loading page

Empirical Approach to Estimate Net Ecosystem Exchange Using High Frequency Mesonet Observations across Potential Switchgrass Establishment Landscapes in Oklahoma
  • +1
  • Kundan Dhakal,
  • Vijaya Gopal Kakani,
  • Pradeep Wagle,
  • Sonisa Sharma
Kundan Dhakal
Oklahoma State University

Corresponding Author:kundan@okstate.edu

Author Profile
Vijaya Gopal Kakani
Oklahoma State University Stillwater
Author Profile
Pradeep Wagle
USDA-ARS Grazinglands Research Laboratory
Author Profile
Sonisa Sharma
Noble Research Institute
Author Profile


Monitoring net ecosystem carbon dioxide (CO2) exchange (NEE) using eddy covariance (EC) flux towers is quite common, but the measurements are valid at the scale of tower footprints. Alternative ways to quantify and extrapolate EC-measured NEE across potential production areas have not been explored in detail. To address this need, we used NEE measurements from a switchgrass (Panicum virgatum L.) ecosystem and detailed meteorological measurements from the Oklahoma Mesonet and developed empirical relationships for quantifying seasonal (April to October) NEE across potential switchgrass establishment landscapes in Oklahoma, USA. We identified ensemble area for potential switchgrass expansion regions and created thematic maps of switchgrass productivity using geostatistics and GIS routines. The purpose of this study was not to calibrate the model for estimating NEE in the future but to explore if model parametrizations based on high temporal frequency meteorological forcing can be used to construct reliable estimates of NEE for evaluating the source-sink status of organic carbon. Based on EC measurements, empirical models, a) rectangular hyperbolic light-response curve and b) temperature response functions, were fitted to estimate gross primary production (GPP) and ecosystem respiration (ER) on a seasonal scale. Model performance validated by comparing EC-measured seasonal NEE for three years showed good-to-strong agreement (0.29 < R2 <0.91; p < 0.05). Additionally, total seasonal NEE estimates were validated with measured biomass data in three additional locations. The estimated seasonal average net ecosystem production (NEP =-NEE) was 3.97 ± 1.92 (S.D.) Mg C ha-1. However, results based on a simple linear model suggested significant differences in NEP between contrasting climatic years. Overall, the results from this study indicate that this new scaling-up exercise involving high temporal resolution meteorological data may be a helpful tool for assessing spatiotemporal heterogeneity of switchgrass production and the potential of switchgrass fields to sequester carbon in the Southern Great Plains of the United States.