Subalpine fir Snow Agesize and Bark Beetle Interactions

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

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

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

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

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.

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.

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

Octopus shaped galleries

Results: Graphical Number of Healthy vs Number of Dying/Dead 90 80 70 60 50 Number of Healthy vs Number of Dying/Dead 40 30 20 10 cm 0 Healthy trees: 79 Gallery Galleries: 6 Dead: No Gallery: 38

Snow Depth: beetle vs no beetle 160 140 120 100 80 Snow Depth: beetle vs no beetle 60 40 20 cm 0 Dead Galleries Snow Depth No Galleries Snow Depth T-Test Results comparing snow depth: 0. 05712

6 trees 38 trees cm T-Test: Dead trees only, snow depth: Gallery vs no gallery: 0. 008548

cm T-Test: Dead trees only, DBH: Gallery vs no gallery: 0. 005039

Snow depth influencing DBH 35 30 Snow depth influencing DBH 25 20 15 10 5 cm 0 0 50 100 150 200

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.

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

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

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

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. Forest and 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/stelprdb 5188058. pdf Student t-test: Unequal variances. http: //en. wikipedia. org/wiki/Student%27 s_ttest#Unequal_variances