PARENT SESSION
Oral Session #40: Carbon sequestration and flux.
Presiding: G. Koch
Tuesday, August 6. 1:00 PM to 4:45 PM. Gila Meeting Room, TCC.

Tree species effects on soil carbon: a case study using molecular beam mass spectrometry.

Hoover, Coeli^*,1, Magrini, Kimberly², Evans, Robert², ¹ USDA Forest Service, Irvine, PA² National Renewable Energy Laboratory, Golden, CO

ABSTRACT- A new analytical technique, molecular beam mass spectrometry (MBMS), offers the opportunity to quickly assess carbon content and character in forest soils without the use of time-intensive wet chemical techniques or intensive sample preparation. Since carbon forms have different lifetimes, the ability to gather such information on a large scale can assist in the development of more realistic soil carbon cycling models. In an Allegheny hardwood stand, soil samples were taken on transects from the base of the stem to a distance of 5m from trees of different species. Samples were taken at depths of 0-10 cm and 10-20 cm, and were air dried, sieved to pass 2mm mesh, and then analyzed in triplicate by pyrolysis molecular beam mass spectrometry (py-MBMS). Principal component analysis and discriminant analysis were used to reduce the complex mass spectra and characterize the chemical nature of the soil carbon in the samples. The analyses were able to distinguish chemical differences in carbon from samples near hemlock versus hardwood species, with hemlock soils near the base of the stem displaying a predominance of carbohydrate derived pyrolysis products (characteristic of more recent biomass), and samples further from the hemlock stem distinguished by the presence of more aromatic compounds. Work continues to further understand and predict the effects of tree species on soil carbon content and character to assist in the parameterization of soil carbon models.

KEY WORDS: soil carbon, mass spectrometry, carbon cycling