@article {539, title = {A record of Lateglacial and early Holocene environmental and ecological change from southwestern Connecticut, USA}, journal = {Journal of Quaternary Science}, volume = {24}, year = {2009}, note = {id: 783; 494LO Times Cited:0 Cited References Count:27Y}, pages = {553-556}, abstract = {Analyses of a sediment core from Highstead Swamp in southwestern Connecticut, USA, reveal Lateglacial and early Holocene ecological and hydrological changes. Lateglacial pollen assemblages are dominated by Picea and Pinus subg. Pinus, and the onset of the Younger Dryas (YD) cold interval is evidenced by higher abundance of Abies and Alnus viridis subsp. crispa. As climate warmed at the end of the YD, Picea and Abies declined and Pinus strobus became the dominant upland tree species. A shift from lacustrine sediment to organic peat at the YD-Holocene boundary Suggests that the lake that existed in the basin during the Lateglacial interval developed into a swamp in response to reduced effective moisture. A change in wetland vegetation from Myrica gale to Alnus incana subsp. rugosa and Sphagnum is consistent with this interpretation of environmental changes at the beginning of the Holocene. Copyright (C) 2009 John Wiley \& Sons, Ltd.}, issn = {0267-8179}, doi = {10.1002/Jqs.1299}, author = {Oswald, W. W. and Foster, D. R. and Doughty, E. D. and Faison, E. K.} } @article {422, title = {A late-glacial transition from Picea glauca to Picea mariana in southern New England}, journal = {Quaternary Research}, volume = {67}, year = {2007}, note = {id: 1841; 160RU Times Cited:5 Cited References Count:61Y}, pages = {502-508}, abstract = {Picea is an important taxon in late-glacial pollen records from eastern North America, but little is known about which species of Picea were present. We apply a recently developed palynological method for discriminating the three Picea species in eastern North America to three records from New England. Picea glauca was dominant at similar to 14,500-14,000 cal yr BP, followed by a transition to Picea mariana between similar to 14,000 and 13,500 cal yr BP. Comparison of the pollen data with hydrogen isotope data shows clearly that this transition began before the beginning of the Younger Dryas Chronozone. The ecological changes of the late-glacial interval were not a simple oscillation in the position of a single species{\textquoteright} range, but rather major changes in vegetation structure and composition occurring during an interval of variations in several environmental factors, including climate, edaphic conditions, and atmospheric CO2 levels. (c) 2007 University of Washington. All rights reserved.}, issn = {0033-5894}, doi = {10.1016/j.yqres.2007.01.010}, author = {Lindbladh, M. and Oswald, W. W. and Foster, D. R. and Faison, E. K. and Hou, J. Z. and Huang, Y. S.} } @article {348, title = {Post-glacial changes in spatial patterns of vegetation across southern New England}, journal = {Journal of Biogeography}, volume = {34}, year = {2007}, note = {id: 1840; 157BN Times Cited:5 Cited References Count:70Y}, pages = {900-913}, abstract = {Aim We analysed lake-sediment pollen records from eight sites in southern New England to address: (1) regional variation in ecological responses to post-glacial climatic changes, (2) landscape-scale vegetational heterogeneity at different times in the past, and (3) environmental and ecological controls on spatial patterns of vegetation. Location The eight study sites are located in southern New England in the states of Massachusetts and Connecticut. The sites span a climatic and vegetational gradient from the lowland areas of eastern Massachusetts and Connecticut to the uplands of north-central and western Massachusetts. Tsuga canadensis and Fagus grandifolia are abundant in the upland area, while Quercus, Carya and Pinus species have higher abundances in the lowlands. Methods We collected sediment cores from three lakes in eastern and north-central Massachusetts (Berry East, Blood and Little Royalston Ponds). Pollen records from those sites were compared with previously published pollen data from five other sites. Multivariate data analysis (non-metric multi-dimensional scaling) was used to compare the pollen spectra of these sites through time. Results Our analyses revealed a sequence of vegetational responses to climate changes occurring across southern New England during the past 14,000 calibrated radiocarbon years before present (cal yr BP). Pollen assemblages at all sites were dominated by Picea and Pinus banksiana between 14,000 and 11,500 cal yr BP; by Pinus strobus from 11,500 to 10,500 cal yr BP; and by P. strobus and Tsuga between 10,500 and 9500 cal yr BP. At 9500-8000 cal yr BP, however, vegetation composition began to differentiate between lowland and upland sites. Lowland sites had higher percentages of Quercus pollen, whereas Tsuga abundance was higher at the upland sites. This spatial heterogeneity strengthened between 8000 and 5500 cal yr BP, when Fagus became abundant in the uplands and Quercus pollen percentages increased further in the lowland records. The differentiation of upland and lowland vegetation zones remained strong during the mid-Holocene Tsuga decline (5500-3500 cal yr BP), but the pattern weakened during the late-Holocene (3500-300 cal yr BP) and European-settlement intervals. Within-group similarity declined in response to the uneven late-Holocene expansion of Castanea, while between-group similarity increased due to homogenization of the regional vegetation by forest clearance and ongoing disturbances. Main conclusions The regional gradient of vegetation composition across southern New England was first established between 9500 and 8000 cal yr BP. The spatial heterogeneity of the vegetation may have arisen at that time in response to the development or strengthening of the regional climatic gradient. Alternatively, the differentiation of upland and lowland vegetation types may have occurred as the climate ameliorated and an increasing number of species arrived in the region, arranging themselves in progressively more complex vegetation patterns across relatively stationary environmental gradients. The emergence of a regional vegetational gradient in southern New England may be a manifestation of the increasing number of species and more finely divided resource gradient.}, issn = {0305-0270}, doi = {10.1111/j.1365-2699.2006.01650.x}, author = {Oswald, W. W. and Faison, E. K. and Foster, D. R. and Doughty, E. D. and Hall, B. R. and Hansen, B. C. S.} } @article {1954, title = {A climatic driver for abrupt mid-Holocene vegetation dynamics and the hemlock decline in New England}, journal = {Ecology}, volume = {87}, year = {2006}, note = {Foster, David ROswald, W Wyatt Faison, Edward K Doughty, Elaine D Hansen, Barbara C S eng Research Support, Non-U.S. Gov{\textquoteright}t Research Support, U.S. Gov{\textquoteright}t, Non-P.H.S. 2007/01/26 09:00 Ecology. 2006 Dec;87(12):2959-66. }, month = {Dec}, pages = {2959-66}, abstract = {The mid-Holocene decline of eastern hemlock is widely viewed as the sole prehistorical example of an insect- or pathogen-mediated collapse of a North American tree species and has been extensively studied for insights into pest-host dynamics and the consequences to terrestrial and aquatic ecosystems of dominant-species removal. We report paleoecological evidence implicating climate as a major driver of this episode. Data drawn from sites across a gradient in hemlock abundance from dominant to absent demonstrate: a synchronous, dramatic decline in a contrasting taxon (oak); changes in lake sediments and aquatic taxa indicating low water levels; and one or more intervals of intense drought at regional to continental scales. These results, which accord well with emerging climate reconstructions, challenge the interpretation of a biotically driven hemlock decline and highlight the potential for climate change to generate major, abrupt dynamics in forest ecosystems.}, keywords = {*Climate, *Ecosystem, Geologic Sediments, new england, Tsuga/*physiology}, isbn = {0012-9658 (Print)0012-9658 (Linking)}, doi = {10.1890/0012-9658(2006)87[2959:ACDFAM]2.0.CO;2}, author = {Foster, D. R. and Oswald, W. W. and Faison, E. K. and Doughty, E. D. and Hansen, B. C.} } @article {1955, title = {Early holocene openlands in southern New England}, journal = {Ecology}, volume = {87}, year = {2006}, note = {Faison, E KFoster, D R Oswald, W W Hansen, B C S Doughty, E eng Research Support, Non-U.S. Gov{\textquoteright}t Research Support, U.S. Gov{\textquoteright}t, Non-P.H.S. 2006/11/09 09:00 Ecology. 2006 Oct;87(10):2537-47. }, month = {Oct}, pages = {2537-47}, abstract = {The pre-historical vegetation structure in temperate forest regions is much debated among European and North American ecologists and conservationists. Frans Vera{\textquoteright}s recent hypothesis that large mammals created mosaics of forest and openland vegetation in both regions throughout the Holocene has been particularly controversial and has provoked new approaches to conservation management. Thirty years earlier, American paleoecologists Herb Wright and Margaret Davis debated whether abundant ragweed pollen at Rogers Lake, Connecticut at 9500 yr BP signified local forest openings or long-distance transport of pollen from Midwestern prairies. Using new pollen records from Harvard Forest and the North American Pollen Database, we address this question and offer insights to the openland discussion. Ragweed and other forbs exceed 3.5\% at five sites in a restricted area of southern New England between 10,100 and 7700 yr BP. Strong evidence suggests this pollen originated from the landscapes surrounding these sites (supporting Davis), as ragweed pollen percentages do not increase with longitude from New England to the Midwest. Ragweed pollen percentages are also unrelated to basin size and therefore unrelated to the proportion of extraregional pollen in New England. High forbs values were associated with increases in oak, decreases in white pine, and relatively high charcoal values. Modern pollen records with similar forb and tree percentages occur along the Prairie Peninsula region of the Upper Midwest. However, the closest analogue to the southern New England early Holocene assemblages comes from Massachusetts{\textquoteright} Walden Pond in the early 18th century. These results and the affiliation of ragweed for open, disturbed habitats suggest that oak-pine forests with large openings persisted for over 2000 years due to dry conditions and perhaps increased fire frequency. This conclusion is corroborated by independent lake level and climate reconstructions. Because these early Holocene openlands have no detectable analogue in New England for the past 7000 years before European settlement, we suggest that all important openlands today are almost exclusively a legacy of Colonial agriculture and should be managed accordingly. Nonetheless, our results may have implications for forest dynamics accompanying projected climate change to more arid conditions in New England over the next century.}, keywords = {*Ambrosia, *Pollen, Ecosystem, Geography, new england, Paleontology}, isbn = {0012-9658 (Print)0012-9658 (Linking)}, doi = {10.1890/0012-9658(2006)87[2537:EHOISN]2.0.CO;2}, author = {Faison, E. K. and Foster, D. R. and Oswald, W. W. and Hansen, B. C. and Doughty, E.} } @article {1946, title = {Postglacial climate reconstruction based on compound-specific D/H ratios of fatty acids from Blood Pond, New England}, journal = {Geochemistry Geophysics Geosystems}, volume = {7}, year = {2006}, note = {031uaTimes Cited:32 Cited References Count:43 }, month = {Mar 28}, abstract = {We determined hydrogen isotope ratios of individual fatty acids in a sediment core from Blood Pond, Massachusetts, USA, in order to reconstruct climate changes during the past 15 kyr. In addition to palmitic acid (C-16 n-acid), which has been shown to record lake water D/H ratios, our surface sediments and down core data indicate that behenic acid (C-22 n-acid), produced mainly by aquatic macrophytes, is also effective for capturing past environmental change. Calibration using surface sediments from two transects across eastern North America indicates that behenic acid records delta D variation of lake water. Down core variations in delta D values of behenic acid and pollen taxa are consistent with the known climate change history of New England. By evaluating the hypothesis that D/H fractionations of long chain even numbered fatty acids (C-24-C-32 n-acids) relative to lake water provide independent estimates of relative humidity during the growing season, we find that differences between lake-level records and isotopically inferred humidity estimates may provide useful insight into seasonal aspects of the hydrologic cycle. Combined analyses of D/H of short and long chain fatty acids from lake sediment cores thus allow reconstructions of both past temperature and growing season relative humidity. Comparison of delta D records from two lakes in New England provides critical information on regional climate variation and abrupt climate change, such as the 8.2 ka event.}, keywords = {atmospheric processes : paleoclimatology, eastern north-america, fatty acids, geochemistry : organic and biogenic geochemistry, geochemistry : stable isotope geochemistry, Holocene, hydrogen isotope, hydrogen isotope ratios, lacustrine organic-matter, lake-sediments, Paleoclimate, record, Stable isotopes, united-states, vegetation history, younger-dryas}, isbn = {1525-2027}, doi = {10.1029/2005GC001076}, author = {Hou, J. Z. and Huang, Y. S. and Wang, Y. and Shuman, B. and Oswald, W. W. and Faison, E. and Foster, D. R.} }