A Prediction Model of Forest Preliminary Precision Fertilization Based on Improved GRA-PSO-BP Neural Network

Table 3

The biomass range () of a single Chinese fir and the percentage of its organs.

Stand age (t/a)	Organ	Site index S = 5		Site index S = 18		Site index S = 21		Site index S = 23
		W (kg)	Percentage (%)	W (kg)	Percentage (%)	W (kg)	Percentage (%)	W (kg)	Percentage (%)
5a	Leaf	1.67 ± 0.58	21.44	3.48 ± 0.95	24.34	3.98 ± 1.04	22.04	4.12 ± 1.39	18.7
	Branch	1.25 ± 0.44	16.05	2.36 ± 0.84	16.50	2.78 ± 1.21	15.4	3.47 ± 1.32	15.7
	Stem	2.60 ± 0.8	33.40	4.40 ± 1.08	30.77	5.64 ± 1.94	31.23	6.37 ± 2.51	33
	Bark	0.53 ± 0.12	6.804	0.96 ± 0.33	6.71	1.46 ± 0.68	8.08	1.98 ± 0.83	9
	Root	1.74 ± 0.66	22.33	3.10 ± 0.92	21.68	4.20 ± 1.46	23.25	5.24 ± 2.07	23.6
	Tree	7.79 ± 2.6	100.00	14.30 ± 4.12	100.00	18.06 ± 6.33	100.00	22.04 ± 8.12	100.00
19a	Leaf	2.64 ± 0.92	4.11	5.27 ± 1.47	5.04	5.98 ± 2.09	5.14	6.34 ± 2.87	4.83
	Branch	4.43 ± 2.05	6.90	7.61 ± 2.44	7.28	8.22 ± 3.08	7.06	9.12 ± 4.43	7.00
	Stem	40.36 ± 15.7	63.00	64.13 ± 20.6	61.34	72.33 ± 24.3	62.12	81.2 ± 29.7	62
	Bark	6.78 ± 2.11	10.60	11.30 ± 4.87	10.84	13.11 ± 5.11	11.3	15.10 ± 7.05	12
	Root	9.97 ± 3.01	16	16.20 ± 5.56	15.50	16.80 ± 6.76	14.38	19.40 ± 8.11	14.8
	Tree	64.18 ± 23.79	100.00	104.51 ± 34.94	100.00	116.44 ± 41.34	100.00	131.16 ± 44.86	100.00
22a	Leaf	4.22 ± 1.27	4.66	6.37 ± 2.02	4.89	6.89 ± 2.94	4.76	7.26 ± 3.16	4.53
	Branch	5.11 ± 2.31	5.64	8.78 ± 3.11	6.74	9.89 ± 3.84	6.84	10.43 ± 4.38	6.50
	Stem	56.7 ± 20.4	62.6	77.32 ± 26.21	59.36	87.34 ± 32.30	60.45	98.53 ± 41.1	61.4
	Bark	9.12 ± 4.1	10.1	14.40 ± 5.98	11.1	15.21 ± 6.12	10.53	16.32 ± 7.14	10.2
	Root	15.5 ± 6.52	17.1	23.40 ± 9.70	17.91	25.16 ± 11.6	17.41	27.89 ± 13.1	17.4
	Tree	90.65 ± 34.6	100.00	130.27 ± 47.02	100.00	144.49 ± 56.8	100.00	160.43 ± 68.8	100.00
25a	Leaf	5.64 ± 1.62	5.3	8.65 ± 2.61	5.70	9.16 ± 3.16	5.60	10.38 ± 4.21	5.73
	Branch	6.10 ± 2.65	5.7	9.76 ± 3.46	6.43	10.78 ± 3.91	6.60	11.70 ± 4.61	6.50
	Stem	63.2 ± 24.7	60	88.70 ± 28.70	58.5	96.80 ± 31.3	59.10	108.3 ± 35.9	59.8
	Bark	11.7 ± 5.22	11	15.90 ± 6.21	10.5	16.80 ± 7.41	10.26	17.70 ± 8.01	9.8
	Root	20.4 ± 7.59	19.1	28.70 ± 9.53	18.87	30.24 ± 11.2	18.5	33.12 ± 13.41	18.3
	Tree	107.04 ± 41.78	100.00	151.71 ± 50.51	100.00	163.78 ± 56.98	100.00	181.2 ± 66.14	100.00