@mastersthesis {911, title = {Restoring Ponderosa Pine Forests in the Black Hills, South Dakota}, volume = {Master of Science}, year = {2001}, pages = {50}, school = {University of Arizona}, address = {Tucson}, abstract = {

Ponderosa pine (Pinus ponderosa Laws.) forests have changed considerably during the past century, partly because recurrent fires have been absent for a century or more. In dense stands of ponderosa pine in the Black Hills of South Dakota, a layer of pine needles has replaced inderstory vegetation. I examined the disturbance history, soil seed bank, and effects of prescribed burning and overstory reduction on understory vegetation in a ponderosa pine stand in the northern Black Hills. Cessation of fires, prolific ponderosa pine regeneration, and logging led to a dense, even-aged stand with very little understory vegetation and few viable seeds in the soil seed bank. Understory vegetation did not respond to the restoration treatments the first growing season, but did respond the second growing season. Paucity of viable seeds in the soil seed bank does not appear to constrain recruitment of understory vegetation in dense ponderosa pine forests of South Dakota.

}, keywords = {black hills, fire history, overstory, pinus ponderosa, ponderosa pine, prescribed fire, restoring, soil seed bank, south dakota, stand age, understory}, author = {Wienk, Cody Lee} } @mastersthesis {571, title = {The Effects of Fire Exclusion on Growth in Mature Ponderosa Pine in Northern Arizona}, volume = {Master of Science}, year = {1983}, pages = {28}, school = {University of Arizona}, address = {Tucson}, abstract = {

Dendrochronological techniques were used to assess the effect of fire exclusion on the radial growth of two age classes (approximately 150 to 300 years old) of mature ponderosa pine. Decline in average radial growth in both classes is coincidental with the establishment of a large ponderosa pine seedling crop in 1919 that has since become an extensive stand of stagnant, overcrowded saplings.

F and t tests of tree ring indices comparing the time period before and after 1920 show that growth has significantly declined since 1920 in both age classes. F and t tests comparing the two age classes suggest that growth was similar before 1920, but the older age class shows a significantly stronger growth decline than the younger age class. Spearman Rank Correlation tests indicate that in both groups there was no trend or a tend toward increasing tree ring indices before 1920 in both age classes, but that after 1920 there was a strong, significant trend toward decreasing tree ring indices in both groups, and that the trend is stronger in the older age class. These results suggest that the older trees are experiencing a more pronounced growth suppression effect than the younger trees.

October and July Palmer Drought Severity Indices from 1931 to 1976 were tested for trend toward drought using the Spearman Rank Correlation. There was no trend toward drought during these months, which have the most significant climatic relationship to ponderosa pine growth in northern Arizona. Therefore the growth decline at Chimney Spring may not be attributed to climate.

No environmental factor has changed at Chimney Spring, other than fire exclusion and subsequent seedling establishment. Competition for soil moisture and nutrients, reduced nutrient cycling and soil moisture losses from litter interception may all be factors contributing to the growth decline in the mature ponderosa pines at Chimney Spring.

Key words: age classes, competition, dendrochronology, \“dog-hair\” thickets, fire exclusion, forest, northern Arizona, Pinus ponderosa, radial growth

10-year index:

}, keywords = {age classes, chimney spring, competition, dendrochronology, dog hair thickets, fire, fire exclusion, forest, mature, northern arizona, palmer drought severity indices, pinus ponderosa, ponderosa pine, radial growth, spearman rank correlation}, author = {Sutherland, Elaine Kennedy} } @mastersthesis {573, title = {Fire History of the Gila Wilderness, New Mexico}, volume = {Master of Science}, year = {1983}, pages = {156}, school = {University of Arizona}, address = {Tucson}, abstract = {

A data base of fire occurrence was established for the Gila Wilderness by analyzing fire scars and compiling fire records. Cross sections of 44 fire scarred ponderosa pine trees (Pinus ponderosa Laws.) were collected from three study areas. Crossdating of more than 800 individual fire scars revealed that extensive surface fires were a common occurrence prior to 1900. Mean fire intervals for a 250-year period prior to 1900 were approximately four to eight years and fire intervals ranged from one to 26 years. Intensive grazing and fire suppression efforts after 1900 resulted in a sudden decrease in number of fires recorded by the sample trees.

A 72-year record (1909-1980) of fire occurrence in the Gila National Forest was compiled from Forest Service records. The fire records and fire scar evidence suggest a need for continued emphasis on fuels reduction and greater flexibility in the Prescribed Natural Fire program.

}, keywords = {crossdate, dendrochronology, fire, fire history, fire scar, gila national forest, gila wilderness, new mexico, pinus ponderosa, ponderosa pine, tree ring}, author = {Swetnam, T.} }