Holocene Changes in the Vegetation of the Midwest

Webb, Thompson; Cushing, Edward J.; Wright, H. E.

doi:10.5749/j.ctttt09b.15

Cited by 132 publications

(177 citation statements)

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“…Changes in the relative importance of these three air masses are believed to have caused shifts in the major ecotones bordering the Great Plains grassland (Bryson 1966;Bryson et al 1970;Ritchie 1976;Bartlein et al 1984), including the well-documented expansion and contraction of the eastern prairie-forest border (Winter 1962;Wright et al 1963;McAndrews 1966;Webb et al 1983) and the coincident shift from temperate grassland (tall grass) to more xerophytic grassland (short grass) prairie (Barnosky et al 1987). General circulation patterns enhanced by the last Milankovitch insolation maximum, modulated by periglacial effects of the waning ice sheet, in large part can explain these patterns (Wright 1992).…”

Section: Resultsmentioning

confidence: 99%

Century scale paleoclimatic reconstruction from Moon Lake, a closed‐basin lake in the northern Great Plains

Laird

Fritz

Grimm

et al. 1996

Limnology & Oceanography

194

152

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Section: Resultsmentioning

confidence: 99%

Century scale paleoclimatic reconstruction from Moon Lake, a closed‐basin lake in the northern Great Plains

Laird

Fritz

Grimm

et al. 1996

Limnology & Oceanography

194

152

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“…At the LGM, landscapes south of the Laurentide Ice Sheet were probably covered by tundra, boreal forest, or boreal grassland (Baker et al, 1989;Muhs et al, 1999;Schwert et al, 1997;Wells and Stewart, 1987;Wright, 1981), all of which would have relatively low albedos in summer (McFadden and Ragotz- 30°N and 60°N for the last 25,000 cal yr B.P. (Berger and Loutre, 1991), (b) times of colder-than-present climate inferred from the presence of spruce macrofossils or pollen, extralimital northern and western land snails, and extralimital northern mammals (data compiled from the following sources: Baker et al, 1986;1989;FAUNMAP, 1994;Frye et al, 1974;Leonard, 1951;Leonard and Frye, 1960;Licciardi et al, 1998;Rousseau and Kukla, 1994;Ruhe, 1969;Schwert et al, 1997;Watts, 1983;Webb et al, 1983;Wells and Stewart, 1987;Wright, 1981). kie, 1967).…”

Section: Discussionmentioning

confidence: 99%

Unprecedented last-glacial mass accumulation rates determined by luminescence dating of loess from western Nebraska

et al. 2003

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A high-resolution chronology for Peoria (last glacial period) Loess from three sites in Nebraska, midcontinental North America, is determined by applying optically stimulated luminescence (OSL) dating to 35-50 m quartz. At Bignell Hill, Nebraska, an OSL age of 25,000 yr near the contact of Peoria Loess with the underlying Gilman Canyon Formation shows that dust accumulation occurred early during the last glacial maximum (LGM), whereas at Devil's Den and Eustis, Nebraska, basal OSL ages are significantly younger (18,000 and 21,000 yr, respectively). At all three localities, dust accumulation ended at some time after 14,000 yr ago. Mass accumulation rates (MARs) for western Nebraska, calculated using the OSL ages, are extremely high from 18,000 to 14,000 yr-much higher than those calculated for any other pre-Holocene location worldwide. These unprecedented MARs coincide with the timing of a mismatch between paleoenvironmental evidence from central North America, and the paleoclimate simulations from atmospheric global circulation models (AGCMs). We infer that the high atmospheric dust loading implied by these MARs may have played an important role, through radiative forcing, in maintaining a colder-than-present climate over central North America for several thousand years after summer insolation exceeded present-day values.

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“…Retrospective studies of this period provide an opportunity to examine vegetational dynamics in response to climatic change. To this end, numerous pollen profiles spanning the Holocene have been published from the midwestern United States, especially Minnesota (22,23). However, a detailed understanding of the vegetational history of the MH remains limited because of similar pollen morphologies of the taxa within Poaceae (the grass family) and because of the likely underrepresentation of pollen from important taxa that are not wind-dispersed, such as insectpollinated forbs.…”

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confidence: 99%

Response of C ₃ and C ₄ plants to middle-Holocene climatic variation near the prairie–forest ecotone of Minnesota

Nelson

Tian

et al. 2003

Proc. Natl. Acad. Sci. U.S.A.

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Paleorecords of the middle Holocene (MH) from the North American mid-continent can offer insights into ecological responses to pervasive drought that may accompany future climatic warming. We analyzed MH sediments from West Olaf Lake (WOL) and Steel Lake (SL) in Minnesota to examine the effects of warm͞dry climatic conditions on prairie-woodland ecosystems. Mineral composition and carbonate ␦ 18 O were used to determine climatic variations, whereas pollen assemblages, charcoal ␦ 13 C, and charcoal accumulation rates were used to reconstruct vegetation composition, C3 and C4 plant abundance, and fire. The ratio of aragonite͞calcite at WOL and ␦ 18 O at SL suggest that pronounced droughts occurred during the MH but that drought severity decreased with time. From charcoal ␦ 13 C data we estimated that the MH abundance of C4 plants averaged 50% at WOL and 43% at SL. At WOL C4 abundance was negatively correlated with aragonite͞calcite, suggesting that severe moisture deficits suppressed C4 plants in favor of weedy C3 plants (e.g., Ambrosia). As climate ameliorated C4 abundance increased (from Ϸ33 to 66%) at the expense of weedy species, enhancing fuel availability and fire occurrence. In contrast, farther east at SL where climate was cooler and wetter, C 4 abundance showed no correlation with ␦ 18 O-inferred aridity. Woody C 3 plants (e.g., Quercus) were more abundant, biomass flammability was lower, and fires were less important at SL than at WOL. Our results suggest that C 4 plants are adapted to warm͞dry climatic conditions, but not to extreme droughts, and that the fire regime is controlled by biomass-climate interactions. P ervasive drought, expected to be associated with climatic change in continental interiors, will have profound ecological, economic, and societal repercussions (1-4). Drought conditions are likely to alter ecosystem function by changing the relative abundance of plant functional groups (e.g., C 3 vs. C 4 ) in natural systems (5-7). For example, episodic droughts that occurred throughout the 20th century in the midwestern United States killed woody C 3 genera, such as Quercus (8-10), and favored better adapted C 3 and C 4 herbaceous species (9). General circulation models coupled with dynamic crop-growth models project that, in agricultural systems, such climatic conditions could significantly reduce both C 3 (e.g., wheat, Triticum aestivum L.) and C 4 (e.g., corn, Zea mays L.) cereal crop yields (11,12), resulting in billions of dollars of economic loss (13,14). Empirical evidence of the response of plant functional groups to climatic conditions characteristic of drought is therefore important for evaluating predictions of future change. However, such evidence is mostly limited to historical records (15, 16), which lack the full range of past drought variability (3), and to short-term experimental manipulations (17, 18), which lack a sufficient temporal dimension for understanding future vegetational response.During the middle Holocene (MH), Ϸ8.0-4.0 thousand years (ka) B.P. (19), the midweste...

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Holocene Changes in the Vegetation of the Midwest

Cited by 132 publications

References 0 publications

Century scale paleoclimatic reconstruction from Moon Lake, a closed‐basin lake in the northern Great Plains

Century scale paleoclimatic reconstruction from Moon Lake, a closed‐basin lake in the northern Great Plains

Unprecedented last-glacial mass accumulation rates determined by luminescence dating of loess from western Nebraska

Response of C ₃ and C ₄ plants to middle-Holocene climatic variation near the prairie–forest ecotone of Minnesota

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Holocene Changes in the Vegetation of the Midwest

Cited by 132 publications

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Century scale paleoclimatic reconstruction from Moon Lake, a closed‐basin lake in the northern Great Plains

Century scale paleoclimatic reconstruction from Moon Lake, a closed‐basin lake in the northern Great Plains

Unprecedented last-glacial mass accumulation rates determined by luminescence dating of loess from western Nebraska

Response of C 3 and C 4 plants to middle-Holocene climatic variation near the prairie–forest ecotone of Minnesota

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Response of C ₃ and C ₄ plants to middle-Holocene climatic variation near the prairie–forest ecotone of Minnesota