Impact of Pleistocene–Holocene climate shifts on vegetation and fire dynamics and its implications for Prearchaic humans in the central Great Basin, USA

Abstract

The effects of climate change during the Terminal Pleistocene-Early Holocene transition on ecosystems and early Prearchaic hunter-gatherers in the central Great Basin of North America are not well understood. We present a palynological reconstruction of regional vegetation and fire history in Grass Valley, central Nevada, from~14 to~7.5k cal a BP showing that Pinus-dominated woodlands were replaced by dry-adapted steppe and desert vegetation accompanied by an increase in regional fire activity at the beginning of the Holocene, in response to summer warming and a drying climate. Following a severe drought period peaking~10.2-9.3k cal a BP, Pinus woodlands partially recovered contemporaneously with the 8.2k cal a BP climate anomaly. Local wetlands provided important resource patches for human foraging societies, and periodic declines of wetlands in response to changing local hydrological conditions may have necessitated adjustments in subsistence and settlement practices and technology.

Terrestrial ecosystem transformations in response to rapid climate change during the last deglaciation around Mono Lake, California, USA

“…Prior studies at high-elevation lakes in the eastern Sierra Nevada show that Early Holocene vegetation communities were open, wooded environments dominated by Pinus , Quercus , and shrubs, also suggesting dispersal upslope and stratification of vegetation previously found in Mono Basin (Anderson, 1990a; Davis, 1999a; MacDonald et al, 2008). Early Holocene dryness has been observed throughout the Sierra Nevada and Great Basin (Davis and Moratto, 1988; Anderson and Smith, 1994; Mensing, 2001; Brugger and Rhode, 2020), based on the decline in mesophilic arboreal taxa at lower elevations and the establishment of the semiarid vegetation assemblages seen today. Similarly, the complete absence of Sporormiella from 11,500–9,200 cal yr BP captures the final extirpation of Pleistocene megafauna in the basin, also consistent with the last appearance dates of megafauna fossils found in the Great Basin (Grayson, 2006).…”

“…Prior work from the Great Basin has suggested that megafauna populations were low in comparison to the Mojave Desert to the south (Grayson, 2016). This appears to be reflected in limited Sporormiella presence in pollen studies from Great Basin wetlands (e.g., Gund Ranch; Brugger and Rhode, 2020). Yet, the high and relatively consistent presence of Sporormiella in Mono Lake sediments indicates higher megafauna activity, and implies that the rim of the Great Basin and Sierra Nevada may have provided more suitable habitats for megafauna than the central Great Basin.…”

“…However, the longer-term assembly of the terrestrial ecosystems of the central Sierra Nevada (Cole, 1983; Davis et al, 1985; Anderson, 1990a; Smith and Anderson, 1992; Anderson and Smith, 1994; Koehler and Anderson, 1994) and western Great Basin (Batchelder, 1970; Jennings and Elliott-Fisk, 1993; Nowak et al, 1994; Woolfenden, 2003; Mensing, 2001; Mensing et al, 2008; Brugger and Rhode, 2020) since the late Pleistocene are documented by a rich history of Quaternary subfossil pollen and macrofossil studies from lakes, wetlands, and middens. This work has shown that much of the Sierra Nevada and Great Basin was covered in a subalpine community of Artemisia -, Pinus -, Abies -, and Juniperus -dominated woodlands that transitioned during the Holocene to more altitudinally stratified montane forests, chaparral/woodlands, and open lowland steppes.…”

Holocene land cover change in North America: continental trends, regional drivers, and implications for vegetation-atmosphere feedbacks

“…Most of the eastern portion of this subregion is the Great Basin shrub steppe, where the few pollen records that exist are from high-elevation sites and low-elevation wetlands that are sensitive to fluctuating water tables, recorded as large fluctuations in Cyperaceae pollen. Increases in open-land cover taxa (Cyperaceae, Poaceae, Asteraceae) between 10-7.5 ka and after 3 ka in this region may reflect either local expansion of alpine meadows and wetlands or expansion of steppe more broadly (Mensing et al, 2008;Brugger and Rhode, 2020;Minckley et al, 2007;Thompson, 1992). Note, however, that desert, steppe, and other open-land arid ecosystems are likely to be underrepresented in these reconstructions, due to a scarcity of dryland sites.…”