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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: Novel application of ALMANAC: Modelling a functional group, exotic warm-season perennial grasses

Authors
item Kiniry, James
item Johnson, Mari-Vaughn
item Venuto, Bradley
item Burson, Byron

Submitted to: American Journal of Experimental Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 6, 2013
Publication Date: May 16, 2013
Citation: Kiniry, J.R., Johnson, M., Venuto, B.C., Burson, B.L. 2013. Novel application of ALMANAC: Modelling a functional group, exotic warm-season perennial grasses. American Journal of Experimental Agriculture. 3(3):631-650.

Interpretive Summary: Introduced perennial warm season grasses such buffelgrass and old world bluestems (OWB) such as King Ranch Bluestem have the potential to dominate landscapes. A computer simulation model that realistically simulates leaf area and plant weight production of these grasses will be valuable to simulate the impact of their establishment on forage productivity, hydrology, soil erosion, nutrient cycling, and wildlife habitat. With this in mind, our objective was to quantify the leaf area index (LAI) over the course of the growing season, the efficiency of light interception, and the amount of plant material produced per unit intercepted light (RUE) for an old world bluestem in central Oklahoma and for four buffelgrass ecotypes in south-central Texas. Subsequenly, we tested these parameters by using the ALMANAC model to simulate buffelgrass on in southern Texas and OWB in Oklahoma. Parameters were derived at two field locations, one for an exemplary King Ranch bluestem and one for buffelgrass. The OWB and the four cultivars of buffelgrass had similar values for LAI, efficiency of light interception, and RUE. The mean maximum LAI values for both species for the season were near 4.0. Overall mean RUE was 1.3 g MJ**-1 IPAR. When applying these parameters in the ALMANAC model for four combinations of soils and counties, the computer simulation model showed mean yields overall near the reported values for each of the grasses. This computer simulation model should be useful for assessing water use, soil erosion, and forage productivity over a wide range of soils and over a wide range of climatic conditions in environments conducive to establishment of these two grasses.

Technical Abstract: Introduced perennial C4 grasses such buffelgrass (Pennisetum ciliare [(L.) Link]) and old world bluestems (OWB), including genera such as Bothriochloa Kuntze, Capillipedium Stapf, and Dichanthium Willemet have the potential to dominate landscapes. A process-based model that realistically simulates leaf canopy area growth and biomass production of grasses in this functional group will be valuable to simulate the impact of their establishment on forage productivity, hydrology, soil erosion, nutrient cycling, and wildlife habitat. With this in mind, the objective of this project was to quantify the leaf area index (LAI) over the course of the growing season, the light extinction coefficient (k) for Beer’s Law, and the radiation use efficiency (RUE) for an old world bluestem in central Oklahoma and for four buffelgrass ecotypes in south-central Texas. Subsequenly, we tested these parameters by using the ALMANAC model to simulate buffelgrass on in southern Texas and OWB in Oklahoma. Parameters were derived at two field locations, one for an exemplary OWB, Plains Bluestem or King Ranch bluestem [Bothriochloa ischaemum (L.) Keng.] and one for buffelgrass. The OWB and the four cultivars of buffelgrass had similar values for LAI, light extinction coefficient (k), and RUE. The mean maximum LAI values for both species for the season were near 4 and the mean k values were near -0.5. Overall mean RUE was 1.3 g MJ**-1 IPAR. When applying these parameters in the ALMANAC model for four combinations of soils and counties, the model showed mean yields overall near the reported values for each of the grasses. This process-based model should be useful for assessing water use, soil erosion, and forage productivity over a wide range of soils and over a wide range of climatic conditions in environments conducive to establishment of these two grasses.

Last Modified: 7/30/2014
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