5. Past Changes in Climate and Tree Growth in the Western Americas 81
that the temperature reconstructions were of best quality between 35°N
and 55°N, but with uncertainty north of 55°N and before around 1750.
Four regional time series were described: British Columbia and the
Pacific Northwest; California; the eastern Rockies and the northern High
Plains and the southwest U.S. deserts; as well as a more extensive western
U.S. series. Other density-based research in western North America
include modeling studies of climate response in old-growth Douglas
Fir (Pseudotsuga menziesii) from Banff (Robertson & Jozsa, 1988) and
Englemann spruce (Picea engelmanii) from Alberta, western Canada
(Parker & Henoch, 1971).
Luckman and his associates have carried out extensive research in
western Canada, particularly for tree-line sites in the Canadian Rockies
(Luckman, 1992). In addition to direct climate studies (based oil
Engelmann spruce, alpine larch [Larix lyalli], and other species), these
records have been applied to the dating of glacial moraine sequences.
Some of the high-elevation chronologies from the northern Rockies
approach 1 millenium in length (Luckman, 1992). Graumlich and
Brubaker (1988) reconstructed mean annual temperatures for Longmire,
Washington, based on ring-width series of alpine larch and mountain
hemlock (Tsuga mertensiana) from the Cascade Mountains. Fritts (1991)
describes a number of climatic reconstructions for the period from 1601 to
1961 that he has developed over the past 2 decades. These include
reconstructions of large-scale anomalies of sea-level pressure, temperature,
and precipitation for the North Pacific, the contiguous United States, and
southwestern Canada. All these studies provide valuable information on
the paleoclimate of western North America that could be compared with
similar South American tree-ring studies within the context of AMIGO.
Tree Rings from Western Southern America
Dendroclimatic analyses in South America and the Southern Hemisphere
as a whole are relatively sparse compared to northern latitudes, although
this situation has recently improved (e.g., Boninsegna et aI., 1990; Lara
& Villalba, 1993).
The earliest South American collections were obtained by Schulman
(1956) and LaMarche for Argentina and Chile (LaMarche, Holmes,
Dunwiddie, & Drew, 1979). More recent dendroclimatic research efforts
in southern and western South America include studies by Villalba,
Boninsegna, Roig, and others. Winter precipitation has been reconstructed
for Santiago, Chile (Boninsegna, 1988; updated from a LaMarche study).
Villalba (1989) used tree rings to infer information on the latitude of the
subtropical high-pressure belt off western South America over the past
500 years. Villalba, Boninsegna, and Cobbs (1989) also employed chronologies of Araucaria species to reconstruct summer temperatures in central-
that the temperature reconstructions were of best quality between 35°N
and 55°N, but with uncertainty north of 55°N and before around 1750.
Four regional time series were described: British Columbia and the
Pacific Northwest; California; the eastern Rockies and the northern High
Plains and the southwest U.S. deserts; as well as a more extensive western
U.S. series. Other density-based research in western North America
include modeling studies of climate response in old-growth Douglas
Fir (Pseudotsuga menziesii) from Banff (Robertson & Jozsa, 1988) and
Englemann spruce (Picea engelmanii) from Alberta, western Canada
(Parker & Henoch, 1971).
Luckman and his associates have carried out extensive research in
western Canada, particularly for tree-line sites in the Canadian Rockies
(Luckman, 1992). In addition to direct climate studies (based oil
Engelmann spruce, alpine larch [Larix lyalli], and other species), these
records have been applied to the dating of glacial moraine sequences.
Some of the high-elevation chronologies from the northern Rockies
approach 1 millenium in length (Luckman, 1992). Graumlich and
Brubaker (1988) reconstructed mean annual temperatures for Longmire,
Washington, based on ring-width series of alpine larch and mountain
hemlock (Tsuga mertensiana) from the Cascade Mountains. Fritts (1991)
describes a number of climatic reconstructions for the period from 1601 to
1961 that he has developed over the past 2 decades. These include
reconstructions of large-scale anomalies of sea-level pressure, temperature,
and precipitation for the North Pacific, the contiguous United States, and
southwestern Canada. All these studies provide valuable information on
the paleoclimate of western North America that could be compared with
similar South American tree-ring studies within the context of AMIGO.
Tree Rings from Western Southern America
Dendroclimatic analyses in South America and the Southern Hemisphere
as a whole are relatively sparse compared to northern latitudes, although
this situation has recently improved (e.g., Boninsegna et aI., 1990; Lara
& Villalba, 1993).
The earliest South American collections were obtained by Schulman
(1956) and LaMarche for Argentina and Chile (LaMarche, Holmes,
Dunwiddie, & Drew, 1979). More recent dendroclimatic research efforts
in southern and western South America include studies by Villalba,
Boninsegna, Roig, and others. Winter precipitation has been reconstructed
for Santiago, Chile (Boninsegna, 1988; updated from a LaMarche study).
Villalba (1989) used tree rings to infer information on the latitude of the
subtropical high-pressure belt off western South America over the past
500 years. Villalba, Boninsegna, and Cobbs (1989) also employed chronologies of Araucaria species to reconstruct summer temperatures in central-