過去千年間のカナダ、ニューブランズウィック州フィッシュ湖からの高解像度森林と火災のダイナミクス

The Acadian Forest is a mixed-wood forest covering the Canadian provinces of New Brunswick and Nova Scotia. Picea rubens (red spruce) is its signature species which has been prominent for circa 2000 years. We extracted a 124 cm surface core from Fish Lake, (46° 8' 38.32″N, 66° 53' 12.64″ W), near Fredericton, New Brunswick. A rplum age-depth model, based upon 4 ¹⁴C and 15 ²¹⁰Pb dates, showed that the core bottom dates to AD 890. We performed a high-resolution pollen analysis on this core at a ~10 year resolution (125 samples total). Over the last millennium, Betula (birch), Tsuga canadensis (eastern hemlock) and Fagus grandifolia (American beech) declined, as Pinus sp. (pine), Abies balsamea (fir) and Picea sp.(spruce), including P. rubens increased. The Medieval Climate Anomaly (MCA - AD 900-1400), Little Ice Age (LIA - AD 1400-1850), and the European settlement period were clearly demarcated in the pollen record. A rise in Ambrosia (ragweed) marked early Acadian French agriculture at ~AD 1680. During the last 300 years of the European period, Poaceae (grasses), Ambrosia, and other herbs all increased, while Pinus strobus (eastern white pine) declined. Macrocharcoal analysis showed that natural forest fires had a continuous presence over the past millennium, with higher fire frequency during the LIA than in the MCA. The MCA had an average spring temperature of 3.2°C, and the LIA had an average spring temperature of 2.2°C.