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Title: Reconstruction of forest and alpine environments over three millennia in the high Toquima Range

Authors: Millar, Constance I

Date: 2020

Publication Anthropological Papers of the American Museum of Natural History. 104: 373-388.

Abstract: Combining tree-ring data and modern temperature observations with paleoclimate proxies and ecological evidence from other Great Basin ranges provides insights into the environmental context of the alpine villages in the Toquima Range during the three millennia of occupation. Throughout this time, the Mt. Jefferson summit plateau above 3380 m, north and east of Alta Toquima and above Dakabah, appears to have been too cold and too harsh to have supported trees. The current alpine condition of the plateau, therefore, is likely to be similar to that in prior millennia. Alta Toquima is located at what appears to be a transition zone of upper pine tree line and alpine conditions. The current young pines established during the late 20th century in the cultural site and on the knob above the house rings are likely the highest extent of pine expansion for >3000 years, meaning the Alta Toquima occupation was likely to have been directly surrounded by alpine conditions (no trees). Mature limber pine forest, however, is likely to have been very close to (below) the cultural site on the slopes of the upper Barker Creek watershed, especially during cool-wet periods, such as the LIA, or warmer-wet periods. This alternated with lower tree line and mature forest ≤ 3330 m during dry periods, such as the MCA, LHDP, and possibly dry periods within the LIA. At other times, forest was likely intermediate in elevation. Dakabah was most likely within mature subalpine forest throughout the past 3000 years, although forests might have been sparser than encountered in the early 21st century, and Dakabah was likely always near the edge of the forest. Above Dakabah, pine growth on the cirque walls was unlikely except the southern aspect slope. The pine tree line advanced upslope to near the cirque top (but not as high as pines that established in the late 20th century) several times, following the LHDP from ~cal a.d. 110–870, and again in the LIA, from ~cal a.d. 1515–1590. During dry intervals (MCA, LHDP), the southern aspect slopes were likely treeless. Modern temperatures measured from 2008–2018 in the South Fork Pine Creek cirque yield mean annual temperatures of 2.3° C (Dakabah) and 1.0° C (upper cirque) and mean annual summer temperatures of 11.9° C (Dakabah) and 10.6° C (upper cirque). Interpolating from evidence for paleo-temperatures elsewhere in the Great Basin suggests that cold/warm extremes were +/– ~2° C for the MCA and LIA, respectively. Modern temperatures and inferences for past temperatures corroborate that thermal conditions were unlikely to constrain tree lines in the Pine Creek and Barker Creek watersheds and that moisture availability had the most influence on tree growth. Abundance of downed remnant wood dating to ~cal a.d. 70 on the slopes above Dakabah, and old deadwood in the mature forests around Alta Toquima and Dakabah, suggest that villagers had adequate fuelwood to support their needs. The archival record of ancient wood (per Grayson and Millar, 2008) appears to be intact, although wood no doubt was removed for use during the cultural period, likely influencing at least density of remnant stems.

Keywords: Archaeology, paleoecology, climate change, dendrochronology

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Citation

    Millar, Constance I. 2020. Reconstruction of forest and alpine environments over three millennia in the high Toquima Range. Anthropological Papers of the American Museum of Natural History. 104: 373-388. Chapter 10.
Last Modified: January 13, 2021