TABLE 4.

Results of the generalized additive mixed models (GAMMs) fitted to study the simulated growth variability (Gr) in P. pinaster D and ND in two consecutive periods (1930−1969 and 1970−2019) in Orera and Miedes sites.

Site	Period	Tree type	Edf	F	t	R 2
Orera	1930−1969	ND	8.68	509.7**	10.35**	0.63
		D	8.57	385.1**
	1970−2019	ND	8.72	456.7**	9.91**	0.66
		D	8.60	340.3**
Miedes	1930−1969	ND	8.68	510.9**	10.41**	0.63
		D	8.57	385.1**
	1970−2019	ND	8.72	457.4**	9.97**	0.59
		D	8.60	340.1**

For each model, the degrees of freedom (Edf) and F values associated with the smooth parameter (DOY, day of the year) and their interaction with tree vigor (ND and D trees) are shown. In addition, the significance of the t statistic comparing vigor classes and the R² of the model are presented. Significant values (P < 0.01) are indicated with **.