Analyses of Forest Foliage I: Laboratory Procedures for Proximate Carbon Fractionation and Nitrogen Determination

Abstract

As part of NASA's Accelerated Canopy Chemistry Program we performed analyses for the determination of carbon constituents and nitrogen content in fresh forest foliage. Foliage from three deciduous species was collected for carbon fraction analysis. Samples were analysed using a series of extractions that yielded different carbon constituents: non-polar, polar, cellulose and lignin. Results showed this to be a satisfactory method for carbon fractionation. Coefficient of variation within and between runs was less than 10%. These results were further supported by an interlaboratory comparison involving two other labs and samples collected as part of NSF's LTER LIDET experiment. Variations in laboratory results were due in part to differences in ash correction calculations. Approximately 1000 additional samples were analysed by wet chemical methods and used as a calibration set for Visible/NIR reflectance. Results showed accuracy of spectrophotometric measurements to approach that of wet chemistry techniques.