthony P. Walker
Oak Ridge National Laboratory
DOE Office of Science Biological and Environmental Research, Terrestrial Ecosystem Science, and Free Air CO2 Enrichment Model Data Synthesis (FACE-MDS).
Walker, A. P., et al. “Decadal biomass increment in early secondary succession woody ecosystems is increased by CO2 enrichment.” Nature Communications 10, 454 (2019) [DOI: 10.1038/s41467-019-08348-1].
SC-23.1 Climate and Environmental Sciences Division, BER
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