The postglacial history of threePiceaspecies in New England, USA

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Abstract
Given the difficulty of separating the threePiceaspecies—P. glauca, P. mariana,andP. rubens(white, black, and red spruce)—in the pollen record, little is known about their unique histories in eastern North America following deglaciation. Here we report the first use of a classification tree analysis (CART) to distinguish pollen grains of these species. It was successfully applied to fossil pollen from eight sites in Maine and one in Massachusetts. We focused on the late glacial/early Holocene (14,000 to 8000 cal yr B.P.) and the late Holocene (1400 cal yr B.P. to present)—the two key periods since deglaciation whenPiceahas been abundant in the region. The result shows a shift from aPiceaforest ofP. glaucaandP. marianain the late glacial to a forest ofP. rubensandP. marianain the late Holocene. The small number ofP. rubensgrains identified from the late glacial/early Holocene samples (Picea(1000 to 500 cal yr B.P.) was likely the first time since deglaciation thatP. rubenswas abundant in the region.