BARK THICKNESS SHOULD YOU CARE? Jim Flewelling GMUG, November 15, 2013

OUTLINE YES – You Should Care. Background: 1994 NW Taper Coop Suspicious volume cutouts. Subsequent volume validations Bark thickness results Background: Structure of Taper Predictions. Solutions.

Yes, You should care! For almost taper and volume equations were derived from data where the key variables included DBH (outside bark), and inside bark volume or stem profile. If the equations are applied to areas where bark thickness is different, results will be bad.

1994 West-sideTaper Coop 726 Douglas fir trees Across the diameter range within stands. 7 predefined regions. Eqns: –Bark thickness at breast height –Inside-bark profiles (conditioned at BH) –Upper stem bark thickness equations Excellent residuals.

1994 West-sideTaper Coop

Suspicious volume cutouts Client was noticing a pattern of low volume cutouts in one of the operating areas. Volume and taper equations are often the innocent “usual suspects” This client put them on trial instead of just complaining.

Subsequent volume validations 11 harvest age DF stands. 109 trees, selected across the DBH range. Standing measurements: DBH, HT, and upper stem diameter (17’, 41’). Felled: Outside bark profile, and bark thickness profile.

Subsequent volume validations 4% mean underestimate outside bark volume. 0.0% mean error in outside bark volume Mean predicted bark ratio =.097 Mean observed bark ratio =.116 Do the Math! No other problems of this magnitude.

Bark Thickness Results From same client Dble Bark / DBH

Bark Thickness Results -2012

Bark Thickness Ratio (%) Mean error = 1.68 percentage points. Mean error by stand range of 7 points. No clear regional effects.

Bark Thickness Ratio - ANOVA Y = Bark Thickness Ratio at breast height (%). Variance between stands =3.95 –Standard error = 1.99 Variance between trees (within stands)=5.43 –Standard error = 2.33

Background - Structure Coop equations: –BR eqn at breast height = f(DBH, HT, region). –ib profile = f(DBH, HT, region) –Profiles then conditioned on DBHib Less common: –ib profile = f(DBH, HT) Software. Ability to supply DBHib?

Solutions Cruising can include bark thickness on a small number of trees. For non-cruise applications, need survey models. Try to find correlated variables.

Solutions – Few Trees / Stand # of StandsTrees/Stand# of treessize of 95% CI on mean

SOLUTIONS- CAUSES Methods? Climate / region / stand conditions ? Seed source ? Recent weather? ??????