Subalpine fir: Snow, A ge/size, and B ark Beetle I nteractions

1. Subalpine fir: Snow, Age/size, and Bark Beetle Interactions Adam Albright Winter Ecology - 2012 Mountain Research Station University of Colorado, Boulder

2. Outline. • Subalpine Fir, snow, and the Bark Beetle • The big question • A possible way to make the connection • Results Presentation • Discussion • Conclusions • Acknowledgments • References

3. Introduction • Subalpine fir – high elevation species • Adapts to extreme environment by heavily investing in needles over roots • Drought stress – major cause of mortality (direct & contributing) Western Balsam Bark Beetle – USGS maps/data indicate major cause of Subalpine mortality Preferentially target older trees, more food/tree. (Bleiker et al, 2003; Antos et al 2008; Bigler et al, 2007)

4. The Big Question • Is  there a connection between snow depth (water supply), tree diameter/age, and incidence of beetle attack in the subalpine fir?

5. Methods • First, appropriate sites were chosen using USGS forest data. • Once within a polygon (from the map) containing beetle-attacked subalpine fir, a random direction was taken for five, 50 X 2 meter belt transects. • Within the transect, the following were recorded: DBH for each subalpine fir, snow depth, health (alive or dead/dying), and presence of beetle gallery.

6. Methods: Cont • Key measurements were graphed for comparison. For four comparisons averages and standard errors were compared. One comparison is a scatterplot. • Each graphed measurement was additionally subjected to a 2-tailed, t-test; this determines if there is a significant difference between the means. • Assumptions: • Normal Distribution • Data sampled independently from the populations being compared.

7. P 2 P Niwot Ridge MSR G.L.V. Credit: Teresa Chapman, Adam Albright

8. Octopus shaped galleries

9. Results: Graphical cm Healthy trees: 79 Galleries: 6Dead: No Gallery: 38

10. cm T-Test Results comparing snow depth: 0.05712

11. 6 trees 38 trees cm T-Test: Dead trees only, snow depth: Gallery vs no gallery: 0.008548

12. cm T-Test: Dead trees only, DBH: Gallery vs no gallery: 0.005039

13. cm

14. Discussion • Correlations: • Snow depth beetle infestation: non-significant correlation • Snow depth for dead trees - beetle to not beetle: possibly shows water supply role in infestation • Dead DBH - Gallery to no gallery: Beetles prefer larger trees. • Snow depth (water supply) influences DBH. Roughly bell-shaped.

15. Discussion cont. • Problems: • Number of healthy to number with galley • Data sampled in clusters • Small sample size: • Time • Place • Tree samples

16. Conclusion • Snow: • Water resources impact tree size and beetle incidence • Beetles: • Within small transects not as prevalent as depicted. • Data points toward less impact than water stress. • Bigger picture: • Snowfall is projected to decrease in the Rockies • Subalpine fir surround many watersheds (Boulder, Longmont, etc) • Future studies needed to further understand link

17. Acknowledgments • Tim “Wintologist” Kittel • My research assistants: Kalin and Chris and Tori • My overabundance of scientific Swag • The bio-geography department for loaning gear

18. References • Antos, Joseph A., Parish, R., Nigh, G. D., (2008) Growth patterns prior to mortality of mature Abies lasiocarpa in old-growth subapline forests of southern British Columbia. Forestand Ecology Management. (225) 1568-1574. • Bigler, Christof, Gavin, D. G., Gunning, C., Veblen, T. T., (2007) Drought induces lagged tree mortality in a subalpine forest in the Rocky Mountains. Oikos. (116) 1983-1994. • Bleiker, Katherine P., Lindgren, S. B., Maclauchlain, L. E., (2003) Characteristics of subapline fir susceptible to attack by western balsam bark beetle. Canadian Journal of Forestry. (33) 1538-1543 • Kegley, Sandra. (2006) Western Balsam Bark Beetle: Dryocoetes confusus Swaine. Online at: http://www.fs.usda.gov/Internet/FSE_DOCUMENTS/stelprdb5188058.pdf • Student t-test: Unequal variances. http://en.wikipedia.org/wiki/Student%27s_t-test#Unequal_variances