In situ study of decadal (1980-2009) losses of natural fire-BC in a temperate forest soil In this field study, temperate forest soils were collected ~ 30 years apart from a plot that has remained unmanaged since the entire area was exposed to intense logging and burning until approximately 1911. The field site is part of a set of permanent experimental plots that has developed into a 100-year fire chronosequence (1). The soil in this experimental plot is a deep, sandy and excessively-drained spodosol. Methods University of Michigan Biological Station soils Soils and field site Soils were collected in summer 1980 and 2009 from a plot affected by intense logging and burning until 1911 at the University of Michigan Biological Station in northern lower Michigan, USA (White et al. 2004, Gough et al. 2007). The region is in the transition zone between mixed hardwood and boreal forests, where the mean annual temperature and precipitation is 5.5oC and 817 mm, respectively. The soil is formed on glacial outwash, and is well-drained, entic Haplorthod (Rubicon series) with 92% sand (Gough et al. 2007). In 1980 a sampling plot with dimensions of 100m x 120m was selected, and soils were sampled at three different depths (A, E, and B horizons; composite of 5 samples) at 12 sites along three transects. These samples were air-dried, sieved and kept at the UMBS soil archive. In 2009 the same sampling design was established in an adjacent plot approximately 30 m from the 1980 sampling site. A sampling plot with dimensions of 100m x 120m was selected, and soils were sampled at four selected points equally spaced along three 120 m transects. At each sampling point, a soil composite was formed by combining 5 soil cores taken within 1 meter radius around the sampling point. These soils were air-dried and sieved (< 2mm). Soil samples collected in summer 2009 and 1980 were shipped to Dr. Bird’s lab at QC. Additional soil samples were collected in 2009 for bulk density determination. Soil samples collected in 2009 were sieved using a 2mm size sieve, and observed charcoal particles > 2mm were stored in ziploc bags for further analyses. Measurements Soil bulk density Bulk density was determined at the UMBS facility by oven drying soils collected from soil cores at 60oC until they reached constant mass. In this study, soil bulk density values are needed to convert organic carbon content to mass of soil organic carbon per unit area. Total C and N contents in soil A subsample of 2009 and 1980 bulk soil samples (< 2mm) will be ground, and analyzed for carbon and nitrogen contents using a CHN gas analyzer (Costech Model 4010). Benzenes Polycarboxilic acids (BPCAs) (H1) Ball-milled soil samples will be digested with nitric acid and purified at Queens College. Each individual BPCA released from the oxidation of charred materials will be identified and quantified using a GC coupled with a flame ionization detector (FID) as described by Brodowski et al. (2005). References Gough, C. M., C. S. Vogel, K. H. Harrold, K. George and P. S. Curtis, 2007: The legacy of harvest and fire on ecosystem carbon storage in a north temperate forest. Global Change Biology 13, 1935-1949. Hammes, K., Schmidt, M.W.I., Smernik, R.J., Currie, L.A., Ball, W.P., Nguyen, T.H., Louchouarn, P., Houel, S., Gustafsson, Ö., Elmquist, M., 2007. Comparison of quantification methods to measure fire-derived (black/elemental) carbon in soils and sediments using reference materials from soil, water, sediment and the atmosphere. Global Biogeochemical Cycles 21, GB3016. Hammes, K., Smernik, R.J., Skjemstad, J.O., Schmidt, M.W.I., 2008a. Characterisation and evaluation of reference materials for black carbon analysis using elemental composition, colour, BET surface area and C-13 NMR spectroscopy. Applied Geochemistry 23, 2113–2122. Schmidt, M.W.I., Skjemstad, J.O., Gehrt, E., Kogel-Knabner, I., 1999. Charred organic carbon in German chernozemic soils. European Journal of Soil Science 50, 351-365. Schneider, M.P.W., Hilf, M., Vogt, U.F., Schmidt, M.W.I., 2010. The benzene polycarboxylic acid (BPCA) pattern of wood pyrolyzed between 200° C and 1000° C. Organic Geochemistry 41, 1082-1088. White, L. L., D. R. Zak and B. V. Barnes, 2004: Biomass accumulation and soil nitrogen availability in an 87-year-old Populus grandidentata chronosequence. Forest Ecology and Management 191, 121-127.