Diameter growth was examined on small diameter whitebark pine 20 years after silvicultural treatments were applied.
Whitebark pine (Pinus albicaulis Engelm.) forests play a prominent role throughout high-elevation ecosystems in the northern Rocky Mountains, however, they are vanishing from the high mountain landscape due to three factors: exotic white pine blister rust invasions, mountain pine beetle outbreaks, and successional replacement by more shade-tolerant tree species historically controlled by wildfire. Land managers are attempting to restore whitebark pine communities using prescribed fire and silvicultural cuttings but are unsure if these techniques are effective. The objective of this study was to determine how whitebark pine regeneration responds to selective thinning and prescribed burn treatments. We studied changes in diameter growth after restoration treatments using ring width measurements obtained from 93 trees at four sites in Montana and Idaho that were treated in the late 1990s 4 sites were located with different combinations of treatments (control, thin only, burn only, thin and burn) through Idaho and Montana. Plots were located within the treatment units and then one to four saplings were selected within these plots and cross-sectional samples extracted (increment cores or stem cookies) from them. Cores were sanded and measured using standardized dendrochronological methods, and basal area increment (BAI) growth calculated using the dplR package in R. The BAI measurements for ten years prior and ten years post treatment were used to calculate growth ratios (GRs), and growth post-treatment to growth pre-treatment were related. GRs greater than 1.0 translated to an increase in growth after treatment, and GRs less than one correspond to a decrease in growth. An ANCOVA was used to explore factors that might influence radial growth response and two-sample t-tests were also conducted to evaluate differences between the average GRs of trees in the control areas and of the trees in the treated areas.
For geographical information on this project and how it fits with other Fire Lab Whitebark Pine research, visit the Whitebark Pine Story Map.
Keane, R. E.; Gray, K. L.; Dickinson, L. J. 2007. Whitebark pine diamter growth response to removal of competition. U.S. Dept. of Agriculture Forest Service Rocky Mountain Research. Research Note 32. Retzlaff, M., R. Keane, D. Affleck, and S. Hood. 2018. Growth Response of Whitebark Pine (Pinus albicaulis Engelm) Regeneration to Thinning and Prescribed Burn Treatments. Forests 9:311. |