Project Funding: 2017 - 2021

NRA: 2016 NASA: Interdisciplinary Research in Earth Science   

Funded by NASA

Abstract:
Interannual variability in the global carbon cycle is large, and primarily driven by processes on land. The land sink removes about a third of the CO2 emitted by anthropogenic activities each year, thus constituting a negative feedback to climate change by slowing the growth rate of atmospheric CO2. The sink is highly variable however, and has ranged between 1 to 4 PgC over the past decade. Understanding the dominant drivers of variability is therefore of large importance for predicting the future evolution of the Earth system. Multiple lines of evidence are used to infer the terrestrial carbon sink and its variability, from land surface models, remote sensing products, atmospheric observations, inventory data, and the residual of global carbon budgets. Eddy-covariance (EC) measurements, however, are the only direct observation of the partitioning of carbon between ecosystems and the atmosphere. For over two decades, data from EC towers have provided a wealth of information on net carbon fluxes, along with the gross fluxes of ecosystem photosynthesis and respiration, and have formed the basis for assessing the efficacy of all other methods for examining the carbon cycle. Important recent research however suggests that the methods used to partition net EC carbon fluxes to photosynthesis and respiration are fundamentally flawed, due to the fact that they do not take into account the inhibition of leaf respiration by light (the effect, after Prof. Basel Kok). Failing to account for the Kok effect in partitioning methods has been shown to lead to an overestimation of photosynthesis by 25%, along with incorrect seasonal dynamics of light- and water-use efficiency. It is hard to overstate the importance of these results, as the implications are that the understanding derived from eddy-covariance observations, and used to develop and test all other estimates of the partitioning of CO2 between ecosystems and the atmosphere to date, is incorrect. Resolving this issue is of the upmost importance. This proposal has three overarching goals. First, we will develop the next-generation of high-resolution upscaled estimates of global photosynthesis, respiration and evapotranspiration using a suite of data from existing and planned remote sensing platforms along with recent theoretical developments in the constrained optimal function of photosynthesis and conductance, and advances in radiative transfer modeling. Second, we will use this framework to develop an ecophysiological understanding of the spatial and temporal influence of the Kok effect on the partitioning of ecosystem-atmosphere CO2 exchange, and the resulting changes in ecosystem light- and water-use efficiency. Third, we will characterize the mechanisms underlying observed variability in the global carbon cycle at multiple spatial scales and timescales, by combining the new high-resolution upscaled estimates of carbon and water fluxes with ancillary remote sensing observations and geostatistical inverse modeling and regression approaches. This proposal will use a suite of NASA and partner agency remote sensing products, along with ground observations, to provide improved observations of the partitioning of carbon between the biosphere and the atmosphere, advanced theory on ecosystem scale photosynthetic light- and water-use efficiency, and a high-resolution framework that combines these advances with a suite of remote sensing observations. By bringing together the 'bottom up' and the 'top down,' we aim to elucidate the controls of inter-annual variability and transform our ability to characterize carbon-climate feedbacks. Our research will lead to improved insight into the processes that govern global carbon uptake and functional responses that control the magnitude of carbon cycle feedbacks, a key goal in order to improve our ability to predict the future evolution of the Earth System.

Publications:

Byrne, B., Liu, J., Bloom, A. A., Bowman, K. W., Butterfield, Z., Joiner, J., Keenan, T. F., Keppel-Aleks, G., Parazoo, N. C., Yin, Y. 2020. Contrasting Regional Carbon Cycle Responses to Seasonal Climate Anomalies Across the East-West Divide of Temperate North America. Global Biogeochemical Cycles. 34(11). DOI: 10.1029/2020GB006598

Famiglietti, C. A., Fisher, J. B., Halverson, G., Borbas, E. E. 2018. Global Validation of MODIS Near-Surface Air and Dew Point Temperatures. Geophysical Research Letters. 45(15), 7772-7780. DOI: 10.1029/2018GL077813

Forbes, W. L., Mao, J., Jin, M., Kao, S., Fu, W., Shi, X., Riccuito, D. M., Thornton, P. E., Ribes, A., Wang, Y., Piao, S., Zhao, T., Schwalm, C. R., Hoffman, F. M., Fisher, J. B., Ito, A., Poulter, B., Fang, Y., Tian, H., Jain, A. K., Hayes, D. J. 2018. Contribution of environmental forcings to US runoff changes for the period 1950-2010. Environmental Research Letters. 13(5), 054023. DOI: 10.1088/1748-9326/aabb41

Huang, K., Xia, J., Wang, Y., Ahlstrom, A., Chen, J., Cook, R. B., Cui, E., Fang, Y., Fisher, J. B., Huntzinger, D. N., Li, Z., Michalak, A. M., Qiao, Y., Schaefer, K., Schwalm, C., Wang, J., Wei, Y., Xu, X., Yan, L., Bian, C., Luo, Y. 2018. Enhanced peak growth of global vegetation and its key mechanisms. Nature Ecology & Evolution. 2(12), 1897-1905. DOI: 10.1038/s41559-018-0714-0

Huang, M., Piao, S., Ciais, P., Penuelas, J., Wang, X., Keenan, T. F., Peng, S., Berry, J. A., Wang, K., Mao, J., Alkama, R., Cescatti, A., Cuntz, M., De Deurwaerder, H., Gao, M., He, Y., Liu, Y., Luo, Y., Myneni, R. B., Niu, S., Shi, X., Yuan, W., Verbeeck, H., Wang, T., Wu, J., Janssens, I. A. 2019. Air temperature optima of vegetation productivity across global biomes. Nature Ecology & Evolution. 3(5), 772-779. DOI: 10.1038/s41559-019-0838-x

Keenan, T. F., Migliavacca, M., Papale, D., Baldocchi, D., Reichstein, M., Torn, M., Wutzler, T. 2019. Widespread inhibition of daytime ecosystem respiration. Nature Ecology & Evolution. 3(3), 407-415. DOI: 10.1038/s41559-019-0809-2

Keenan, T. F., Riley, W. J. 2018. Greening of the land surface in the world's cold regions consistent with recent warming. Nature Climate Change. 8(9), 825-828. DOI: 10.1038/s41558-018-0258-y

Keenan, T. F., Williams, C. A. 2018. The Terrestrial Carbon Sink. Annual Review of Environment and Resources. 43(1), 219-243. DOI: 10.1146/annurev-environ-102017-030204

Kolus, H. R., Huntzinger, D. N., Schwalm, C. R., Fisher, J. B., McKay, N., Fang, Y., Michalak, A. M., Schaefer, K., Wei, Y., Poulter, B., Mao, J., Parazoo, N. C., Shi, X. 2019. Land carbon models underestimate the severity and duration of drought's impact on plant productivity. Scientific Reports. 9(1). DOI: 10.1038/s41598-019-39373-1

Liu, Y., Piao, S., Gasser, T., Ciais, P., Yang, H., Wang, H., Keenan, T. F., Huang, M., Wan, S., Song, J., Wang, K., Janssens, I. A., Penuelas, J., Huntingford, C., Wang, X., Altaf Arain, M., Fang, Y., Fisher, J. B., Huang, M., Huntzinger, D. N., Ito, A., Jain, A. K., Mao, J., Michalak, A. M., Peng, C., Poulter, B., Schwalm, C., Shi, X., Tian, H., Wei, Y., Zeng, N., Zhu, Q., Wang, T. 2019. Field-experiment constraints on the enhancement of the terrestrial carbon sink by CO2 fertilization. Nature Geoscience. 12(10), 809-814. DOI: 10.1038/s41561-019-0436-1

Luo, X., Croft, H., Chen, J. M., He, L., Keenan, T. F. 2019. Improved estimates of global terrestrial photosynthesis using information on leaf chlorophyll content. Global Change Biology. 25(7), 2499-2514. DOI: 10.1111/gcb.14624

Luo, X., Keenan, T. F. 2020. Global evidence for the acclimation of ecosystem photosynthesis to light. Nature Ecology & Evolution. 4(10), 1351-1357. DOI: 10.1038/s41559-020-1258-7

Luo, X., Keenan, T. F., Fisher, J. B., Jimenez-Munoz, J., Chen, J. M., Jiang, C., Ju, W., Perakalapudi, N., Ryu, Y., Tadic, J. M. 2018. The impact of the 2015/2016 El Nino on global photosynthesis using satellite remote sensing. Philosophical Transactions of the Royal Society B: Biological Sciences. 373(1760), 20170409. DOI: 10.1098/rstb.2017.0409

Qiu, B., Xue, Y., Fisher, J. B., Guo, W., Berry, J. A., Zhang, Y. 2018. Satellite Chlorophyll Fluorescence and Soil Moisture Observations Lead to Advances in the Predictive Understanding of Global Terrestrial Coupled Carbon-Water Cycles. Global Biogeochemical Cycles. 32(3), 360-375. DOI: 10.1002/2017GB005744

Schwalm, C. R., Huntzinger, D. N., Michalak, A. M., Schaefer, K., Fisher, J. B., Fang, Y., Wei, Y. 2020. Modeling suggests fossil fuel emissions have been driving increased land carbon uptake since the turn of the 20th Century. Scientific Reports. 10(1). DOI: 10.1038/s41598-020-66103-9

Shiga, Y. P., Tadic, J. M., Qiu, X., Yadav, V., Andrews, A. E., Berry, J. A., Michalak, A. M. 2018. Atmospheric CO 2 Observations Reveal Strong Correlation Between Regional Net Biospheric Carbon Uptake and Solar-Induced Chlorophyll Fluorescence. Geophysical Research Letters. 45(2), 1122-1132. DOI: 10.1002/2017GL076630

Stocker, B. D., Zscheischler, J., Keenan, T. F., Prentice, I. C., Penuelas, J., Seneviratne, S. I. 2018. Quantifying soil moisture impacts on light use efficiency across biomes. New Phytologist. 218(4), 1430-1449. DOI: 10.1111/nph.15123

Stocker, B. D., Zscheischler, J., Keenan, T. F., Prentice, I. C., Seneviratne, S. I., Penuelas, J. 2019. Drought impacts on terrestrial primary production underestimated by satellite monitoring. Nature Geoscience. 12(4), 264-270. DOI: 10.1038/s41561-019-0318-6

Sun, W., Fang, Y., Luo, X., Shiga, Y. P., Zhang, Y., Andrews, A. E., Thoning, K. W., Fisher, J. B., Keenan, T. F., Michalak, A. M. 2021. Midwest US Croplands Determine Model Divergence in North American Carbon Fluxes. AGU Advances. 2(2). DOI: 10.1029/2020AV000310

Sun, W., Luo, X., Fang, Y., Shiga, Y. P., Zhang, Y., Fisher, J. B., Keenan, T. F., Michalak, A. M. 2023. Biome-scale temperature sensitivity of ecosystem respiration revealed by atmospheric CO2 observations. Nature Ecology & Evolution. DOI: 10.1038/s41559-023-02093-x

Talsma, C. J., Good, S. P., Jimenez, C., Martens, B., Fisher, J. B., Miralles, D. G., McCabe, M. F., Purdy, A. J. 2018. Partitioning of evapotranspiration in remote sensing-based models. Agricultural and Forest Meteorology. 260-261, 131-143. DOI: 10.1016/j.agrformet.2018.05.010

Terrer, C., Jackson, R. B., Prentice, I. C., Keenan, T. F., Kaiser, C., Vicca, S., Fisher, J. B., Reich, P. B., Stocker, B. D., Hungate, B. A., Penuelas, J., McCallum, I., Soudzilovskaia, N. A., Cernusak, L. A., Talhelm, A. F., Van Sundert, K., Piao, S., Newton, P. C. D., Hovenden, M. J., Blumenthal, D. M., Liu, Y. Y., Muller, C., Winter, K., Field, C. B., Viechtbauer, W., Van Lissa, C. J., Hoosbeek, M. R., Watanabe, M., Koike, T., Leshyk, V. O., Polley, H. W., Franklin, O. 2019. Nitrogen and phosphorus constrain the CO2 fertilization of global plant biomass. Nature Climate Change. 9(9), 684-689. DOI: 10.1038/s41558-019-0545-2

Zhang, Y., Keenan, T. F., Zhou, S. 2021. Exacerbated drought impacts on global ecosystems due to structural overshoot. Nature Ecology & Evolution. 5(11), 1490-1498. DOI: 10.1038/s41559-021-01551-8

Zhu, P., Zhuang, Q., Welp, L., Ciais, P., Heimann, M., Peng, B., Li, W., Bernacchi, C., Roedenbeck, C., Keenan, T. F. 2019. Recent Warming Has Resulted in Smaller Gains in Net Carbon Uptake in Northern High Latitudes. Journal of Climate. 32(18), 5849-5863. DOI: 10.1175/JCLI-D-18-0653.1

More details may be found in the following project profile(s):

• NASA Terrestrial Ecology (TE) Project Profile
• North American Carbon Program (NACP) Project Profile