Abstract

ORTEGA-ROSAS, Carmen Isela; PENALBA, M. Cristina; LOPEZ-SAEZ, José Antonio  and  VAN DEVENDER, Thomas R.. The pine-oak forest in the Sierra Madre Occidental, Sonora, northwestern Mexico, a thousand years ago. Act. Bot. Mex [online]. 2008, n.83, pp.69-92. ISSN 2448-7589.

The Ciénega de Camilo is a Sphagnum palustre seep in a canyon in dense pine-oak forest with four species of pine and seven of oak in the Sierra Madre Occidental of eastern Sonora, Mexico. Analyses of pollen and non-pollen palynomorphs in two sediment cores show that pine-oak forest has been at the site during the last thousand years. When sedimentation began about 1000 years ago (1058 ±60 and 870 ±70 cal. BP (calibrated years before present)), pine was more abundant than today with an additional species with large pollen grains now present at higher elevation. The abundance and diversity of ferns were higher. Non-pollen palynomorphs suggest moister (presence of Copepoda), and eu- to mesotrophic conditions at the base, followed by drier conditions (unidentified amerospores, type 55A, Zygnemataceae, and Pediastrum), leading to the most recent mesotrophic-ombrotrophic environment characterized by Pleospora, type 82E, and the Sphagnum palustre seep. The inferred wet period at around 1000 cal. BP followed by drier and warmer climates is contemporaneous with the maximum development of the Sonoran and Chihuahuan desert archeological cultures.

Keywords : climate change; Late Holocene; Mexico; non-pollen palynomorphs; palaeoecology; pollen.

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