期刊
HOLOCENE
卷 26, 期 4, 页码 578-591出版社
SAGE PUBLICATIONS LTD
DOI: 10.1177/0959683615612586
关键词
droughts; Fagus grandifolia; fire; Great Lakes region; LOI; pollen
资金
- US National Science Foundation [DEB-0716471]
- University of Wisconsin-Madison's Climate, People, and Environment Program at the Center for Climatic Research
- Division Of Environmental Biology
- Direct For Biological Sciences [1353896] Funding Source: National Science Foundation
Mesic tree species such as Fagus grandifolia and Tsuga canadensis experienced multiple abundance declines in eastern North America during the last 8000 years, but the causes remain unclear. This paper presents a new sub-centennial record of Holocene vegetation, fire and sedimentological changes at Spicer Lake, IN, to test hypotheses about the role of fire and hydrological variations on shifts in vegetation composition. Four pollen zones are reported: Abies-Picea forests (15-11.8 ka BP), Pinus-dominated mixed forest (11.8-10.6 ka BP), transitional mixed forest (10.6-6.8 ka BP), and deciduous forest characterized by the expansion and high variability of F. grandifolia (after 6.8 ka BP). Macroscopic charcoal indicates five to seven fires between 6.1 and 4.4 ka BP and no fires between 4.4 and 2 ka BP, despite several large declines in F. grandifolia, and more fires after 1.8 ka BP likely linked to declining F. grandifolia abundances after 1.1 ka BP. Six peaks in mineralogenic sediments are suggestive of hydroclimate variability, but do not consistently correspond to shifts in F. grandifolia abundances. A Bayesian change-point analysis of 15 regional F. grandifolia pollen records identifies peak probabilities of events at 4.8 and 1.1 ka BP, similar in timing to variations in T. canadensis at other sites. Hence, fire can be ruled out as a driver of the mid-Holocene declines of F. grandifolia, but more work is needed to confidently establish the regional timing of F. grandifolia declines and to link them to past droughts and T. canadensis declines in eastern North America.
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