CLIMAX COMMUNITIES : SHIFTS WITH TIME 



309 



that the chronology will be carried even further back. 119 Some of 

 the record was completed and some of the cross-matching was 

 made possible by fragments of wood from ancient pueblos and 

 some even with charcoal, which was better preserved than wood. 

 It should be noted that an even longer chronology has been worked 

 out for the giant redwoods, which is complete for 3,000 years. 



When the pueblo dendrochronology was completed, it was a 

 major contribution to archaeology since some thirty prehistoric 

 ruins were immediately given absolute dates, and later hundreds 

 more were dated. This usefulness of the method was immediately 

 apparent to archaeologists, who accepted it and adapted it to their 

 purposes. At the same time, their findings in archaeology have 

 contributed to the establishment of dendrochronology as a means 

 of studying past climate. 



Recent ring studies in moist cool regions indicate that no better 

 climate than the arid Southwest could have been selected for the 

 initial investigations. In extremely dry regions, growth and size of 

 rings are closely related to annual precipitation and the correlation 

 is not complicated by light or temperature effects. It is now known 

 that in the north, or at high altitudes, tree growth is most respon- 

 sive to temperature and that in temperate regions with adequate 

 rainfall, both temperature and moisture factors are reflected in 

 the rings. 90 



This does not mean that tree-ring studies are successful only in 

 arid regions but rather that their interpretation may be more dif- 



TO PREHISTORIC 

 TIMES 



THIS YEAR'S 



TREE CUT 

 THIS YEAR 



SECTIONS FROM HISTORIC BEAMS 



FlG. 166. A diagram illustrating how the bridge method is used to extend 

 knowledge of dated rings, an important part of the building of complete and 

 continuous chronologies. The usual desirable overlap is fifty years.— After 

 Glock. 107 



