History of late- and post-glacial vegetation and disturbance around Upper South Branch Pond, northern Maine

Abstract

The changing character of vegetation and the effects of disturbance on vegetation are inferred from pollen, plant macrofossils, charcoal, and microlepidopteran larvel head capsules in sediment cores from Upper South Branch Pond, Maine. Following deglaciation 12 500 – 12 000 years ago, a herb–shrub tundra developed which included moss species characteristic of calcareous, mineral soils. Fire and infestation by microlepidopterans were unimportant initially but became important upon arrival of spruce, paper birch, balsam fir, white pine, and tamarack trees (ca. 10 200 – 9500 years BP). Fires were infrequent in the watershed between 7500 and 5000 years BP. The relatively stable forests of this period, dominated by hemlock and yellow birch, grew in what may have been the moistest part of the Holocene. The maximum postglacial abundance of microlepidopteran larvae is centered around the hemlock decline (ca. 4800 years BP). Subsequently, the forest was composed largely of deciduous trees and white pine. Fire incidence was greater, and fewer fossils of microlepidoptera were deposited. Lack of major disturbances between ca. 3300 and 2600 years BP coincided with increases in hemlock, tamarack, yellow birch, and arbor vitae. Increases in boreal conifers began by about 1700 years ago, suggesting cooler, and perhaps wetter, climate. An increase in microlepidoptera accompanied the recent expansion of boreal conifers.