A Record of Late-Quaternary Moisture-Balance Change and Vegetation Response from the White Mountains, New Hampshire

Abstract

Changes in regional moisture availability over time affect hydrologic systems, such as lakes, and ecological processes, such as plant growth and reproduction. Long-term changes in moisture balance may help to explain broadscale changes in forest composition during the Quaternary period. In this article, Holocene lake-level changes and fossil pollen from Echo Lake, New Hampshire, are documented and the relationship between moisture-balance fluctuations and vegetation change in northern New England over the past 12,000 years is examined. Ground-penetrating radar profiles and five sediment cores provide evidence for two periods of low water levels at ca. 11,000–8,000 cal yr BP and at ca. 5,000–2,000 cal yr BP, respectively. During the first interval of low water level, dry-tolerant white pine (Pinus strobus) became common in the surrounding watershed. By ca. 8,000 cal yr BP, when the water level rose, hemlock (Tsuga), beech (Fagus), and birch (Betula), which prefer high soil-moisture levels, had increased in abundance. The second period of low water levels coincided with a decline in hemlock populations that has been widely attributed to a pathogen outbreak. The correlation between lake-level and vegetation change suggests that moisture availability, in addition to temperature, helps to shape vegetation dynamics by directly affecting plant populations and by influencing plant-pathogen and other ecological interactions.