Optimum plant density and harvest age for maximizing productivity and minimizing competition in a Calliandra short-rotation-coppice plantation in West Java, Indonesia

Figures & data

Table 1. Survival rates (%) of seedlings at six months after planting and stools after cropping.

Spacing (m)	1 × 1.5	1.5 × 1.5	1.5 × 2	2 × 2	–
SRF (seedlings)^a	82.17	84.92	93.34	98.26	–
SRC (stools, cropped at): ^b				Average (age):
6 months old	50	40	50	30	42.5
12 months old	90	80	70	70	77.5
18 months old	90	100	100	90	95.0
24 months old	90	100	100	100	97.5

^aMeasured at 6 months after planting

^bMeasured at 6 month intervals after parent stand cropping

Table 2. Summary of Anova test (p= .05) on the SRF plantation.

Variables	Tree density	Harvest age	Density*Harvest age
Diameter	.00^a	.00^a	.00^a
Productivity	.00^a	.00^a	.01^a
Number of stems	.00^a	.11^ns	.82^ns

^aSignificance at α: .05; ns: not significant

Figure 1. (a) SRF competition indexes; (b) average number of stems/tree; (c) average diameter of the SRF.

Figure 2. Average primary wood biomass (kg/tree).

Table 3. Average numbers and diameters of coppices by spacing and cropping age.

Felling age	Spacing
	Number of coppices			Diameter of 12-month-old coppices (cm)
	12 months	18 months	24 months	12 months	18 months	24 months
1 × 1.5 m	2.67^a	3.36^a	3.39^a	4.69^a	4.57^a	4.90^a
1.5 × 1.5 m	3.25^a	4.41^a	4.46^a	5.28^ab	5.21^b	5.41^a
2 × 1.5 m	3.63^bc	5.73^b	5.99^b	5.65^b	7.35^c	7.61^b
2 × 2 m	4.78^c	6.61^bc	6.81^c	6.80^c	8.97^d	8.53^c

Numbers followed by the same letter in the same column indicate non-significant differences, based on an HST test (P=.05)

Figure 3. (a) Competition Index, (b) numbers of coppices; (c) coppice wood biomass; (d) survival rates at different harvest ages of the SRC.

Table 4. Calorie (kJ) and lignin (%) values for primary and coppiced wood.

Density	Age
	Primary wood						Coppiced wood after one year resulting from stools cut at:
	12 months		18 months		24 months		12 months		18 months		24 months
	Cal.	Lignin	Cal.	Lignin	Cal.	Lignin	Cal.	Lignin	Cal.	Lignin	Cal.	Lignin
1 × 1.5 m	17,756	15.6	18,929	22.1	19,163	24.16	19,000	15.21	18,933	16.76	19,255	18.99
1.5 × 1.5 m	17,350	13.22	18,832	20.16	19,125	22.71	19,205	15.12	19,029	17.89	18,979	16.41
2 × 1.5 m	17,430	12.88	18,820	21.4	19,029	22.66	19,113	14.99	19,184	17.98	18,987	17.86
2 × 2 m	16,902	12.74	18,807	21.98	19,071	22.48	19,071	14.84	18,979	18.76	19,125	16.94

Table 5. Soil chemical and biological properties at time of primary wood harvesting.

Variables	12 months				18 months				24 months
	1.5 × 1	1.5 × 1.5	1.5 × 2	2 × 2	1.5 × 1	1.5 × 1.5	1.5 × 2	2 × 2	1.5 × 1	1.5 × 1.5	1.5 × 2	2 × 2
pH	5.2	5.2	5.8	6.6	5.3	5.9	6.4	6.6	5.1	5.7	6.6	6.5
Corg (%)	1.98	2.18	3.32	3.98	2.41	2.98	3.88	3.92	2.26	3.14	3.82	4.26
N (%)	0.045	0.076	0.58	1.44	0.062	0.076	1.21	1.92	0.085	0.092	1.06	1.24
P (ppm)	2.6	4.1	6.6	9.3	6.2	8.1	9.4	11.6	8.7	9.3	12.2	14.1
K (me/100g)	1.1	1.7	2.3	4.8	2.1	2.8	3.4	4.7	2.2	2.7	3.8	4.6
Ca (ppm)	2.4	2.6	3.4	3.8	2.2	3.1	3.8	4.1	2.8	3.3	3.9	4.3
Mg (ppm)	1.6	1.9	2.2	2.6	1.8	2.3	3.1	3.4	1.9	2.4	2.9	3.6
Fe (ppm)	6.4	5.6	2.8	2.9	4.1	4.4	2.8	2.8	3.7	3.5	2.5	2.7
TM^a	2.7	3.8	8.4	11.1	5.8	8.4	12.5	20.1	9.8	11.4	22.7	40.6

^aTotal Microbes (10⁷×Cfu/g)