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Changes for Forestry

The updated COMET-VR will allow you to generate a carbon value for Forest areas.  Currently,  this aspect is under development and revisions to the process are sure to come in the future.  The forestry tool uses the Forest Service COLE Lite software to generate carbon values. COLE enables the user to examine forest carbon characteristics of any state in the continental United States. COLE data are based on USDA Forest Service Forest Inventory & Analysis and Resource Planning Assessment data, enhanced by other ecological data.

Updated Rotations and Management Scenarios

The COMET-VR Tool now has a host of new management scenarios for agriculture.  These new scenarios were developed to describe rotations sampled on the NRI MLRA's and are attributed at the county level.

Modern crop rotations (1970- present) were developed for each modified MLRA based on 1997 NRI data. These include non-irrigated and irrigated systems, which represent the dominant crop rotations in each region. Individual crop files were developed to represent higher grain yields, increases in plant bio-mass and nitrogen fertilizer additions. To represent the change in land management due to the Conservation Reserve Program (CRP), the non-irrigated crop rotations were also modeled showing the conversion to grass starting in 1986. Irrigation was represented in the model starting in 1970 and provided all the necessary water required by the plant to meet potential evapotranspiration.

COMET-VR has some new innovative cropping practices like the addition of "pulse" crops made up of field peas and green cover crops. Updating COMET-VR for fruit and nut orchards is also being looked at.

Updated Carbon Calculations using Century 4.5

COMET-VR will be transitioned to use Century 4.5.  This version of the Century agro-ecosystem model represents a major change in the technical aspects of the model implementation, and includes new algorithms and structures for the physical soil, erosion, deposition, and depth distribution of organic C.   The changes to COMET-VR will consists of monthly and daily time-step versions.  This will be completed sometime in the future.

Updated Uncertainty Estimates

The COMET-VR Tool uncertainty estimates will be enhanced with a new algorithm and ground truth data.  The uncertainty estimate modifications are PLANNED improvements that will be completed in the upcoming months.

To assess the uncertainty of the model results, we are modeling over 40 long term research sites (refer to locations on LRR Inset and Sample Site map) that have the necessary data inputs for the Century model. These data allow for the ability to capture the uncertainty in C changes due to the implementation of conservation systems in these areas. For the areas of the U.S. not represented by long term research sites, an analysis will be made to determine the uncertainty of the model results and may result in some areas not having uncertainty estimates for the Century model results.

DayCent Calculations

The Century DAYCENT Model Analysis is being transitioned into the COMET-VR Tool to provide accurate estimates of Agricultural Soil N2O and Net Greenhouse Gas (GHG) changes.

The DAYCENT ecosystem model will be used to estimate direct and indirect N2O emissions, NO3 leaching, a major contributor to indirect N2O emissions, and net greenhouse gas fluxes for agricultural systems in the USA. DayCent includes maintenance respiration, daily soil hydrology and soil temperature submodels, and trace gas submodels.

N2O fluxes estimated by DAYCENT and NO3 leaching estimates will be compared with field data for different cropping systems to determine uncertainty estimates.

To estimate national GHG fluxes, the USA was divided into NRCS MLRA agricultural regions and the primary cropping systems represented by NRCS NRI data in each region were simulated. Decadal mean N2O, CO2, and CH4 fluxes were estimated for the USA using DAYCENT.

The GHG/DayCent modifications are PLANNED improvements and a target completion date has not been determined.