A 7600 yr vegetation and fire history from Anthony Lake, northeastern Oregon, USA, with linkages to modern synoptic climate patterns

Abstract

We used pollen and high-resolution charcoal analysis of lake sediment to reconstruct a 7600 yr vegetation and fire history from Anthony Lake, located in the Blue Mountains of northeastern Oregon. From 7300 to 6300 cal yr BP, the forest was composed primarily of Populus, and fire was common, indicating warm, dry conditions. From 6300 to 3000 cal yr BP, Populus declined as Pinus and Picea increased in abundance and fire became less frequent, suggesting a shift to cooler, wetter conditions. From 3000 cal yr BP to present, modern-day forests composed of Pinus and Abies developed, and from 1650 cal yr BP to present, fires increased. We utilized the modern climate-analogue approach to explain the potential synoptic climatological processes associated with regional fire. The results indicate that years with high fire occurrence experience positive 500 mb height anomalies centered over the Great Basin, with anomalous southerly component of flow delivering dry air into the region and with associated sinking motions to further suppress precipitation. It is possible that such conditions became more common over the last 1650 cal yr BP, supporting an increase in fire despite the shift to more mesic conditions.

A Link Between Hydroclimate Variability and Biomass Burning During the Last Millennium in the Interior Pacific Northwest

“…Raw CHAR values from Anthony Lake in northwestern Oregon (44.95°N, −118.20°W, 2,174 m a.s.l.) show little systematic trend over the past 1000 years (Long et al., 2019). Two charcoal records from subalpine forests in the Upper Columbia River Basin which experience multi‐centennial fire return intervals (Figure 1, Cooley and Rockslide lakes, 1,515 m a.s.l.…”

Holocene fire history reconstruction of a mid-elevation mixed-conifer forest in the Eastern Cascades, Washington, USA

“…The seasonal disparity likely allowed for the accumulation of biomass (fuel) followed by substantial fire activity during the subsequent dry fire season (Prichard et al, 2009; Walsh et al, 2015). Or perhaps, greater interannual climate variability during the middle Holocene, likely through mechanisms proposed in Heyer et al (2017) and/or Long et al (2019), increased the likelihood that lightning strikes ignited fuels that were drier due to lower winter snowpacks and increased spring/summer temperatures. Either way, drier than present summers combined with increased biomass abundance during the late middle Holocene supports our interpretation that an increase in fire activity was caused by a combination of climatic factors and fuel availability/condition.…”

Late glacial through Early Holocene environments inferred using pollen from coprolites and sediments recovered from Paisley Caves, Oregon

“…The Summer Lake basin is presently located at a convergence zone of moist Pacific air parcels moving inland from the southwest and continental climate characterized by a high-pressure system centered above the Central Great Basin in Nevada to the southeast of the Chewaucan Basin, which have varied over the Holocene (Reinemann et al, 2009; Carter et al, 2017; Long et al, 2019). Geographically located in the rain shadow of the Cascade Range, the NGB region currently has warm summers and cold winters (mean July and January temperatures 17.7°C and 2.2°C, respectively).…”

“…The climate began to warm after the YD, eventually resulting in climatic conditions being warmer during the earliest portions of the Holocene (11,000-9000 cal yr BP), with evidence of a brief period of increased precipitation that resulted in a transgression of Summer Lake to moderately high levels, although not as high as during the BA (Hudson et al, 2021). Conditions reached thermal and aridity maxima after 9000 cal yr BP, after which climatic conditions began to cool but remained arid (Friedel, 1993;Bartlein et al, 1998Bartlein et al, , 2011Cohen et al, 2000;Benson et al, 2002;Mensing et al, 2004;Minckley et al, 2007;Long et al, 2019;Hudson et al, 2021).…”