5. Past Changes in Climate and Tree Growth in tnt: Western Americas 77
50'
300 kms
Figure 5.1. Map showing sites in northwestern Canada and Alaska sampled by
the TRL at LDEO. Most were sampled in the late 1980s. Some of the Alaskan
chronologies, first sampled in the late 1970s-1980s, were updated in the 1990s.
ARR is Arrigetch site shown in Figure 5.2.
(Schweingruber, Briffa, & Nogler, 1993). Figure 5.1 shows an additional
network of tree-ring chronologies sampled at various intervals within the
past two decades by researchers at the Tree-Ring Laboratory (TRL) at
the Lamont-Doherty Earth Observatory (LDEO) . These three data bases
comprise only part of the tree-ring data network that exists for northern/
western North America. Below are several examples of the kinds of
studies conducted for this region by researchers at the TRL of LDEO
based on climatically sensitive chronologies from these and other western
North American tree-ring data .
Western North American Tree-Ring Studies: TRL-LDEO
Northern Treeline
The northern limit of tree growth is largely determined by temperaturerelated factors (e.g. , Bryson , 1966). Hence , northern forests may be
subject to considerable modification if projected climatic warming effects