@mastersthesis {572, title = {The Effect of Prescribed Burning on Southwest Ponderosa Pine Growth}, volume = {PhD}, year = {1989}, school = {University of Arizona}, abstract = {Study objectives included determining whether prescribed burning affected ponderosa pine growth; mathematically modeling the growth response to burning; and determining whether forest management history affected growth response. I sampled 188 trees from two areas near Flagstaff, Arizona; one area (Brannigan Flat) had been logged and thinned, and the other (Chimney Spring) had not; both were burned in 1976. Within each study area, control and burned plots were of similar age, vigor, height, and competition index. Trees at Chimney Spring were older, less vigorous, and taller, and had a higher competition index than at Brannigan. For each tree, periodic basal area increment (PBAI) was calculated for the years 1974-1984. To determine which variable would best model growth, postfire PBAI (individual years, 1977-1984) was correlated with previous growth (average PBAI 1974-1976); crown ratio; competition index; thinning index; and diameter. Two models of growth response were developed; one oriented toward satisfying theoretical and research goals, and the other, toward management applications. Growth was modeled using stepwise multiple linear regression, and the dependent variable was postfire PBAI. Research Model independent variables were previous growth, years (climate), and treatment-year interaction, and 72\% of total variance was explained. Fire affected growth significantly and negatively for two years, and then burned trees grew similarly to control trees. Management Model independent variables were crown ratio, competition index, crown ratio, subject tree diameter, year, and treatment, and 52\% of total variance was explained. This model, too, indicated a slight negative effect of burning on growth. Management history was not a significant determinant of growth response. Both models validated well; the ratio of observed-to-predicted residual mean square was 1.04 and 0.91 (Research and Management Models, respectively). Thinning index was not significantly related to postfire growth, but a change in carbohydrate allocation from stem wood to crown and root expansion could have resulted in observed burning effects. Management implications include (1) short-term growth decline may result from burning, (2) management history did not affect growth response, and (3) burning impact is greatest in dense stands of small trees.}, keywords = {Watershed Management}, url = {http://ezproxy.library.arizona.edu/login?url=http://proquest.umi.com/pqdweb?did=746080281\&sid=4\&Fmt=2\&clientId=43922\&RQT=309\&VName=PQD}, author = {Sutherland, Elaine Kennedy} } @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} }