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Abstract: Permineralized infructescences are described from the Cerro del Pueblo Formation, Coahuila, Mexico. Morphological and anatomical observations of 584 infructescences support the identification and reconstruction of an infructescence, with fruit [...]

Abstract: The Princeton chert is one of the most completely studied permineralized floras of the Paleogene. Remains of over 30 plant taxa have been described in detail, along with a [...]

Abstract: The Early Eocene (Ypresian) London Clay Formation contains one of the most important fruit and seed assemblages from the Paleogene, including a large diversity of taxa (>350 spp.) preserved [...]

Abstract: Hybridization is a key mechanism for increased diversification and speciation among modern plants and is especially important in certain families such as Rosaceae and Anacardiaceae. This mechanism is found [...]

Abstract: The history of plant fossil collecting in the Okanagan (Okanogan) Highlands of British Columbia and northeastern Washington is closely intertwined with the history of geological surveys and mining activities [...]

Abstract: Published estimates on the paleoclimate of the Florissant fossil beds site of Colorado (34.1 Ma) have led to extremely different estimates of paleoelevation. The purpose of this paper is [...]

Five Neogene floras in southern Washington and northwest Oregon indicate that the uplift of the Cascade Range occurred after ~8-6 Ma. Miocene floras west of the range (Wilkes and Faraday floras) resemble paleofloras of correlative age to the east (Rattlesnake Hills, Palouse Falls, and lower Ringold). The statistical similarity of Miocene floras east and west of the Cascade Range axis demonstrates that a similar mesic, warm climate across the Pacific Northwest existed during the Middle and Late Miocene. These floras represent mixed hardwood-conifer forests that commonly contained Taxodium (bald cypress) and other mesophytic taxa. Based on Jaccard similarity coefficients calibrated with climatic data from modern plant communities, these paleofloras indicate a climate that was summer-wet, unlike that of the Pacific Northwest today. The annual precipitation was >100 cm, and the estimated mean annual temperatures of the fossil sites were 12-13°C. The Miocene floras indicate that the development of a Cascade rain shadow in eastern Washington did not develop until after the deposition of the lower Ringold Formation in eastern Washington. That conclusion is reinforced by a well-documented climate and sediment sequence in the Snake River Valley, Idaho. There, well-dated pollen sections record a sharp decrease (by ~30%-50%) in the annual precipitation regime after the Late Miocene Banbury Basalt and Poison Creek formations and before ~3.4 Ma. The existence of extensive late Ringold sediments uplifted on the north side of Saddle Mountain indicates that the structural lifting of the Cascade Range had begun by 3.1 Ma (Pliocene). These data all suggest that the lifting of the Cascades occurred after Miocene time, and that the Cascade rain shadow developed during the Pliocene. Cinq flores neogenes du sud de l'Etat de Washington et du nord-ouest de l'Etat de l'Oregon indiquent que le soulevement de la chaine des Cascades s'est produit plus recemment que ~8 a 6 Ma. Les flores du Miocene a l'ouest de la chaine (les flores de Wilkes et de Faraday) ressemblent aux paleoflores d'un age correlatif a l'est (les collines Rattlesnake, les chutes de Palouse et la Formation de Ringold inferieure). La similarite statistique des flores miocenes a l'est et a l'ouest de l'axe de la chaine de Cascades demontre qu'un climat similaire chaud et mesique existait a travers le nord-ouest du Pacifique au Miocene moyen et tardif. Ces flores representent des forets mixtes de coniferes et de feuillus qui contenaient generalement Taxodium (cypres des marais) et d'autres taxons mesophiles. En se basant sur les coefficients de similarite de Jaccard, etalonnes avec des donnees climatiques de communautes de plantes modernes, ces paleoflores indiquent un climat qui etait humide en ete, ce qui n'est pas le cas dans le nord-ouest du Pacifique de nos jours. La precipitation annuelle etait alors > 100 cm et la temperature moyenne annuelle, estimee des sites fossiliferes, etaient de 12 a 13°C. Les flores du Miocene indiquent qu'une ombre pluviometrique des Cascades, dans l'est de l'etat de Washington, s'est developpee seulement apres la deposition de la Formation de Ringold inferieure dans l'est de l'Etat de Washington. Cette conclusion est appuyee par une sequence sedimentaire et climatique bien documentee dans la vallee de la riviere Snake, en Idaho. La, des sections de pollen datees correctement enregistrent une soudaine decroissance (d'environ 30 a 50 %) dans le regime de precipitation annuelle apres la generation, au Miocene tardif, des formations du basalte de Banbury et de Poison Creek, et avant ~3,4 Ma. L'existence de sediments extensifs datant du Ringold tardif, souleves sur le flanc nord du mont Saddle, indique que le soulevement structural de la chaine des Cascades avait debute des 3,1 Ma (Pliocene) Selon ces donnees, le soulevement des Cascades s'est produit apres le Miocene et l'ombre pluviometrique des Cascades s'est developpee au cours du Pliocene. [Traduit par la Redaction], Introduction The Cascade Range casts a rain shadow eastward, causing present-day plant and animal communities on the eastern and western sides of the Cascade Range to be different: The western [...]

1. The effects of precipitation on litter quality and surface litter decomposition were evaluated across a natural rainfall gradient, ranging from 500 to 5500mm mean annual precipitation, on the island of Hawaii. 2. Litter of Metrosideros polymorpha from the driest (500 mm) and wettest (5500 mm) extremes of the gradient was decomposed at five sites along the precipitation gradient. Metrosideros polymorpha litter collected from all sites was also decomposed at a single common site (2500 mm), and M. polymorpha litter collected from each site was decomposed at the site of collection (in situ). 3. Initial litter quality varied significantly with precipitation at the site. Leaf mass per area (LMA) and phosphorus content decreased, while lignin and nitrogen content both increased, with increasing site precipitation. 4. Mass loss of all common litter types increased with increasing precipitation, as did in situ decomposition, which gave k-values ranging from 0.22 to 1.06. When decomposition at the same site was evaluated, litter from the driest site decomposed up to 2.5 times more rapidly than wet-site litter. 5. Decomposition at the common site showed an inverse correlation between inherent decomposability of litter (i.e. litter quality) and precipitation at the site from which litter originated, with k-values ranging from 0.71 for litter from the driest site to 0.28 for litter from the wettest site. Decomposability correlated strongly and inversely with initial lignin concentrations. 6. Proportional nutrient release from in situ litter was slower than mass loss, but nitrogen and phosphorus mineralization generally increased with increasing precipitation. 7. At the common site, there was an inverse relationship between rate of nutrient release and precipitation at the site where litter was collected. The systematic variation in litter decomposability due to changes in annual precipitation appears to buffer the direct effects of precipitation on carbon and nutrient turnover. Keywords: climate, climate controls on decomposition, decomposition, Hawaii, lignin and nitrogen effects on litter quality, mass loss, Metrosideros polymorpha, N, nutrient release, P, rainfall