A growth-effective age-based periodic site-index for the estimation of dynamic forest site productivity under environmental changes

Table 3 Summary statistics of the periodic mean annual stand volume increment model (Eq. 11) as a function of conventional site index (\(SI\)) and periodic site index (\(pSI\))

SI	Variable		Std.Error	t-value	Pr( >\|t\|)	\(R^2\)	\(RMSE\)	\(AIC\)	n
SI	Parameter	Estimate	Std.Error	t-value	Pr( >\|t\|)	\(R^2\)	\(RMSE\)	\(AIC\)	n
\(SI\)	\({\alpha }_{1}\)	1.04600	0.07968	13.128	< 0.0001	0.46	4.765	32,347	5435
	\({\alpha }_{2}\)	0.13780	0.01362	10.117	< 0.0001
	\({\alpha }_{3}\)	−0.00062	0.00004	−14.286	< 0.0001
	\({\alpha }_{4}\)	0.00017	0.00001	25.550	< 0.0001
	\({\boldsymbol{\alpha }}_{5}\)	0.05277	0.00097	54.514	< 0.0001
\(pSI\)	\({\alpha }_{1}\)	1.67917	0.11231	14.952	< 0.0001	0.51	4.517	31,768	5435
	\({\alpha }_{2}\)	0.10858	0.01283	8.461	< 0.0001
	\({\alpha }_{3}\)	−0.05277	0.00376	−14.035	< 0.0001
	\({\alpha }_{4}\)	0.00017	0.00001	27.508	< 0.0001
	\({\boldsymbol{\alpha }}_{5}\)	0.04735	0.00076	61.907	< 0.0001

ISSN: 1297-966X