Climatic Inferences from Dendroecological Reconstructions - Dendroclimatology - page 280

1.Manitou Experimental Forest, CO, Boyden et
al. 2005.

W 109

2. Turkey Springs, San Juan Mountains, CO,
Romme unpublished

Colorado

Utah

3. Archuleta Mesa, NM, Brown and Wu 2005.

1

4. Monument Canyon Research Natural Area,
NM, Falk and Swetnam, unpublished.

3

N 37

5.Chuska Mountains, AZ, Savage 1991.

2

6 5 6. Powell Plateau, Grand Canyon National Park,

AZ, Fule et al. 2002.

7

4

8

7. Walhalla Plateau,
AZ, Mast & Wolf 2004.

Grand Canyon National New Mexico

9

Park,

10

8. Gus Pearson Natural Area, AZ, Mast et al.
1999.

Arizona

11 12

9. Maverick Fort Apache Reservation, AZ,
Cooper 1960.

Km

10. Malay gap, San Carlos Reservation, AZ,
Cooper 1960.

200

0 400

Mexico

11. Santa Catalina Mountains, Iniquez and
Swetnam, unpublished.

12. Rhyolite Canyon, Chiricahua National
Monument, AZ, Barton et al. 2001.

Fig. 9.9 Map of the Southwest and southern Rocky Mountains showing locations of the 12 sites
where ponderosa pine age structure data have been collected and composted for analysis in this
chapter. The gray shaded area is the approximate range of ponderosa pine in this region

of trees also appear to approximately coincide with drier periods in the 1750s-
1760s, 1850s-1860s, and 1950s-1960s. Note also that a most recent cohort in the
1980s-1990s also coincides with a wet period in the Southwest that occurred from
approximately 1977 to 1992 (Swetnam and Betancourt 1998 ) , although many of the
datasets used here lack counts of tree seedlings and saplings in these recent decades.
Earlier wet periods (1610s-1640s and 1690s-1710s) may coincide with very slight
establishment episodes, but these cohorts are not well resolved, probably because
fewer trees overall are included in this earlier part of the record.
Although this is a relatively coarse-scale spatial and temporal analysis of pon-
derosa pine age structure patterns in the Southwest, the results (Fig. 9.10 ) suggest
that there are several key features of local to regional recruitment dynamics that
were responsive to climatic variability. It is well known that ponderosa pine pro-
duces large cone crops only erratically, and that successful germination of the seeds
is enhanced by warm, wet summers (Pearson 1950 ; Savage et al. 1996 ) . Successful
establishment and survival of seedlings into saplings is dependent on (1) favorable
moisture conditions (i.e., lack of drought), (2) the absence of surface fires for a suffi-
cient length of time to allow the saplings to develop thicker, more heat-resistant bark
(e.g., Fig 9.8 ) , and (3) sufficient time for meristems to be elevated above grasses and