Development and evaluation of robust tree biomass equations for rubber tree (Hevea brasiliensis) plantations in India

Forest Ecosystems

Table 3 Parameters^a and model fit statistics for the age-specific models of aboveground biomass (AGB). For ease of comparing slopes (β) the 95% confidence limits were presented

Model	Stand age (yrs)	Intercept (ln(α))	Slope (β)^b	Model	fit	criteria
Model	Stand age (yrs)	Intercept (ln(α))	Slope (β)^b	R ²	AIC	RMSE
1	6	−2.9	2.57 (2.49–2.65)	0.997	−70.8	0.077
	15	−2.01	2.25 (2.11–2.39)	0.984	−84.0	0.095
	27	−0.32	1.84 (1.53–2.15)	0.909	−45.5	0.717
	34	−2.12	2.43 (2.18–2.68)	0.958	−64.3	0.143
	All ages	−2.83	2.60 (2.46–2.74)	0.954	−170.6	0.271
2	6	−3.49	0.97 (0.94–1.00)	0.998	−66.6	0.089
	15	−3.64	0.96 (0.90–1.02)	0.980	−79.4	0.107
	27	−1.71	0.78 (0.67–0.89)	0.938	−51.4	0.059
	34	−3.08	0.93 (0.87–0.99)	0.983	−80.5	0.092
	All ages	−3.31	0.95 (0.91–0.99)	0.976	−217.1	0.192
3	6	−4.85	3.79 (3.22–4.36)	0.93	−24.2	0.365
	15	−11.28	5.85 (4.71–6.99)	0.858	−42.3	0.285
	27	−5.53	3.79 (2.73–4.85)	0.79	−32.8	0.274
	34	−4.15	3.23 (2.63–3.83)	0.876	−44.8	0.246
	All ages	−3.49	3.04 (2.81–3.27)	0.911	−126.6	0.376

Model fit statistics of the best model for a given plantation age are in bold face
^aAll parameters were significantly different from zero. Therefore P values were not included
^bFigures in parentheses represent 95% confidence limits of the slope. Two or more slopes are significantly different from each other only if their confidence limits do not overlap