76
R.D. D'Arrigo and G.c. Jacoby
In remote areas of both hemispheres, instrumental records are often
short and sparsely distributed. They can also have missing values as well
as changes in station location or methodology. Climatically sensitive treering chronologies , several centuries to millenia in length, can considerably
lengthen the limited climatic information available for these regions. Our
goal here is to describe some examples of recent dendroclimatic research
in western North and South America. We then briefly outline several
comparative studies that could be developed to exploit these data within
the context of the AMIGO project.
Tree-Ring Width and Maximum-Latewood Density
In addition to the more traditionally used ring-width parameter,
maximum-latewood density is increasingly being employed in dendrochronological studies. Yet the similarities and differences in physiological and climatic response reflected in these two variables are still
being investigated ' (e.g. , D'Arrigo, Jacoby , & Free, 1992; Hughes ,
Schweingruber , Cartwright, & Kelly, 1984; Jacoby, Ivanciu, & Ulan ,
1988; Schweingruber, 1988). Based on studies thus far , it appears that
ring widths respond to year-to-year summer conditions but may also
integrate climatic effects throughout the year and on a long-term basis
(e.g., D'Arrigo et al. , 1992; Jacoby & D'Arrigo, 1989). By comparison ,
the maxirrium-latewood density parameter appears most sensitive to highfrequency conditions over a long warm-season interval (Briffa, Jones, &
Schweingruber, 1992; Conkey, 1986; D'Arrigo et al. , 1992; Jacoby et al. ,
1988). In our laboratory, a computer-assisted image analysis system
(Thetford, D'Arrigo, & Jacoby, 1991) is used for generation of density
and also ring-width data.
Tree-Ring Data Bases from Western North America
Tree-ring chronologies have been produced for many regions of western
North America. A recent example is an extensive transect of tree-ring
width and maximum-latewood density chronologies that has been compiled
for the western United States and Canada by Schweingruber of the
Swiss Federal Institute of Forest , Snow and Landscape Research
(Schweingruber, 1988). This data base includes some 70 sites, ranging
from southern Arizona to Alaska, with most of the chronologies extending
back before 1750. Density data from this transect were used to reconstruct
summer temperature patterns across western North America since 1600
(Briffa et al. , 1992). Another tree-ring data base has been developed
from an extensive east-west transect of sites across the boreal forest zone
of North America sampled by Schweingruber and Jacoby in 1989. Some
of these data have also been used for dendroclimatic reconstruction
R.D. D'Arrigo and G.c. Jacoby
In remote areas of both hemispheres, instrumental records are often
short and sparsely distributed. They can also have missing values as well
as changes in station location or methodology. Climatically sensitive treering chronologies , several centuries to millenia in length, can considerably
lengthen the limited climatic information available for these regions. Our
goal here is to describe some examples of recent dendroclimatic research
in western North and South America. We then briefly outline several
comparative studies that could be developed to exploit these data within
the context of the AMIGO project.
Tree-Ring Width and Maximum-Latewood Density
In addition to the more traditionally used ring-width parameter,
maximum-latewood density is increasingly being employed in dendrochronological studies. Yet the similarities and differences in physiological and climatic response reflected in these two variables are still
being investigated ' (e.g. , D'Arrigo, Jacoby , & Free, 1992; Hughes ,
Schweingruber , Cartwright, & Kelly, 1984; Jacoby, Ivanciu, & Ulan ,
1988; Schweingruber, 1988). Based on studies thus far , it appears that
ring widths respond to year-to-year summer conditions but may also
integrate climatic effects throughout the year and on a long-term basis
(e.g., D'Arrigo et al. , 1992; Jacoby & D'Arrigo, 1989). By comparison ,
the maxirrium-latewood density parameter appears most sensitive to highfrequency conditions over a long warm-season interval (Briffa, Jones, &
Schweingruber, 1992; Conkey, 1986; D'Arrigo et al. , 1992; Jacoby et al. ,
1988). In our laboratory, a computer-assisted image analysis system
(Thetford, D'Arrigo, & Jacoby, 1991) is used for generation of density
and also ring-width data.
Tree-Ring Data Bases from Western North America
Tree-ring chronologies have been produced for many regions of western
North America. A recent example is an extensive transect of tree-ring
width and maximum-latewood density chronologies that has been compiled
for the western United States and Canada by Schweingruber of the
Swiss Federal Institute of Forest , Snow and Landscape Research
(Schweingruber, 1988). This data base includes some 70 sites, ranging
from southern Arizona to Alaska, with most of the chronologies extending
back before 1750. Density data from this transect were used to reconstruct
summer temperature patterns across western North America since 1600
(Briffa et al. , 1992). Another tree-ring data base has been developed
from an extensive east-west transect of sites across the boreal forest zone
of North America sampled by Schweingruber and Jacoby in 1989. Some
of these data have also been used for dendroclimatic reconstruction