Whitebark pine populations are declining across their entire range due to the combined effects of mountain pine beetle, whitebark pine blister rust, and changing fire regimes. This species is incredibly important for ecosystem diversity as well as snowpack and soil retention in the high elevation sites. Efforts are underway to restore whitebark pine forests using a wide variety of mechanical and prescribed burning techniques to reduce competition around living whitebark pine trees to improve tree vigor and promote regeneration. One experimental mechanical method, called “daylighting”, involves the removal of tree competition in a small circle around individual whitebark pine trees. In this study, 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 m 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 (IPNF) on the border of Idaho and Montana, USA. 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 of DBH, height, live crown percentage, rust %, and live canopy % of all treated and control trees, and height increases, diameter increases, and rust presence examined.
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.
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.
Publications not available at this time. |