High resolution pollen analyses of sediment core LEDC10-1 from Lake Elsinore yield the first well-dated,
terrestrial record of sub-centennial-scale ecologic change in coastal southern California between ~32 and
9 ka. In the Lake Elsinore watershed, the initial, mesic montane conifer forests dominated by Pinus, and
Cupressaceae with trace amounts of Abies and Picea were replaced by a sequence of multiple, extended
severe mega-droughts between ~27.5 and ~25.5 ka, in which halophytic and xerophytic herbs and shrubs
occupied an ephemeral lake. This prolonged and extended dry interval, which corresponds with warm
waters offshore, imply strengthening of the North Pacific High and persistent below-average winter
precipitation. The subsequent, contrasting monotonic occurrence of montane conifers reflects little
variation in cold, mesic climate until ~15 ka. Postglacial development of Quercus woodland and chaparral
mark the return to more xeric, warmer conditions at this time. A brief reversal at ~13.1e~12.1 ka, as
reflected by an expansion of Pinus, is correlative with the Younger Dryas and interrupts development of
warm, postglacial climate. Subsequent gradual expansion of xeric vegetation post e Younger Dryas denotes
the establishment of a winter hydroclimate regime in coastal southern California that is more
similar to modern conditions. Pollen-based reconstructions of temperature and precipitation at Lake
Elsinore are generally correlative with pollen-based paleoclimatic reconstructions and foraminifera based
sea surface temperatures from Santa Barbara Basin in marine core ODP 893. The conspicuous
absence of the ~27.5e~25.5 ka glacial “mega-drought” in the Santa Barbara Basin pollen record highlights
the sensitivity of Lake Elsinore to hydroclimate change, and thus, the importance of this new record that
indicates that mega-drought can occur during the full glacial when climatic boundary conditions and
forcings differed substantially from the present.
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Subregional variability in the response of New England vegetation to postglacial climate change
We analysed a dataset composed of multiple palaeoclimate and lake‐sediment pollen records from New England to explore how postglacial changes in the composition and spatial patterns of vegetation were controlled by regional‐scale climate change, a subregional environmental gradient, and landscape‐scale variations in soil characteristics.
The 120,000‐km2study area includes parts of Vermont and New Hampshire in the north, where sites are 150–200 km from the Atlantic Ocean, and spans the coastline from southeastern New York to Cape Cod and the adjacent islands, including Block Island, the Elizabeth Islands, Nantucket, and Martha's Vineyard.
We analysed pollen records from 29 study sites, using multivariate cluster analysis to visualize changes in the composition and spatial patterns of vegetation during the last 14,000 years. The pollen data were compared with temperature and precipitation reconstructions.
Boreal forest featuring
Postglacial changes in the composition and spatial pattern of New England forests were controlled by long‐term trends and abrupt shifts in temperature and precipitation, as well as by the environmental gradient between coastal and inland parts of the region. Substrate and soil moisture shaped landscape‐scale variations in forest composition.
- NSF-PAR ID:
- 10076152
- Publisher / Repository:
- Wiley-Blackwell
- Date Published:
- Journal Name:
- Journal of Biogeography
- Volume:
- 45
- Issue:
- 10
- ISSN:
- 0305-0270
- Page Range / eLocation ID:
- p. 2375-2388
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract In the southern Great Lakes Region, North America, between 19,000 and 8,000 years ago, temperatures rose by 2.5–6.5°C and spruce
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Araucaria araucana ) occurs, is poorly known. Here we ask: (a) What is the Holocene vegetation and fire history at the north‐eastern extent ofA. araucana forest? (b) How have climate and humans influenced the past distribution ofA. araucana ?Location Northernmost Patagonia, Argentina and Chile (37–40°S).
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Nothofagus pollen after ~6,590 BP suggests increases in shrubland and moisture in association with cooler conditions and greater seasonality and ENSO activity.Araucaria pollen appeared at L. Portezuelo at ~6,380 BP, but was low in abundance until ~370 BP, when it rose with charcoal levels. This increase inAraucaria and fire coincided with a regional influx of Mapuche American Indians.Nothofagus deforestation andPinus silviculture marked Euro‐American settlement beginning in the 19–20th century.Main conclusions (a) Rapid postglacial warming and drying limited the distribution of
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