Holocene vegetation and fire regimes in subalpine and mixed conifer forests, southern Rocky Mountains, USA

• DOI: 10.1071/wf07028
• Publication Date: 2009-02-10T03:02:33Z
• Authors: R. S. Anderson; C. D. Allen; J. L. Toney; R. B. Jass; A. N. Bair
• Keywords: Abies lasiocarpa; Picea engelmannii; Subalpine forest; Alpine climate; Tree line; Deglaciation

Our understanding of the present forest structure western North America hinges on our ability to determine antecedent conditions. Sedimentary records from lakes and bogs in southern Rocky Mountains Colorado New Mexico provide information relationships between climate vegetation change, fire history since deglaciation. We a new pollen record Hunters Lake (Colorado) as an example high-elevation Rockies. then series six sedimentary ~2600 3500-m elevation, including sites presently at alpine–subalpine boundary, within Picea engelmannii–Abies lasiocarpa mixed conifer forest, forests there. High Artemisia low but increasing percentages Pinus suggest prior 13 500 calendar years before (cal yr BP) was tundra or steppe, with open spruce woodland ~11 900 cal BP. Subalpine (Picea engelmannii, Abies lasiocarpa) existed around lake for remainder Holocene. At lower elevations, ponderosa and/or contorta expanded 11 10 200 BP; ~8600 4700 edulis after ~4700 Sediments near transition contained five times less charcoal than those entirely subalpine forests, 40 bog forest. Higher episode frequencies occurred ~12 000 9000 BP (associated initiation expansion south-west monsoon abundant lightning, significant biomass during turnover) ~2000–1000 (related periodic droughts long-term trend towards wetter conditions greater biomass). Fire subalpine–alpine were average 5 events/1000 over Holocene, corresponding one event every ~100 years. (5) Holocene-length additional evidence anomalous nature 20th-century regime, where fires largely suppressed national policy.