Global Earth System Modelling
Most tree species predominantly associate with a single type of mycorrhizal fungi, which can affect plant nutrient acquisition and biogeochemical cycling. Uncertainties in mycorrhizal distributions are non-trivial and current estimates disagree in up to 50% over 40% of the land area, including tropical forests. Remote sensing capabilities for mycorrhizal detection show promise for refining these estimates further. We address for the first time the impact of mycorrhizal distributions on global carbon and nutrient cycling. Using the state-of-the-art carbon-nitrogen economics within the Community Land Model version 5 (CLM5) we found Net Primary Productivity (NPP) increased throughout the 21st century by 20%; however, as soil nitrogen has progressively become limiting, the costs to NPP for nitrogen acquisition — i.e., to mycorrhizae — have increased at a faster rate by 60%. This suggests that nutrient acquisition will increasingly demand a higher portion of assimilated carbon to support the same productivity.
Braghiere, R. K., Fisher, J. B., Allen, K., Brzostek, E., Shi, M., Yang, X., Ricciuto, D.M., Fisher, R.A., Zhu, Q., Phillips, R.P., 2022. Modeling Global Carbon Costs of Plant Nitrogen and Phosphorus Acquisition. J. Adv. Model. Earth Syst. 14, e2022MS003204, https://doi.org/10.1029/2022MS003204
Braghiere, R. K., Fisher, J. B., Fisher, R. A., Shi, M., Steidinger, B. S., Sulman, B. N., Soudzilovskaia, N. A., Yang, X., Liang, J., Peay, K. G., Crowther, T. W. and Phillips, R. P., 2021. Mycorrhizal Distributions Impact Global Patterns of Carbon and Nutrient Cycling, Geophys. Res. Lett., 48(19), https://doi.org/10.1029/2021GL094514
Braghiere, R. K., Wang, Y., Doughty, R., Sousa, D., Magney, T., Widlowski, J.-L., Longo, M., Bloom, A.A., Worden, J., Gentine, P., Frankenberg, C., 2021. Accounting for canopy structure improves hyperspectral radiative transfer and sun-induced chlorophyll fluorescence representations in a new generation Earth System model. Remote Sens. Environ. 261, 112497. https://doi.org/10.1016/j.rse.2021.112497
Braghiere, R. K., Quaife, T., Black, E., He, L., and Chen, J. M.: Underestimation of Global Photosynthesis in Earth System Models Due to Representation of Vegetation Structure. Global Biogeochemical Cycles, 2018GB006135. https://doi.org/10.1029/2018GB006135, 2019.
Hogan, R. J., Quaife, T., and Braghiere, R.: Fast matrix treatment of 3-D radiative transfer in vegetation canopies: SPARTACUS-Vegetation 1.1, Geosci. Model Dev., 11, 339-350, https://doi.org/10.5194/gmd-11-339-2018, 2018.
The effects of biomass burning aerosols on energy and mass fluxes in the Amazon
Braghiere, R.K., Yamasoe MA, do Rosário NM, da Rocha H, de Souza Nogueira J, de Araújo AC. 2020. Characterization of the radiative impact of aerosols on CO2 and energy fluxes in the Amazon deforestation arch using artificial neural networks. Atmospheric Chemistry and Physics 20: 3439–3458. doi:10.5194/acp-20-3439-2020
Braghiere, R.K., Yamasoe, M.A., 2013.: Evaluation of CO2 flux modification as a function of aerosol optical depth at Bananal Island, Tocantins, Brazil, in: AIP Conference Proceedings. pp. 552–555. doi:10.1063/1.4804829
Other forest types
Addressing the impact of 3D vegetation structure on shortwave radiation transfer in Earth System Models (ESMs) is important for accurate weather forecasting, carbon budget estimates, and climate predictions. While leaf-level photosynthesis is well characterized and understood, estimates of global level carbon assimilation in the literature range from 110 to 175 PgC.yr-1. In this NASA JPL Carbon Club presentation, I explore how neglecting canopy structure leads to significant uncertainties in shortwave radiation partitioning, as well as second order derived canopy properties, such as leaf area index (LAI). I compare two different parameterization schemes of clumping index retrieved from digital hemispherical photography and 3D radiative transfer modeling over flux-tower sites in North America. Finally, I touch on how the clumping index might be integrated into hyperspectral ESMs to explore the theoretical relationship between canopy structure and photosynthesis, as well as estimates of vegetation indices, such as NDVI, NIRv, and SIF.
Braghiere, R. K., Quaife, T., Black, E., Ryu, Y., Chen, Q., Kauwe, M. G. De, & Baldocchi, D. (2020). Influence of sun zenith angle on canopy clumping and the resulting impacts on photosynthesis. Agricultural and Forest Meteorology, 291(May), 108065. doi:10.1016/j.agrformet.2020.108065
Li, F., Hao, D., Zhu, Q., Yuan, K., Braghiere, R.K., He, L., Luo, X., Wei, S., Riley, W.J., Zeng, Y., Chen, M., Fa Li, C., 2022. Vegetation clumping modulates global photosynthesis through adjusting canopy light environment. Glob. Chang. Biol. 00, 1–16. doi:10.1111/GCB.16503