Effects of low stand density afforestation on the growth,stem-form and timber assortment structure of Cunninghamia lanceolata plantations

doi:10.12302/j.issn.1000-2006.202007021

JOURNAL OF NANJING FORESTRY UNIVERSITY ›› 2021, Vol. 45 ›› Issue (3): 165-173.doi: 10.12302/j.issn.1000-2006.202007021

Effects of low stand density afforestation on the growth,stem-form and timber assortment structure of Cunninghamia lanceolata plantations

XIONG Guangkang¹(), LI Yueqiao¹^,^*(), XIONG Youqiang¹, DUAN Aiguo², CAO Dechun¹, SUN Jianjun¹, NIE Linya¹, SHENG Weitong²

1. Experimental Center of Subtropical Forestry,Chinese Academy of Forestry, Fenyi 336600 China
2. Research Institute of Foresty Chinese, Academy of Forestry, Beijing 100091 China

Received:2020-07-09 Revised:2020-10-25 Online:2021-05-30 Published:2021-05-31
Contact: LI Yueqiao E-mail:xgk0315@163.com;stsgzq@163.com

Abstract

Abstract:

【Objective】 The goal of this study was to clarify the growth process, shape, quality characteristics, timber species structure and dynamic change characteristics of the economic benefits of low-density Cunninghamia lanceolata plantations in the Dagangshan area of Jiangxi Province. 【Method】 Using the traditional planting density of 2 500 individuals/hm ² as the control, the growth and development of two low-density Chinese fir experimental forests with an initial planting density of 1 111 and 1 667 individuals per hectare in Fenyi County of Jiangxi Province were monitored and analyzed for 25 years. 【Result】 The average tree height, average diameter at breast height (DBH), under branch height, and stock volume increased with stand age and decreasing densities. The average DBH of different stand densities at 19-25 years of age differed significantly, and the height under branches and volume increased the fastest at 8-19 years and 22-25 years of age, respectively. The results showed that the degree of natural differentiation increased with an increase in forest age and decreased with a decrease in densities. The cumulative withering rate was 25 years, and the difference between densities was significant. The average crown width of trees first increased, then decreased, and then increased slowly with an increase in age, and reached significant differences among densities at 19 years old. The annual average sparse rate and degree of crown overlap of natural lines first increased and then decreased slowly with an increase in forest age; the annual average natural sparsity rate reached a maximum value at 22 years of age, and the canopy overlap degree reached a maximum value at 8 years of age. The difference between the densities was significant. At 25 years, the breast height form ratio and heartwood ratio of 1 111 individuals per hectare and 1 667 individuals per hectare were higher than 2 500 individuals per hectare , and the rate of broken shoots, ratio of height to diameter, and young-adult wood ratio were lower than 2 500 individuals per hectare , and the difference in the height diameter ratio density was significant. At the near mature age of 19-25 years, the proportion of large diameter trees and volume of large-diameter timber increased with the decrease in stand densities, and 1 111 individuals per hectare and 1 667 individuals per hectare occurred in this period. The results showed that the total volume, total timber output, and economic timber output of the low-density stands were close to 2 500 individuals per hectare , and the total volume, total timber output, and economic timber output of 1 667 individuals per hectare stand exceeded 2 500 individuals per hectare at 25 years, respectively. The economic benefit analysis showed that the net income and net present value of the 1 667 individuals per hectare stand were the highest, which were 1.09 and 1.10 times higher than those of the 2 500 individuals per hectare , respectively, whereas 1 111 individuals per hectare had the highest benefit-cost ratio and internal rate of return, which were 7.35 and 30.20%, respectively. 【Conclusion】 The initial planting density of 1 111 individuals per hectare and 1 667 individuals per hectare can be selected and applied in the plantations of Cunninghamia lanceolata in the Dagangshan area of the Jiangxi Province.

Key words: Cunninghamia lanceolata, low stand density afforestation, tree growth, stem-form, timber assortment structure

CLC Number:

S725

XIONG Guangkang, LI Yueqiao, XIONG Youqiang, DUAN Aiguo, CAO Dechun, SUN Jianjun, NIE Linya, SHENG Weitong. Effects of low stand density afforestation on the growth,stem-form and timber assortment structure of Cunninghamia lanceolata plantations[J]. JOURNAL OF NANJING FORESTRY UNIVERSITY, 2021, 45(3): 165-173.

Figures/Tables 8

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重复 replication	坡位 slope position	坡向 aspect	坡度/(°) gradient	样地编号 plot number	株行距/m planting density	行数 rows	列数 columns	样地面积/ m² plot area	定植株数 planting
Ⅰ	下坡	东南	36	1	3×3	8	7	504	56
				2	2×3	8	11	528	88
				3	2×2	10	12	480	120
Ⅱ	下坡	东	34	4	3×3	8	7	504	56
				5	2×3	8	10	480	80
				6	2×2	10	12	480	120
Ⅲ	中下	北	39	7	3×3	8	7	504	56
				8	2×3	7	11	462	77
				9	2×2	10	12	480	120

林龄/a age	活立木株数/(株·hm^-2) living standing trees			枯损木株数/(株·hm^-2) damaged wood			累积枯损率/% cumulative natural sparsity
林龄/a age	A	B	C	A	B	C	A	B	C
4	1 111.00± 0.00 a	1 667.00± 0.00 a	2 500.00± 0.00 a	0.00± 0.00 a	0.00± 0.00 a	0.00± 0.00 a	0.00± 0.00 a	0.00± 0.00 a	0.00± 0.00 a
8	1 038.33± 30.01 a	1 611.67± 15.04 b	2 354.33± 54.99 c	72.67± 30.01 b	55.33± 15.04 ab	145.67± 54.99 a	6.55± 2.73 a	3.31± 0.90 a	5.83± 2.20 a
19	985.67± 69.72 c	1 365.67± 192.17 b	1 889.00± 229.59 a	125.67± 69.24 b	301.33± 192.17 ab	611.00± 229.5 9a	11.31± 6.27 a	18.06± 11.54 a	24.44± 9.18 a
22	879.67± 11.55 c	1 093.00± 53.70 b	1 423.67± 150.77 a	231.33± 11.55 c	573.67± 54.28 b	1 076.33± 150.77 a	20.83± 1.03 a	34.43± 3.25 a	43.06± 6.03 a
25	820.33± 102.08 b	1003.33± 83.94 b	1 257.33± 157.87 a	291.00± 101.53 c	663.00± 84.50 b	1 215.67± 168.22 a	26.19± 9.16 b	39.80± 5.06 a	50.28± 6.31 a

林龄/ a age	造林密度 initial planting density			径级株树占比/% diameter tree																																						直径分布特征 diameter distribution characteristics
				小径木/cm small diameter timber																			中径木/cm middle diameter timber						大径木/cm large diameter timber													直径分布特征 diameter distribution characteristics
				小径木/cm small diameter timber																			中径木/cm middle diameter timber						大径木/cm large diameter timber													变异系数CV		峰度 kurtosis	偏度 skewness
				2		4		6		8		10		12			14		16		18		20		22		24		26		28		30		32		34		36		38	变异系数CV		峰度 kurtosis	偏度 skewness
8	A	15.43					0.64		3.82		7.01		20.38		26.75	19.11		17.20		4.46		0.64																0.191		-0.336			-0.128
	B	14.27	0.45		0.45		0.45		6.54		13.81		23.27		22.79	24.24		7.14		0.88																		0.203		0.127			-0.423
	C	12.93			0.88		3.24		9.73		21.83		23.01		28.32	10.32		2.65																				0.216		-0.225			-0.298
19	A	22.66											2.01		2.68	8.72		16.78		15.44		14.77		16.11		12.08		7.38		3.36	0.67							0.189		-0.201			0.118
	B	20.62							0.47		2.00		3.85		8.91	13.42		16.62		13.99		18.81		9.39		9.59		2.45		0.51								0.217		-0.457			0.003
	C	18.74							1.84		2.57		6.62		15.81	17.65		18.38		14.71		9.93		7.35		2.21		2.94										0.224		-0.158			0.239
22	A	24.19											1.48		1.48	4.55		11.26		15.80		15.04		14.29		13.54		12.79		5.27	3.76			0.75				0.193		-0.065			0.110
	B	22.68									0.63		1.24		3.14	10.07		16.57		14.70		11.16		19.41		6.20		10.63		4.33	1.92							0.199		-0.523			0.152
	C	20.32							0.49		1.46		2.93		12.20	16.10		17.07		13.66		14.63		9.76		5.85		1.95		3.41	0.49							0.223		-0.164			0.392
25	A	26.06											0.81		1.53	4.58		8.39		10.68		16.02		11.45		12.21		12.21		9.92	8.39	2.29				1.53		0.202		-0.222			0.103
	B	24.53											1.29		3.77	7.58		11.58		16.05		11.73		11.20		10.69		9.25		9.40	4.37	2.43				0.66		0.211		-0.826			0.178
	C	22.31									1.46		2.91		13.11	11.17		16.50		12.62		8.74		11.17		8.25		5.83		1.46	3.88	2.91						0.231		-0.320			0.496

造林密度/(株·hm^-2) initial planting density	胸高形率 taper	高径比 height diameter ratio	断梢率/% breaking rate	心材占比/% heartwood ratio	幼成龄材比率/% young adult ratio
2 500	0.684±0.049 a	77.869±3.926 a	13.490±2.309 a	78.142±4.51 a	0.797±0.174 a
1 667	0.689±0.048 a	73.899±4.312 b	8.787±3.305 a	83.301±3.21 a	0.764±0.131 a
1 111	0.687±0.049 a	69.219±4.325 c	11.469±2.433 a	79.254±3.79 a	0.740±0.135 a
均值mean	0.687±0.048	73.662±5.437	11.249±3.117	80.330±4.06	0.767±0.145

林龄/a age	造林密度 initial planting density	薪材/ (m³·hm^-2) fuelwood	小条木/ (m³·hm^-2) stripe wood	经济材/(m³·hm^-2) economic timber				总出材量/ (m³·hm^-2) total timber output
林龄/a age	造林密度 initial planting density	薪材/ (m³·hm^-2) fuelwood	小条木/ (m³·hm^-2) stripe wood	小径材 little diameter timber	中径材 medium diameter timber	大径材 big diameter timber	合计 tolal	总出材量/ (m³·hm^-2) total timber output
8	A	0.02	3.18	53.38	19.89	0.00	73.27	76.47
	B	0.08	7.74	81.37	9.69	0.00	91.06	98.88
	C	0.33	16.17	94.67	4.06	0.00	98.73	115.23
19	A	0.00	0.13	24.11	121.79	124.08	269.99	270.12
	B	0.00	1.14	51.47	159.28	90.84	301.59	302.74
	C	0.00	2.88	97.31	169.83	58.95	326.09	328.96
22	A	0.00	0.09	14.72	109.70	186.09	310.50	310.60
	B	0.00	0.34	32.83	139.86	158.17	330.86	331.20
	C	0.00	1.15	69.64	160.23	101.44	331.31	332.46
25	A	0.00	0.05	9.75	92.76	268.01	370.52	370.58
	B	0.00	0.06	20.56	122.40	252.90	395.87	395.93
	C	0.00	0.30	47.36	148.55	194.42	390.32	390.62

Effects of low stand density afforestation on the growth,stem-form and timber assortment structure of Cunninghamia lanceolata plantations

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造林密度 initial planting density	成本/(元·hm^-2) cost					总产出/ (元·hm^-2) out put	纯收入/ (元·hm^-2) net income	净现值/ (元·hm^-2) NPV	效益成本比 BCR	内部收益率/% IRR
造林密度 initial planting density	清林整地 site preparation	苗木 nursery stock	造林 afforestation	3年抚育 tending for 3 years	采伐运输 cut transport	总产出/ (元·hm^-2) out put	纯收入/ (元·hm^-2) net income	净现值/ (元·hm^-2) NPV	效益成本比 BCR	内部收益率/% IRR
A	525	250.05	40	540	96 350	815 950	718 246	65 088	7.35	30.20
B	525	375.08	60	540	102 941	834 490	730 049	66 046	6.99	29.70
C	525	562.50	90	540	101 562	759 946	656 666	59 075	6.36	28.35