U.S. flagAn official website of the United States government
                    Here's how you know **Official websites use .gov**
                            
                            A **.gov** website belongs to an official government organization in the United States.
 **Secure .gov websites use HTTPS**
                            
                            A **lock** (                            
                              A locked padlock                                                      
                            
                            ) or **https://** means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.


Menu Agricultural Research Service
						
                    U.S. DEPARTMENT OF AGRICULTURE
 Soil and Water Management Research: St. Paul, MN
 close



    Research

                    Research Projects
                                    Publications
                                    Collaborations
                                    News
                                    Software
                People

                    Staff Listing
                                    CareersSearch small
                    Search
            
            ARS Home
                                About ARS
                                Contact Us




ARS Home Midwest Area St. Paul, Minnesota Soil and Water Management Research Research Publications at this Location





- ARS National Programs
- Search for a scientific manuscript
- Search for a research project
- ARS Software
- Programs and Projects
- Collaborations
- Subjects of Investigation
- Publications

Title:   Author  item
                                            CHEN, MING - University Of Minnesotaitem
                                            GRIFFIS, TIMOTHY - University Of Minnesotaitem
                                            Baker, Johnitem
                                            WOOD, JEFFREY - University Of Minnesotaitem
                                            XIAO, KE - University Of Minnesota
  Submitted to: Journal of Geophysical Research-Biogeosciences
                                    Publication Type: Peer Reviewed Journal
                                    Publication Acceptance Date: 1/24/2015
                                    Publication  Date: 2/26/2015
                                    Publication URL: https://handle.nal.usda.gov/10113/60455Citation: Chen, M., Griffis, T.J., Baker, J.M., Wood, J.D., Xiao, K. 2015. Simulating crop phenology in the Community Land Model and its impact on energy and carbon fluxes. Journal of Geophysical Research: Biogeosciences. 120(2):310-325. DOI: 10.1002/2014JG002780.Interpretive Summary: Global climate models (GCMs) are a valuable tool to predict the impact of rising greenhouse gas concentrations on climate. Among the key processes that they must simulate are the exchange of heat, water, and carbon dioxide  between the surface and the atmosphere. To this point, most land-atmosphere schemes in such models have been developed with data from natural ecosystems, so they do not perform well in agricultural regions. Recently, however, several new land surface schemes have been developed to address this deficiency. We tested two of them (CLM4-Crop and CLM-CornSoy) against measured data from agricultural fields at Rosemount, MN. The results indicated that accuracy, particularly in predicting CO2 exchange, was heavily dependent on accurate  representation of phenology, i.e. the timing of planting, emergence, and harvest. The models consistently overestimated early season growth, and also overestimated net (absorbed) radiation, probably due to unrealistic assumptions about the leaf angle distribution in corn and soybeans. Finslly, one of the models, CLM4-Crop, overestimated the fraction of roots  in deep soil layers, which apparently caused it to underestimate soil moisture. These results will be useful in improving these models, leading to more accurate GCM results.
                                Technical Abstract: A reasonable representation of crop phenology and biophysical processes in land surface models is necessary to accurately simulate energy, water and carbon budgets at the field, regional, and global scales. However, the evaluation of crop models that can be coupled to earth system models is relatively rare. Here, we evaluated two such models (CLM4-Crop and CLM-CornSoy), both implemented within the Community Land Model (CLM) framework, at two AmeriFlux corn-soybean sites to assess their ability to simulate phenology, energy, and carbon fluxes. Our results indicated that the accuracy of net ecosystem exchange and gross primary production simulations was intimately connected to the phenology simulations. The CLM4-Crop model consistently overestimated early growing season leaf area index, causing an overestimation of gross primary production, to such an extent that the model simulated a carbon sink instead of the measured carbon source for corn. The CLM-CornSoy simulated LAI, energy, and carbon fluxes showed stronger correlations with observations compared to CLM4-Crop. Net radiation was biased high in both models and was especially pronounced for soybeans. We hypothesize that the leaf optical parameter, 'L, needs to be modified towards a more horizontal leaf angle distribution to better represent crops. CLM4-Crop overestimated deep root fraction and underestimated soil water content during mid-growing season in all soil layers at the two sites, which caused unrealistic water stress, especially for soybean. Future work regarding the detailed parameterizations of leaf angle and root distributions and early growing season phenology is needed to improve crop simulations within CLM.


Return to top


Connect with ARS Sign up


ARS Home
                            USDA.gov
                            Plain Writing
                            Policies & Links
                            Civil Rights Statements
                            FOIA
                            Accessibility Statement
                            Privacy Policy
                            Non-Discrimination Statement
                            Quality of Information
                            USA.gov
                            WhiteHouse.gov