Holocene Tree Line and Climate Change on the Queen Charlotte Islands, Canada

Abstract

Palynological study of two subalpine ponds on the Queen Charlotte Islands reveals changes in tree line and climate during the Holocene. The findings agree with previous reconstructions, from nearby Louise Pond on the Queen Charlotte Islands, that suggest a warmer-than-present climate and higher-than-present tree lines in the early Holocene (ca. 9600–660014C yr B.P.). Basal ages at SC1 Pond and Shangri-La Bog indicate that the basins did not hold permanent water before 720014C yr B.P., consistent with a warmer and drier early Holocene previously inferred from Louise Pond. Pollen and plant macrofossils indicate the initial establishment of subalpine conditions by 6090 ± 9014C yr B.P., similar to the 5790 ± 13014C yr B.P. age for cooling inferred from Louise Pond. Conditions similar to present were established at SC1 Pond by 3460 ± 10014C yr B.P., confirming the previous estimate of 340014C yr B.P. at Louise Pond. This 340014C yr B.P. vegetation shift on the Queen Charlotte Islands corresponds with the beginning of the Tiedemann glacial advance in the south-coastal mountains of British Columbia (ca. 330014C yr B.P.), the Peyto and Robson glacial advances between 3300 and 280014C yr B.P. in the Rocky Mountains, and climatic cooling inferred from palynological studies throughout southern British Columbia, northern Washington, and southeast Alaska. These findings confirm that changes in regional climate influenced changes in vegetation in coastal British Columbia.