The effect of tree density and height on tree-flagging of Lodgepole Pines in Niwot’s sub-alpine forest Michael D. Schuster

Winter Ecology – Spring 2010 Mountain Research Station – University of Colorado, Boulder

Mechanisms of tree flagging

• Predominately carried out by wind • Krummholz: “Crooked Wood” in German; These are the type of trees/shrubs near or at treeline • Reasons for bareness of trunk: lack of SR

In the Big Picture

• • • • Why is this important?

Useful for forestry practices Can put in context of CC scenario Affects passage of mammals

Observations and Hypothesis

• • I noticed that the trees had varying heights of bare trunk and branches, and this general height changed when the trees were either taller or closer together Hypothesis: affected by amount of sun reaching lower branches, not by krummholz or wind as much – As the avg height increases, the height of the bare tree will also increase – As the L.P. Pine density increases, the height of bare tree should also increase (more trees-more coverage-less sun to ground)

Methods

• • • • 10x10 m transect Clinometer, field tape, flags, snow probe Total density, density of conifers Avg height (clinometer), snow depth

Average tree heights of Lodgepole Pines in the Niwot sub-alpine forest

2 0 6 4 20 18 16 14 12 10 8 1 2

Average Lodgepole Pine density per 10m2 transect, Niwot sub-alpine forest

0,7 0,6 0,5 0,4 0,3 0,2 0,1 0 1 2 3 4

Site # (increasing with elevation)

5 3 6 4 5

Site # (increasing elevation)

6 Avg tree height Height of bare tree

90 20 10 40 30 60 50 80 70 0 0 5

% of bare tree per change in height

10

total height of tree (m)

15 20 Site 1 y = -0,1213x + 45,267 R² = 0,0002 Site 2 y = -3,4429x + 87,972 R² = 0,2168 Site 3 y = -0,4471x + 48,932 R² = 0,0168 Site 4 y = -0,1682x + 52,699 R² = 0,012 Site 5 y = 0,1492x + 61,042 R² = 0,0027 Site 6 25 y = 2,9495x + 11,364 R² = 0,1885

% of bare trunk per density of transect

70 60 50 40 30 20 10 0 0 y = 0,3732x + 38,458 R² = 0,826 10 20 30 40

number of conifers

50 60 70 P-value = 0.0128

Site # 4 5 6 2 3 1 P value 0.366941

0.037538

0.067436

0.00619

0.010393

0.762244

Conclusions

• • • • • Total L.P. Pine height increases with elevation Bare trunk height is variable—other factors Density increases with elevation % of bare trunk increases with increase in total height No significant results—other variables are affecting the outcome

Other variables to consider

– Slope of transect – Aspect of transect (tried to keep this constant) – Elevation – Type of forest (are there deciduous trees) – Amount of exposure (wind – Snow depth (how does this affect height of bare tree) – Inaccuracies with measurements (10 m distance of transect, from tree, density average)

Suggestions for next time

• • • • Bring an altimeter, measure elevation More accurate measurments of snow depth Find a better way to measure density Choose transects carefully, controlling for: – Slope, aspect, exposure, types of trees (no deciduous) Finally, for next time: BRING A CAMERA

Works Cited

• Reference articles Arno, Steven F. Timberline: Mountain and Arctic Forest Frontiers. Chp.1 excerpt, prepared by CU. New York, 2007. • Pictures: – – http://www.daviddarling.info/images/vegetation_flagging.gif

http://www2.swgc.mun.ca/botany/burntisland/images/Flagging%201.

jpg