An application of mixed-effects model to evaluate the role of age and size on radial variation in wood specific gravity in teak (Tectona grandis)

Journal of Wood Science

Official Journal of the Japan Wood Research Society

Table 12 Between-subject comparison for AR(1) + RE structure and polynomial model for RRD

Parameter	Estimate	Std error	DF	t Value	Pr >\|t\|
Radii 1–2 RRD 1 Radii 1–2 RRD 2	− 0.01928 − 0.01650	0.007871 0.005214	348 348	− 2.45 − 3.16	0.0148 0.0017
Radii 1–2 RRD 3	− 0.01194	0.002324	348	− 5.14	< 0.0001
Radii 1–2 RRD 4	− 0.00567	0.006265	348	− 0.90	0.3661
Radii 1–2 RRD 5	0.002247	0.01327	348	0.17	0.8656
Radii 1–2 RRD 6	0.01175	0.0215	348	0.55	0.5851
Radii 1–2 RRD 7	0.02277	0.03065	348	0.74	0.4581
Radii 1–2 RRD 8	0.03524	0.04049	348	0.87	0.3847
Radii 1–2 RRD 9	0.04911	0.05083	348	0.97	0.3347
Radii 1–2 RRD 10	0.0643	0.06148	348	1.05	0.2963

The temporal heterogeneity of the mean WSG appears to be similar for both growth categories only after RRD 4
Both sides of the same tree may show a similar onset of intra-annual wood formation. However, exogenous and endogenous factors are likely to be reduced in the short radius at the beginning of wood formation. On the long radius, there may be a higher rate of cell production which may have reduced the bulk density
DF degree of freedom