Whitebark Pine - Daylighting Restoration Treatments

The locations of the two treatment units where trees were individually daylighted in this study. Map of unit locations with marked individual trees, Square Lake on left and Flattop further right.

At the Stateline study area, we evaluated increases in diameter and height over ten years (2008-2018) after two types of daylighting treatments (removing competition in a 2 m and 4 m radius around selected trees) on two units along the Idaho-Montana, USA divide. In 2008, 694 young whitebark pine trees, with a minimum height of 0.5 meters and a maximum DBH of 10 cm, and without visual sign of lethal blister rust cankers, were selected and tagged in two large areas on the Idaho Panhandle National Forest. 287 of the whitebark pine were tagged and treated as control trees, while 407 more were assigned either a 2-meter or 4-meter thinned radius, separated equally within 3 height classes. After the 2008 release treatments, re-measurements were taken in 2013 and 2018. To examine height and diameter increases and blister rust presence, we measured DBH, height, live crown percentage, blister rust %, and live canopy % of all treated and control trees.

We found that while there were increases in diameter (average of 1.2 cm for 2 m radii and 1.6 for 4 m radii) and height growth (an average of 0.03 m for 2 m radii and 0.04 m for 4 m radii) over the 10 years, daylighting around trees using a 2 m radius resulted in no significant increases in either height or diameter growth for individual whitebark pine trees when compared to untreated controls.

There were statistically significant differences in growth for trees in the 4 m radius treatment compared to the control, but these differences were small (an average of 0.05 cm for diameter; 0.001 m for height).

While selected trees in 2008 had no blister rust cankers on their boles and branches with blister rust were pruned, we found a significant increase in blister rust presence from 2013 to 2018 (~56% increase). However, the increase in blister rust presence was similar across trees in both treated areas and controls.

Average increases in diameter (cm) and height (m) over ten years when separated by height classes (0.5-1.4 m, 1.5-3 m, >3 m). There was no significant difference in ten-year growth among the height classes.

Growth of tagged trees DBH (cm) for the three measurement intervals across the two units (Flattop and Square Lake) and for the two units combined for each of the treatments (control, 2-meter radius, and 4-meter radius). It is apparent that trees daylighted to 4 m radius grew faster than trees in the control and 2 m daylight treatment.

Growth of tagged trees height (meters) for the three measurement intervals across the two units (Flattop and Square Lake) and for the two units combined for each of the treatments (control, 2-meter radius, and 4-meter radius). It is apparent that trees daylighted to 4 m radius grew faster than trees in the control and 2 m daylight treatment.

Collaborators

• Research Collaborators:

  • Bruce Ericson, Superior Ranger District, Lolo National Forest
  • Karl Buermeyer and Jhen Rawling, Blackrock Ranger District, Bridger-Teton National Forest
  • Idaho-Panhandle National Forest
  • Katharine Gray, California State University at Chico

• Funding Contributor(s):

  • USFS Rocky Mountain Research Station
  • RMRS Fire, Fuel, and Smoke Science Program
  • National Fire Plan