Fossil pollen assemblages from Cliff Palace Pond, Kentucky, characterize changes in forest composition through the past 9,500 years of the Holocene. Early-Holocene spruce and northern white cedar stands were replaced by mixed mesophytic forests after 7300 B.P. Hemlock declined around 4800 B.P., and eastern red cedar became locally important. After 3000 B.P, mixed oak-chestnut and pine forests were dominant. The fossil charcoal record from Cliff Palace Pond demonstrates that Late Archaic and Woodland peoples cleared forest gaps to cultivate native plants in the Eastern Agricultural Complex and that anthropogenic fires served to increase populations of fire-tolerant oaks, chestnut, and pines in upland forests of the northern Cumberland Plateau.

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Auroral optical emission rates, absence of quantities such as the incoming thermal ion and electron densities, and low-energy particle flux, the neutral atmosphere, the time electron fluxes were measured in an IBC I aurora history of the aurora, and a steady aurora [see by a rocket-borne payload, simultaneously with the Donahue et al., 1970; Swider and Narcisi, 1977; overpass of the Atmosphere Explorer C satellite. Auroral ionization rates deduced from the rocket both electron impact on atomic oxygen and dissoci-was planned to fulfill the above requirements. ative recombination of 0•. The AE-C motor was used to adjust the satellite orbit to pass over the Churchill Research Range

Abstract. A ground-based and rocket investigation of the response of the neutral atmosphere to E region auroral heating has been carried out at Poker Flat, Alaska. The temporal evolution of the atomic oxygen to molecular nitrogen ratio (O/N2) in the lower thermosphere has been monitored using the optical emissions from the aurora as a diagnostic. Comparisons between the changes in the O/N 2 ratio and the auroral Joule and particle heating have shown several examples of close similarity between the durations of the heating events and the depletions. Using the thermospheric winds measured during the rocket flights and the temporal structure of the depletions, the upper limit on the horizontal scale size of the depletions has been estimated at 200-400 km. Moreover, in situ rocket measurements of atomic oxygen showed significant differences at points separated horizontally by approximately 220 km. It is also concluded from the near coincidence between the depletion events and the Joule heating events that the dynamical mechanism(s) that drive the depletions were not far distant from the observing site, that is, local processes are sometimes dominant • during periods of moderate auroral activity.We suggest that the observation of a strong wind shear in the 100-to 120-km altitude region [Larsen et al., 1997] could be responsible for turbulence that contributes to the changes in minor constituent composition.

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