Thinning Low Site Ponderosa Pine

Forestry Technical Note Number MT-10

If you encounter any problems with the file provided on this page, please contact Technical Resources at 406-587-6822.

This technical note is also available in Adobe Reader format.

Forestry Technical Note Number MT-10 (PDF; 235 KB)

May 1985.
By W. J. Sauerwein, Regional Forester, Soil Conservation Service, Regional Technical Service Center, Portland, Oregon.

Throughout the semi-humid western forest zone lies a belt of low site Ponderosa pine. This pine ecotype, made up principally of pine-grass and pine-short shrub communities, stretches from the Black Hills of South Dakota to eastern Washington and Oregon, and from the Mongollon rim of Arizona to the Canadian line in Montana.

One of the limitations to use and management has been overcrowded stand conditions. Many thinnings have been introduced in these stands since the early 1900s. Work begun by Pearson ¹ in the Southwest, and later Krauch ², and Gaines and Kotok ³, give us much data on the subject. Recently, Barrett ⁴, Boldt ⁵, McConnell and Smith ⁶, Pearson and Jameson ⁷, and Schubert ⁸, have given us additional ideas and insights-into this limitation.

A summary of diameter growth rates of more recent thinnings are shown in figure 1, from Barrett's, Boldt's ** and Schubert's data. Figure 2 gives some insight into relationships of D+ and herbage production from McConnell and Smith, and Pearson and Jameson. Figure 3 shows D+  canopy cover relationships.

In figure 1, note that Barrett's and Schubert's data are comparable. Both are about the same site index, although the climate in each area is considerably different. Boldt's data follows a similar curvilinear relationship below Barrett's and Schubert's data. The site index is only 55 however, and located in the Black Hills. On Boldt's sequentially thinned plots (Boldt 3, figure 1) site index is 70. The benefit of two releases instead of one seems apparent. This does not include the gain in diameter growth by raising the average diameters in the second thinning, but only true diameter growth.

Extra wide spacing by Barrett did not increase diameter growth rate.

In figure 2, McConnell and Smith's and Pearson and Jameson's data show wide spacing to be beneficial in additional herbage production. Exceptionally wide spacing does not apparently increase herbage yield. Composition may change however. Time is also a function of composition.

Figure 3 shows relationship between D+ and crown canopy in Pearson and .Jameson's and McConnell and Smith's studies. Since we use four crown canopy divisions as management criteria for our grazing guides in grazeable woodlands, this should clarify the relationship. Note that D+8 to D+14 gives a crown canopy range of 20 to 35 percent. If we consider the old timber stocking guide of 0 to 10, 10 to 40, 40 to 70, and 70+ for canopy classes, this canopy range would fall in one class 10 to 40 percent. D+8 to D+14 would appear to be a reasonable spacing guide for low site Ponderosa pine where woodland grazing is feasible.

From figures 1 and 2 we can conclude that spacing as shown here is important, and that D+9 to 11 spacing generally at least doubles diameter growth rates found in natural unthinned stands. The same spacing, that is, D+9 to 11, increases herbage yields by 100 percent or more. Our Western Pine Woodland Information Stick spacing guides for managed Ponderosa pine approximate these research findings.

Bibliography

1. Pearson, G. A,, 1950. Management of Ponderosa pine in the Southwest. U.S. Department of Agriculture, Monograph 6, 218pp.
2. Krauch, Hermann, 1939. The influence of release in relation to diameter growth of Ponderosa pine. U.S. Forest Service, Southwestern Forest and Range Experiment Station, Research Note 59, 2pp.
3. Gaines, Edward M., and E. S. Kotok, 1954. Thinning Ponderosa  pine in the Southwest. U.S. Forest Service, Rocky Mountain Forest and Range Experiment Station. Pap. 17, 30pp, illustrated
4. Barrett, James W., 1965. Spacing and understory vegetation affect growth of Ponderosa pine saplings. U.S. Forest Service Research Note PNW-27, 8pp.
5. Boldt, Charles E., 1970. Sequential Thinnings Boost Productivity of a Ponderosa Pine Stand in the Black Hills of South Dakota. U.S. Forest Service Research Note RM-172, 8pp.
6. McConnell, Burt R., and Smith, Justin G., 1965. Understory response three years after thinning pine. Journal of Range Management, Vol. 18:129-132. And Supplemental Progress Report (amended July 12, 1967).
7. Pearson, Henry A., and D. A. Jameson, 1967. Relationship between timber and cattle production on Ponderosa pine range: The Wild Bill Ranger. U.S. Forest Service, Rocky Mountain Forest and Range Experiment Station, 10 pp, illustrated.
8. Schubert, Gilbert H., 1971. Growth Response of Even-aged Ponderosa Pine Related to Stand Density Levels in Arizona. Journal of Forestry, Vol. 69:857-860.

Additional Notes

Prepared by Prepared by H. E. Hunter, State Staff Forester, SCS, Bozernan, Montana.

• Figure 2 Additional Notes
• Figure 3 Additional Notes
• Calculations

Caution

Use this material as a general guide. These curves have not been tested in Montana. Figures one and three should apply well to ponderosa pine stands in Montana with comparable site indices.

Figure two should apply to climax ponderosa pine stands or climax Douglas-fir (Pseudotsugsi taxifolia) stands invaded by ponderosa pine, where the understory is predominantly grass. Figure two and the sample calculations have little application where the understory is dominated by shrubs or where the climax forest type is alpine fir (Abies lasiocarpa), grand fir (Abies grandis), western hemlock (Tsuga heterophylla), western red cedar (Thuja plicata).

If you have any questions regarding this technical note, please contact one of the following:

Robert Logar, State Forester
Phone: (406) 587-6836
Email: Robert.Logar

Ronald Nadwornick, State Resource Conservationist
Phone: (406) 587-6998
Email: Ron.Nadwornick

< Back to Forestry Technical Notes

Last Modified: 08/18/2008