Summary Diatom assemblages for 3 cores from the center, moat and surrounding burn (0, 12, and 30 m) of the BBC collapse scar

• Other Authors: F.S.Chapin, JenniferHarden, A.McGuire
• Format: Dataset
• Language: unknown
• Published: Bonanza Creek LTERBoreal Ecology Cooperative Research Unit University of Alaska FairbanksP.O. Box 756780 FairbanksAK99775USA907-474-6364907-474-6251 2005
• Subjects: moat; diatoms; fires; macrofossil; bog; density; carbon; nitrogen; soil samples; charcoal; Bonanza; Fairbanks; Kathleen; Moser; permafrost; Alaska
• Online Access: http://hdl.handle.net/10255/dryad.18167; http://metacat.lternet.edu/knb/metacat/knb-lter-bnz.189.8/xml

This data set contains diatom assemblages for 3 cores from the center, moat and surrounding burn (0, 12, and 30 m) of the BBC collapse scar. Three well-preserved cores were collected in March 2003 with a gasoline-powered permafrost corer. Cores were stored frozen and sampled using a radial saw. The cores were sampled every two cm for macrofossil, diatom analysis and chemistry. Diatoms have been shown to be a useful indicator of peatland succession, local hydrology, and fire disturbance (Kienel et al., 1999, Moser et al., 2000, Rühland et al., 2000). Diatoms are more sensitive to changes in water levels than the commonly used peat indicators such as pollen and macrofossil analysis (Rühland et al., 2000). In this study, we employed diatom analysis to indicate shifts in water chemistry and to ascertain the response of this ecosystem to disturbance. To survey the diatom community, we processed three cores sampled every 2 cm by depth from the bog, moat and burn using methods described by the Paleoecological Environmental Assessment and Research Laboratory (PEARL) at Queen’s University and personal communications (Kathleen Rühland and John P. Smol). We digested the dried material, consisting of organic matter with varying amounts of sediment, in Kjeldahl digestion tubes in a heating block. We used 50:50 solution by molecular weight of concentrated H2SO4 and HNO3 and digested for 3 days at 95?C or until the disappearance of all organic matter. We diluted the resulting solution with deionized water to a neutral pH. We mounted the samples using the Pleurax high refractive index mounting medium (prepared by W. Dailey, University of Pennsylvania). To determine the prevalence of the different diatoms, we counted 400 valves (or for one sparse sample, four slides) for each sample. We identified samples according to Foged (1981), Krammer and Lange-Bertalot (1991) and personal communications with K. Rühland. We measured bulk density, %C and %N for all soil samples. We oven-dried at 50 - 65°C and ground all samples before analysis. We analyzed samples for %C and %N using a Carlo Erba EA1108 CHNS analyzer (CE Instruments, Milan, Italy) and a COSTECH ECS 4010 CHNS-O analyzer (Costech Analytical Technologies Inc., Valencia, CA,USA). Sample standard errors were ± 0.01% for nitrogen, ± 0.45% for carbon. To indicate fire events in the surrounding ecosystem, charcoal layers in the cores were quantified. We estimated charcoal by emptying dried samples of a known volume and depth (on mean 4.5 cm3) over a 10 cm x 10 cm grid and counting macroscopic charcoal fragments (greater than 0.05 mm in diameter) in each cm grid cell.