Research Article

Geographic Patterns and Stand Variables Influencing Growth and Vigor of Populus tremuloides in the Sierra Nevada (USA)

Table 3

Generalized linear mixed model of aspen stem basal area increment (BAI; cm2 year−1) for aspen trees in 20 stands around Lake Tahoe Basin. −2 Log Likelihood = 299.6. Dependent variable = . Categorical variable for location: North/east, south/west. Elevation in km. : Estimate for standardized coefficients of fixed effects.

EffectParameterEstimates.e.df

FixedIntercept0.163300.4114180.400.69623.0
 North/east−0.357400.11651−3.070.2006−2.4
 South/west0.00000
Dbh (cm)0.345500.06081495.68<0.000146.6
Dbh2−0.001460.0003149−4.89<0.0001−10.0
Dbh × Elevation0.5−0.147800.041219−3.590.0019−29.7
Crown ratioa1.737800.32211495.40<0.00013.4
Vicinity BA (m2 ha−1)−0.004930.0021149−2.330.0214−1.3
Percent conifer BAb−0.300700.1014149−2.970.0035−1.6

RandomStand ( )0.037050.0222
Residual0.233000.0269

aCrown ratio (arcsine transformed) = Sin−1(CR0.5).
bPercent conifer BA (arcsine transformed) = Sin−1((0.01 * percent conifer BA)0.5) where percent composition in terms of vicinity BA included BA of the sample aspen and all neighbor trees.