@mastersthesis {658, title = {Temperature reconstructions spanning the Continental Divide: Bristlecone and limber pine trees as proxy data}, volume = {Phd}, year = {1998}, school = {Arizona State University}, abstract = {Variability in the intensity and magnitude of the Pacific North American (PNA) circulation pattern and the reverse-PNA affects high and low frequency temperature variations on either side of the Continental Divide, on the Colorado Plateau. The PNA circulation pattern corresponds with cooler temperatures on the Colorado Plateau, whereas the reverse-PNA circulation pattern corresponds with warmer temperatures on the Colorado Plateau associated with a high pressure ridge over the Rocky Mountains. Temperature was reconstructed using three Pinus aristata (bristlecone pine) chronologies and one Pinus flexilis (limber pine) chronology from subalpine sites located on either side of the Continental Divide in Colorado and Arizona. The standardized ring-indices of the four chronologies (scAD 548-1994) were correlated with historic temperature data from twelve ground stations and upper air temperature data from four radiosonde stations in Arizona, Colorado, New Mexico and Utah. Temperature reconstructions across a transect spanning the Continental Divide on the Colorado Plateau provide valuable insight to temporal changes in large scale circulation patterns. Reconstructions of annual temperature indicate there were several periods when temperatures were below the modern mean east of the Continental Divide when they were above the modern mean west of the Continental Divide. Variability in the direction of temperature change on either side of the Continental Divide may reflect a westward displacement of the high pressure ridge at different times in history. Reconstructions of annual temperature also indicate 850 mb temperature east of the Divide is slightly higher when the PNA circulation pattern occurs as a teleconnection to El Nino Southern Oscillation (ENSO) events. In contrast, annual 700 mb temperature west of the Divide is slightly lower. Temperature reconstructions also indicate higher mean annual temperatures occurred between scAD 550 to 600, scAD 900-980, and scAD 1040-1080, and scAD 1130-150 than between 1950 and the present. These reconstructions suggest low frequency cycles of above average temperatures have occurred throughout history. These results indicate more research is required to determine whether recent warming trends identified by other researchers reflect anthropogenic warming or natural cycles. }, keywords = {Bristlecone, Continental divide, Limber pine, Pinus, Temperature reconstructions}, url = {http://ezproxy.library.arizona.edu/login?url=http://proquest.umi.com/pqdweb?did=732946061\&sid=18\&Fmt=2\&clientId=43922\&RQT=309\&VName=PQD}, author = {Diane Douglas} } @mastersthesis {904, title = {Fire Regime of the Lodgepole Pine (Pinus contorta var. murrayana) Forests of the Mt. San Jacinto State Park Wilderness, California}, volume = {Master of Science}, year = {1984}, note = {

Please contact the Laboratory of Tree Ring Research to view this thesis.

}, month = {08/1984}, pages = {93}, school = {Cornell University}, address = {Ithaca}, abstract = {

For the purpose of providing recommendations for the fire management plan of the Mt. San Jacinto State Park Wilderness, California, the natural fire regime of the lodgepole pine forests within the wilderness was determined. Fire-scarred lodgepole pine trees were cored, and their growth rings crossdated against a composite ring series, to obtain fire date estimates of fires that have burned within the forests during the last 300 years. U.S. Forest Service fire records and personal accounts were also used to determine recent fire history.

Results indicate that the fires within the lodgepole pine forests of Mt. San Jacinto probably were quite small (\< 0.4 ha). Because of this, the fire regime is probably one of low-intensity fires. Fires started principally by lightning and they generally did not spread far because of low woody fuel loading on the ground. These small fires, however, occurred quite frequently throughout the lodgepole pine forests. Fires probably burned every one to two years, and in many years, more than one fire burned. The average fire return interval for separate locations within the lodgepole pine forests was not determined exactly because most of the burned trees had only one fire-scar.

The effects of this fire-regime on the forest vegetation composition was determined. This was accomplished with multiple regression analyses of vegetative and physiographic data collected from the area of each verified fire.

In the 2500 to 2900 m elevation range, white fir generally increased in importance (relative basal area) over lodgepole pine as years since the fire increased. However, the relationships of lodgepole pine and white fir importances to the time since the fire were not statistically significant. Above 2800 m elevation, neither lodgepole pine nor limber pine importance was affected by the fire regime. Throughout the lodgepole pine forests of this wilderness area, the fire regime has not greatly affected the forest vegetation composition.

To compare two methods of obtaining fire year estimates from living, fire-scarred trees, both wedging and coring was done on ten fire-scarred lodgepole pine trees. The rings of the wedges and cores were then crossdated against a composite ring series, and the respective fire year estimates of each method were compared for each tree. Seven pairs of wedges and cores were crossdated, and each pair gave the same fire year estimate for the respective tree. In the situation of single-scarred trees, the coring method, along with dendrochronology dating, should be attempted instead of wedging, which is more destructive to the tree than coring.

Based on this study, I recommend that the fire management plan for the lodgepole pine forests of the Mt. San Jacinto State Park Wilderness contain two options for fire control. First, in areas that have heavy use by recreationists and cultural or historical benefits, fire suppression should begin immediately after a fire has been detected. Second, in all other areas, a \“let burn\” policy should be attempted, whereby the fire would be allowed to die out on its own. This would save the expense of fire suppression, which can be very costly in remote wilderness areas. These fires should be monitored in case they do burn near valuable areas. Prescribed burning is not recommended because of the weak relationship of the fire regime to the forest vegetation composition.

}, keywords = {california, coring, dendrochronology, fire, fire management, fire scar, Limber pine, lodgepole, mt san jacinto, mt san jacinto state park wilderness, pine, pinus contortata, regime, suppression, tree ring, var murrayana, wedging, white fir}, author = {Paul Sheppard} }