Describes the status of our knowledge of ponderosa pine silviculture in the southwestern States of Arizona, Colorado, New Mexico, and Utah. Economic value, impact on other uses, and the timber resource are discussed first, followed by ecological background, site quality, growth and yield, and silviculture and management. Relevant literature is discussed along with observations, experience, and results of unpublished research. Treatise is intended to serve as a reference tool for guidance in making management decisions and prescribing silvicultural treatments.Research needs are also considered.

A severe May wildfire decimated an unthinned ponderosa pine stand in northern Arizona, while an adjacent thinned stand was relatively undamaged. Radial growth increased on burned trees where crown kill was less than 60% and decreased where crown kill was more than 60%. Burning initially stimulated growth of herbaceous vegetation in both stands. Herbage nutrient value was temporarily enhanced due to burning. Artificially seeded areas produced most herbage 2 years after burning.

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The longest and heaviest needle fascicles were associated with greater thinning intensities of ponderosa pine (Pinus ponderosa Laws.) stands 8 years after treatment. The foliar nutrient concentrations did not change significantly between the various thinning regimes. In addition the total forest floor in thinned and unthinned ponderosa pine stands ranged from 17.7 to 34.4 metric tons/ha. On a dry weight basis the F2 horizon constituted 74–88% of the total forest floor. However, nutrient concentrations increased from the foliage to the L to the F1 to the F2 which had the greatest concentrations of nutrients but were not affected by thinning intensity. The greater concentrations in the F2 were probably indicative of the more advanced degree of decomposition. Total nutrients in the forest floor were inversely proportional to the degree of thinning. In the stands at the growing stock level of 6.9 and 48.2 m2/ha (unthinned) total nitrogen was 213 and 301 kg N/ha, respectively. Other nutrient values were 17 and 27 kg P/ha, 18 and 32 kg S/ha, 56 and 75 kg K/ha, 119 and 154 kg Ca/ha, 75 and 126 kg Mg/ha, 26 and 34 kg Zn/ha, and 88 and 156 kg Mn/ha in the stands with growing stock levels of 6.9 and 48.2 m2/ha, respectively.