Dissimilarity coefficients for fossil pollen spectra from Iowa and western illinois during the last 30,000 years

Baker, Richard G.; Nest, Julieann Van; Woodsworth, George

doi:10.1080/01916122.1989.9989355

Cited by 12 publications

(3 citation statements)

References 22 publications

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“…Although several other statistics exist (Overpeck, 1985), this one has several desirable properties and has become widely used (Anderson et al, 1989;Baker et al, 1989;Huntley, 1990). Anderson et al ( 1989) evaluated "critical values" or "cutoff points" for this statistic by comparing squared chord distances among the same vegetation type with those among different vegetation types.…”

Section: Dissimilarity Distributionmentioning

confidence: 98%

Climate and vegetation patterns in surface samples from arid western U.S.A.: Application to Holocene climatic reconstructions

Davis

1995

Palynology

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Nearly 1,400 samples from over 50 sources have been assembled and analyzed to characterize the contemporary pollen rain of the arid western U.S.A. Of the nearly 300 pollen types recorded, Pinus, Quercus, and Cupressaceae are the most common arboreal types; Chenopodiaceae-Amaranthus. Gramineae, Artemisia, Ambrosia, and "Other Compositae" are the most frequent non-arboreal pollen types. Forest vegetation is represented by 661 samples, steppe by 450 samples, and desert by 116 samples. Ambrosia, Cactaceae, Cruciferae, Leguminosae, Larrea, Malvaceae, Nyctaginaceae, and Prosopis achieve maximum percentages in hot -dry climate (>20°C mean annual temperature and <250 mm mean annual precipitation); Artemisia, Juniperus, Sarcobatus, Caryophyllaceae, Liguliflorae, Other Compositae, and Polygonaceae have minor peaks in cold dry climate (<15°C and <250 mm)

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Section: Dissimilarity Distributionmentioning

confidence: 98%

Climate and vegetation patterns in surface samples from arid western U.S.A.: Application to Holocene climatic reconstructions

Davis

1995

Palynology

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“…The disequilibrium hypothesis, on the other hand, holds that biotic factors such as the long life span of trees, rates of seed dispersal, rates of soil development, and the availability of habitat for seedling establishment may cause tree migration rates to lag significantly behind rates of climate change (Davis 1981a, Pennington 1986. Under this hypothesis, the no-analogue pollen assemblages represent disequilibrium associations containing plant taxa that lagged to varying degrees behind the rapid climate changes at the end of the Pleistocene (Delcourt and Delcourt 1985, Davis 1986, Baker et al 1989. In general, the extent to which the vegetation is in equilibrium with climate is scale dependent , with the equilibrium hypothesis clearly applicable to temporal scales Ͼ10 4 yr and the disequilibrium hypothesis relevant at timescales Յ10 2 yr.…”

Section: Introductionmentioning

confidence: 99%

Dissimilarity Analyses of Late-Quaternary Vegetation and Climate in Eastern North America

Williams

Shuman

Webb

2001

Ecology

156

224

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Plant formations different from any extant today apparently were widespread in North America and Europe during the last deglaciation, produced by the independent biogeographic responses of plant taxa to climate change. Dissimilarity analyses of modern and fossil pollen samples in eastern North America show that the unique plant associations centered around the Great Lakes at 14 000 calendar years before present (yr BP), with high dissimilarities during 17 000–12 000 yr BP. The late‐glacial fossil pollen assemblages are characterized by (1) high abundances of boreal conifers such as spruce and larch relative to their Holocene values, (2) high abundances of herbaceous types (sedge, sage, and ragweed), (3) high abundances of broad‐leaved deciduous types (ash, hornbeam, poplar, hazel, and willow), and (4) the low abundance or absence of pine, alder, and birch. When the fossil pollen samples are assigned to biomes using the affinity score technique, the late Pleistocene pollen samples are assigned to mixed parkland, a biome that is not extant in North America today. The fastest vegetational changes occurred 13 000–11 000 yr BP, when the late Pleistocene vegetation reorganized into the Holocene biomes, which have persisted to today. Simulations by the Community Climate Model, version 1 (CCM1), suggest that late‐glacial climates were also unlike modern climates, featuring a “hypercontinental” mixture of colder‐than‐present winters, warmer‐than‐present summers, and lower‐than‐present precipitation. Dissimilarity analyses of the pollen data and CCM1 simulations for 21 000, 16 000, 14 000, 11 000, and 6000 yr BP show that (1) the temporal and spatial distribution of high dissimilarities in the vegetation (relative to present) coincide with dissimilarities in simulated climate, (2) the timing and spatial distribution of changes in the vegetation and simulated climate also agree, and (3) the largest climatic and vegetational changes follow the peak period of dissimilarity from present. Taken together, these three lines of evidence support the hypothesis that the no‐analogue plant associations were in equilibrium with orbital‐ and millennial‐scale climate change. Nonclimatic factors such as low atmospheric CO2 concentrations and the presence of now‐extinct megafauna species may have increased the openness of the Pleistocene vegetation, but by themselves cannot explain the observed mixture of boreal, temperate, and herbaceous taxa in the no‐analogue pollen assemblages, nor can they explain the prevalence of no‐analogue pollen samples during the late glacial period.

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“…Wright, 1967;Overpeck et al, 1985). Numerical techniques for determining the closest analogues vary and include the creation of dissimilarity coefficients (the quantitative measure of dissimilarity between samples) (Prentice, 1980;Baker et al, 1989) which can be statistically weighted to shift the emphasis between different pollen types. Working on a record from Northwest Crater at Tower Hill in Western Victoria, Kershaw and Bulman (1996) were the first in Australia to apply the analogue method using a modern (pre-European) database of 73 sites within Victoria, South Australia and New South Wales to which estimates of climate for each site had been added .…”

Section: Australian Contextmentioning

confidence: 99%

Development and testing of transfer functions for generating quantitative climatic estimates from Australian pollen data

Cook

Kaars

2006

J Quaternary Science

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Cook, E. J. and van der Kaars, S. 2006. Development and testing of transfer functions for generating quantitative climatic estimates from Australian pollen data.ABSTRACT: We review attempts to derive quantitative climatic estimates from Australian pollen data, including the climatic envelope, climatic indicator and modern analogue approaches, and outline the need to pursue alternatives for use as input to, or validation of, simulations by models of past, present and future climate patterns. To this end, we have constructed and tested modern pollenclimate transfer functions for mainland southeastern Australia and Tasmania using the existing southeastern Australian pollen database and for northern Australia using a new pollen database we are developing. After testing for statistical significance, 11 parameters were selected for mainland southeastern Australia, seven for Tasmania and six for northern Australia. The functions are based on weighted-averaging partial least squares regression and their predictive ability evaluated against modern observational climate data using leave-one-out cross-validation. Functions for summer, annual and winter rainfall and temperatures are most robust for southeastern Australia, while in Tasmania functions for minimum temperature of the coldest period, mean winter and mean annual temperature are the most reliable. In northern Australia, annual and summer rainfall and annual and summer moisture indexes are the strongest. The validation of all functions means all can be applied to Quaternary pollen records from these three areas with confidence.

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Dissimilarity coefficients for fossil pollen spectra from Iowa and western illinois during the last 30,000 years

Cited by 12 publications

References 22 publications

Climate and vegetation patterns in surface samples from arid western U.S.A.: Application to Holocene climatic reconstructions

Climate and vegetation patterns in surface samples from arid western U.S.A.: Application to Holocene climatic reconstructions

Dissimilarity Analyses of Late-Quaternary Vegetation and Climate in Eastern North America

Development and testing of transfer functions for generating quantitative climatic estimates from Australian pollen data

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