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Knowledge of aboveground biomass, or standing crop, is required in many agricultural and rangeland applications, as standing crop constitutes both amount of forage available for grazing and fuel available for burning. But measurement can be tedious, time-consuming, and doing so directly involves clipping and removal of biomass. Many non-destructive biomass sampling methods are either imprecise or require too broad of an area to sample experimental plots. We sought to develop a method of non-destructive biomass sampling that is both rapid and precise enough to accurately represent standing crop at fine spatial scales in northern mixed grass prairie. We measured leaf area index (LAI) based on above- and below-canopy photosynthetically active radiation (PAR) readings using a ceptometer (Accupar LP-80). High-biomass plots generate a larger difference in above- and below-canopy PAR and a greater LAI value: the greater the leaf area in a plot, the less radiation hits the below-canopy sensor. We purposely sampled quadrats along a gradient of low to high biomass. Canopy cover of functional groups, visual obstruction, litter depth, and degree of biomass �uprightness� were also measured on each quadrat, to identify additional factors that could improve fit in linear models. We clipped and sorted biomass into live and dead categories by functional groups, dried, and weighed. Preliminary analysis indicated that leaf area index alone is a good predictor of biomass (R2 = 0.85). Further analyses will extend calibration work to additional prairie types and will test whether structural and compositional variables improve linear model fit. This non-destructive method will allow us to determine fuel loads immediately ahead of prescribed fire.