The regional vegetational history of the High Peaks (Adirondack Mountains) New York

We completed palynological investigations of four lake sites along an elevation gradient (661 to 1320 m) in the High Peaks region of the Adirondack Mountains of New York (U.S.A.). Our studies provide a record of the regional vegetational history of the east-central Adirondacks. The overall vegetational and climatic changes inferred for the High Peaks are similar to those elsewhere in the Northeast. However, there are significant differences in the timing and order of arrival of many taxa. These differences may result from the rugged topography and isolated position of the Adirondacks, or from climatic and edaphic variations among regions. The High Peaks region was deglaciated approximately 13,000 yr BP. From ice retreat until about 12,000 yr BP the vegetation at ail elevations was dominated by herbs and probably consisted of tundra. Picea was the first tree taxon to immigrate (prior to 12,000 yr BP at low elevations), and Ficea-dominated woodlands were well-established at all elevations below 1200 m by 12,000 yr BP. Picea declined rapidly at all elevations beginning at about 10,500 yr BP. An expansion of Alnus populations (Alnus crispa) accompanied the Picea decline. This Alnus maximum is more pronounced at high elevations. Populus also immigrated at this time, and Larix and Abies populations expanded. The early Holocene was characterized by the increasing importance of Betula (probably Betula papyrifera), the immigration and rapid expansion of Pinus strobus (about 9500 yr BP), and the subsequent arrival and spread of Acer saccharum, Tsuga, and Fagus between 9700 and 7000 B.P. Mixed conifer-hardwood forests became established. Pinus strobus, Tsuga and most deciduous taxa were more abundant at low-elevation sites; Abies and Betula were more common at high-elevation sites. By about 7000 yr BP, Pinus strobus had decreased in abundance, and Tsuga dominated forests with Pinus strobus, and hardwoods became established at low-elevation sites. Abies and Betula continued to dominate at higher elevations. Forests at lower elevations experienced significant changes at 4800 yr BP. Tsuga declined abruptly, perhaps because of a pathogen, and Betula (probably Betula luted), Acer saccharum, Acer pensylvanicum, and Fagus increased. Thus, low-elevation sites shifted from conifer dominance to hardwood dominance, while Betula and Abies remained dominant at high elevations. Tsuga began to recover by about 3400 yr BP and expanded at low elevations. Picea began to expand again about 2000 yr BP. The existing vegetation zones became established within the past 2000 years. Tsuga, Fagus, and Acer saccharum appear to have decreased in abundance at low elevations during this time interval.