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A 23,000-year microscopic charcoal record from Anderson Pond, Tennessee, USA (2017)

Ballard, J. P., Horn, S. P., Li, Z.-H.

American Association of Stratigraphic Palynologists (AASP)

In: Palynology

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Publication Date: 2017-06-03

Description: Charcoal records of past fires are important for reconstruction of palaeoenvironments and palaeoclimate, particularly when compared with pollen records of past vegetation, but such records are scarce in the southeastern US. To address the question of how fire activity changed from the Last Glacial Maximum (LGM) into the Holocene as vegetation changed, we chose a site in central Tennessee for which a pollen record exists back to 23,000 cal yr BP. We developed a new microscopic charcoal record based on point counting of microscopic charcoal fragments on pollen slides from Anderson Pond studied by Hazel Delcourt (1979) . The record we produced spans the interval from the LGM to recent and is directly tied to the original pollen record. Charcoal:pollen ratios and charcoal area concentrations are high during the late glacial and track the coniferous pollen record from the LGM to the late glacial, at which point spruce and jack pine pollen markedly diminished along with fire activity. From around 15,000 cal yr BP to the beginning of the middle Holocene, charcoal indices are low. High fire activity began around 8200 cal yr BP, and remained high from ca. 8200–5000 cal yr BP, an interval broadly corresponding to the Mid-Holocene Warm Period (MHWP). The evidence of higher fire activity during the MHWP is coincident with increased percentages of indeterminate pollen grains that are interpreted to signal drier conditions. Charcoal area concentrations declined following the MHWP. Viewed against the original pollen record, the patterns in microscopic charcoal abundance from the LGM to recent at Anderson Pond argue for the strong influence of vegetation as well as climate in driving fire occurrence in eastern temperate North America.

Print ISSN: 0191-6122

Electronic ISSN: 1558-9188

Topics: Geosciences

Published by American Association of Stratigraphic Palynologists (AASP)

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Norepinephrine inhibits calcium-dependent potentials in rat sympathetic neurons (1979)

J. P. Horn ; D. A. McAfee

American Association for the Advancement of Science (AAAS)

In: Science. 204(4398): 1233-5.

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Publication Date: 1979-06-15

Description: Norepinephrine reversibly antagonizes three calcium-dependent potentials recorded from rat postganglionic neurons. Norepinephrine inhibits the development of a shoulder on the aciton potential, the magnitude of the hyperpolarizing afterpotential, and the rate of rise and amplitude of the calcium spike. The action of norepinephrine is antagonized by the alpha-adrenergic antagonist phentolamine, but not by MJ 1999, a beta-adrenergic antagonist. These results suggest that activation of an alpha-adrenergic receptor may antagonize a voltage-sensitive calcium current.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Horn, J P -- McAfee, D A -- New York, N.Y. -- Science. 1979 Jun 15;204(4398):1233-5.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/221979" target="_blank"〉PubMed〈/a〉

Keywords: Animals ; Calcium/antagonists & inhibitors/*physiology ; Dopamine/pharmacology ; Electric Conductivity ; Ganglia, Autonomic/*drug effects ; In Vitro Techniques ; Ion Channels/*drug effects ; Isoproterenol/pharmacology ; Membrane Potentials/*drug effects ; Neurons/drug effects ; Norepinephrine/*pharmacology ; Rats ; Receptors, Adrenergic, alpha/drug effects

Print ISSN: 0036-8075

Electronic ISSN: 1095-9203

Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics