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Lodgepole Pine

Mortality for Mid-Rotation and Old-Growth Lodgepole Pine

For lodgepole pine with DBH>4, annual survival probability (Ps) is predicted using a logistic model.

Pslogistic = exp(c) / (1+exp(c))

Where: C = 3.92227014 + 0.17237881 * dbh - 0.00092726 * Dbh2 + 0.39225725 * DbhInc + 0.63492435 * stSc - 0.05898038 * Dbh2 / stBa - 0.06646968 * stBagt

DBH is in cm

DbhInc is the current diameter increment (cm/y)

stSc = Pl relative composition of the stand by BA

stBa is the stand basal area (m2/ha)

stBagt is the basal area in thicker trees (m2/ha)

For very large, old trees and stands there are two additional mortality penalties, designed to account for wind damage and increased mortality in heavily stocked  stands. These features were not captured in the logistic model above, and are based on the work of Yang (2002).  The following only applies if the MAFlag is selected. 

1) If the quadratic mean DBH of the logdepole pine in the stand (QMDpl) exceed 22cm and the current tree is thicker than the QMDpl, survival of the tree is reduced by a factor proportional to the square of the amount QMDpl exceeds 22:

Z = (QMDpl - 22) ^ 2 / 100

SRF1 = (1 + Z * QMDpl / DBH) / (1 + Z)

2) If the stand basal area exceeds 55 m2/ha in mixed stands (BAsw/BAtotal<0.8), or 45 m2/ha in pine dominated stands, survival of all pine trees is reduced

SRF2 = ((BAtotal - 55) / 80) if mixedwood

SRF2 = ((BAtotal - 45) / 80) if pine-dominated

If unmodified by the criteria above, all SRFx=1. The final annual survival probability, applied to the tree expansion factor is:

Pslogistic = exp(c) / (1+exp(c)) * SRF1 * SRF2


In addition. i{ users select Pl in the MaxDenAdj and the stand density is above the self-thinning line, an additional penalty on survival will be applied.