uid=HFR,o=lter,dc=ecoinformatics,dc=org all public read doi:10.6073/pasta/a9713e65ec1cbe01d1a3e159d4465a1a Wyatt Oswald https://orcid.org/0000-0001-6217-1831 David Foster https://orcid.org/0000-0003-1171-3762 2023 English

The abrupt, range-wide decline of Tsuga canadensis ~5500 calibrated years before present (cal. yr BP) is one of the most-studied events in North American paleoecology. Little attention, however, has been given to an earlier Tsuga decline, dated to ~6000 cal. yr BP in southern Ontario, Canada. To investigate whether this event occurred elsewhere in eastern North America, we analyzed the middle-Holocene interval of a lake-sediment record from Knob Hill Pond, located in northern Vermont, USA, an area of historically high Tsuga abundance. A dramatic, short-lived drop in Tsuga pollen abundance does occur at ~6000 cal. yr BP in the Knob Hill Pond record, indicating that Tsuga populations declined in various parts of its range. We hypothesize that both middle-Holocene declines of Tsuga were caused by the deleterious effects of pronounced droughts on this moisture-sensitive tree. Close examination of pollen data from a transect of sites across New England reveals that the earlier decline of Tsuga is present in other records, although some aspects of the event appear to have varied geographically. While northern and higher-elevation sites exhibit a nearly full recovery of Tsuga populations between the two declines, records further to the south are characterized by a stair-step pattern of progressive decline. At sites near its southern range limit, relatively warm conditions between ~6000 and 5500 cal. yr BP were apparently not conducive to the reestablishment and survival of Tsuga, and thus it was unable to recover between the drought events.

climate hemlock lakes paleoecology pollen sediments vegetation dynamics LTER controlled vocabulary disturbance populations LTER core area Harvard Forest HFR LTER USA HFR default

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Creative Commons Zero v1.0 Universal https://spdx.org/licenses/CC0-1.0.html CC0-1.0 https://harvardforest.fas.harvard.edu/exist/apps/datasets/showData.html?id=hf187 Knob Hill Pond (Marshfield VT). Coordinates based on WGS84 datum. -72.3737 -72.3737 +44.3605 +44.3605 370 370 meter -12000 2010 genus Betula species spp. birch genus Fagus species spp. beech genus Picea species spp. spruce genus Pinus species spp. pine genus Quercus species spp. oak genus Tsuga species spp. hemlock complete Information Manager Harvard Forest

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(978) 724-3302 hf-im@lists.fas.harvard.edu Harvard Forest

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For detailed methods, please see: Day, L. T., Oswald, W. W., Doughty, E. D., Foster, D. R. 2013. Analysis of hemlock pollen size in Holocene lake sediments from New England. Quaternary Research 76: 362-365.

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(978) 724-3302 (978) 724-3595 https://harvardforest.fas.harvard.edu https://ror.org/059cpzx98 pointOfContact The Harvard Forest Long-Term Ecological Research (LTER) program examines ecological dynamics in the New England region resulting from natural disturbances, environmental change, and human impacts. National Science Foundation LTER grants: DEB-8811764, DEB-9411975, DEB-0080592, DEB-0620443, DEB-1237491, DEB-1832210. hf187-01-pollen-Knobhill.csv pollen hf187-01-pollen-Knobhill.csv 445999 39b8a392f130faf6ded3d889fef3c21f 1 \r\n column , https://harvardforest.fas.harvard.edu/data/p18/hf187/hf187-01-pollen-Knobhill.csv cal.age.bp calibrated age before present in years number 0.00001 real NA missing value depth depth in sediment column centimeter 1 whole NA missing value taxa name of taxa name of taxa count number of pollen grains or spores of individual taxa number 0.5 real NA missing value 15594 hf187-02-age-Knobhill.csv age hf187-02-age-Knobhill.csv 895 f2bc2372e1457772c2363f9d3eb364ce 1 \r\n column , https://harvardforest.fas.harvard.edu/data/p18/hf187/hf187-02-age-Knobhill.csv depth depth in sediment column centimeter 1 whole NA missing value cal.age.bp calibrated age before present (years; present=1950 AD) number 0.00000001 real NA missing value notes notes and methods of age determination; 210Pb=lead-210 dating; 14C=radiocarbon dating; Euro settlement=determined by rise in abundance of weedy and agricultural taxa notes and methods of age determination; 210Pb=lead-210 dating; 14C=radiocarbon dating; Euro settlement=determined by rise in abundance of weedy and agricultural taxa c14 un-calibrated radiocarbon years number 1 whole NA missing value error analytical error for 14C dates in years number 1 whole NA missing value 25 hf187-03-microchar-Knobhill.csv microchar hf187-03-microchar-Knobhill.csv 3413 eb28dd47480d1fabc25da2356d78b39e 1 \r\n column , https://harvardforest.fas.harvard.edu/data/p18/hf187/hf187-03-microchar-Knobhill.csv depth depth in sediment column centimeter 1 whole NA missing value char.area area of charcoal pieces greater than 10 and less than 180 microns in length millimeter 0.00001 real NA missing value exotic.char number of exotic marker grains encountered during charcoal analysis number 1 whole NA missing value pollen.sum number of pollen grains and spores of upland taxa encountered during pollen analysis number 0.1 real NA missing value exotic.pollen number of exotic maker grains encountered during pollen analysis number 1 whole NA missing value exotic.added total number of exotic marker grains added to sample numberPerCentimeterCubed 1 whole NA missing value sed.vol volume of the sediment samples centimeterCubed 1 whole NA missing value 94 historical paleological numberPerCentimeterCubed