Development of the mixed conifer forest in northern New Mexico and its relationship to Holocene environmental change

Chihuahuenos Bog (2925 in) in the Jemez Mountains of northern New Mexico contains one of the few records of late-glacial and postglacial development of the mixed conifer forest in southwestern North America. The Chihuahuenos Bog record extends to over 15,000 cat yr BP. An Artemisia steppe, then an open Picea woodland grew around a small pond until ca. 11,700 cat yr BP when Pinus ponderosa became established. C/N ratios, delta C-13 and delta N-15 values indicate both terrestrial and aquatic organic matter was incorporated into the sediment. Higher percentages of aquatic algae and elevated C/N ratios indicate higher lake levels at the opening of the Holocene, but a wetland developed subsequently as climate warmed. From ca. 8500 to 6400 cat yr BP the pond desiccated in what must have been the driest period of the Holocene there. C/N ratios declined to their lowest Holocene levels, indicating intense decomposition in the sediment. Wetter conditions returned after 6400 cat yr BP, with conversion of the site to a sedge bog as groundwater levels rose. Higher charcoal influx rates after 6400 cat yr BP probably result from greater biomass production rates. Only minor shifts in the overstory species occurred during the Holocene, suggesting that mixed conifer forest dominated throughout the record. (C) 2008 University of Washington. All rights reserved.