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United States Department of Agriculture

Agricultural Research Service

Research Project: DEVELOPMENT OF MODELS AND CONSERVATION PRACTICES FOR WATER QUALITY MANAGEMENT AND RESOURCE ASSESSMENTS

Location: Grassland, Soil and Water Research Laboratory

Title: Switchgrass leaf area index and light extinction coefficients

Authors
item Kiniry, James
item Johnson, Mari-Vaughn
item Mitchell, Robert
item Vogel, Kenneth
item Kaiser, Jerry -
item Bruckerhoff, Steve -
item Cordsiemon, Ron -

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 5, 2010
Publication Date: January 10, 2011
Citation: Kiniry, J.R., Johnson, M., Mitchell, R., Vogel, K.P., Kaiser, J., Bruckerhoff, S.B., Cordsiemon, R.L. 2011. Switchgrass leaf area index and light extinction coefficients. Agronomy Journal. 103(1):119-122.

Interpretive Summary: Computer models that predict plant production simulation often depend on accurate simulation or measurement of leaf light interception. With the recent interest in converting large tracts of land to biofuel species cropping, modeling vegetative yield with greater accuracy has become more imperative. We investigated the stability of the light extinction coefficient (k) in Beer’s Law to identify sources of error that might affect simulations of biomass yields for the important biofuel species switchgrass (Panicum virgatum L.). Data used included measurements on Alamo switchgrass for 56 dates over multiple years at Temple, TX and single date measurements on various switchgrass cultivars and Miscanthus (Miscanthus X giganteus) at Lincoln, NE and Elsberry, MO. Variability in k values was not related to fraction of light intercepted , time of day, or incident light level. Only the magnitude of leaf area index (LAI) showed a significant impact on the k value. The mean k value for the pooled Alamo switchgrass data at Temple (k=-0.37) was similar to the previously published k value for Alamo switchgrass (k=-0.33) and similar to Alamo k values in Nebraska (k=-0.31) and Missouri (k=-0.38). Other switchgrass cultivars showed k values similar to Alamo’s in Nebraska (mean k=-0.29), but were higher than Alamo’s in Missouri (mean k=-0.89). However, the LAI values for non-Alamo cultivars at Missouri were lower (mean LAI = 3.9) than they were at Nebraska (mean LAI = 14.3). We conclude that, of the potential sources of variability explored, only LAI affected k, with higher LAI values associated with lower k values. Beer’s Law promises to continue to be a valuable system of simulating fraction of light interception of Alamo switchgrass and other important biofuel grasses.

Technical Abstract: Biomass production simulation modeling for plant species is often dependent upon accurate simulation or measurement of canopy light interception and radiation use efficiency. With the recent interest in converting large tracts of land to biofuel species cropping, modeling vegetative yield with greater accuracy has become more imperative. We investigated the stability of the light extinction coefficient (k) in Beer’s Law to identify sources of error that might affect simulations of biomass yields for the important biofuel species switchgrass (Panicum virgatum L.) Data used included measurements on Alamo switchgrass for 56 dates over multiple years at Temple, TX and single date measurements on various switchgrass cultivars and Miscanthus (Miscanthus X giganteus) at Lincoln, NE and Elsberry, MO. Variability in k values was not related to fraction of light intercepted (P=0.86), time of day (P=0.48), or incident solar radiation (P=0.09). Only the magnitude of leaf area index (LAI) showed a significant impact on the k value (P=0.0001). The mean k value for the pooled Alamo switchgrass data at Temple (k=-0.37) was similar to the previously published k value for Alamo switchgrass (k=-0.33) and similar to Alamo k values in Nebraska (k=-0.31) and Missouri (k=-0.38). Other switchgrass cultivars showed k values similar to Alamo’s in Nebraska (mean k=-0.29), but were higher than Alamo’s in Missouri (mean k=-0.89). However, the LAI values for non-Alamo cultivars at Missouri were lower (mean LAI = 3.9) than they were at Nebraska (mean LAI = 14.3). We conclude that, of the potential sources of variability explored, only LAI affected k, with higher LAI values associated with lower k values. Beer’s Law promises to continue to be a valuable system of simulating fraction of light interception of Alamo switchgrass and other important biofuel grasses.

Last Modified: 8/19/2014
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