Impact of Paleocene/Eocene greenhouse warming on North American paratropical forests

The Paleocene / Eocene boundary (c. 55.2 ma) represents transient greenhous e warming of < 220 ky duration that had a critical impact upon. North Ameri can mammals but an apparently Limited impact upon subtropical plants. The e ffect of enhanced warming on biomes already tolerant of paratropical / trop ical climate conditions is essentially unknown. at the Paleocene / Eocene b oundary because most research has centered on high latitude changes in plan t turnover Fossil pollen and spores from the US Gulf Coast allow an assessm ent of the impact:that Paleocene / Eocene climate events had on a Paleo-par atropical / tropical vegetation. type. Pollen data from two marginal marine sections either side of the boundary in. Alabama, USA, demonstrate secular but subdued changes in composition that are manifest primarily as a restru cturing of the vegetation type. Taxa found in the Paleocene remain dominant in the early Eocene (greater than or equal to 89% of taxonomic groups), an d both extinction and immigration rates are moderate. Immigrants probably c ame from at least two different continents, Europe and South America, which implies a highly individualistic response of plant species from different Paleocene biomes to greenhouse warming. Diversity changes are not pronounce d across the boundary but within-sample diversity changes reflect a more he terogeneous, or possibly more successional, early Eocene vegetation type th an, the late Paleocene. This does not lead to greater between-sample divers ity because the Paleocene palynofloras are moderately more diverse, if less heterogeneous at the within-sample Level. Results imply that on time-scale s of 10(5) years, Paleocene / Eocene warming is correlative with only minor compositional and diversity changes in paratropical vegetation. types.