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The Model > Juvenile Growth > Black Spruce

Black Spruce

Height and diameter growth for juvenile black spruce

For black spruce, annual height growth for seedlings (height ≥ 1.3m) is predicted based on preliminary relationships fitted to the Alberta LFS SDS and MP data (Yao PhD thesis 199,5). This function predicts height growth using primarily total age; only very slight impacts for density and species composition are present. Site index and other competing vegetation has no effect on the predictions.

Height growth for saplings (height ≥1.3m, DBH<4 cm) of these species is based on the increment predicted by the regional site curve, given the breast height (BH) age of the tree. Annual diameter growth of saplings is the difference in diameters predicted from the regional height-diameter relationships using present and future tree height.

HiJvsb = jHtsb(Age + 1) - jHtsb (Age)

 Where: HiJvsb is the black spruce height increment

 jHtsb = 22.167321 * Exp(0.710512 * Bareroot + (0.607727 * Container) + (0.225849 * Health) + (-0.0000068565 * stTotDen) + (-0.766986 * trSc) + (0.096612 * DW)) * (Exp(0.096272 * Age) - 1 + (0.333583 * Container)) / 100

Bareroot = 1 if bareroot stock, default is 0

Container = 1 if container stoc,k, default is 0

Health = 1 if healthy and 0 if damaged, defaults to 1

stTotDen = stand total density

trSc = relative total density of black spruce

sitecls = is set to 0 if site index is <= 18 and set to 1 if site index > 18

DW = drainage 1 if well drained and 0 if poorly drained, defaults to 1

Age = tree age

Height growth for saplings (height > 1.3m, DBH<4 cm) of these species is based on the increment predicted by the regional site curve, given the breast height (BH) age of the tree. Annual diameter growth of saplings is the difference in diameters predicted from the regional height-diameter relationships using present and future tree height.

HiJvsb = siteHt(spp, BHAge + 1, site) - siteHt(spp, BHAge, site)

Where: siteHt is height predicted by the regional site index curve

BHAge is breast height age

Site is the black spruce site index

Diameter growth for juvenile Black Spruce

DIncr = prDBH(spp, Ht) - prDBH(spp, Ht - HtInc)

where: prDBH is the predicted DBH

if Ht <=1.3 m then prDBH = "-1" dbh does not exist

else "case where Height > 1.3 but less than asymptote of diameter height curve"

prDBH = Log(1 - ((Ht - 1.3) / A) ^ (1 / A(C))) / A(B) A, B, C = are coefficients from the Huang 1994, height diameter model

Diameter Increment Reduction Factor for high density stands

The reduction factor reduces the diameter increment by a factor of 1.0 to 0.5 as density increases from 20,000 to 70,000 stems per hectare.

DIncr = redFact * DIncr

Where:

redFact = 0.5 * (stTotDen - 20000) / 50000), Maximum reduction is 0.5

stTotDen = stand total density

Survival probability (Ps) for black spruce (DBH<4 cm)

Since a model for black spruce could not be fit, owing to insufficient data, Ps for juvenile black spruce is assumed to be 0.995.