Parameterizing perennial bioenergy crops in Version 5 of the Community Land Model based on site-level observations in the Central Midwestern United States

Authors: CHENG, YANYAN - Pacific Northwest National Laboratory; HUANG, MAOYI - Pacific Northwest National Laboratory; CHEN, MIN - Pacific Northwest National Laboratory; GUAN, KAIYU - University Of Illinois; Bernacchi, Carl; PENG, BIN - University Of Illinois; TAN, ZELI - Pacific Northwest National Laboratory

Submitted to: Journal of Advances in Modeling Earth Systems
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/7/2019
Publication Date: 12/19/2019
Citation: Cheng, Y., Huang, M., Chen, M., Guan, K., Bernacchi, C.J., Peng, B., Tan, Z. 2019. Parameterizing perennial bioenergy crops in Version 5 of the Community Land Model based on site-level observations in the Central Midwestern United States. Journal of Advances in Modeling Earth Systems. 12(1). https://doi.org/10.1029/2019MS001719.
DOI: https://doi.org/10.1029/2019MS001719

Interpretive Summary: The Community Land Surface Model is a computer program that uses the biological and environmental information to predict how plant ecosystems interact with their environments. The model is state of the art, yet it is still missing many major ecosystem types. Bioenergy crops, which are crops grown specifically to meet growing energy demands, need to be represented in these models in order to predict where best to grow them and what impacts their growth may have on the land, water, and air. This research incorporates two long-lived grass species that are very productive and ideal for bioenergy needs, and then tests the model using measurements from a number of field experiments that exist in the Midwestern US. The work from this research has strong potential that can lead to informing land mangers, farmers, and policy makes on the opportunities and challenges of land use change.

Technical Abstract: The expansion of bioenergy crops is an important strategy to mitigate climate change. However, representations of key bioenergy crops are largely missing in land models, which imposes limitations to effectively quantify their biogeophysical and biogeochemical effects in the coupled Earth system. In this study, we implement two new perennial bioenergy crops, Miscanthus and switchgrass, into the Community Land Model Version 5 by modifying parameters associated with photosynthesis, phenology, allocation, decomposition, and carbon cost of nitrogen uptake and integrating concomitantly land management practices. Sensitivity analyses indicate that carbon and energy fluxes of the perennial crops are most sensitive to photosynthesis and phenology parameters. Validation of simulated fluxes against site-level measurements demonstrates that the model is capable of capturing the overall patterns of surface energy and carbon fluxes, as well as physiological transitions from leaf emergence to senescence. Compared to annual crops, the perennial crops feature longer growing seasons, greater leaf areas, and higher productivity, leading to increased transpiration, lower annual runoff, and larger terrestrial carbon uptake. With more extensive rooting systems, these crops are more drought-tolerant with more extensive rooting systems, which also contributes to enhanced infiltration and reduced surface runoff. Our model simulations demonstrate that with higher CO2 assimilation rates and lower demands for nutrients and water, high-yielding perennial crops are promising alternatives of bioenergy feedstocks compared to traditional annual crops not only for mitigating climate change through increasing terrestrial carbon uptake, but also for environmental conservation purposes by reducing fertilizer application and therefore alleviating surface- and ground-water contaminations.