Simulating Agriculture in the Community Land Model Version 5. Issue 8 (7th August 2020)

• Record Type: Journal Article
• Authors: Lombardozzi, Danica L.; Lu, Yaqiong; Lawrence, Peter J.; Lawrence, David M.; Swenson, Sean; Oleson, Keith W.; Wieder, William R.; Ainsworth, Elizabeth A.
• Is Part Of: Journal of geophysical research. Volume 125:Issue 8(2020)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2020-08-07
• Subjects: global crop model -- agricultural management -- Community Land Model -- Earth system modeling; Geobiology -- Periodicals; Biogeochemistry -- Periodicals; Biotic communities -- Periodicals; Geophysics -- Periodicals; 577.14
• DOI: 10.1029/2019JG005529
• Languages: English
• ISSNs: 2169-8953

Abstract

Abstract: Agricultural expansion and management have greatly increased global food production and altered Earth's climate by changing physical and biogeochemical properties of terrestrial ecosystems. Few Earth system models represent agricultural management practices due to the complexity of the interactions between human decisions and biological processes on global scales. We describe the new capabilities of representing crop distributions and management in the Community Land Model (CLM) Version 5, which includes time‐varying spatial distributions of major crop types and their management through fertilization and irrigation, and temperature‐based phenological triggers. Including active crop management increases peak growing season gross primary productivity (GPP), increases the amplitude of Northern Hemisphere net ecosystem exchange, and changes seasonal and annual patterns of latent and sensible heat fluxes. The CLM5 crop model simulates the global observed historical trend of crop yields with relative fidelity from 1850 to 1990. Cropland expansion was important for increasing crop production, especially during the first century of the simulations, while fertilization and irrigation were important for increasing yields from 1950 onward. From 1990 to present day, observed crop production continued to increase while CLM5 production levels off, likely because intensification practices are not represented in the model. Specifically, CLM does not currently include increasing planting density, crop breeding and genetic modification, representations of tillage, or other management practices that may also affect crop‐climate and crop‐carbon cycle interactions and alter trends in yields. These results highlight the importance of including crop management in Earth system models, particularly as global data sets for parameterization and evaluation become more readily available. Plain Language Summary: While agricultural expansion and management practices are critical for increasing global food production, there is limited understanding of how they impact fluxes of carbon, water, and energy from the land surface to the atmosphere. Global land models are useful for understanding these possible climate impacts, yet few global land models explicitly represent crops or crop management given the complexity of interactions between human decisions, crop phenology, and land processes at global scales. Our analysis illustrates that representing specific crop types, as well as irrigation and fertilization, in the Community Land Model (CLM) increases the amount of carbon that plants draw out from the atmosphere and also changes patterns of evapotranspiration. Additionally, crop yield estimates from CLM compare well to observed crop yields until ~1990, when modeled crop yields level off. This occurs because CLM does not represent management practices associated with modern agricultural intensification. Overall, our results illustrate the impact that crop expansion and management may have on climate and highlight that global models should represent specific crop types and crop management to accurately capture carbon, water, and energy fluxes from the land surface. Key Points: The Community Land Model (CLM) globally represents specific crop types and agricultural management practices Representing crop distribution and management in CLM changes carbon, water, and energy fluxes from the land surface CLM simulates observed crop yields through most of the historical period and can be used to evaluate management within the Earth system